Abstract 2143: Anti-TGFβ antibody treatment rescues doxorubicin- mediated bone loss in preclinical osteolytic breast cancer metastasis models.

Anthracyclines (doxorubicin) are one of the most effective and widely used chemotherapeutic agent for the treatment of several cancer types, including early stage and metastatic breast cancer. However, doxorubicin has been known to cause long-term bone damage and growth defects in patients with childhood cancers, which was also confirmed by several preclinical studies. This raises concern regarding the usage of doxorubicin for the treatment of patients with metastatic breast cancer who are already at increased risk of osteolytic bone damage leading to severe bone loss due to. A number of clinical and preclinical studies have indicated that doxorubicin causes both long term and short term bone damages by lowering bone mineral density, increasing bone loss and may disrupt bone homeostasis by directly affecting bone marrow stem cells, however, the underlying mechanism is poorly understood. We have previously reported that treatment with doxorubicin increases circulating levels of TGFβ, a cytokine which has been implicated in the increase in osteoclast differentiation and survival, suppression of osteoblast differentiation and has been associated with advancement of breast cancer to bone metastasis. We hypothesize, breast cancer patients undergoing doxorubicin treatment will experience accelerated bone loss due to an increase in serum TGFβ levels and blocking TGFβ will rescue this bone loss, at least partially. We have tested the efficacy of anti-TGFβ antibody 1D11, in blocking doxorubicin-mediated bone damage in cardiac injection and orthotopic models of breast cancer to bone metastasis. X-ray image analysis revealed that doxorubicin treatment resulted in an eightfold increase in osteolytic lesion areas (P=0.002) and microCT analysis has shown almost 50% decrease in BV/TV (P=0.0005), in a preclinical murine model metastatic breast cancer. Doxorubicin treatment has also decreased BV/TV in non-tumor bearing animals, suggesting a direct damaging effect of this agent to bone at the sites which are not affected by cancer infestation. As anticipated, treatment with anti-TGFβ antibody 1D11 was able to rescue doxorubicin-mediated bone loss in all three preclinical models tested. At the cellular level, direct effect of doxorubicin treatment on the bone marrow microenvironment included decreased osteoblast survival and reduced mineralized matrix formation and increased osteoclast formation, thereby affecting both bone formation and bone resorption. Taken together, we conclude that, doxorubicin therapy decreases bone formation and increases bone resorption causing additional bone loss in patients with osteolytic bone disease and an anti-TGFβ therapy may be affective in controlling that bone loss. Citation Format: Tapasi Rana, Anwesa Chakrabarti, Michael Freeman, Swati Biswas. Anti-TGFβ antibody treatment rescues doxorubicin- mediated bone loss in preclinical osteolytic breast cancer metastasis models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2143. doi:10.1158/1538-7445.AM2013-2143