Expression of tesmin (MTL5) in non‑small cell lung cancer: A preliminary study

Lung cancer is the most commonly diagnosed cancer and the most frequent cause of death worldwide. Tesmin (testis‑specific metallothionein‑like protein; MTL‑5) is a 60‑kDa protein which has cysteine‑rich motifs (CXC domain), characteristic of metallothioneins (MTs). Tesmin expression has been observed in germ cells during spermatogenesis, oogenesis and also in various cell nuclei after exposure to heavy metal ions. Yet, the role of tesmin in carcinogenesis is unknown. The aim of the present study was to evaluate the localization and intensity of tesmin expression in non‑small cell lung cancer (NSCLC) and its association with the clinicopathological data of patients. A total of 121 cases of NSCLC and 20 cases of non‑cancerous tissue samples from the surgical margin (control) were used for immunohistochemistry (IHC). In addition, 20 cases of frozen NSCLC tissues and 20 cases of control were used for the in vivo study. Normal lung fibroblasts (IMR‑90) and lung cancer cell lines NCI‑H1703 (lung squamous cell carcinoma), NCI‑H522 and A549 (both adenocarcinomas of the lung) were used for western blot analysis (WB) and RT‑PCR studies. Positive cytoplasmic tesmin expression was observed in 88.42% of the examined cases of NSCLC. Statistical analysis showed increased IHC tesmin expression in cancer cells compared to that noted in the controls. In addition, MTL5 mRNA and WB tesmin protein expression were also higher in cancer cases compared to the controls. A positive correlation between tesmin and Ki‑67 IHC expression was demonstrated (r=0.32; P<0.001). Higher WB tesmin expression was also associated with shorter overall survival (P<0.05, Mantel‑Cox test). The in vitro study revealed higher tesmin protein (WB) and MTL5 (qPCR) in lung cancer cell lines compared to the lung fibroblast control cell line. Higher tesmin expression in cancer cells compared to control cells may suggest a role of tesmin in NSCLC carcinogenesis. A positive correlation between tesmin and Ki‑67 could indicate a possible role of tesmin in the proliferation of NSCLC.