The use of gene array analysis to determine down-stream molecular expression patterns of trastuzumab (T) treatment

Abstract

14135 Background: Breast cancers expressing the HER/2 amplicon are more aggressive and are associated with a poorer prognosis. HER/2 over-expression has been correlated with expression of proteins responsible for invasion, metastases, rapid growth, angiogenesis and apoptosis. However, it is unknown if T treatment of HER/2 over-expressing tumors reverses these phenotypes. Methods: BT 474 and SK-BR3 breast cancer cell lines contain the HER/2 amplicon. Under growth conditions demonstrating inhibitory effects of T by MTT and 3 H-Thymidine incorporation, (0.25–50 micrograms/ml for up to 9 days), RNA extracts from treated and un- treated cells were analyzed and compared by whole human genome, gene array analysis. Results: Specific gene products reported to be up-regulated in HER/2 over-expressed breast cancer lines or responsible for aggressive behavior were assessed for down regulation by T treatment including: topoisomerase II, heregulin, egfr-1,2,3 and 4, p27, ki67, mapKinase, akt, caspase-3, caspase-7, caspase-9, bcl-2, veg-f, veg-f receptor, p38, sapk/jnk, erk1/2, LGALS1 galectin-1, LGALS3 galectin-3, proline-4-hydrolase P4HA2, FN1 fibronectin -1, CDH3 p-cadherin, laminin receptor protein -1, pro2605 and insulin like growth factor binding protein-3. No significant change in these mRNA levels were observed due to T treatment. In contrast, over 1000 other gene were found to be specifically and significantly up or down regulated including the down regulation of S100 Calcium binding protein associated with increase metastatic potential. Conclusions T treatment does not reverse the expression of a large array of proteins conferring poor prognostic features on HER/2+ tumor. The use of gene array analysis to study T induced gene expression is a robust method to assess downstream protein expression patterns mediated by antibody binding to receptor. No significant financial relationships to disclose.