Key cellular signaling pathways have been identified in prostate cancer that have led to approved drugs. These include enzalutamide, targeting the androgen receptor, or temsirolimus, targeting the PI3K-AKT-mTOR pathway. Tumors can develop resistance to the drugs, however, prompting the need for effective combination therapies.
To address the challenge of identifying new combinations, recent work published in Systems Biology and Applications highlights a proteomic and pharmacology approach to quickly monitor response to treatments. The work comes from a team led by ETH Zurich and the Dana-Farber Cancer Institute.
“Even starting with a chemical compound library comprised of 1000 approved drugs a screen for a triple combination would result in 175 × 106 experiments, which are still too many experiments to carry out for high content screening of phenotypic readouts,” the team notes in their paper.
Using a human prostate cancer cell line, the tested six drugs used in treating prostate cancer or targeting the PI3K-AKT-mTOR. A total of 21 treatment conditions were established by using single and paired drug combinations. The team then sought to analyze how the cancer cells might respond to the drugs in the short-term, or 24 hours.
The team used a targeted proteomics approach to observe the molecular responses. A curated list of 490 proteins was prepared prior to the screen from literature, previous microarray data, and from the REACTOME database of protein-protein interactions. The total proteome was then extracted from the tested cells and analyzed by LC-MS/MS. From these results, 52 proteins were determined to be consistently quantifiable from the cell lysates.
In the protein expression data, the team found patterns of strong responders—proteins that were consistently downregulated or upregulated across many of the perturbation conditions.
“The downregulated proteins, HN1, PAK1, and SPAG5, are potential early indicators of drug efficacy and point to previously less well-characterized response pathways in [prostate cancer] cells,” the team notes. “Some of the upregulated proteins such as 14-3-3 proteins and KLK2 may be useful early markers of adaptive response and indicate potential resistance pathways targetable as part of combination therapy to overcome drug resistance.”
The team concludes that this systematic mass-spectrometry method of observing short-term response may help to discover response markers and anti-resistance targets.
Image: A figure depicting the experimental scheme of relating in vitro drug responses to changes in prostate cancer patients. Image courtesy of C. Sander, R. Aebersold, and Springer Nature.