<p>Connexin 32 downregulation is critical for chemoresistance in oxaliplatin-resistant HCC cells associated with EMT</p>

Abstract

Background: Oxaliplatin (OXA)-based chemotherapy is critical in the management of advanced hepatocellular carcinoma (HCC); however, acquired drug resistance has largely restricted its clinical efficacy. This study aims to explore the key mechanisms and regulatory factors determining chemosensitivity in HCC. Methods: We developed OXA-resistant (OR) HCC cells and used multiple methods, including real-time RT-PCR, Western blot, immunofluorescence, transwell invasion assay, wound-healing assay, MTT assay, gene transfection, and immunohistochemistry to achieve our goals. Results: We found that OR HCC cells showed a typical epithelial–mesenchymal transition (EMT) phenotype. Meanwhile, the expression of Cx32, a major member of the liver connexin (Cx) family, was lowly expressed in OR HCC cells. Downregulation of Cx32 in parental HCC cells led to EMT induction and thereby reduced OXA cytotoxicity, while Cx32 upregulation in OR HCC cells could reverse the EMT phenotype and partially restore chemosensitivity to OXA. Finally, in human HCC tissue samples, Cx32 was positively correlated with the expression of the EMT marker E-cadherin and negatively correlated with the expression of Vimentin. Conclusion: Our findings demonstrated that downregulation of Cx32 may be an important determinant for HCC cells to acquire EMT-related acquired drug resistance to OXA, and targeting Cx32 could be a novel strategy to overcome OXA resistance in HCC.

High STRN Expression Promotes HCC Invasion and Migration but Not Cell Proliferation or Apoptosis through Facilitating Epithelial-Mesenchymal Transition

“…Accumulating evidence has shown that EMT plays a crucial role in HCC invasion and metastasis [4][5][6]; EMT is characterized by the loss of epithelial cell polarity and cellcell contacts by downregulation of E-cadherin expression and upregulation of the expression of mesenchymal markers such as Vimentin [8]. Our previous investigation revealed that a partial EMT process was often activated in HCC tissues [15,16], supporting the hypothesis that EMT is partially responsible for HCC progression through mediating cell migration, invasion, and metastasis. In the present study, overexpression of STRN enhanced the migration and invasion capacities of Huh7 cells and induced the EMT phenotype.…”

“…. IHC was carried out on 4 μm thick, formalin-fixed, paraffin-embedded sections according to the two-step protocol that we described previously [15,16]. Anti-STRN (1 : 50, Proteintech), anti-Ecadherin (1 : 50, Abcam), and anti-Vimentin (1 : 100, Abcam) primary antibodies were used for immunohistochemical analysis.…”

“…Immunofluorescence Assay. Immunofluorescence assay was performed according to the standard protocols that we described previously [15,16]. Samples were blocked with 2% BSA in PBS and probed with primary antibodies (anti-STRN, 1 : 50; anti-E-cadherin, 1 : 200; and anti-Vimentin, 1 : 200) overnight at 4°C.…”

Redox-Mediated Mechanism of Chemoresistance in Cancer Cells

“…CCN2 regulates cell proliferation, chemotaxis, and migration, while ID-1 is involved in blocking cell differentiation [162,163,164]. The Cx32 tumor suppressor protein is associated with positive expression of E-cadherin and negative expression of vimentin [165,166]. Cx32 level is decreased in hepatocellular carcinoma resistant to oxaliplatin [165].…”

“…The Cx32 tumor suppressor protein is associated with positive expression of E-cadherin and negative expression of vimentin [165,166]. Cx32 level is decreased in hepatocellular carcinoma resistant to oxaliplatin [165]. Ataxin-2-line (ATXN2L) promotes migration and invasion and is elevated in oxaliplatin-resistant gastric cancer [167,168].…”