Background: Collagen type VI alpha 1 (COL6A1) has been found to be dysregulated in several human malignancies. However, the role of COL6A1 in osteosarcoma (OS) progression remains largely unclear. Here, we aimed to explore the clinical significance and biological involvement of COL6A1 in the OS cell migration and invasion. Material and Methods: We used immunohistochemistry, qRT-PCR and western blot to detect the expression of COL6A1 in 181 OS patient samples. Chromatin immunoprecipitation (ChIP) and PCR were carried out to verify the regulatory interaction of p300, c-Jun and COL6A1 promoter. The invasion and migration function of COL6A1 in OS was detected in vitro and in vivo . RNA sequence was performed to detect the downstream pathway of COL6A1, and then co-immunoprecipitation (co-IP), ubiquitination assays and rescue experiments were performed to determine the regulatory effect of COL6A1 and signal transducers and activators of transcription (STAT1). Exosomes derived from OS cell lines were assessed for the ability to promote cancer progression by co-cultured assay and exosomes tracing. Results: COL6A1 was commonly upregulated in OS tissues, especially in lung metastasis tissues, which was associated with a poor prognosis. c-Jun bound p300 increased the enrichment of H3K27ac at the promoter region of the COL6A1 gene, which resulted in the upregulation of COL6A1 in OS. Overexpression of COL6A1 promoted OS cell migration and invasion via interacting with SOCS5 to suppress STAT1 expression and activation in an ubiquitination and proteasomal degradation manner. Most interestingly, we found that exosomal COL6A1 derived from OS cells convert normal fibroblasts to cancer-associated fibroblasts (CAFs) by secreting pro-inflammatory cytokines, including IL-6 and IL-8. The activated CAFs could promote OS cell invasion and migration by mediating TGF-β/COL6A1 signaling pathway. Conclusion: Our data demonstrated that upregulation of COL6A1 activated by H3K27 acetylation promoted the cell migration and invasion by suppressing STAT1 pathway in OS cells. Moreover, COL6A1 can be packaged into OS cell-derived exosomes and activate CAFs to promote OS metastasis.

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BackgroundWe recently reported that STAT1 plays a tumor suppressor role, and ERK was inversely correlation with STAT1 expression in esophageal squamous cell carcinoma (ESCC). Here, we investigated the mechanism(s) that are responsible for the ERK regulates STAT1 in ESCC.MethodsWe performed the immunoprecipitation (IP) to detect the ubiquitin of STAT1 upon MEK transfection or U0126 treatment and co-IP to confirm the binding of STAT1 and ERK in ESCC cell lines.ResultsWe found evidence that the ubiquitin-proteasome pathway can efficiently degrade STAT1 in ESCC cells, as MG132 treatment rapidly and dramatically increased STAT1 expression in these cells. This process is not dependent on the phosphorylation of the two important STAT1 residues, Y701 and S727, as site-directed mutagenesis of these two sites did not affect STAT1 degradation. We also found that ERK promotes proteasome degradation of STAT1, supported by the observations that pharmacologic inhibition of ERK resulted in a substantial increase of STAT1 whereas expression of constitutively active ERK further reduced the STAT1 protein level. In addition to suppressing STAT1 expression, ERK limited STAT1 signaling by decreasing the production of IFNγ.ConclusionTo conclude, ERK is an effective negative regulator of STAT1 signaling in ESCC, by promoting its proteasome degradation and decreasing IFNγ production. Our data further supports that targeting ERK and/or STAT1 may be useful for treating ESCC.Electronic supplementary materialThe online version of this article (10.1186/s12885-018-4539-7) contains supplementary material, which is available to authorized users.

STAT1, which carries tumor suppressor functions in several models, consists of two isoforms, namely STAT1α and STAT1β. The biological function and significance of STAT1β has never been examined in human cancer. We examined STAT1β function in esophageal squamous cell carcinoma (ESCC) by transfecting a STAT1β gene into various ESCC cell lines. The interaction between STAT1α and STAT1β was examined by using co-immunoprecipitation and confocal microscopy. The prognostic significance of STAT1β expression, detectable by immunohistochemistry and western blot, was evaluated in a large cohort of ESCC patients. Enforced expression of STAT1β induced and prolonged the expression and phosphorylation of STAT1α in ESCC cells, and these effects were amplified by gamma-interferon (IFN-γ). We also found that STAT1β interacts with STAT1α and decreases STAT1α degradation by the proteasome. Moreover, STAT1β substantially increased the DNA binding and transcription activity of STAT1. STAT1β also sensitized ESCC cells to chemotherapeutic agents, including cisplatin and 5-flurouracil. Using western blot and immunohistochemistry, we found that STAT1β was frequently decreased in esophageal cancer, as compared to their adjacent benign esophageal epithelial tissue. Loss of STAT1β significantly correlated with lymph node metastasis, invasion and shorter overall survival in ESCC patients. Therefore, STAT1β plays a key role in enhancing the tumor suppressor function of STAT1α, in ESCC, in a manner that can be amplified by IFN-γ.

BackgroundEsophageal squamous cell carcinoma is one of leading causes of cancer-related deaths in Chaoshan region a high-risk region for esophageal cancer. Extracellular regulated protein kinases (ERK) usually play an important role in cell proliferation and differentiation. However, accumulating evidence has shown that the ERK was aberrantly expressed in cancers and correlated with STAT1 depression.ResultsThe activated ERK downregulates STAT1 expression in ESCC cell lines and U0126 increases expression of STAT1. Our immunohistochemistry result also confirms that the expression of ERK inversely correlated with that of STAT1 in ESCC tumors. In addition, a significantly higher expression of ERK/p-ERK was found in ESCC tissues in comparison with case-matched normal esophageal tissues (p < 0.05). Moreover, the immunohistochemical analysis demonstrated that ERK expression was paralleled with the differentiation and clinical stage. In 74 patients with follow-up data, those with ERKlow tumors survived significantly longer than those with ERKhigh tumors (p = 0.04); patients with ERKlow/STAT1high tumors had the longest survival (p = 0.001).Materials and MethodsTo investigate whether ERK can mediated STAT1 expression in ESCC, we used the MEK plasmid and U0126, a MEK inhibitor, to treat the cell. To further confirm our in-vitro study, we detected the ERK, p-ERK and STAT1 expression in 131 ESCC cases and 22 case-matched normal esophageal tissues adjacent to the tumors specimens.ConclusionsThese findings provide pathological evidence that ERK/p-ERK is negatively correlated with STAT1 in ESCC. Our data suggests that inhibition of ERK and/or restoration of STAT1 expression maybe useful therapeutic strategies for ESCC.