Protein Inhibition Therapy Holds Promise for Treating Several Cancer Types

Regulating PD-L1 protein that helps cancer evade immune system suggests new therapeutic approach.

Inhibiting a protein that helps cancer evade the immune system showed promising results during a recent study.

Presented at the 2015 American Association for Cancer Research annual meeting, the study found that regulation of the PD-L1 protein holds therapeutic promise for the treatment of several cancers, including the most common form of lung cancer. Researchers discovered how PD-L1 is regulated by the tumor suppressing gene, p53, which allows non-small cell lung cancer to grow.

There are currently therapies that inhibit PD-L1, but the study noted these treatments do not always work.

"We identified a novel mechanism by which p53 regulates PD-L1 and tumor immune evasion through control of miR-34a expression," James Welsh, MD, associate professor of Radiation Oncology, said in a press release.

The p53 gene promotes tumor growth when it mutates, which plays a role in many types of cancer. Meanwhile, the miR-34a microRNA, a gene commonly found in the lung, is frequently missing or under-expressed in tumors.

"Although clinical studies have shown promise for targeting PD-1/PD-L1 signaling in non-small cell lung cancer, little is known about how PD-L1 expression is regulated," Welsh said. "Our study showed that it's regulated by miR-34a that has been activated by p53."

The study noted that evaluating the mechanics involved in crucial signaling pathways may lead to new therapy options for patients. The researchers subsequently conducted a close examination into how the findings can be tied to existing treatments.

In an animal study, the investigational drug MRX34, which mimics miR-34's tumor-suppressing abilities, increased the CD8 cells in the immune system in combination with radiotherapy.

A clinical trial of MRX34 recently began.

"Our results suggest that miR-34a delivery combined with standard therapies, such as radiotherapy, may represent a novel therapeutic approach for lung cancer," said researcher Maria Angelica Cortez, PhD.