ABSTRACT
BACKGROUND: Src is a non-receptor tyrosine kinase involved in signalling and crosstalk between growth-promoting pathways. We aim to investigate the relationship of active Src in response to trastuzumab of HER2-positive breast carcinomas. METHODS: We selected 278 HER2-positive breast cancer patients with (n=154) and without (n=124) trastuzumab treatment. We performed immunohistochemistry on paraffin-embedded tissue microarrays of active Src and several proteins involved in the PI3K/Akt/mTOR pathway, PIK3CA mutational analysis and in vitro studies (SKBR3 and BT474 cancer cells). The results were correlated with clinicopathological factors and patients' outcome. RESULTS: Increased pSrc-Y416 was demonstrated in trastuzumab-resistant cells and in 37.8% of tumours that correlated positively with tumour size, necrosis, mitosis, metastasis to the central nervous system, p53 overexpression and MAPK activation but inversely with EGFR and p27. Univariate analyses showed an association of increased active Src with shorter survival in patients at early stage with HER2/hormone receptor-negative tumours treated with trastuzumab. CONCLUSIONS: Src activation participates in trastuzumab mechanisms of resistance and indicates poor prognosis, mainly in HER2/hormone receptor-negative breast cancer. Therefore, blocking this axis may be beneficial in those patients.
Subject(s)
Antibodies, Monoclonal, Humanized/pharmacology , Antineoplastic Agents/pharmacology , Breast Neoplasms/enzymology , Central Nervous System Neoplasms/enzymology , Receptor, ErbB-2/metabolism , src-Family Kinases/metabolism , Adult , Aged , Aged, 80 and over , Antibodies, Monoclonal, Humanized/therapeutic use , Antineoplastic Agents/therapeutic use , Breast Neoplasms/drug therapy , Breast Neoplasms/mortality , Breast Neoplasms/pathology , Cell Line, Tumor , Central Nervous System Neoplasms/drug therapy , Central Nervous System Neoplasms/mortality , Central Nervous System Neoplasms/secondary , Chemotherapy, Adjuvant , Class I Phosphatidylinositol 3-Kinases , DNA Mutational Analysis , Drug Resistance, Neoplasm , Enzyme Activation , Female , Humans , Kaplan-Meier Estimate , Middle Aged , Molecular Targeted Therapy , Phosphatidylinositol 3-Kinases/genetics , Signal Transduction , Trastuzumab , src-Family Kinases/antagonists & inhibitorsABSTRACT
BACKGROUND: Trastuzumab resistance hampers its well-known efficacy to control HER2-positive breast cancer. The involvement of PI3K/Akt pathway in this mechanism is still not definitively confirmed. METHODS: We selected 155 patients treated with trastuzumab after development of metastasis or as adjuvant/neoadjuvant therapy. We performed immunohistochemistry for HER2, ER/PR, epidermal growth factor 1-receptor (EGFR), α-insulin-like growth factor 1-receptor (IGF1R), phosphatase and tensin homologue (PTEN), p110α, pAkt, pBad, pmTOR, pMAPK, MUC1, Ki67, p53 and p27; mutational analysis of PIK3CA and PTEN, and PTEN promoter hypermethylation. RESULTS: We found 46% ER/PR-positive tumours, overexpression of EGFR (15%), α-IGF1R (25%), p110α (19%), pAkt (28%), pBad (22%), pmTOR (23%), pMAPK (24%), MUC1 (80%), PTEN loss (20%), and PTEN promoter hypermethylation (20%). PIK3CA and PTEN mutations were detected in 17% and 26% tumours, respectively. Patients receiving adjuvant trastuzumab with α-IGF1R or pBad overexpressing tumours presented shorter progression-free survival (PFS) (all P≤0.043). Also, p110α and mTOR overexpression, liver and brain relapses implied poor overall survival (OS) (all P≤0.041). In patients with metastatic disease, decreased PFS correlated with p110α expression (P=0.024), whereas for OS were the presence of vascular invasion and EGFR expression (P≤0.019; Cox analysis). CONCLUSION: Our results support that trastuzumab resistance mechanisms are related with deregulation of PTEN/PI3K/Akt/mTOR pathway, and/or EGFR and IGF1R overexpression in a subset of HER2-positive breast carcinomas.
