Association of high TUBB3 with resistance to adjuvant docetaxel-based chemotherapy in gastric cancer: translational study of ITACA-S.

BACKGROUND: No predictive markers for chemotherapy activity have been validated in gastric cancer (GC). The potential value of class III ß-tubulin (TUBB3) as biomarker for prognosis and resistance to taxane-based therapy was reported. METHODS: We analyzed GC samples of patients enrolled in the Intergroup Trial of Adjuvant Chemotherapy in Adenocarcinoma of the Stomach (ITACA-S), a randomized adjuvant study comparing 5-fluorouracil/leucovorin (5-FU/LV) and docetaxel-based sequential chemotherapy. TUBB3 was quantitated by selected reaction monitoring mass spectrometry and patients were stratified using a threshold of 750 attomoles per microgram (amol/µg). Cox proportional modeling and Kaplan-Meier survival analysis were used to assess the impact of TUBB3 expression on overall survival (OS) and disease-free survival. RESULTS: Patients with TUBB3 protein levels >750 and <750 amol/µg were 21.9% and 78.1%, respectively, and were well-balanced between treatment arms. TUBB3 protein levels were not prognostic. Whereas no survival differences according to the 2 arms were observed in the subgroup with low TUBB3 expression (5-year OS 47% vs 40%; p = 0.44), patients with high TUBB3 had a clinically meaningful poorer OS when receiving docetaxel-based versus 5-FU/LV chemotherapy (5-year OS 31% vs 54%; p = 0.09), with a statistically significant interaction between TUBB3 and treatment (p = 0.049). CONCLUSIONS: The quantification of TUBB3 might be considered as a negative predictive biomarker of benefit from taxane-based therapy in GC. Studies are needed to evaluate its role in the neoadjuvant setting.

Therapeutically Induced Changes in HER2, HER3, and EGFR Protein Expression for Treatment Guidance.

Protein-targeted therapies are expected to selectively kill tumor cells that express the targeted protein biomarker. Although a tumor mass may initially respond to targeted therapies based on expression of the targeted protein, all cells within a tumor may not express the targeted protein above a critical threshold level; therefore, those cells that do not express, or that downregulate expression of, the targeted protein may not be responsive to therapy. The ability to monitor the dynamic expression of these protein biomarkers throughout the course of therapy may allow for treatment to be personalized in real-time in response to the evolving nature of the tumor. This report demonstrates, by monitoring a single patient through multiple therapies, how targeted mass spectrometry is an effective, quantitative method that provides real-time analysis of multiple therapeutically associated targeted proteins that can be used to personalize a patient's treatment strategy throughout the course of care.

Lineage infidelity of MDA-MB-435 cells: expression of melanocyte proteins in a breast cancer cell line.

The origin of cell lines is critical in defining cell type-specific biological functions. Several reports suggested that the MDA-MB-435 cell line, a cell line extensively used for studying breast cancer biology, has a gene expression pattern most compatible with melanocyte origin. However, we demonstrate that MDA-MB-435 cells express breast-specific or epithelial-specific markers. Also, MDA-MB-435 cells were induced to express breast differentiation-specific proteins and secrete milk lipids as observed in other well-established breast cancer cell lines. Notably, MDA-MB-435 cells also expressed melanocyte-specific proteins as did another highly aggressive breast cancer cell line. MDA-MB-435 xenograft tissue sections stained entirely positive for epithelium-specific markers but only partially positive for melanocyte-specific markers. Thus, MDA-MB-435 is most likely a breast epithelial cell line that has undergone lineage infidelity.

Enhanced sensitization to taxol-induced apoptosis by herceptin pretreatment in ErbB2-overexpressing breast cancer cells.

The recombinant humanized anti-ErbB2/HER2 monoclonal antibody Herceptin (Trastuzumab) has been shown to significantly enhance the tumoricidaleffects of antitumor drugs such as paclitaxel (Taxol) in patients with ErbB2-overexpressing breast cancers. Here, we investigated the molecular mechanisms by which Herceptin enhances the antitumor effects of Taxol. Because activation of p34(Cdc2) is required for Taxol-induced apoptosis and because overexpression of ErbB2 blocks Taxol-induced apoptosis by inhibiting p34(Cdc2) activation, we studied the effect of Herceptin treatment on p34(Cdc2) kinase activation and apoptosis in Taxol-treated human breast carcinoma cell lines MDA-MB-435, SKBr3, MDA-MB-453, and 435.eB, which is an ErbB2 transfectant of MDA-MB-435. Herceptin treatment down-regulated ErbB2, reduced the inhibitory phosphorylation of Cdc2 on Tyr-15, and down-regulated the expression of p21(Cip1), a Cdc2 inhibitor. Herceptin plus Taxol treatment led to higher levels of p34(Cdc2) kinase activity and apoptosis in ErbB2-overexpressing breast cancer cells, which is likely attributable to inhibition of Cdc2-Tyr-15 phosphorylation and p21(Cip1) expression. Because significant dephosphorylation of Cdc2-Tyr-15 and down-regulation of p21(Cip1) occur at least 24 h after Herceptin treatment, we investigated whether 24 h Herceptin pretreatment will render ErbB2-overexpressing breast cancer cells more sensitive to Taxol-induced apoptosis compared with the simultaneous treatment of Herceptin plus Taxol. Indeed, Herceptin pretreatment increased Taxol-induced apoptosis and cytotoxicity in vitro and more effectively inhibited the growth of tumor xenografts with enhanced in vivo apoptosis. Thus, Herceptin treatment of ErbB2-overexpressing cells can inhibit ErbB2-mediated Cdc2-Tyr-15 phosphorylation and p21(Cip1) up-regulation, which allows effective p34(Cdc2) activation and induction of apoptosis upon Taxol treatment. Herceptin pretreatment renders ErbB2-overexpressing breast cancers more susceptible to Taxol-induced cell death, which may have important clinical therapeutic implications.