By Pooja Narendra and Rohit Kolhatkar
The typical DNA routinely used in laboratories consists mainly of nucleotide sequences required for its intended application and sequences required for its fast and convenient production in bacteria. For developing DNA as a therapeutic tool, there are several concerns associated with the presence of bacterial sequences. The major concern is its recognition as foreign material and the cellular response associated with it. Today, biotechnological tools can be used to make DNAs devoid of bacterial sequences. These specialized DNAs are tiny circles and are much smaller than conventional DNA. Their smaller size means that a lower amount is required for the same effect when compared to larger DNA. Furthermore, these tiny circles (frequently referred as minicircle DNA or minivectors) also exhibit higher functional efficiency than conventional DNA with bacterial sequences. Overall, tiny circular DNAs lacking bacterial sequences have the potential to bring a major paradigm shift in using nucleic acids as therapeutic agents. We are investigating the possibility of using these as lung cancer treatment.
In genetics, a translocation is described as the transfer of a segment of one chromosome to a new site on the same chromosome or to a non-homologous chromosome. Translocations are common in cancer, and some translocations produce oncogenes that are responsible for the cause of cancer. Identifying oncogenes in various cancers has evolved as a powerful approach in diagnosis and in choosing treatment options for cancer patients. An aberrant translocation in a significant number of lung cancer patients produces an oncogene called EML4-ALK. Tumors in these patients are addicted to EML4-ALK oncogene, thus making it an attractive therapeutic target. We are investigating the utility of tiny DNA circles to destroy EML4-ALK in cells using a cellular mechanism known as RNA interference (RNAi).
As with most DNA molecules, these tiny circles are highly negatively charged, making them inefficient in crossing the cell membrane. To address this, we are developing polymers that can form nanoparticulate complexes with tiny circular DNA, prevent their degradation, and facilitate their transfer across cell membranes. Another challenging task is their targeted delivery to tumors. To achieve this, we are currently exploring proteins that are selectively expressed on EML4-ALK positive tumors. Our recent observations indicate that an adhesion protein Nectin-4 is expressed on the surface of tumor cells that also express EML4-ALK. This is an exciting observation since we can now explore the potential of this protein to target therapeutic entities selectively to tumors positive for EML4-ALK.
Selection of patients based on their genetic profiling and modulating the cellular machinery through efficient delivery of DNA and RNA are some key aspects driving our current drug discovery process. Combining these approaches with successful delivery of tiny circular DNA might prove to be a significant advancement in our fight against cancer.