Possible Biomarker to Identify Who Would Benefit from Immunotherapy

While immunotherapy has made a big impact on cancer treatment, the fact remains that only about a quarter of patients respond to these treatments.

“This begs the question: Why does it work in those patients? We don’t understand the mechanism at work very well,” says Weiping Zou, M.D., Ph.D., the Charles B. de Nancrede Professor of Surgery, Immunology and Biology at the University of Michigan.

Zou and colleagues offer a clue in a new study published in the Journal of Clinical Investigation.

Researchers studied mice with colon cancer, ovarian cancer, melanoma and lung cancer to understand how expression of the protein PD-L1 affects response to its blockade. This is a key target of immunotherapy drugs.

The researchers found a key link in the antigen-presenting cells — macrophages and dendritic cells found in the tumor microenvironment and the nearby lymph nodes.

“The antigen-presenting cells are the real guide. PD-L1 expression in these cells is responsible for response to therapy. This reshapes our understanding of checkpoint blockade therapies and the biomarkers that may predict clinical efficacy,” Zou says.

Interestingly, his team first pinpointed the human cancer associated antigen-presenting cells in 2003, in a paper in Nature Medicine. That paper demonstrated that dendritic cells express PD-L1 and that blockade of PD-L1 on antigen-presenting cells causes tumor regression in model systems. But this was when immunotherapy research was in its early stages, before today’s therapies were introduced.

When the Food and Drug Administration approved immunotherapy drugs designed to block PD-L1 and PD-1, the indication said patients’ tumors must express PD-L1. But these therapies have worked in patients whose tumor cells did not express PD-L1. And they have failed in patients whose tumor cells do.

“Clearly, that’s not a reliable biomarker,” Zou says.

In the new study, researchers examined tissue samples from melanoma and ovarian cancer patients treated with immunotherapies. In both cancers, researchers found a link between the percentage of antigen-presenting cells expressing PD-L1 and an objective clinical response to treatment.

Currently, tumor tissue is tested broadly for PD-L1 expression. Without looking at individual cells within the tissue, it could mask the true source of PD-L1 expression. This study suggests that a more complicated analysis looking for additional markers might be more informative in guiding treatment.

This article has been republished from materials provided by the University of Michigan. Note: material may have been edited for length and content. For further information, please contact the cited source.

Reference
Lin H, Wei S, Hurt EM, Green MD, Zhao L, Vatan L, Szeliga W, Herbst R, Harms PW, Fecher LA, Vats P, Chinnaiyan AM, Lao CD, Lawrence TS, Wicha M, Hamanishi J, Mandai M, Kryczek I, Zou W. Host expression of PD-L1 determines efficacy of PD-L1 pathway blockade-mediated tumor regression. J Clin Invest. 2018 Jan 16. pii:96113. doi: 10.1172/JCI96113. [Epub ahead of print] PubMed PMID: 29337305.