“We see this more as an augmented therapy, particularly in patients where nothing else works,” said Dr Kmeic. He added that in this age of personalized medicine, he sees the use of CRISPR as just one potential tool in cancer treatment, not the only option.
This study adds to similar lab-based work in other types of cancer, providing further proof of principle that CRISPR could potentially contribute to cancer therapeutics. However, CRISPR delivery methods for use in humans are still in development, and are some way from being realized.
“The direct treatment of cancer cells is very challenging since A) editing methods are far from 100% and we do want to kill 100% of cancer, and B) delivery of biologics, for example; proteins, mRNA … to tumors is quite challenging due to tumor heterogeneity,” said Vince Rotello, PhD, from the University of Massachusetts at Amherst, who researches innovative drug-delivery techniques.
Despite these multiple hurdles yet to be overcome, developing CRISPR-based therapeutics is the main goal of dozens of biotechnology companies. The first human trials of these therapies may not be so far away, albeit for cells modified with CRISPR outside of the body and then reinjected back into the patient.
“In 2020 there will be a number of programs in the clinic exclusively using ex vivo edited T cells,” said Tom Barnes, PhD, senior vice president of Innovative Sciences at Intellia Therapeutics. “But going after cancer with in vivo editing is a tall order and I don’t know of anyone doing that right now. Academics can make tumors shrink in a mouse and I wonder how well this is going to ultimately translate. Humans are much more challenging,” he added.
Treating solid tumors in cancer patients comes with its own set of unique challenges for CRISPR-based drug developers, including safety. One critical concern is that any off-target editing of cells could persist for decades after the initial treatment, and little is known about the consequences of off-target effects.
“The big challenge in ‘CRISPRing’ the tumor directly is that none of the technologies are point-precision specific to where it goes. If you are going after a gene that the tumor is critically dependent on, then fine, but the chances you’re going to get away without damaging healthy tissue are small,” said Dr Barnes.
Despite these concerns and the large amount of work ahead needed to translate these early lab-based results into humans, oncology might be the perfect place to experiment with the undoubtedly great potential of CRISPR. Hard-to-treat cancers such as those of the lung and pancreas have yet to see significant improvement in survival with new immunotherapy drugs, making them attractive options for testing novel approaches like CRISPR.
“CRISPR has incredible potential for fighting multiple diseases. There are a number of places where tough ethical questions are raised (embryo editing, gene drives), but oncology is a place where we can safely explore a vast range of therapeutic modalities, many of which have not yet been conceived,” said Dr Rotello.
- Bialk P, Wang Y, Banas K, Kmiec E. Functional gene knockout of NRF2 increases chemosensitivity of human lung cancer A549 cells in vitro and in a xenograft mouse model. Mol Ther Oncolytics. 2018;11:75-89.