Inhibiting TGF-beta signaling preserves the function of highly activated, in vitro expanded natural killer cells in AML and colon cancer models
Inhibiting TGF-beta signaling preserves the function of highly activated, in vitro expanded natural killer cells in AML and colon cancer models
Folashade Otegbeye 0 1
Evelyn Ojo 1
Stephen Moreton 1
Nathan Mackowski 1
Dean A. Lee 1
Marcos de Lima 0 1
David N. Wald 1
0 Department of Medicine, Division of Hematology and Oncology, University Hospitals Cleveland Medical Center , Cleveland , Ohio, United States of America, 2 Case Western Reserve University , Cleveland , Ohio, United States of America, 3 Nationwide Children's Hospital Division of Hematology/Oncology, Columbus, Ohio, United States of America, 4 Department of Pathology, University Hospitals Cleveland Medical Center , Cleveland, Ohio , United States of America
1 Editor: Nupur Gangopadhyay , CCAC , UNITED STATES
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
Funding: FO receives salary support for this
research effort through grant funding from the
American Society of Hematology (Research
Training Award for Fellows). The work was funded
partially through a grant to DNW from the
Leukemia and Lymphoma Society. Research-grade
LY2157299 was provided by Lilly Oncology. Colon
Natural killer cells harnessed from healthy individuals can be expanded ex vivo using
various platforms to produce large doses for adoptive transfer into cancer patients. During such
expansion, NK cells are increasingly activated and more efficient at killing cancer cells.
Adoptive transfer however introduces these activated cells into a highly immunosuppressive
tumor microenvironment mediated in part by excessive transforming growth factor beta
(TGF-beta) from both cancer cells and their surrounding stroma. This microenvironment
ultimately limits the clinical efficacy of NK cell therapy. In this study, we examined the use of a
TGF-beta receptor kinase inhibitor, LY2157299, in preserving the cytotoxic function of ex
vivo expanded, highly activated NK cells following sustained exposure to pathologic levels
of TGF-beta in vitro and in a liver metastases model of colon cancer. Using myeloid
leukemia and colon cancer cell lines, we show that the TGF-beta driven impairment of NK cell
cytotoxicity is mitigated by LY2157299. We demonstrate this effect using quantitative
cytotoxicity assays as well as by showing a preserved activated phenotype with high NKG2D/
CD16 expression and enhanced cytokine production. In a mouse liver metastases model of
colon cancer, we observed significantly improved eradication of liver metastases in mice
treated with adoptive NK cells combined with LY2157299 compared with mice receiving NK
cells or TGF beta inhibition alone. We propose that the therapeutic efficacy of adoptive NK
cell therapy clinically will be markedly enhanced by complementary approaches targeting
TGF-beta signaling in vivo.
cancer studies were supported by a Case
Comprehensive Cancer Center GI SPORE grant
awarded to DNW. Tissue analysis was supported
by the Tissue Resources, Cytometry and Imaging
Microscopy and the Hematopoietic Biorepository
and Cellular Therapy Core Facilites of the Case
Comprehensive Cancer Center (P30 CA043703).
The funders had no role in study design, data
collection and analysis, decision to publish, or
preparation of the manuscript.
Competing interests: Research grade LY2157299
was provided at no cost by Lilly Oncology for this
study solely for the purpose of enriching our
scientific interest. Lilly Oncology however had no
role in our study direction, design, data collection,
data analysis, our decision to publish our results or
the preparation of this manuscript. None of the
authors listed have any financial, employment,
consultancy or product development declarations
to be made regarding Lilly Oncology. This does not
alter our adherence to PLOS ONE policies on
sharing data and materials.
The clinical development of adoptive immunotherapy with natural killer (NK) cells has been
facilitated by various ex vivo expansion platforms that yield cell doses sufficient to achieve
some clinical efficacy [1±13]. These expansion platforms typically involve co-culture of freshly
isolated NK cells with irradiated antigen-presenting cells or feeder cells which are themselves
sensitive to NK cell killing [4±12]. In the process of feeder cell killing, NK cells expand robustly
and also acquire increasingly activated phenotypes resulting in large numbers of highly
activated NK cells capable of efficient tumor killing at low effector to target ratios.
To ensure the efficacy of these highly activated NK cells in cancer therapy, it is critical that
these cells maintain their cytotoxic activity in vivo. A major obstacle in this regard is that the
tumor micro-environment is enriched with several immunosuppressive cytokines, one of
which is transforming growth factor beta 1 (TGF-beta) [13±18]. TGF-beta is produced in
excess by tumor cells themselves, as well as by regulatory T cells, myeloid derived suppressor
cells (MDSCs) and other stromal cells in the tumor microenvironment. Circulating TGF-beta
levels ranging from 5ng/ml to >20ng/ml have been described in both hematologic
malignancies and solid tumor patients [19±23]. These levels are higher than seen in healthy volunteers
and correspond with impaired cellular immunity [16±19, 24±26]. Levels below 1ng/ml have
been described in the peripheral blood and bone marrow of healthy volunteers [
acute myeloid leukemia and myelodysplastic syndrome patients have levels ranging from 6 to
]. In a study of 45 colorectal cancer patients, Narai et al reported circulating total
TGF-beta levels greater than 15ng/ml in patients with metastatic disease [
]. Those with liver
metastases had the highest levels, up to 45ng/ml.
