Researchers have identified a novel drug that effectively thwarts pancreatic tumours that are addicted to the cancer-causing mutant KRAS gene.
Because early detection of pancreatic cancer is difficult, it has a low survival rate, accounting for just over 3% of all new cancer cases in the US, but leading to nearly 8% of all cancer deaths, according to the National Cancer Institute.
The KRAS gene was recognised more that 25 years ago as the component of Kirsten sarcoma virus responsible for oncogenesis. Since then, mutations of KRAS have been described in a large proportion of solid tumors ranging from more than 90% of pancreatic carcinomas to 20% to 30% of pulmonary adenocarcinomas.
Through a pre-clinical study, Said Sebti, PhD, associate director for basic research at VCU Massey Cancer Center, identified a novel drug that effectively thwarts pancreatic tumors that are addicted to the cancer-causing mutant KRAS gene.
“We discovered a link between hyperactivation of the CDK protein and mutant KRAS addiction, and we exploited this link preclinically to counter mutant KRAS-driven pancreatic cancer, warranting clinical investigation in patients afflicted with this deadly disease,“ said Dr Sebti, who is also the Lacy Family Chair in Cancer Research at Massey and a professor of pharmacology and toxicology at the VCU School of Medicine. “Our findings are highly significant as they revealed a new avenue to combat an aggressive form of pancreatic cancer with very poor prognosis due mainly to its resistance to conventional therapies.”
In 90 percent of pancreatic cancers, KRAS is mutated. Prior studies have shown that some tumours harbouring mutant KRAS are in fact addicted to the mutant gene, meaning they cannot survive or grow without it. Sebti set out to discover if there is a drug that can specifically kill those tumours with a mutant KRAS addiction.
Searching for a suitable drug
Dr Sebti and colleagues used a three-pronged approach to tackle this question.
First of all, they mapped the blueprint of pancreatic cancer cells through global phosphoproteomics, showing them how the addicted and non-addicted tumours differ at the phosphoprotein level. They found two proteins, CDK1 and CDK2, which signalled which cells were addicted to mutant KRAS.
Additionally, they analysed a comprehensive database from the Broad Institute of MIT and Harvard which contains genome-wide CRISPR gRNA screening datasets. They discovered that CDK1 and CDK2 as well as CDK7 and CDK9 proteins were associated with mutant KRAS-addicted tumors.
Finally, they evaluated 294 FDA drugs to selectively kill mutant KRAS-addicted cancer cells over non-KRAS-addicted cancer cells in the lab. They determined the most effective drug in preclinical experiments was AT7519, an inhibitor of CDK1, CDK2, CDK7 and CDK9.
“Using three entirely different approaches, the same conclusion presented itself clearly to us: pancreatic cancer patients whose tumors are addicted to mutant KRAS could benefit greatly from treatment with the CDK inhibitor AT7519,” Dr Sebti said.
To further validate these findings in fresh tumours taken from pancreatic cancer patients the researchers found that AT7519 suppressed the growth of xenograft cells from five mutant KRAS pancreatic cancer patients who relapsed on chemotherapy and/or radiation therapies.
Though AT7519 had previously been tested unsuccessfully in a number of clinical trials, none of the trials were for pancreatic cancer.
“If our findings are correct and translate in humans, then we should be able to see a positive response in pancreatic cancer patients whose tumors are addicted to mutant KRAS,” Dr Sebti said.
As well as pancreatic cancer, the study authors believe these findings may also have clinical implications for colorectal and non-small cell lung cancer patients with prevalent KRAS mutations.
Source: Virginia Commonwealth University
Journal information: Kazi, A., et al. (2021) Global Phosphoproteomics Reveal CDK Suppression as a Vulnerability to KRas Addiction in Pancreatic Cancer. Clinical Cancer Research. doi.org/10.1158/1078-0432.CCR-20-4781.
