Methylation status, mRNA and protein expression of the SMAD4 gene in patients with non-melanocytic skin cancers.

BACKGROUND: SMAD4 is a potent tumor suppressor. SMAD4 loss increases genomic instability and plays a critical role in the DNA damage response that leads to skin cancer development. We aimed to investigate SMAD4 methylation effects on mRNA and protein expression of SMAD4 in cancer and healthy tissues from patients with basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and basosquamous skin cancer (BSC). METHODS AND RESULTS: The study included 17 BCC, 24 cSCC and nine BSC patients. DNA and RNA were isolated from cancerous and healthy tissues following punch biopsy. Methylation-specific polymerase chain reaction (PCR) and real-time quantitative PCR methods were used to examine SMAD4 promoter methylation and SMAD4 mRNA levels, respectively. The percentage and intensity of staining of the SMAD4 protein were determined by immunohistochemistry. The percentage of SMAD4 methylation was increased in the patients with BCC (p = 0.007), cSCC (p = 0.004), and BSC (p = 0.018) compared to the healthy tissue. SMAD4 mRNA expression was decreased in the patients with BCC (p˂0.001), cSCC (p˂0.001), and BSC (p = 0.008). The staining characteristic of SMAD4 protein was negative in the cancer tissues of the patients with cSCC (p = 0.00). Lower SMAD4 mRNA levels were observed in the poorly differentiated cSCC patients (p = 0.001). The staining characteristics of the SMAD4 protein were related to age and chronic sun exposure. CONCLUSIONS: Hypermethylation of SMAD4 and reduced SMAD4 mRNA expression were found to play a role in the pathogenesis of BCC, cSCC, and BSC. A decrease in SMAD4 protein expression level was observed only in cSCC patients. This suggests that epigenetic alterations to the SMAD4 gene are associated with cSCC. TRIAL REGISTRATION: The name of the trial register: SMAD4 Methylation and Expression Levels in Non-melanocytic Skin Cancers; SMAD4 Protein Positivity. The registration number: NCT04759261 ( https://clinicaltrials.gov/ct2/results?term=NCT04759261 ).

Investigating KRAS/BRAF mutation in oropharyngeal squamous cell carcinomas: a preliminary study.

OBJECTIVES: This study aims to investigate the role of KRAS/BRAF gene mutation in the pathogenesis of oropharyngeal squamous cell carcinoma (OSCC). PATIENTS AND METHODS: A total of 26 OSCC patients (23 males, 3 females; mean age 60 years; range 41 to 77 years) diagnosed between January 2003 and November 2013 were included in the study. The methods used in our study were quantitative fluorescence polymerase chain reaction for KRAS/BRAF mutation analysis. RESULTS: Ten of the tumors were located at the tongue base, 12 in the tonsil and four at the floor of mouth. The mean tumor size was 3.8 cm. Six of the tumors were well differentiated, 18 were moderately differentiated and two were poorly differentiated. All cases were analyzed for KRAS and BRAF gene mutations and none of them showed gene mutations. CONCLUSION: We could not find any relation between OSCC and KRAS/BRAF gene mutations in our short case file. The role of mutations should be analyzed in larger series in OSCC to predict new targeted therapy modalities.