Pathologic levels of TGF beta have been shown to impair both the innate and adaptive
cellular immunity of cancer patients [14,25±28]. Postulated mechanisms by which TGF-beta impairs
NK cell function include down-regulated expression of activating receptors like NKG2D and
CD16 (the FCγR mediating antibody-dependent, cellular cytotoxicity (ADCC)) and cytokine
mediators/enzymes. It also counteracts the NK pro-survival effects of IL-2 and stimulates
further proliferation of regulatory T cells. Small molecule kinase inhibitors and monoclonal
antibodies targeting the TGF-beta receptor have been explored as a means of enhancing cellular
immune response pre-clinically [15,27±29]. There is at least one active clinical trial exploring
the combination of a TGF-beta receptor inhibitor, LY2157299 (Galunisertib, Eli Lilly) with the
PD-1 monoclonal antibody Nivolumab, with a goal of enhancing the liberated T-cell response.
In the process of developing allogeneic adoptive transfer of NK cells as a therapeutic strategy
against various malignancies, we have adopted ex vivo expansion of NK cells using
antigen-presenting feeder cells. In the process of generating large cell yields during expansion, the resulting
NK cells are also significantly more activated and better efficient at killing both liquid and solid
tumor targets. Our hypothesis is that these highly activated NK cells will again have limited
clinical efficacy in vivo after being continually exposed to the immunosuppressive, TGF-beta rich
microenvironment of cancer patients following adoptive transfer. This will limit the clinical
efficacy of such therapeutic endeavors. In this study we explored inhibiting TGF-beta signaling as
a strategy to preserve and/or enhance the cytolytic efficacy of ex vivo expanded, highly activated
NK cells in the TGF-beta rich milieu of myeloid leukemia and metastatic colon cancer.
Materials and methods
NK cell culture and activation
Procurement of peripheral blood samples from healthy volunteers with written informed
consent for research use. The Institutional Review Board (IRB) of University Hospitals Cleveland
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Medical Center approved the procurement and use of blood samples for this study. Peripheral
blood mononuclear cells (MNCs) were separated into buffy coats following density gradient
centrifugation of whole blood over Ficoll-Paque Plus (GE Healthcare Life Sciences). MNCs
were subjected to CD3 depletion followed by CD56 enrichment using MACS human CD3
depletion and human NK cell enrichment kits respectively according to the manufacturer's
instructions (Miltenyi Biotech). The CD3-, CD56+ NK cells (>98% purity confirmed by flow
cytometry) were either incubated overnight in media supplemented with IL-2 (GoldBio) for
next day assays or were expanded over 14 days in co-culture with irradiated feeder cells
(K562-mbIL21) and IL-2 (50U/mL) as described by Somanchi et al [
]. NK cells were
subsequently maintained in IL-2 supplemented media either alone or in combination with human
TGF-beta 1 (Cell Signaling) at 5-10ng/ml for up to 96 hours. The base medium was RPMI
1640 + Glutamine 2.05mM (HyClone), 10% Cosmic Calf Serum (HyClone) and 1%
Immediately prior to all in vitro assays, NK cells were centrifuged out of cell culture and
resuspended in fresh media to remove continued IL2, TGF beta or LY2157299 exposure of the
NK cells and their co-cultured targets.
NK cell cytotoxicity against various cancer cell lines was obtained using a quantitative flow
cytometry assay. Cancer cells used were a myeloid leukemia (HL60), and colon cancer cell
lines (HCT116 and HT29) cultured in the base medium described above and all were obtained
from ATCC. Target cells were labeled with Calcein-AM (Calbiochem) and then co-incubated
with NK cells at varying effector (NK cell) to target ratios. 10,000 target cells were used per
triplicate well for all experiments. At the end of 4 hours incubation, the number of live
CAMlabeled target cells per 100uL of cell suspension was quantified by rapid flow cytometry with
an Attune NxT flow cytometer (Thermo Fisher Scientific). Cytotoxicity results are expressed
as the proportion of Calcein-AM (CAM) bright cells.
NK Cell Cytotoxicity = (Number of CAM bright cells in a target cell alone well minus
Number of CAM bright cells in NK + target co-culture) divided by Number of CAM bright cells in a
target cell alone well.
NK cell phenotyping
In cell culture assays NK cells were phenotyped by flow cytometry for CD16 and NKG2D at
various time points using anti-CD56-APC (BD-Biosciences), and anti-CD16-PE
(BD-Biosciences). Antibody staining of single cell-suspensions was performed by manufacturer's
instructions/protocol. Stained cells were analyzed by flow cytometry.
Quantification of human IFN-gamma, TNF-alpha, Perforin and Granzyme B was performed
using commercially available ELISA kits (R&D signaling). For IFN-gamma and TNF-alpha
quantification, cell-free supernatants were collected after 4h of co-incubation at 37ÊC of 40,000
NK cells and 10,000 colon cancer cells (HT29). For Perforin and Granzyme B quantification,
cell-free supernatants were collected after 2h of co-incubation of 106 NK cells and 106 HL60
cells. Results shown are the means of triplicate wells ± standard deviation measurements.
