To summarize the paper: some gastric cancer models are sensitive to all-trans retinoic acid (ATRA). ATRA is an active metabolite of vitamin A, and is already used clinically to treat some hematological cancers. The researchers tested the compound at several concentrations on a number of gastric cancer cell lines, where they show moderate to significant reductions in growth (from 30% to 60% reduction). Next, they tested ATRA on xenografted tumor cells on immuno-compromised mice, where they also show a reduction in tumor size. They hypothesize that ATRA exerts its effects through immuno-modulation.
Firstly, very cool, and congrats to the authors - I definitely see first evidence of the potential of ATRA to treat gastric cancer.
While I might have misunderstood some parts, I do think there are some elements that warrant precautions here: 1. we can see that some of the untreated mice also show reduction in tumor size, albeit less significant, meaning there could be issues with the cells or protocol, 2. I find it hard to conclude anything about ATRA exerting its effect through the immune system in a study of cell models and immuno-compromised mice.
Nevertheless, given the frankly poor prognosis of gastric cancer (many patients in early stages of the disease now get their stomach removed, and more often than not, these tumors metastize aggressively), and the well known safety profile of ATRA, I think the study is very welcome, and should warrant further investigation. Given the hypothesized mechanism of action, I think testing on humanized mice, using more and more distinct patient-derived cells would bring convincing proof to move ATRA forward to clinical trials.