The Potential Prognostic Value of Connexin 43 Expression in Head and Neck Squamous Cell Carcinomas

Abstract

Gap juctions are transmembrane communication channels known to be involved in the control of cell proliferation by mediating the exchange of ions and small molecules between cells. Gap junctions are composed of connexon hemichannels made up of 6 connexin proteins, which abnormal expression and functions have been linked to tumor progression and poorer prognosis. Here, we studied the prognostic impact of the most prevalent connexin isotype, connexin 43 (Cx43) in head and neck squamous cell carcinomas (HNSCC). Tissue microarrays made from tumor samples of 90 HNSCC patients were immunostained for Cx43 and cell cycle regulation-related biomarkers including p53, Ki67, p16, aurora A, geminin, and p21 proteins. Scoring and histopathologic evaluation were performed in digital slides. A 4-tier scoring distinguishing the percentage of positively stained tumor cells was used including score 1: <5%, score 2: 6% to 20%, score 3: 21% to 60%, and score 4: >60%. For statistics, Kaplan-Meier curves with log-rank tests, Cox-regression, and Pearson χ/Fisher exact tests were used.A significant positive correlation was found between Cx43 expression and disease-specific survival of patients (P=0.004). The rate of p21 protein-positive tumor cells also proved to be a significant positive prognostic marker (P=0.014). Cx43 levels also showed a significant positive correlation with p53 expression (P=0.036). However, there was no statistical association between Cx43 levels and the rest of the markers tested neither with T, N, or M stage.In conclusion, our data suggest that reduced Cx43 expression and low p21 protein levels may have a significant negative impact on HNSCC prognosis.

The Potential Impact of Connexin 43 Expression on Bcl-2 Protein Level and Taxane Sensitivity in Head and Neck Cancers–In Vitro Studies

“…In our previous study, we found that Cx43 could be regarded as a prognostic factor in head and neck cancers, and the reduction of its expression level is associated with a significantly poorer prognosis [14]. This was confirmed by Puzzo et al in laryngeal cancers [24].…”

“…Bcl-2 categories were: 1: <10% positive tumor cells; 2: 11 to 30% positive tumor cells, 3: 31 to 60% positive tumor cells; and 4: >60% positive tumor cells [40,41]. Cx43 staining was evaluated as follows: 1: <5% positive tumor cells; 2: 6 to 20% positive tumor cells, 3: 21 to 60% positive tumor cells; and 4: >60% positive tumor cells [14]. For statistical analysis, scores were dichotomized along different threshold values.…”

“…Besides, Cx43 is also a tumor suppressor. The decreased expression of Cx43 correlates with tumor formation and poor prognosis in solid tumors such as breast cancer and HNSCCs [14,15].…”

Gap junctions and cancer: communicating for 50 years

“…Similarly recent studies tracking connexin levels as a cancer prognostic indicator produced a diverse set of outcomes. Over a dozen studies in the last decade correlate high connexin expression with a significantly better prognosis (e.g., Cx43 in prostate 39 , pancreatic 40 , breast 41 , head and neck SCC 42 , non-small-cell lung 43 , and colorectal 44 cancers; and Cx26 in colorectal 45 and intestinal type-gastric 46 cancers). In contrast, more than a dozen studies correlate high connexin expression with a poor prognosis (e.g., Cx43 in oral SCC 47 , esophageal SCC 48 and non-muscle invasive urothelial bladder cancer 49 ; and Cx26 in breast cancer 50,51 , lung SCC 52 , esophageal SCC 53 , colorectal cancer 37 and papillary and follicular thyroid cancer 54 ).…”

Connexins in cancer: bridging the gap to the clinic

“…No correlation at DNA or mRNA levelArtesi et al [51]HNSCCCx43FCx43 expression = better disease-specific survival of patients P = 0.004Cx43 positively correlated with p53 expression ( P = 0.036). No statistical association between Cx43 levels and T, N or M stageDanos et al [200]Liver (hepatitis B-related) HCCCx43FHigh Cx43 = delayed tumour recurrence ( P = 0.001), longer DFS ( P = 0.026) and OS ( P = 0.000) in patients with serum alpha-fetoprotein < 400 ng/mlAll P ⩽ 0.026In patients with serum alpha-fetoprotein < 400 ng/ml, Cx43 expression is an independent predictor of later recurrence and longer OSWang et al [201]LungCx26UCx26-positive SCC tumours associated with increased survival (cancer-related deaths, not OS) P = 0.0391Multivariate analysis demonstrated that Cx26 expression ( P = 0.0448) is an independent prognostic predictorIto et al [202]Cx43FBetter mean OS and PFS in NSCLC patients with high Cx43, including the chemotherapy-responder group P < 0.001Cx43, a reliable surrogate marker for predicting the chemotherapy response and prognosis of patients with advanced NSCLCDu et al [203]Oral SCCCx43UHigh membrane expression of Cx43 = short OS P = 0.0088No correlation for Cx26 or Cx45. Cx43 expression in dysplasia-free mucosa may indicate a very early stage of tumour progressionBrockmeyer et al [204]PancreaticCx43FReduced Cx43 associated with higher TNM stage and lymph-node metastasis P < 0.001Also associated with the degree of differentiation ( P = 0.002)Liang et al [205]ProstateCx26FLow Cx26 expression in noncancerous tissue in prostatectomy sections = reduced BRFS and risk of metastasis P = 0.002Cx26 is only predictive when assessed in the noncancerous areas of the tissueBijnsdorp et al [206]Cx43FReduced Cx43 = shorter postoperative BRFS P < 0.001Patients with lower Cx43 have higher preoperative PSA levelsBenko et al [207]Cx43FReduced Cx43 = shorter postoperative BRFS P < 0.001Reduced levels of Cx43 associated with high levels of preoperative PSA, a high Gleason score, an advanced pT stage and seminal vesicle invasion (all P < 0.05)Xu et al [208]Sarcoma (EWS/PNET)…”