TGFBR3L is associated with gonadotropin production in non-functioning gonadotroph pituitary neuroendocrine tumours

Pituitary https://doi.org/10.1007/s11102-023-01310-x TGFBR3L is associated with gonadotropin production in nonfunctioning gonadotroph pituitary neuroendocrine tumours Anders Jensen Kolnes1,2 · Kristin Astrid Berland Øystese1,2 · Evelina Sjöstedt3,4 · Nicoleta Cristina Olarescu1,2 · Ansgar Heck1,2 · Jens Pahnke5,6,7 · Daniel Dahlberg8 · Jon Berg-Johnsen1,8 · Geir Ringstad9 · Olivera Casar-Borota4,10 · Jens Bollerslev1,2 · Anders Palmstrøm Jørgensen2 Accepted: 6 March 2023 © The Author(s) 2023 Abstract Purpose Transforming growth factor-beta receptor 3-like (TGFBR3L) is a pituitary enriched membrane protein selectively detected in gonadotroph cells. TGFBR3L is named after transforming growth factor-beta receptor 3 (TGFBR3), an inhibin A co-receptor in mice, due to sequence identity to the C-terminal region. We aimed to characterize TGFBR3L detection in a well-characterized, prospectively collected cohort of non-functioning pituitary neuroendocrine tumours (NF-PitNETs) and correlate it to clinical data. Methods 144 patients operated for clinically NF-PitNETs were included. Clinical, radiological and biochemical data were recorded. Immunohistochemical (IHC) staining for FSHβ and LHβ was scored using the immunoreactive score (IRS), TGFBR3L and TGFBR3 were scored by the percentage of positive stained cells. Results TGFBR3L staining was selectively present in 52% of gonadotroph tumours. TGFBR3L was associated to IRS of LHβ (median 2 [IQR 0–3] in TGFBR3L negative and median 6 [IQR 3–9] in TGFBR3L positive tumours, p < 0.001), but not to the IRS of FSHβ (p = 0.32). The presence of TGFBR3L was negatively associated with plasma gonadotropin concentrations in males (P-FSH median 5.5 IU/L [IQR 2.9–9.6] and median 3.0 [IQR 1.8–5.6] in TGFBR3L negative and positive tumours respectively, p = 0.008) and P-LH (median 2.8 IU/L [IQR 1.9–3.7] and median 1.8 [IQR 1.1-3.0] in TGFBR3L negative and positive tumours respectively, p = 0.03). TGFBR3 stained positive in 22% (n = 25) of gonadotroph tumours with no correlation to TGFBR3L. Conclusion TGFBR3L was selectively detected in half (52%) of gonadotroph NF-PitNETs. The association to LHβ staining and plasma gonadotropins suggests that TGFBR3L may be involved in hormone production in gonadotroph NF-PitNETs. Keywords Pituitary adenomas · Plasma gonadotropins · Tumour volume · Transforming growth factor beta receptor 3 like (TGFBR3L) · Transforming growth factor beta receptor 3 (TGFBR3) Significance Statement Transforming growth factor-beta receptor 3-like (TGFBR3L), is a pituitary specific membrane protein in gonadotroph cells, named after transforming growth factor-beta receptor 3 (TGFBR3) due to a sequence identity to the C-terminal region. We describe that TGFBR3L is present at protein level in half of gonadotroph NF-PitNETs. The relation between TGFBR3L and gonadotropin expression and plasma levels may suggest a role in gonadotropin production and secretion. The lack of an association to cavernous sinus invasiveness, and lack of consecutive MRI follow-up data limits the conclusion concerning the potential role in tumour growth and aggressiveness. In human gonadotroph NF-PitNETs, the role of TGFBR3, a known inhibin A co-receptor in mice, appears to be limited since its detection is not associated to gonadotropins measurements, nor to the TGFBR3L expression. Anders Jensen Kolnes and Kristin Astrid Berland Øystese shared first authorship. Extended author information available on the last page of the article 13 Pituitary Introduction Pituitary neuroendocrine tumours (PitNETs), also known as pituitary adenomas, can arise from any of the cell lineages of the anterior pituitary gland, and can be clinically functioning or non-functioning [1–3]. Per definition, clinically non-functioning PitNETs (NF-PitNETs) do not cause signs or symptoms of hormone hypersecretion [4]. Still, the tumours may cause symptoms due to local mass effect, such as hypopituitarism, visual disturbances, and headache. Surgery is the treatment of choice, but usually delayed until vision is affected [4, 5]. Clinically NF-PitNETs arise most commonly from the gonadotroph cells (~ 73%) [1, 3, 6]. NF-PitNETs are classified by immunohistochemical (IHC) staining for pituitary hormones and cell-lineage specific pituitary transcription factors. Transcription factors were recently introduced into the classification of PitNETs and allow the characterization of hormone-negative tumours [1, 3]. The majority of gonadotroph PitNETs produce gonadotropins, but they rarely cause clinical symptoms of hormone hypersecretion and are thus considered non-functioning [7, 8]. Still, patients with gonadotroph PitNETs frequently have elevated plasma levels of the gonadotropins (FSH and LH) or their subunits [9–13]. Furthermore, most gonadotroph PitNETs secrete gonadotropins or gonadotropin subunits when cultured in vitro [11, 14, 15]. We have recently shown that FSHβ staining of the gonadotroph PitNETs correlated with circulating plasma FSH levels, suggesting that some of the FSH produced by the tumours enters the circulation. However, we found no correlation between LHβ staining and circulating plasma LH levels [16]. Indeed, both in vivo and in vitro, FSH or FSHβ appears to be secreted more commonly than LH or LHβ [9, 11–13]. The regulation of gonadotropin synthesis and secretion is complex and involves GnRH, inhibins, activins, follistatin and moreover negative feedback from estradiol and testosterone [17, 18]. Activins and inhibins belong to the TGF-β superfamily, and are involved in numerous processes throughout the body. The production and secretion of FSHβ and LHβ is stimulated by the pulsatile secretion of GnRH from the hypothalamus, through the GnRHR receptor, in concert with effects of activins in pituitary gonadotroph cells [17, 18]. The production is negatively regulated through negative endocrine feedback mechanisms from the ovaries in females and testicles in males (estrogen, inhibin B, progesterone and testosterone) [19]. In addition, the expression and secretion of gonadotropins are regulated by paracrine and autocrine mechanisms through follistatin, activins and their respective receptors and coreceptors. The interplay between the different participants of the gonadotroph regulation is complex and not fully characterized in humans [17]. 13 Transforming growth factor beta receptor 3 like (TGFBR3L) is a transmembrane protein selectively expressed in pituitary gonadotroph cells [20–24]. TGFBR3L shows sequence similarity to transforming growth factor betareceptor 3 (TGFBR3), also called betaglycan, that has been detected in rodent pituitary gland and is suggested as an inhibin A co-receptor [24, 25]. Recently, TGFBR3L was shown to function as an inhibin B co-receptor in mice, as TGFBR3L knockout female mice presented a modest increase in FSH levels that was sufficient to enhance ovarian folliculogenesis and litter size [23]. Recently, we found that TGFBR3L correlated positively wi (...truncated)