Understanding Herceptin Resistance with Dual Function Array
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Increasing evidence shows the importance of epigenetic mechanisms (e.g. CpG island methylation) in the transcriptional down-regulation of critical tumor suppressors and growth regulatory genes in breast cancer. The patterns of aberrant methylation are non-random and tumor type-specific, and can be distinct with tumor types such as breast tumors. Further, it is also well-known that chromosomal deletions are a major mechanism of gene inactivation in human cancer. The extent to which these two mechanisms affect the same or different sets of genes in breast cancer is mostly unexplored. Herceptin is a monoclonal antibody developed by Genentech and used in the treatment of HER2-overexpressing metastatic breast cancer. Although this therapy is quite successful in treating some patients, approximately 5% of tumors from these patients are resistant to the treatment. 
 
 
 
 
 
 
 
 Our interest is to understand the epigenetic and genetic differences which confer Herceptin resistance in patients. This project will examine whether resistance to Herceptin therapy in breast cancers is mediated by the combined effects of aberrant DNA methylation and deletion, particularly on genes of the growth receptor tyrosine kinase (RTK) pathways. Our aim is to develop a new high throughput gene-array method for analysis of both methylation and deletion, taking advantage of existing array CGH (comparative genomic hybridization) technology. We will focus our analysis on the relative contribution of aberrant gene methylation and gene copy number changes in causing specific dysfunctions of the receptor kinase pathways. A key component of our analysis will be comparing the HER2-positive/Herceptin-sensitive with the HER2 -positive/Herceptin-resistant breast cancer cell lines. We have access to custom-made BAC (bacterial artificial chromosome) DNA arrays, which contain 500 known genes involved in RTK pathways. This approach allows us to detect specific aberrant methylation and gene deletions. Finally, we will compare the biological functions with the genomic profiles in these cell lines to select gene candidates related to Herceptin sensitivity. We can confirm our resistant cells with DNA methyltransferase inhibitors or reintroduction of the target genes into the resistant cells.
 
 
 
 
 
 
 
 Aberrant gene methylation and gene deletions are predominant mechanisms of gene silencing in breast tumors, yet the extent of their interaction is unknown. The new dual-function array will be capable of assessing the contribution of both of these mechanisms. This will lead to a substantially improved understanding of breast tumorigenesis that is not biased towards genetic events, as has been done in the past. Most importantly, the application of this method to elucidating the mechanism of Herceptin resistance would lead to new combination treatments to overcome the resistance and potentially would increase the success rate of Herceptin therapy.