Killing Cancer without Killing the Cell

NISHANT KAKAR

Nishant Kakar, Featured ImageMy research centers on finding, analyzing and testing trends with specific biomarkers in cancerous tumors. According to the literature, a number of different types of cancers, including head and neck, cervical, bladder, ovarian, and esophageal cancers, contain large amounts of a protein called EGFR (epidermal growth factor receptor). From this finding, many scientists have dedicated their research to exploring ways to get rid of EGFR, either by degrading it, or preventing it from forming. Some methods target EGFR directly, but others target a different protein called HSP90 (heat shock protein 90). HSP90 is known as a “molecular chaperone” to EGFR and many other proteins: it orients EGFR’s structure for optimal performance.

This study is centered on finding, analyzing, and testing trends in cancerous tumors.

The first process where EGFR is directly targeted is known as EGFR inhibition. The drug Erlotinib is specifically degrades EGFR by inhibiting its tyrosine kinase activity, making it a good candidate for the treatment. However, some forms of EGFR have mutated to become resistant to the drug, making it a less than ideal option.

The process that targets HSP90, the “molecular chaperone,” is aptly called HSP90 inhibition. The drug AT13387 can inhibit its activity, which means that it also degrades its client protein, EGFR. Given that this inhibition leads to the reduced expression of many essential proteins, in addition to the cancer-linked EGFR, this process is effective. The only problem? In the process of degrading these proteins, it releases too many toxins, and so does more harm than good.

To summarize, Erlotinib does not release toxins, but cannot target mutant EGFR, while AT13387 overcomes this resistance, but makes the cell a toxic environment. With these problems in mind, my study investigates whether these two drugs can be combined for better effect. Using a technique called a clonogenic survival assay, I applied these drugs in different combinations to different types of cells.

I conducted three experiments in my study: AT13387 concentration dependent treatment, Erlotinib concentration dependent treatment, and Erlotinib & AT13387 combination therapy. In the first experiment, the AT13387 concentration dependent treatment enabled me to determine the optimal dosage amount. In this way I could ensure low survival rates in cancerous, EGFR-dependent cell lines, and while maintaining high survival rates in non-cancerous cell lines. In the second experiment, the Erlotinib concentration dependent treatment found the ideal dosage that could wipe off the EGFR-dependent cell lines, while releasing the least toxins.

Once I determined these ideal dosages (10nM for AT13387 and 3uM for Erlotinib), I moved on to my third experiment: Erlotinib &AT13387 combination therapy. Six different samples in each cell line were tested using the optimal dosage levels. The samples consisted of a control, an individual Erlotinib treatment, an individual AT13387 treatment, a concurrent Erlotinib & AT13387 treatment, a sequential Erlotinib treatment with AT13387 treatment 24 hours later, and a sequential AT13387 treatment with Erlotinib treatment 24 hours later. These samples were tested in cells without the cancerous EGFR protein, cells with mutant EGFR, and two types of cells with EGFR. In the noncancerous cells, both concurrent and sequential treatments both resulted in high survival rates. That meant that the toxins produced by treatment remained at low levels. In the mutant EGFR cell line, the concurrent application of the two drugs resulted in cell death, more so than when I treated them with individual or sequential doses of the drugs. Finally, in the cells with EGFR, applying the two drugs concurrently killed the cells, but it also wiped away all traces of cancer.

As a result, my second experiment was most successful: it showed that treating mutant EGFR with concurrent doses of Erlotinib and AT13387 was better than any other treatment tested. A combination of these drugs could kill off EGFR-dependent cancers entirely, while producing little toxic waste in the process.

Nishant Kakar is a Brevia staff writer. He can be reached at nkakar@college.harvard.edu.