ABSTRACT
PURPOSE: To investigate the expression of proteins fosfatidilinositol-4,5-bifosfate 3-quinase (PIK3CA) and phosphatase and tensin homolog (PTEN) in HER2-positive breast cancer and verify their associations with clinical and pathological variables. METHODS: We assessed PTEN and PIK3CA status using immunohistochemistry (IHC), which was performed in formalin-fixed paraffin-embedded biopsies from 50 patients with HER2-positive breast cancer. Medical records were studied for collection of clinical-pathological information, including overall survival (OS). The HIC markers PTEN and PIK3CA were analyzed semi-quantitatively by two blinded independent researchers. The relationship between the variables were evaluated using the chi-square test and Kaplan-Meier curves plus log-rank test for survival. RESULTS: In IHC, the expression level of PIK3CA was 86%, and loss of PTEN expression was observed in 46% of the cases. The expression of the markers showed no significant correlation with each other or with the clinical and pathological parameters studied: tumor grade, staging, ER, PR, Ki67 and recurrence. The highest expression of PIK3CA was associated with lower number of deaths (p=0.016) and longer OS of patients (p=0.001). The PTEN marker showed no significant effect on OS. CONCLUSIONS: The PIK3CA expression showed a protective effect in relation to the OS of patients with HER2-positive breast cancer.
Subject(s)
Class I Phosphatidylinositol 3-Kinases/metabolism , PTEN Phosphohydrolase/metabolism , Adult , Aged , Aged, 80 and over , Breast Neoplasms/mortality , Breast Neoplasms/pathology , Female , Humans , Immunohistochemistry , Middle Aged , Survival AnalysisABSTRACT
The oncogenic cytoplasmic p21 contributes to cancer aggressiveness and chemotherapeutic failure. However, the molecular mechanisms remain obscure. Here, we show for the first time that cytoplasmic p21 mediates 5-Fluorouracil (5FU) resistance by shuttling p-Chk2 out of the nucleus to protect the tumor cells from its pro-apoptotic functions. We observed that cytoplasmic p21 levels were up-regulated in 5FU-resistant colorectal cancer cells in vitro and the in vivo Chorioallantoic membrane (CAM) model. Kinase array analysis revealed that p-Chk2 is a key target of cytoplasmic p21. Importantly, cytoplasmic form of p21 mediated by p21T145D transfection diminished p-Chk2-mediated activation of E2F1 and apoptosis induction. Co-immunoprecipitation, immunofluorescence, and proximity ligation assay showed that p21 forms a complex with p-Chk2 under 5FU exposure. Using in silico computer modeling, we suggest that the p21/p-Chk2 interaction hindered the nuclear localization signal of p-Chk2, and therefore, the complex is exported out of the nucleus. These findings unravel a novel mechanism regarding an oncogenic role of p21 in regulation of resistance to 5FU-based chemotherapy. We suggest a possible value of cytoplasmic p21 as a prognosis marker and a therapeutic target in colorectal cancer patients.
ABSTRACT
The fragile histidine triad (FHIT) gene encloses an active common chromosomal fragile site, FRA3B. This gene is known to be associated with genomic instability, apoptosis and DNA damage. FHIT disturbances have been related to carcinogenesis in different types of human tumor. Despite this, there are some controversies about the exact role of the FHIT gene in relation to tumor biology. Several pieces of evidence support the hypothesis that FHIT acts as a tumor suppressor gene. A loss or decrease in the Fhit protein expression appears to be related to tumor progression, poor prognostic factors and lower survival rates. The most frequent causes of FHIT expression changes are gene mutations, epigenetic alteration and loss of heterozygosity. This literature review aims to clarify the involvement of the FHIT gene in carcinogenesis, tumor progression and clinical outcome in prevalent solid malignancies, such as breast, lung, cervical, esophageal, gastric and colorectal cancers.
