Calreticulin promotes cell motility and enhances resistance to anoikis through STAT3–CTTN–Akt pathway in esophageal squamous cell carcinoma

Abstract

We have shown earlier that overexpression of Calreticulin (CRT) contributed to a poor prognosis for patients with esophageal squamous cell carcinoma (ESCC). Here, we have shown an important role of CRT in tumorigenesis through enhancing cell motility and anoikis resistance. SiRNA-mediated knockdown of CRT caused impaired cell migration, invasion and resistance to anoikis. Notably, CRT downregulation decreased the expression of Cortactin (CTTN), which has been previously reported as a candidate oncogene associated with anoikis through the PI3K-Akt pathway. In addition, Akt phosphorylation was abolished after CRT downregulation and its activation can be refreshed by CRT upregulation, suggesting that CRT-enhanced cell resistance to anoikis through the CRT-CTTN-PI3K-Akt pathway. Moreover, the CTTN mRNA level was decreased in CRT-siRNA cells, coupled with the inactivation of STAT3. Expression of both CTTN and p-STAT3 was reduced in tumor cells following incubation with the JAK-specific inhibitor, AG490. Chromatin immunoprecipitation assay showed direct binding of p-STAT3 to the conservative STAT3-binding sequences in CTTN promoter. Furthermore, overexpression of CTTN in CRT-downregulated ESCC cells restored its motility and resistance to anoikis. This study not only reveals a role of CRT in motility promotion and anoikis resistance in ESCC cells, but also identifies CRT as an upstream regulator in the CRT-STAT3-CTTNAkt pathway.

Cortactin in cell migration and cancer at a glance

“…In some cancers, overexpression of cortactin might also result from upregulation of transcription factors that activate transcription of CTTN (Du et al, 2009;Hill et al, 2006). Additionally, there are instances where cortactin is hyperphosphorylated by overexpressed kinases, such as Src and HER2 in cancer cells, leading to increased cell migration (Garcia-Castillo et al, 2009;Wu et al, 1991).…”

Tumor-derived Mutations in the Gene Associated with Retinoid Interferon-induced Mortality (GRIM-19) Disrupt Its Anti-signal Transducer and Activator of Transcription 3 (STAT3) Activity and Promote Oncogenesis

“…Phosphorylation of cortactin by Src family kinases initiates a sequential cellular dynamic process; 1) neutralizes cross-linked actin network (58), 2) enhances actin assembly in vivo (59), and 3) plays an essential role in the formation of podosome (59). This protein has been previously reported as a target of STAT3 (60) and is overexpressed in a number of metastatic tumors (61)(62)(63)(64)(65). Similarly, MMP-9, a protease involved tumor invasion, is also up-regulated in these cells (Fig.…”

miR326 Maturation Is Crucial for VEGF-C–Driven Cortactin Expression and Esophageal Cancer Progression

“…Elevated levels of CTTN in human cancers are more commonly associated with gene amplification, and little is known about its translational/transcriptional regulation. The only evidence of transcriptional regulation in esophageal cancer is based on the ability of calreticulin to induce CTTN activity through STAT3 signaling (32). Here, we identify VEGF-C as a novel regulator of CTTN expression in ESCC cells.…”