Active human TGF-beta levels were measured in the serum of human colon cancer murine
xenografts following the manufacturer's protocol (R&D signaling). To prepare mouse sera for
the TGF-beta assay, cardiac blood collected immediately following mouse euthanasia was
transferred to pre-cooled micro-centrifuge tubes containing EDTA and centrifuged for 30 min
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at 1,500g at 4ÊC. The supernatant plasma was collected and stored in micro-centrifuge tubes at
-80ÊC. Samples were thawed at room temperature on the day of TGF beta assay.
Colon cancer liver metastases mouse model and human NK cell adoptive
100,000 HCT116 cells were surgically implanted into NSG mouse spleens (following
hemisplenectomy); 4 groups, 3 mice/group. The control group received tail vein injections of 3%
FBS/PBS and twice daily oral gavage of inhibitor carrier. A TGF-B inhibitor only group
received tail vein injections of 3% FBS/PBS and twice daily oral gavage of LY2157299
(TGFbeta inhibitor) at a dose of 75mg/kg twice daily for 2 weeks. A third group (NK alone) received
5 x 106 NK cells each (tail vein), weekly for two weeks, starting 10 days after hemi-splenectomy.
The fourth group (NK + TGF-B inhibitor) received 5 x 106 NK cells each (tail vein), weekly for
two weeks, starting 10 days post-op and the TGF-beta inhibitor LY2157299 by oral gavage
twice daily at 75mg/kg for two weeks. Mice receiving NK cells also received IL2 (75,000U IP)
three times a week (MWF) for two weeks. The vehicle for LY2157299 was constituted per
manufacturer (Eli Lilly) instructions [
]. The vehicle for mouse injections (cells and IL2) was
sterile filtered PBS with 3% calf serum.
This study was carried out in strict accordance with recommendations in the Guide for the
Care and Use of Laboratory Animals of the National Institutes of Health. Mouse surgeries
were performed under ketamine/xylazine anesthesia, and all efforts were made to minimize
suffering in the peri-operative period and during oral gavaging including post-operative
analgesia per institutional guidelines. All mice were euthanized at a pre-determined end point 1
week after the second NK cell infusion in treated mice. Euthanasia was performed using
carbon dioxide asphyxiation followed by cervical dislocation. All procedures used in mouse care,
surgeries and euthanasia for the purpose of this study were approved by the Institutional
Animal Care and Use Committee of Case Western Reserve University.
All continuous measurements (NK cell expression of CD16, NKG2D, and change in
cytotoxicity during in vitro studies were compared using the student T-test between two groups
(control NK cells were reference sample). Tumor burden measurements computed from imaging
in colon cancer liver metastasis xenograft was compared using ANOVA among groups ( 3).
P-values demonstrated are at significance levels of 0.05 for two-tailed hypotheses. Chart
indicators for p-values are if <0.05; if 0.01, if 0.001, if 0.0001 and ns if 0.05
Ex vivo expansion of NK cells leads to increased cytotoxic activity against
leukemia and colon cancer
Ex vivo expanded NK cells exhibit increased cytotoxic activity against colon cancer and
myeloid leukemia cells. We compared the cytotoxic function of freshly isolated NK cells which
were overnight activated in IL2 with NK cells from the same donor that were expanded for 2
weeks using irradiated K562mIL21 feeder cells. The expanded NK cells were more efficient at
killing both colon cancer and myeloid leukemia cells. For example at a 1:2 NK cell to target cell
ratio, there was 24% killing of HCT116 cells as compared to 2% killing with fresh NK cells;
p = 0.043 (Fig 1A). Overnight-activated NK cells required an effector to target ratio of 5:1 to
achieve 50% killing while expanded cells achieved this at 2:1 ratio. In addition to HCT116
cells, expanded NK cells also exhibited high cytotoxicity on HT29 cells (Fig 1B). At a 1:1 ratio
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Fig 1. Expanded NK cells demonstrate increased cytotoxicity against HCT116 and HT29 cells as compared to fresh, IL-2 activated cells. The indicated NK
cells were assessed for cytotoxic activity against target cancer cells using a calcein AM flow cytometry assay following 4 hours co-incubation. (A) Percentage cell
death of HCT116 cells induced by NK cells at the indicated Effector:Target cell ratios. (B and C) Percentage HT29 cell death induced by NK cells from 3 individual
healthy donors at Effector:Target ratios of 1:1 (B) and 4:1 (C). Bars represent data using IL2-activated NK cells (FRESH) and following expansion of NK cells from
the same donor (EXPANDED). p<0.05; p 0.01; p 0.001; p 0.0001; ns p 0.05.
using 3 different NK cell donors, the expanded NK cells killed 45±86% of HT29 cells (Fig 1B).
This cytotoxic effect was significantly better than the overnight activated NK cells which killed
4±28% of the HT29 cells. Again, expanded NK cells demonstrated superior killing efficiency at
4:1 ratios, with >90% killing across all donors at a 4:1 ratio as compared to 29%-40% using
fresh NK cells (Fig 1C).
