Hypoxia-Independent Gene Expression Mediated by SOX9 Promotes Aggressive Pancreatic Tumor Biology

Abstract

Pancreatic cancer aggressiveness is characterized by its high capacity for local invasion, ability to promote angiogenesis, and potential to metastasize. Hypoxia is known to represent a crucial step in the development of aggressive malignant features of many human cancers. However, micrometastatic tumors are not typically subjected to hypoxic events during early stages of dissemination; therefore, it is unclear how these tumors are able to maintain their aggressive phenotype. Thus, the identification of regulators of hypoxia-related genes in aggressive/ metastatic tumors represents a fundamental step for the design of future therapies to treat pancreatic cancer. To this end, transcriptomic profiles were compared between the nonmetastatic pancreatic cancer cell line FG (LMET) and its angiogenic/metastatic derivate L3.6pl (HMET) under normoxic or hypoxic conditions. Cluster analysis revealed a number of transcripts that were induced by hypoxia in nonmetastatic cancer cells. Strikingly, this cluster was determined to be constitutively activated under normoxia in the metastatic cancer cells and could not be further induced by hypoxia. A subset of these transcripts were regulated by the transcription factor SOX9 in the aggressivemetastatic cells, but driven by hypoxia-inducible factor-1a (HIF-1a) in the parental nonmetastatic cell line. Moreover, these transcripts were enriched in cancer-related networks including: WNT, CXCR4, retinoic acid, and (FAK) focal adhesion kinase, gene PTK2 signaling pathways. In functional assays, inhibition of SOX9 expression in HMET cells led to increased apoptosis and reduced migration in vitro and a significant reduction in primary tumor growth, angiogenesis, and metastasis following orthotopic tumor cell injection. At the molecular level, the control of SOX9 expression was associated with changes in the methylation status of the SOX9 promoter. Finally, SOX9 upregulation was verified in a series of tumor specimens of patients with pancreatic carcinoma.

HNF1A is a novel oncogene that regulates human pancreatic cancer stem cell properties

“…As the promoters of HNF1A upregulated genes were enriched for transcription factor known to play roles in PDA including GATA (likely GATA5 or GATA6) (Roe et al, 2017; Martinelli et al, 2017; Zhong et al, 2011), PDX1 (Roy et al, 2016), and SOX9 (Camaj et al, 2014; Kopp et al, 2012; Tsuda et al, 2018), it is possible that HNF1A may work in concert with other transcription factors to elicit its full oncogenic function in PDA. A similar interaction between the transcription factors Foxa1 and Gata5 was recently described in driving metastasis in murine models of PDA (Roe et al, 2017).…”

The Intricate Role of CXCR4 in Cancer

“…Also, a subpopulation of CSCs expressing CD133 and CXCR4 in invasive pancreatic tumors was found to be the determinant of metastasis (Hermann et al, 2007). While HIF-1α is known to be a major factor contributing to CXCR4 expression in pancreatic and other cancers, recent studies in pancreatic cancer cells and tumors demonstrated that transcription factors such as SOX9 upregulate CXCR4 expression independently of HIF-1α, which may have consequences not only for pancreatic cancer but also for other cancers such as SCLC where SOX transcription factors are known to be overexpressed (Camaj et al, 2014). CXCR4 antagonist AMD3100 significantly inhibited the proliferation, migration, and invasion of pancreatic cancer cells (Gao, Wang, Wu, Zhao, & Hu, 2010).…”

HIF-3α Promotes Metastatic Phenotypes in Pancreatic Cancer by Transcriptional Regulation of the RhoC–ROCK1 Signaling Pathway

“…Hypoxia contributes to disease progression and promotes tumor growth and invasion, and clinical studies have shown that high levels of hypoxia directly correlate with a poor prognosis in pancreatic cancer (7). The observed correlation between tumor hypoxia and patient prognosis is ascribed to therapeutic failure and hypoxiainduced pro-metastatic potential, as several studies have shown that hypoxia stimulates a more invasive, metastatic phenotype via multiple mechanisms (8)(9)(10)(11).…”