Hsp47 drives obesity-associated breast cancer progression by enhancing asporin deposition in adipose tissue.

Fibrosis is an important feature of adipose tissue in obese individuals; nevertheless, roles of obesity-associated extracellular matrix (ECM) deposition in breast cancer progression largely remain elusive. Here, we show that expression of Hsp47, a chaperone protein involving collagen secretion, is induced in adipose tissue from obese humans and mice. Adipocyte-specific Hsp47 deletion (Adi-KO) suppresses the high-fat diet (HFD)-induced obesity and mammary tumor progression, accompanied by a reduction in ECM deposition. Matrisome analyses lead to the identification of asporin as a new target of Hsp47 in adipose tissue. Co-immunoprecipitation results confirm that the recruitment of Hsp47 enhances asporin secretion in adipocytes. We further show that knockout of asporin suppresses HFD-induced mammary tumor growth, while exogenous of asporin partially rescues tumor growth in the decellularized mammary gland derived from Hsp47 Adi-KO mice. These results indicate that asporin at least partially mediates Hsp47 function in HFD-associated tumor progression. Digital spatial profiling (DSP) analyses show that Hsp47 depletion significantly increases the accumulation of CD8 T cells in tumor and tumor-associated adipose tissues. These results implicate that Hsp47, along with-it mediated ECM deposition, suppresses the anti-tumor immunity under HFD conditions. These findings reveal Hsp47 as a novel target for mitigating obesity-associated breast cancer progression.