Exposure to pathologic TGF-beta levels impairs expanded NK cell function
in a time-dependent manner
At TGF-beta levels similar to that found in AML patients (5ng/ml), NK cell killing of the
myeloid leukemia cell line HL60 was progressively impaired at 24 hours (11±14% decrease,
p = 0.002), 72 hours (33±41% decrease, p<0.0001) and 96 hours exposure (70±78% decrease,
p<0.0001) (Fig 2A). This reduced cytotoxic activity correlated with an NK cell receptor
phenotype consisted with less active NK cells. For example, there was a 65±68% decline in NKG2D
expression as early as 24 hours in the NK cells (Fig 2B; p = 0.005). CD16 expression did not
change in the first 24 hours of exposure but decreased by 56% at 96 hours (Fig 2C; p = 0.037).
There was no appreciable difference by increasing the TGF-beta ligand concentration from
5ng/ml to 10ng/ml (Fig 2B and 2C).
Fig 2. Sustained exposure to pathologic levels of TGF-beta impairs the function of highly activated, expanded NK cells. After 2 weeks of expansion, NK cells
were maintained in culture supplemented with 200U/ml IL2 with or without TGF-beta at 5ng/ml and 10ng/ml. (A) Change in cytotoxicity of expanded NK cells
against HL60 cells (4:1 ratio) following exposure to indicated doses of TGF-beta after 24h, 60h and 96h. Change presented is in comparison to NK cells maintained
without TGF-beta. (B and C) Change in activated phenotype following 24h and 96h exposure to the indicated doses of TGF-beta as compared to control NK cells.
Change in proportion of NK cells expressing NKG2D (B) and CD16 (C) are shown. T: TGF-beta ligand. p<0.05; p 0.01; p 0.0001; ns p 0.05.
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Fig 3. Inhibiting TGF beta signaling using the small molecule kinase inhibitor LY2157299 preserves the cytotoxic function of expanded NK cells, even after
sustained exposure to pathologic levels of TGF-beta. After 2 weeks of expansion, NK cells were maintained in culture supplemented with 200U/ml IL2 alone or
in combination with TGF-beta 1 (5ng/ml) and/or LY2157299 (5uM) for the indicated times and tested by flow cytometry and cytotoxic assays. (A, B, C and D)
Mean fluorescence intensity (MFI) of NKG2D after 24h (A) and 72h (B); and for CD16 after 24h (C) and 72h (D). (E, F, G and H) Change in cytotoxicity
compared to control NK cells (not treated with TGF-beta or LY2167299) against HT29 cells at 24h (E) and 72h (F); and against HCT116 at 24h (G) and 72h (H).
Individual results from three different donors using NK to target ratios of 1:1 are presented in each figure. (I) Similar 72 hour results using NK cells obtained from
two donors is shown against HL60 cells using NK to HL60 ratios of 1:1 and 4:1. T: TGF-beta; G: LY2157299. p<0.05; p 0.01; p 0.001; p 0.0001; ns
TGF-beta inhibition maintains the function of expanded NK cells despite
sustained exposure to pathologic TGF-beta levels
We assessed the phenotype and cytotoxic function of ex vivo expanded NK cells treated with
TGF-beta alone or in combination with LY2157299, a clinically used oral small molecule
kinase inhibitor of TGF-beta receptor 1. Despite continued exposure to TGF-beta, the
`activated' NK cell phenotype consisting of NKG2D+CD16 bright NK cells was preserved by the
addition of LY2157299 (Fig 3A to 3D). NKG2D expression was decreased by approximately
53% at 24 hours and 61%-72% by 72 hours with TGFbeta alone; p = 0.025 and 0.035
respectively (Fig 3A and 3B). This change was significantly ameliorated at 24 and 72 hours after
treatment with the addition of LY2157299 (p = 0.029 and 0.012 respectively). A change in CD16
expression was not evident at 24 hours (Fig 3C) but was decreased by 11%-43% by 72 hours
(Fig 3D); p = 0.071. These changes were again prevented by the addition of LY2157299.
We also measured killing of colon cancer and leukemia cell lines by the ex vivo expanded
NK cells in the presence of TGFbeta and/or LY2157299. At a NK to target ratio of 1:1,
TGFbeta exposure resulted in a 54%-73% decrease in killing of HT29 cells (Fig 3E) after 24 hours
and 9±77% after 72 hours (Fig 3F) The addition of LY2157299 preserved the cytotoxic function
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Fig 4. TGF-beta signaling impairs the production of TNF-alpha, IFN-gamma, Perforin and Granzyme B by ex vivo expanded NK cells. Functional assay of
expanded NK cells after 72h exposure to 5ng/ml TGF-beta ligand by measuring release of TNF-alpha and IFN-gamma into the supernatant at the end of a 4hr
cytotoxicity assay. ELISA quantification of TNF-alpha (A) and IFN-gamma (B) in the supernatant of 40,000 NK cells co-cultured with 10,000 HT29 cells/well.
