Immune cells the missing ingredient in new bladder cancer treatment

New research offers a possible explanation for why a new type of cancer treatment hasn’t been working as expected against bladder cancer.

In this study, a team of scientists from H3 Biomedicine headed by Dr Ping Zhu, found that some invasive bladder cancer tumours block the immune cells from accessing it by activating a cell signalling pathway called the peroxisome proliferator-activated receptor gamma (PPAR-γ) pathway.

The study finds that checkpoint immunotherapy, which is designed to activate the immune system, is not effective on some bladder cancers because there are no immune cells in the tumours. The finding explains what is happening at a cellular level to prevent the immune cells from getting into the tumour and points scientists in the right direction towards developing a combination therapy that could work.

Bladder cancer is the fifth most common cancer in Canada. There is only one line of chemotherapy available, cisplatin-based therapy, for invasive tumours. Once cancers become resistant, only checkpoint immunotherapy is approved as second-line treatment.

Atezolizumab is a checkpoint immunotherapy drug that strengthens the body’s immune response and recently became the first new bladder cancer drug to be approved in more than twenty years. Initial results were very promising but subsequent clinical trials have shown that only one in five patients showed an objective response to treatment. The reason for that has puzzled researchers, until now.

“The most efficient way to combat a cancer would be to have the immune system take care of it itself. This is ultimately what we want to achieve,” he said.