CMTM5 is downregulated and suppresses tumour growth in hepatocellular carcinoma through regulating PI3K-AKT signalling
Xu and Dang Cancer Cell Int
CMTM5 is downregulated and suppresses tumour growth in hepatocellular carcinoma through regulating PI3K-AKT signalling
Gang Xu 0
Chengxue Dang 0
0 Department of Surgical Oncology, The First Affiliated Hospital Xi'an Jiaotong University , No. 277 West Yanta Road, Xi'an 710061, Shaanxi , People's Republic of China
Background: Human chemokine like factor (CKLF)-like MAL and related proteins for vesicle trafficking transmembrane, domain-containing member 5 (CMTM5) has been shown to involved and may function as a tumour suppressor in tumorigenesis. The current study aimed to investigate the expression and function of CMTM5 in human hepatocellular carcinoma (HCC). Methods: CMTM5 expression was examined by immunohistochemistry, and its clinical significance was analysed in 76 HCC specimens. The role and molecular mechanisms of CMTM5 in cell proliferation, apoptosis and invasion were examined in vitro and in vivo. Results: CMTM5 expression was significantly downregulated in HCC tissues as well as cell lines. The expression of CMTM5 was absent in 77.6% of HCC tissues compared with 3.9% in normal liver tissues. Low CMTM5 expression was significantly correlated with poor overall survival in patients with HCC (P = 0.009). Restoring CMTM5 expression in Huh7 cells significantly inhibited cell growth, promoted cell apoptosis, and reduced cell metastatic and invasion ability compared with mock transfected cells in vitro. Overexpression of CMTM5 also suppressed xenograft tumour growth in vivo in a HCC xenograft model. Reduced cell growth and metastasis ability mediated by CMTM5 overexpression was associated with downregulation of PI3K/AKT and its downstream Bcl2, cyclinD1, cyclinE, MMP2 and MMP9 expressions, and an upregulation of p21, Bax, Bad, cleaved caspase3 expressions. Conclusions: Our data suggest that CMTM5 might function as a tumour suppressor in human HCC, and represent a valuable potential therapeutic target for HCC.
CMTM5; Hepatocellular carcinoma; Tumour suppressor; PI3K-AKT
Background
Liver cancer is a common malignant and the fourth
leading cause of cancer deaths in China [
1
]. It is estimated
466,100 new cases of liver cancer in 2015 in China, with
422,100 new deaths due to this disease [
1
]. Hepatocellular
carcinoma (HCC) is the most common type and accounts
for 70–85%of liver cancer [
2
]. People with early-stage
HCC can be treated with surgery, either removing part
of the liver or transplantation, with 5-year survival rates
that exceed 70%. Most people, however, cannot have
surgical treatment and so the overall 5-year survival is
about 15% [
3
]. Therefore, it is important to understand
the molecular mechanisms involved in HCC
carcinogenesis, and find novel approaches that can effectively inhibit
HCC cell growth and metastasis.
Human chemokine-like factor (CKLF)-like MARVEL
transmembrane domain-containing family (CMTM) is a
novel family consisting of nine genes, CKLF and CMTMI
to CMTM8. CMTMs, linking classical chemokines and
the transmembrane-4 superfamily (TM4SF), play
important roles in immune system, male reproductive system
and carcinogenesis [
4, 5
]. CMTM5 was firstly reported
by in 2003, and located at 14q11.2 [4]. It is structurally
similar to the TM4SF which can by collecting a variety
of other molecules (such as AKT, EGFR) form four cross
membrane protein network, thus mediated cell
proliferation, apoptosis, migration, adhesion, differentiation, and
closely related to tumour formation [
4, 6, 7
]. It has been
reported that CMTM5 acted as a tumour-suppressor
gene and was specifically down-regulated in many human
cancers, such as cervical carcinoma [
8
], pancreatic
cancer [
9
], myeloid leukemia [
10
], ovarian cancer [
11
], oral
squamous cell carcinoma (OSCC) [
12
] and prostate
cancer [
13
]. However, the clinical significance and function
of CMTM5 in HCC remains unclear.
In this study, we aimed to detect the expression
patterns of CMTM5 and their correlations with
clinicopathological characteristics in HCC patients.
Furthermore, we explored the effect and mechanisms of
CMTM5 on cell growth and metastasis based on HCC
cell line in vitro and in vivo.
Methods
Tissue samples and cell culture
The study was approved by the ethics committee of
Chinese PLA General Hospital (CHN-PLAGH-ZL-002),
and informed consent was obtained from each patient
according to the committee’s regulations. Tissue samples
collected from 76 patients who underwent curative liver
resection at the Department of Gastroenterology and
Hepatology at the Chinese PLA General Hospital between
2007 and 2010 were used for CMTM5
immunohistochemistry detection. TNM classification was determined
according to the 2002 International Union Against Cancer
guidelines. Tumour differentiation was graded according
to the Edmondson-Steiner classification. Clinical
characteristics of all patients are shown in Table 1. The time
to overall survival (OS) time were defined as the inter (...truncated)