De-silencing hypermethylated tumor supressor genes
Initial Award Abstract
Lung cancer is the leading cause of cancer death in the United States with 157,000 deaths expected in 2010. The 5-year survival rate is less than 16%, presenting a compelling need for novel therapies. Cancer cells have lost the self-checking mechanism that prevents uncontrolled replication and initiates programmed cell death if they become abnormal. One way cancer cells can lose this ability is through epigenetic silencing where perfectly functional genes that would otherwise suppress cancer are silenced at the DNA level. This silencing is performed by methyltransferase enzymes that marks the DNA in such a way that DNA coils up and the tumor suppressor gene is silenced.|
In this proposal, we aim to explore a new method of de-silencing genes by using a class of molecules developed by the Dervan lab. These molecules, called Py-Im polyamides, can be built to target and bind specific sequences in DNA. They can be targeted towards the DNA regions most relevant to the silenced genes. They have previously been shown to interfere with interactions between proteins and DNA at the target DNA sequences, and should have the same effect in interfering with the methyltransferase enzymes.
Studies with a FDA-approved therapy that inhibits the methyltransferase enzymes by permanently tying the protein to DNA has shown that this strategy of de-silencing genes can encourage programmed cell death and increase the effectiveness of other standard chemotherapy drugs in cancer cells. Unfortunately, the drug had such severe side effects that it has not found wide use, and is not used in lung cancer. Because the Py-Im polyamides would inhibit the methyltransferase enzymes in a different way, this class of molecules may exhibit gentler side effects. We will first run a cell-free test tube study to see if Py-Im polyamides will inhibit the methyltransferase enzymes. Second, we will test a focused library of Py-Im polyamides targeted to de-silence the p16, DAPK, and RASSF1A tumor suppressor genes in lung cancer cells. The study will monitor whether polyamides successfully remove the silencing marks on DNA and whether the targeted tumor suppressor genes are de-silenced. A positive result would justify further study of the Py-Im polyamides’ therapeutic potential and may suggest Py-Im polyamides can be a generalized method towards de-silencing key tumor suppressor genes in lung cancer, and other cancers.