ABSTRACT
Transforming growth factor beta (TGF-ß) is a multi-functional cytokine that plays a significant role in multiple diseases, including fibrosis and tumor progression. Whilst the biologic effects of TGF-ß are well characterized, it is unclear how TGF-ß signaling is regulated to impart specific responses within certain cell types. One mechanism of regulation may be through TGF-ß activation, since TGF-ß is always expressed in a latent form (L-TGF-ß). Campbell et al.(2020) recently presented a new structural model to demonstrate how the integrin αvß8 might specifically control TGF-ß activation and signaling. In this model, αvß8 binds to cell surface L-TGF-ß1 to induce a conformational change, which exposes mature TGF-ß peptide to TGF-ß receptors (TGF-ßRs), allowing initiation of TGF-ß signaling from within the latent complex. This model also predicts that TGF-ß signaling would be directed specifically towards the TGF-ß expressing cell surface. We sought to test the validity of the new structural model by creating a cell-based assay which utilizes luciferase TGF-ß reporter cells (TMLC). TMLC cells express high levels of TGF-ßRs, but do not express cell surface L-TGF-ß. We modified TMLC reporter cells to express cell surface L-TGF-ß1 in a mutant form, which prevents the release of mature TGF-ß from the latent complex. The newly generated cell lines were then used in a novel functional assay to investigate whether integrin αvß8 could potentiate cell intrinsic TGF-ß signaling from within the latent complex in vitro.
ABSTRACT
Urothelial cancer (UC) is one of the most common cancers in Europe and is also one of the costliest to treat. When first line therapies show initial success, around 50% of cancers relapse and proceed to metastasis. In this study we assessed the Protein inhibitor of activated signal transducers and activators of transcription (PIAS)1 as a potential therapeutic target in urothelial cancer. PIAS1 is a key regulator of STAT1 signalling and may be implicated in carcinogenesis. In contrast to other cancer types PIAS1 protein expression is not significantly different in malignant areas of UC specimens compared to non-malignant tissue. In addition, we found that down-regulation and overexpression of PIAS1 had no effect on the viability or colony forming ability of tested cell lines. Whilst other studies of PIAS1 suggest an important biological role in cancer, this study shows that PIAS1 has no influence on reducing the cytotoxic effects of Cisplatin or cell recovery after DNA damage induced by irradiation. Taken together, these in vitro data demonstrate that PIAS1 is not a promising therapeutic target in UC cancer as previously shown in different entities such as prostate cancer (PCa).
