Scientists from King's College London have found a way to boost the immune system to help it fight back against cancer.

The advance involves the targeting of the enzyme Heme Oxygenase-1 (HO-1), which is active in a variety of cancers (Clin Cancer Res 2018; doi:10.1158/1078-0432.CCR-17-2587). HO-1 can promote the growth of tumors by preventing the immune system from effectively attacking cancer cells.

Scientists have shown in the laboratory that chemotherapy can trigger immune responses against cancer, but the King's team have found that these responses are suppressed by macrophages, which reside in the tumor and produce the HO-1 enzyme.

Researchers found that, in preclinical trials, a drug being tested for the treatment of jaundice (SnMP), effectively prevented the suppression of the immune response stimulated by chemotherapy, allowing the immune system to efficiently attack the cancer.

The authors, James Arnold, PhD, and James Spicer, PhD, from King's College London, are working with Cancer Research UK to develop these observations into a first-in-human clinical trial for this combination treatment.

"In lab tests, SnMP plus chemotherapy combination compared favorably to the current checkpoint inhibitor therapy used in the clinic, suggesting there could be significant scope for targeting HO-1 in patients," Arnold noted.

"The full benefit to patients will be better understood once we move these exciting observations into clinical trials. However, in our preclinical models, when combined with chemotherapy, the efficacy of tumor control was comparable to that of the gold-standard immunotherapy currently being used in the clinic."