Cancer cells rely on certain survival signals to stay alive, and the new drugs, IAP antagonists, work by blocking these signals. However, when, in mice, they were targeting the same protein that makes tumours vulnerable to death, the researchers found that this also over-activated cells, called osteoclasts, which tear down bone and can lead to bone wellness diseases such as osteoporosis.
According to senior author Deborah V. Novack, MD, PhD, associate professor of medicine, ‘These investigational drugs are getting broad attention right now because they seem to be very effective against primary tumours. There is also excitement because until now, these drugs have not appeared to have major side effects.’
Novack’s team tested bisphosphonates in these mice. These long-established drugs are known to inhibit osteoclasts and treat osteoporosis, and Novack says, ‘We found that bisphosphonate treatment protected bone from the negative effects of these drugs. While bisphosphonates are common for breast cancer patients, they’re not, for example, commonly given to lung cancer patients. But since IAP antagonists are now in lung cancer trials, we’re saying doctors may want to consider bisphosphonate treatment for lung cancer or other cancer patients receiving these drugs. Or at least closely monitor the bone status.’
As a result of the research, which is published in Cancer Discovery, Novack urged that oncologists need to think about protecting bone in patients taking IAP antagonists, even if that patient’s type of cancer doesn’t typically spread to bone. This could make a huge impact on the wellness of many people, as there are currently numerous IAP antagonists in early clinical trials against breast, lung, pancreatic, ovarian, prostate, liver, skin and blood cancers.
Novack explained, ‘For many of these cancers, doctors are not watching bone. Osteoporosis is not the biggest concern when treating cancer, but if they’re not doing bone scans, they may miss a cancer spreading to bone.’ Staff scientist and the paper’s first author, Chang Yang, MD, PhD, added, ‘These trials do not necessarily look for long-term effects of the drugs. If the cancer is going to metastasize to bone, it may take six months to two years to see that outcome. This may not be seen during the clinical trial.’