According to the Centers for Disease Control, breast cancer is the second most prevalent type of cancer diagnosed in American women, topped only by skin cancer. In 2012, there were more than 122 cases of breast cancer in the U.S. per 100,000 population.
Needless to say, the amount of research in this area has been enormous, and it has been successful to a certain extent. One big hurdle is that there are several types of breast cancer.
One type, which is called hormone-dependent, is promoted by hormones such as estrogen or progesterone, and can be treated by drugs that block the receptors for these hormones on cancer cells.
A second type, called HER2-positive, has cells with receptors for a naturally-occurring protein called epidermal growth factor — and this can be treated by a drug called Herceptin.
Yet a third type of breast cancer has neither the hormone receptors nor the growth factor receptors — and thus is called "triple negative breast cancer" or TNBC. This is the most difficult type to treat, since there has been no targeted therapy available for it. Only about 30 percent of patients with TNBC have positive responses to chemotherapy. Recent research has, however, provided some clues about how this more difficult form of breast cancer might be treated.
Working with colleagues from several institutions, Drs Justin M. Balko and Luis J. Schwarz from Genentech in San Francisco, examined breast tumor samples from 111 patients at a Peruvian hospital in Lima, and mouse models of TNBC to determine which gene or genes might be targets for TNBC therapy.
In particular they examined two gene products — the proteins Janus kinase 1 and 2 (JAK 1 and 2), which are known to be involved in cancer progression. They found that JAK2 was expressed to a greater than normal extent in TNBC tumors. Using the mouse model of this type of breast tumor, the researchers found that inhibiting JAK2, without inhibiting JAK1 enabled a specific chemotherapy (the drug ruxolitinib) to work. When both JAK1 and JAK2 were inhibited, the drug didn't work.
Although this work is preliminary, it strongly suggests that drugs that target JAK2 specifically will be more effective in treating TNBC than broader spectrum drugs. Now the search for these more specific treatments must be undertaken.
Studies of this type should remind us that "cancer" is multifaceted — and there is no one cure for all the many types of the disease.