Significance of TGFBR3 allelic loss in the deregulation of TGFβ signaling in primary human endometrial carcinomas

TGF-β superfamily co-receptors in cancer

Transforming growth factor-β (TGF-β) superfamily signaling via their cognate receptors is frequently modified by TGF-β superfamily co-receptors. Signaling through SMAD-mediated pathways may be enhanced or depressed depending on the specific co-receptor and cell context. This dynamic effect on signaling is further modified by the release of many of the co-receptors from the membrane to generate soluble forms that are often antagonistic to the membrane-bound receptors. The co-receptors discussed here include TβRIII (betaglycan), endoglin, BAMBI, CD109, SCUBE proteins, neuropilins, Cripto-1, MuSK, and RGMs. Dysregulation of these co-receptors can lead to altered TGF-β superfamily signaling that contributes to the pathophysiology of many cancers through regulation of growth, metastatic potential, and the tumor microenvironment. Here we describe the role of several TGF-β superfamily co-receptors on TGF-β superfamily signaling and the impact on cellular and physiological functions with a particular focus on cancer, including a discussion on recent pharmacological advances and potential clinical applications targeting these co-receptors.

Canonical TGFβ Signaling and Its Contribution to Endometrial Cancer Development and Progression-Underestimated Target of Anticancer Strategies

Endometrial cancer is one of the leading gynecological cancers diagnosed among women in their menopausal and postmenopausal age. Despite the progress in molecular biology and medicine, no efficient and powerful diagnostic and prognostic marker is dedicated to endometrial carcinogenesis. The canonical TGFβ pathway is a pleiotropic signaling cascade orchestrating a variety of cellular and molecular processes, whose alterations are responsible for carcinogenesis that originates from different tissue types. This review covers the current knowledge concerning the canonical TGFβ pathway (Smad-dependent) induced by prototypical TGFβ isoforms and the involvement of pathway alterations in the development and progression of endometrial neoplastic lesions. Since Smad-dependent signalization governs opposed cellular processes, such as growth arrest, apoptosis, tumor cells growth and differentiation, as well as angiogenesis and metastasis, TGFβ cascade may act both as a tumor suppressor or tumor promoter. However, the final effect of TGFβ signaling on endometrial cancer cells depends on the cancer disease stage. The multifunctional role of the TGFβ pathway indicates the possible utilization of alterations in the TGFβ cascade as a potential target of novel anticancer strategies.

Osteoinductive effect of soluble transforming growth factor beta receptor 3 on human osteoblast lineage

The development of bone requires carefully choregraphed signaling to bone progenitors to form bone. Our group recently described the requirement of transforming growth factor beta receptor 3 (TGFβR3), a receptor involved in TGFβ pathway signaling, during osteoblast lineage commitment in mice. The TGFβ pathway is known to play multiple osteo-inductive and osteo-inhibitory roles during osteoblast development and TGFβR3 human mutations are associated with reduced bone mineral density, making TGFβR3 a unique target for bone inductive therapy. In this article, we demonstrated increased mineralization of human pediatric bone-derived osteoblast-like cells (HBO) when treated with soluble TGFβR3 (sR3) using Alizarin Red staining. Osteogenic commitment of HBO cells was demonstrated by induction of osteogenic genes RUNX2, osteocalcin, osteopontin, and osterix. Evaluation of the canonical TGFβ pathway signaling demonstrated that sR3 was able to induce bone formation in HBO cells, mainly through activation of noncanonical targets of TGFβ pathway signaling including AKT, ERK, and p38 MAP kinases. Inhibition of these osteogenic noncanonical pathways in the HBO cells also inhibited mineralization, suggesting they are each required. Although no induction of SMAD1, 5, and 9 was observed, there was the activation of SMAD2 and 3 suggesting that sR3 is primarily signaling via the noncanonical pathways during osteogenic induction of the HBO. Our results highlight the important role of TGFβR3 in osteoblast induction of mineralization in human bone cells through noncanonical targets of TGFβ signaling. Future studies will focus on the ability of sR3 to induce bone regeneration in vivo using animal models.

Betaglycan Gene (TGFBR3) Polymorphism Is Associated with Increased Risk of Endometrial Cancer

We investigated single nucleotide polymorphism (SNP) of the betaglycan gene (TGFBR3) encoding the TGFβ co-receptor in endometrial cancer (EC) and its association with betaglycan expression. The study group included 153 women diagnosed with EC and 248 cancer-free controls. SNP genotyping and gene expression were analyzed using TaqMan probes. Three out of the eight SNPs tested, i.e., rs12566180 (CT; OR = 2.22; 95% CI = 1.15-4.30; p = 0.0177), rs6680463 (GC; OR = 2.34; 95% CI = 1.20-4.53; p = 0.0120) and rs2296621 (TT; OR = 6.40; 95% CI = 1.18-34.84; p = 0.0317) were found to be significantly associated with increased risk of EC (adjusted to age, body mass index, menarche and parity). Among the analyzed SNPs, only rs2296621 demonstrated the impact on the increased cancer aggressiveness evaluated by the WHO grading system (G3 vs. G1/2, GT-OR = 4.04; 95% CI = 1.56-10.51; p = 0.0026; T-OR = 2.38; 95% CI = 1.16-4.85; p = 0.0151). Linkage disequilibrium (LD) analysis revealed high LD (r2 ≥ 0.8) in two haploblocks, constructed by rs2770186/rs12141128 and rs12566180/rs6680463, respectively. In the case of C/C haplotype (OR = 4.82; 95% CI = 1.54-15.07; p = 0.0116-Bonferroni corrected) and T/G haplotype (OR = 3.25; 95% CI = 1.29-8.15; p = 0.0328-Bonferroni corrected) in haploblock rs12566180/rs6680463, significantly higher frequency was observed in patients with EC as compared to the control group. The genotype-phenotype studies showed that SNPs of the TGFBR3 gene associated with an increased risk of EC, i.e., rs12566180 and rs2296621 may affect betaglycan expression at the transcriptomic level (rs12566180-CC vs. TT, p < 0.01; rs2296621-GG vs. TT, p < 0.001, GT vs. TT, p < 0.05). Functional consequences of evaluated TGFBR3 gene SNPs were supported by RegulomeDB search. In conclusion, polymorphism of the TGFBR3 gene may be associated with an increased EC occurrence, as well as may be the molecular mechanism responsible for observed betaglycan down-regulation in EC patients.