ELISA quantification of perforin (C) and granzyme B (D) release after 2 hours of co-culturing 106 NK cells with 106 HL60 cells are presented. All assays presented
are results of triplicates. T: TGF-beta; G: LY2157299. p<0.001; p 0.0001; ns p 0.05.
of NK cells in the presence of TGF-beta ligand, and a modest gain of function in cells from one
donor. Changes in NK cell cytotoxicty after 24 hours exposure to TGFbeta were more modest
against HCT116; -9%, -53%; and -13% in individual donors (Fig 3G). After 72 hours
TGFbeta exposure, a more marked decrease in cytotoxic activity against HCT116 was noted; -67%,
-13% and -29% (Fig 3H).
Against HL-60 cells, there was a 54%-64% decrease in NK cell mediated killing after 72 hours
with TGF-beta exposure at a 1:1 NK cell to target ratio (Fig 3I). Increasing the NK cell ratio to
4:1 was still associated with roughly a 40% decrease in cytotoxic function. Again, the addition of
the TGF-beta inhibitor LY2157299 preserved the high cytotoxic function of these NK cells.
The production of TNF-alpha and IFN-gamma by these otherwise highly activated NK cells
was also significantly impaired following TGF-beta exposure. During co-culture with HT29
cells, NK cells previously incubated with TGF-beta released 40% less TNF-alpha; p = 0.0007
(Fig 4A) and 19% less IFN-gamma than control NK cells; p = 0.069 (Fig 4B). Compared with
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control NK cells, TGF-beta treated NK cells maintained in culture with LY2157299 showed
a slight trend to increased production of TNF-alpha (1.25-fold, p = 0.05) and IFN-gamma
(1.06-fold, p = 0.4). In addition to functional cytotoxicity assays, we measured the release of
Perforin and Granzyme B by NK cells co-cultured with a leukemia target cell line (HL60). We
again noted a decrease in the levels of both perforin (by 57%; p<0.00001) and granzyme B (by
38%; p<0.0001) by NK cells exposed to TGF beta ligand (Fig 4C and 4D)
TGF-beta inhibition results in superior tumor eradication by highly
activated NK cells in a metastatic colon cancer mouse model
We examined the therapeutic efficacy of ex vivo expanded NK cells in an immunodeficient
mouse (NSG) model of colon cancer liver metastasis using HCT116 cells. Four weeks after
splenic implantation of HCT116 cells all mice were euthanized. At autopsy, control and
LY2157299 alone mice had hemorrhagic ascites and grossly enlarged livers, riddled with
metastatic deposits without evidence of normal liver tissue (Fig 5A); panel 1 and 2. Mice treated with
NK cells alone also had gross evidence of liver metastases however nodule burden was less and
there was some morphologic evidence of normal liver architecture (Fig 5A); panel 3. Mice that
Fig 5. TGF-beta inhibition enhances activated NK cell function in a colon cancer model of liver metastases. A liver metastases model of colon cancer xenograft
using HCT116 cells was established. All mice were autopsied at 32 days after cell injection and H&E sections were obtained. Tumor burden on H&E sections was
measured for each mouse liver. (A) Autopsy findings of gross liver morphology in one representative mouse from each of the four treatment groups. (B)
Representative light microscopy of H&E stained liver sections. (C) Average tumor burden in H&E stained liver sections (N = 3 mice/group) was quantified using
the VENTANA digital Image viewing software. p <0.05; p 0.001.
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received NK cells and LY2157299 had mostly normal liver morphology with rare gross nodules
(Fig 5A); panel 4. H&E stains of liver sections for all 3 mice per group were consistent with
gross anatomy (Fig 5B and 5C). Quantification of the tumor burden showed a 25% decrease in
mice treated with NK cells alone (p<0.05) and by approximately 90% in those treated with NK
cells and LY2157299; p<0.001 (Fig 5C). Of note, circulating human TGF-beta levels (active) in
the mice of all treatment groups was an average of 10.98pg/ml + 1.736pg/ml. These levels are
comparable to serum levels of active TGF-beta in colorectal cancer patients. [
TGF-beta inhibition enhances NK cell infiltration into liver tissue in colon
cancer metastasis model
In our metastatic colon cancer xenograft, we examined FFPE liver sections for NK cell
infiltration using immunohistochemistry for human specific CD45 antibody. Mice that received NK
cells in addition to LY2157299 had an average of 82 infiltrating NK cells per 10X field
compared to an average of 8 cells in similar fields in mice that did not receive TGF-beta inhibition;
p = 0.0036 (Fig 6). Of note, mice were necropsied 14 days after the last of two NK cell infusions
Fig 6. Robust NK cell infiltration into liver tissue observed in mice who received TGF-beta inhibition in addition to NK cell infusion. FFPE sections of liver
tissue from mice with metastatic colon cancer were subjected to immunohistochemistry with human specific CD45. Manual counts of CD45 positive cells (NK
cells) was done in four representative 10X fields using the VENTANA digital image viewing software. Mice that received NK cells alone (NK only) and NK cells
with LY2157299 (NK+G).
