A study by Massachusetts General Hospital has identified a previously unknown immune system mechanism underlying breast cancer prevention, creating potential for future immunotherapy.
The study found T helper 2 cells (Th2)—a type of regulatory immune cell—can “directly block spontaneous breast carcinogenesis [from becoming cancerous]” by regulating cancers cell to become unable to differentiate, according to lead author Dr. Shawn Demehri.
Though previous research showed that Th2 took part in cancer growth and proliferation rather than prevention, Demehri’s 2016 work showed that a specific messenger molecule in the immune system, called thymic stromal lymphopoietin (TSLP) is able to activate Th2 attack against breast cancer cells.
The study that Th2 cells could force the breast cancer cells to grow into terminal proliferation stages; a stage where cells would no longer be able to divide and proliferate, leading to eventual cell death as the cell ages.
“The Th2 cells force the cancer cells to go back to their original programming of making a breast gland that has no potential for growth or metastasis,” he said.
Once the Th2 cells are stimulated by the TSLP to enter breast cancer tumor masses, they will also release chemical messages that directly act on tumor cells, changing the tumor cells from high-grade to low-grade breast cancer cells.
High-grade cancer cells have a high risk of proliferation and metastasis—being able to spread to other sites to cause secondary tumors elsewhere—whereas low-grade tumors resemble normal cells and are slower growing and less likely to spread to other places, thereby making them easier to treat.
The breast cancer cells are induced to become low-grade cells. Though may look similar to normal breast gland cells, they are not entirely the same, instead forming tissues that are lumpy to the touch.
Th2 cells are “upstream activators” of the adaptive immune response, meaning that they regulate and control immune response against a targeted pathogen.
This makes them better targets for immunotherapy as compared to conventional immunotherapy that targeted the cytotoxic T cells (Tc) that engage in close combat with cancer cells rather than regulating the entire process, as Th2 cells can regulate the response of the Tc cells, mounting a more “robust antitumor immune response.”
By Marina Zhang
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