Alpha tocopherol transfer protein (αTTP) is expressed in endometrial carcinoma and is correlated with FIGO stage and 5-year survival

Abstract

Background: Increased oxidative stress plays an important role in cancer development. Vitamin E is considered a potent anti-oxidant and its transfer protein αTTP facilitates its cellular delivery. We hypothesize that αTTP could be present in and have an impact on endometrial cancer.

Materials and methods: Ishikawa endometrial cancer cells were treated with BSO and AAPH to mimick oxidative stress conditions. αTTP was detected by immunocytochemistry and western blot. αΤΤP expression was then assessed in 191 endometrioid endometrial carcinomas. Immunopositivity was correlated with grade, FIGO stage, and 5-year survival. Immuno-reactivity was assessed with a semi-quantitative score.

Results: AAPH- and BSO-induced αTTP expression in Ishikawa cells. Immunohistochemical assessment of the 191 endometrial cancer cases showed that αTTP expression correlated with FIGO stage (p = 0.014) but not with grade. Five-year survival was significantly better in cases of lower αTTP expression compared to cases with higher expression (p = 0.041).

Conclusions: The current results show that αTTP plays a role in endometrial carcinoma. Possibly endometrial cancer cells attempt to protect themselves from increasing oxidative stress by up-regulating αTTP. Selective molecular interventions targeting oxidative stress escape strategies, e.g., by overexpression of αTTP, could, therefore, allow oxidative stress to damage cancer cell membranes and thus restrict cancer progression.

Keywords: Alpha tocopherol transfer protein; Endometrial cancer; Survival.

Fig. 1

a αTTP IRS after 4, 8, 24, and 48 h of oxidative stress induction using either BSO or AAPH are presented. For the first 24 h, both agents significantly induced αTTP expression. Thereafter, only AAPH continued to be effective. b Representative microphotographs of αΤΤP expression in Ishikawa cells after 24-h treatment with either BSO or AAPH are shown. αTTP expression was significantly elevated compared to control

Fig. 2

αΤΤP expression in Ishikawa treated with either BSO or AAPH was quantified by western blot and compared to controls. The stimulation duration was 24 h. αΤΤP expression was normalized to beta-actin which served as a loading control. Normalized αΤΤP signals of samples treated with BSO and AAPH are plotted relative to controls. Both pro-oxidants significantly induced αΤΤP expression compared to control

Fig. 3

Representative microphotographs of αTTP expression in tissue sections of formalin-fixed paraffin-embedded endometrial cancer tissues are shown. αTTP positivity was exclusively restricted to endometrial cancer cells—with stroma, blood and lymph vessels staining negative—and significantly correlated with FIGO stage. Scale bar equals 100 µm

Fig. 4

Survival analysis of endometrial cancer cases stratified as either of low (IRS ≤6 i.e. IRS 0–IRS 6) or high (IRS >6 i.e. IRS 8–IRS 12) αTTP expression is shown. a Kaplan–Meier curves illustrate a significantly reduced 5-year survival in cases with increased (IRS >6) αTTP expression. b Microphotographs of αΤΤP expression in tissue sections of formalin-fixed paraffin-embedded endometrial cancer tissues according to the above mentioned stratification are depicted. Scale bar equals 100 µm