High PHLPP expression is associated with better prognosis in patients with resected lung adenocarcinoma

PH domain Leucine-rich-repeats protein phosphatase (PHLPP) is a novel family of Ser/Thr protein dephosphatases that play a critical role in maintaining the balance in cell signaling. PHLPP negatively regulates PI3K/Akt and RAF/RAS/' signaling activation, which is crucial in development, growth, and proliferation of lung cancer. The aim of this study was to investigate the association of PHLPP expression with biological behavior and prognosis of lung adenocarcinoma.

One hundred and fifty eight patients with pathologically documented stage I, II or IIIA lung adenocarcinoma were recruited in this study. Expression of PHLPP, p-AKT and p-ERK were evaluated by immunohistochemistry (IHC) in paraffin-embedded resected specimens. The correlation of their expression, which was dichotomized to low expression (a score of 0, 1) versus high expression (a score of 2, 3), with the clinicopathological parameters and prognosis of the patients also analyzed.

High PHLPP expression rate in lung adenocarcinoma was 23.4 %. PHLPP expression level was significantly associated with tumor differentiation (p = 0.025) and tumor stage (p = 0.024). Patients with high expression of PHLPP showed significantly longer average survival time and higher 3 years survival rate than those with low expression of PHLPP (45 months versus 38 months, 85.8 % versus 73.5 % respectively) (Log rank test x(2) = 7.086, p =0.008). A significant inverse correlation was observed between PHLPP expression and p-AKT (r = -0.523, p = 0.000) or p-ERK (r = -0.530, p = 0.000).

Our results suggest that high levels of PHLPP might reflect a less aggressive lung adenocarcinoma phenotype and predict better survival in patients with lung adenocarcinoma. PHLPP can be a potential prognostic marker to screen patients for favorable prognoses.