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and 9 days after the last dose of LY2157299. Pictures of representative sections are provided in
Despite the promise of NK cell therapy, the approach has been limited due to several factors
including challenges in generating sufficient levels of NK cells for infusion as well as difficulties
in maintaining a high level of activity in vivo of the infused cells. The development of robust
feeder cell lines for ex vivo NK cell expansion has enabled the production of massive doses of
NK cells [4±12]. These strategies include the use of antigen presenting cells as stimuli for NK
cell activation and subsequent proliferation. As an example, the K562-mbIL21 cells used in
our study are K562 cells transduced to express membrane-bound interleukin 21 and 4-1BB
ligand resulting in up to 21,000 fold proliferation of NK cells after three weeks co-culture [
Besides a high level of expansion, an added advantage of ex vivo expansion is that the resulting
NK cells are also significantly activated compared to resting NK cells and are more efficient
at killing cancer targets. Consequently, it becomes even more pertinent to ensure that these
highly activated killer cells remain protected from the immunosuppressive tumor
microenvironment after infusion. Studies have shown that the tumor microenvironment produces high
levels of factors such as IL-10 and TGFbeta leading to NK cell dysfunction [12±23,25].
In this report we show that TGF-beta inhibition with a clinically used agent, LY2157299,
can effectively mitigate TGF-beta-mediated NK cell dysfunction using in vitro and in vivo
model systems of leukemia and colon cancer. We have demonstrated that the marked
impairment in function of highly activated NK cells starting from 24 hours exposure to a
TGFbeta rich milieu correlates with a significant decrease in expression of the activating receptors
NKG2D and CD16. Inhibiting TGF-beta signaling in this setting maintained the activated
phenotype of these NK cells and resulted in more effective NK cell-mediated eradication of colon
cancer liver metastases in a mouse model.
LY2157299 and TEW-7197 are the only two small molecule inhibitors of TGF-beta receptor
1 currently in clinical trials for various malignancies, particularly advanced stage, solid tumors
like pancreatic, prostate and hepatocellular carcinoma [30±32]. These trials are either ongoing
or recently completed with results not yet published. For our current research we chose the
compound LY2157299 as it is further along in clinical development and the
safety/pharmacokinetic profile has been well characterized in the aforementioned cancer trials as well as in
healthy individuals (NCT01965808). There are now clinical trials aimed at enhancing the
effector T cell response from checkpoint blockade via TGF-beta inhibition by combining
LY2157299 with Nivolumab in various advanced solid tumors (NCT02423343) and with
Durvalumab in pancreatic cancer (NCT02734160). There are also ongoing trials of adoptively
transferred NK cells predominantly for hematologic malignancies without complementary
TGF beta inhibition. From our current study, we propose complementing adoptive transfer of
NK cells with such TGF-beta inhibiting agents to maintain these cells in their highly activated
state and ensure better clinical efficacy. We have focused now on colon cancer and leukemia
models; in future studies we will assess the general applicability of this strategy for other tumor
S1 Table. Tables comparing cytotoxic activity of fresh, IL2 activated versus
feederexpanded NK cells.
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S2 Table. Tables showing functional analysis of NK cells following exposure to TGF-beta 1
S3 Table. Functional analysis of NK cells in vitro with or without inhibition of TGF beta
S4 Table. Comparisons of TNF-alpha, IFN-gamma, Perforin and Granzyme release.
S1 Fig. Representative images of colon cancer metastasis xenograft showing CD45 IHC of
liver FFPE sections staining for human NK cells.
S2 Fig. Dose titration of LY2157299 for preservation of NK cell cytotoxic function.
We would like to acknowledge the support of two Case Comprehensive Cancer Center Core
Facilities (P30 CA043703). These are the Tissue Resources, Cytometry and Imaging
Microscopy Core for mouse xenograft histopathology analysis; and the Hematopoietic Biorepository
and Cellular Therapy Core Facilities for the procurement of healthy volunteer blood samples
as NK cell sources.
Conceptualization: Folashade Otegbeye, David N. Wald.
Data curation: Folashade Otegbeye, Evelyn Ojo, David N. Wald.
Formal analysis: Folashade Otegbeye, Evelyn Ojo, David N. Wald.
Funding acquisition: Folashade Otegbeye, David N. Wald.
Investigation: Folashade Otegbeye, Evelyn Ojo, Stephen Moreton, Nathan Mackowski, David
Methodology: Folashade Otegbeye, Evelyn Ojo, David N. Wald.
Project administration: Folashade Otegbeye, Dean A. Lee, Marcos de Lima, David N. Wald.
Resources: Folashade Otegbeye, Dean A. Lee, Marcos de Lima, David N. Wald.
Software: Folashade Otegbeye.
Supervision: Folashade Otegbeye, Marcos de Lima, David N. Wald.
Validation: Folashade Otegbeye, Evelyn Ojo, Dean A. Lee, Marcos de Lima.
Visualization: Evelyn Ojo.
Writing ± original draft: Folashade Otegbeye.
Writing ± review & editing: Folashade Otegbeye, David N. Wald.
