Transforming growth factor beta receptor type III is a tumor promoter in mesenchymal-stem like triple negative breast cancer

Abstract

IntroductionThere is a major need to better understand the molecular basis of triple negative breast cancer (TNBC) in order to develop effective therapeutic strategies. Using gene expression data from 587 TNBC patients we previously identified six subtypes of the disease, among which a mesenchymal-stem like (MSL) subtype. The MSL subtype has significantly higher expression of the transforming growth factor beta (TGF-β) pathway-associated genes relative to other subtypes, including the TGF-β receptor type III (TβRIII). We hypothesize that TβRIII is tumor promoter in mesenchymal-stem like TNBC cells.MethodsRepresentative MSL cell lines SUM159, MDA-MB-231 and MDA-MB-157 were used to study the roles of TβRIII in the MSL subtype. We stably expressed short hairpin RNAs specific to TβRIII (TβRIII-KD). These cells were then used for xenograft tumor studies in vivo; and migration, invasion, proliferation and three dimensional culture studies in vitro. Furthermore, we utilized human gene expression datasets to examine TβRIII expression patterns across all TNBC subtypes.ResultsTβRIII was the most differentially expressed TGF-β signaling gene in the MSL subtype. Silencing TβRIII expression in MSL cell lines significantly decreased cell motility and invasion. In addition, when TβRIII-KD cells were grown in a three dimensional (3D) culture system or nude mice, there was a loss of invasive protrusions and a significant decrease in xenograft tumor growth, respectively. In pursuit of the mechanistic underpinnings for the observed TβRIII-dependent phenotypes, we discovered that integrin-α2 was expressed at higher level in MSL cells after TβRIII-KD. Stable knockdown of integrin-α2 in TβRIII-KD MSL cells rescued the ability of the MSL cells to migrate and invade at the same level as MSL control cells.ConclusionsWe have found that TβRIII is required for migration and invasion in vitro and xenograft growth in vivo. We also show that TβRIII-KD elevates expression of integrin-α2, which is required for the reduced migration and invasion, as determined by siRNA knockdown studies of both TβRIII and integrin-α2. Overall, our results indicate a potential mechanism in which TβRIII modulates integrin-α2 expression to effect MSL cell migration, invasion, and tumorigenicity.

Deep sequencing of myxoinflammatory fibroblastic sarcoma

“…With regard to chromosome 1, the most frequent target was TGFBR3 , affected by breaks and/or loss of one copy in four cases and the JU‐PI cell line, and gain of one copy in one. TGFBR3 is a co‐factor in TGF beta signal transduction, and while some reports have suggested that it may have an oncogenic role in certain contexts, most data support a suppressor role in various carcinomas . The latter scenario could fit with the current results, but the expression of TGFBR3 was not lower in tumors with loss of one copy of the 5′‐end or of the entire gene.…”

Altering the Proteoglycan State of Transforming Growth Factor β Type III Receptor (TβRIII)/Betaglycan Modulates Canonical Wnt/β-Catenin Signaling

“…Mechanistically, T␤RIII regulates these pathways either by altering the actin cytoskeleton, via T␤RIII/␤-arrestin2 cytoplasmic interactions (24), or by GAG chain interactions with FGF2 (23). Overall, T␤RIII also acts as a tumor suppressor in prostate (19), lung (25), pancreatic (18), and breast cancer (16,21,26,27) but has been shown to promote metastasis in specific mesenchymal stem-like breast cancers (28), indicating its complex roles for T␤RIII in cancer.…”

Primary cancer cell culture: mammary-optimized vs conditional reprogramming

“…Higher levels of EMT genes under EpiC as compared to CRC conditions paralleled previous reports of EpiC cultured cells undergoing EMT (Nakles et al, 2013) in comparison to retention of cuboidal architecture (Saenz et al) and suppression of the EMT-related TGFB pathway (Ligaba et al, 2015) under CRC conditions. Here we documented upregulated TGFBR3 expression, a protein linked to a subtype of triple negative breast cancers in women (Jovanović et al, 2014), under EpiC conditions. Provocatively we found the TFBS for ZEB1, an EMT-linked gene, enriched in CRC-associated DEGs.…”

“…The same spectrum of histopathology is found in human triple negative breast cancers (Lehmann et al, 2011). One of the human mesenchymal-stem like (MSL) triple negative histologies demonstrates TGFBR3 over-expression (Jovanović et al, 2014). …”