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1. Geller MA , Miller JS . Use of allogeneic NK cells for cancer immunotherapy . Immunotherapy . 2011 December; 3 ( 12 ): 1445 ± 1459 . https://doi.org/10.2217/imt.11.131 PMID: 22091681
2. Cheng M , Vhen Y , Xiao W , Sun R , Tian Z. NK cell-based immunotherapy for malignant diseases . Cell Mol Immunol . 2013 May; 10 ( 3 ): 230 ± 52 . https://doi.org/10.1038/cmi. 2013 .10 PMID: 23604045
3. Knorr DA , Bachanova V , Verneris MR , Miller JS . Clinical utility of natural killer cells in cancer therapy and transplantation . Semin Immunol . 2014 Apr; 26 ( 2 ): 161 ±72 https://doi.org/10.1016/j.smim. 2014 . 02 . 002 PMID: 24618042
4. Cho D , Campana D . Expansion and activation of natural killer cells for cancer immunotherapy . Korean J Lab Med . 2009 Apr; 29 ( 2 ): 89 ±96 https://doi.org/10.3343/kjlm. 2009 . 29 .2.89 PMID: 19411773
5. Childs RW , Berg M. Bringing natural killer cells to the clinic: ex vivo manipulation . Hematology Am Soc Hematol Educ Program . 2013 ; 2013 : 234 ± 46 . https://doi.org/10.1182/asheducation-2013. 1 .234 PMID: 24319186
6. Tomchuck S , Leung W , Dallas M. Isolation, expansion and function of cord blood natural killer cells . J Immunol May 1 , 2013 , 190 (1 Supplement) 69 .51;
7. Szmania S , Lapteva N , Garg T , Greenway A , Lingo J , Nair B et al. Ex vivo-expanded natural killer cells demonstrate robust proliferation in vivo in high-risk relapsed multiple myeloma patients . J Immunother . 2015 Jan; 38 ( 1 ): 24 ± 36 . https://doi.org/10.1097/CJI.0000000000000059 PMID: 25415285
8. Spanholtz J , Preijers F , Tordoir M , Trilsbeek C , Paardekooper J , de Witte T et al. Clinical-grade generation of active NK cells from cord blood hematopoietic progenitor cells for immunotherapy using a closed-system culture process . PLoS One . 2011 ; 6 ( 6 ):e20740. https://doi.org/10.1371/journal.pone. 0020740 PMID: 21698239
9. Somanchi SS , Senyukov VV , Denman CJ , Lee DA . Expansion, purification, and functional assessment of human peripheral blood NK cells . J Vis Exp. 2011 Feb 2 ;( 48).
10. Shah N , Martin-Antonio B , Yang H , Ku S , Lee DA , Cooper LJ et al. Antigen presenting cell-mediated expansion of human umbilical cord blood yields log-scale expansion of natural killer cells with anti-myeloma activity . PloS One 2013 Oct 18 ; 8 ( 10 ): e76781. https://doi.org/10.1371/journal.pone. 0076781 PMID: 24204673
11. Lapteva N , Durett AG , Sun J , Rollins LA , Huye LL , Fang J et al. Large-scale ex vivo expansion and characterization of natural killer cells for clinical applications . Cytotherapy . 2012 Oct; 14 ( 9 ): 1131 ± 43 . https:// doi.org/10.3109/14653249. 2012 .700767 PMID: 22900959
12. Kang L , Voskinarian-Berse V , Law E , Reddin T , Bhatia M , Hariri A et al. Characterization and ex vivo Expansion of Human Placenta-Derived Natural Killer Cells for Cancer Immunotherapy . Front Immunol . 2013 May 1 ; 4:101 https://doi.org/10.3389/fimmu. 2013 .00101 PMID: 23641243
13. Bierie B , Moses HL . Tumour microenvironment: TGFbeta: the molecular Jekyll and Hyde of cancer . Nat Rev Cancer . 2006 Jul; 6 ( 7 ): 506 ±20 https://doi.org/10.1038/nrc1926 PMID: 16794634
14. Bellone G , Aste-Amezaga M , Trinchieri G , Rodeck U . Regulation of NK cell functions by TGF-beta 1 . J Immunol . 1995 Aug 1 ; 155 ( 3 ): 1066 ±73 PMID: 7636180
15. Bergmann L , Schui DK , Brieger J , Weidmann E , Mitrou PS , Hoelzer D. The inhibition of lymphokineactivated killer cells in acute myeloblastic leukemia is mediated by transforming growth factor-beta 1 . Exp Hematol . 1995 Dec; 23 ( 14 ): 1574 ±80 PMID: 8542949
16. Konjevic G , Jurisic V , Jovic V , Vuletic A , Mirjacic Martinovic K , Radenkovic S et al. Investigation of NK cell function and their modulation in different malignancies . Immunol Res . 2012 Apr; 52 ( 1 ±2): 139 ±56 https://doi.org/10.1007/s12026-012 -8285-7 PMID: 22442005
17. Lee HM , Kim K-S , Kim J. A comparative study of the effects of inhibitory cytokines on human natural killer cells and the mechanistic features of transforming growth factor-beta . Cell Immunol . 2014 Jul; 290 ( 1 ): 52 ± 61 . https://doi.org/10.1016/j.cellimm. 2014 . 05 .001 PMID: 24879062
18. Baginska J , Viry E , Paggetti J , Medves S , Berchem G , Moussay E et al. The critical role of the tumor microenvironment in shaping natural killer cell-mediated anti-tumor immunity . Front Immunol . 2013 Dec 25 ; 4:490 https://doi.org/10.3389/fimmu. 2013 .00490 PMID: 24400010
19. Lee JC , Lee KM , Kim DW , Heo DS . Elevated TGF-beta1 secretion and down-modulation of NKG2D underlies impaired NK cytotoxicity in cancer patients . J Immunol . 2004 Jun 15 ; 172 ( 12 ): 7335 ±40 PMID: 15187109
20. Narai S , Watanabe M , Hasegawa H , Nishibori H , Endo T , Kubota T et al. Significance of transforming growth factor beta1 as a new tumor marker for colorectal cancer . Int J Cancer . 2002 Feb 1 ; 97 ( 4 ): 508 ± 11 PMID: 11802214
21. Akiyama T , Matsunaga T , Terui T , Miyanishi K , Tanaka I , Sato T et al. Involvement of transforming growth factor-B and thrombopoietin in the pathogenesis of myelodysplastic syndrome with myelofibrosis . Leukemia . 2005 Sep; 19 ( 9 ): 1558 ±66 https://doi.org/10.1038/sj.leu. 2403875 PMID: 16034467
22. Blobe GC , Dong M. Role of transforming growth factor-beta in hematological malignancies . Blood. 2006 Jun 15 ; 107 ( 12 ): 4589 ± 96 . https://doi.org/10.1182/blood-2005 -10-4169 PMID: 16484590
23. Hong C , Muller L , Whiteside TL , Boyiadzis M. Plasma exosomes as markers of therapeutic response in patients with acute myeloid leukemia . Front Immunol . 2014 Apr 10 ; 5:160 https://doi.org/10.3389/ fimmu. 2014 .00160 PMID: 24782865
24. Hirayama Y , Sakamaki S , Tsuji Y , Sagawa T , Chiba H , Matsunaga T et al. Thrombopoietin concentrations in peripheral blood correlated with platelet numbers in two patients with thrombocytopenia by chronic graft-versus-host disease . Am Journal of Hematology . ( 2003 ) 73 : 285 ± 289
25. Dasgupta S , Bhattacharya-Chatterjee M , O'Malley BW , Chatterjee SK . Inhibition of NK cell activity through TGF-B1 by down-regulation of NKG2D in a murine model of head and neck cancer . J Immunol . 2005 Oct 15 ; 175 ( 8 ): 5541 ± 50 . PMID: 16210663
26. Trotta R , Dal Col J , Yu J , Ciarlariello D , Thomas B , Zhang X et al. TGF-beta utilizes SMAD3 to inhibit CD16-mediated IFN-gamma production and antibody-dependent cellular cytotoxicity in human NK cells . J Immunol . 2008 Sep 15 ; 181 ( 6 ): 3784 ± 92 . PMID: 18768831
27. Chretien AS , Le Roy A , Vey N , Prebet T , Blaise D , Fauriat C et al. Cancer-Induced Alterations of NKMediated Target Recognition: Current and Investigational Pharmacological Strategies Aiming at Restoring NK Mediated Anti-Tumor Activity . Front Immunol . 2014 Mar 24 ; 5: 122 . https://doi.org/10. 3389/fimmu. 2014 .00122 PMID: 24715892
28. Yang B , Liu H , Shi W , Wang Z , Sun S , Zhang G et al. Blocking transforming growth factor-β signaling pathway augments antitumor effect of adoptive NK-92 cell therapy . Int Immunopharmacol . 2013 Oct; 17 ( 2 ): 198 ±204 https://doi.org/10.1016/j.intimp. 2013 . 06 .003 PMID: 23806302
29. Yoon J-H , Jung SM , Park SH , Kato M , Yamashita T , Lee I et al. Activin receptor-like kinase 5 inhibition suppresses mouse melanoma by ubiquitin degradation of Smad4, thereby derepressing eomesodermin in cytotoxic T lymphocytes . EMBO Mol Med . 2013 Nov; 5 ( 11 ): 1720 ±39 https://doi.org/10.1002/emmm. 201302524 PMID: 24127404
30. Herbertz S , Sawyer JS , Stauber AJ , Gueorguieva I , Driscoll KE , Estrem ST et al. Clinical development of galunisertib (LY2157299 monohydrate), a small molecule inhibitor of transforming growth factor-beta signaling pathway . Drug Des Devel Ther . 2015 Aug 10 ; 9: 4479 ±99 https://doi.org/10.2147/DDDT. S86621 PMID: 26309397
31. Park C-Y, Kim D-K , Sheen YY . EW- 7203 , a novel small molecule inhibitor of transforming growth factor-β (TGF-β) type I receptor/activin receptor-like kinase-5, blocks TGF-β1-mediated epithelial-to-mesenchymal transition in mammary epithelial cells . Cancer Sci . 2011 Oct; 102 ( 10 ): 1889 ±96 https://doi. org/10.1111/j.1349- 7006 . 2011 . 02014 .x PMID: 21707864
32. Connolly EC , Freimuth J , Akhurst RJ . Complexities of TGF-β targeted cancer therapy . Int J Biol Sci . 2012 ; 8 ( 7 ): 964 ±78 https://doi.org/10.7150/ijbs.4564 PMID: 22811618