Breast Cancer (BC) initiation and metastasis is accompanied by extensive extracellular matrix (ECM) deposition and remodelling. Tissue fibrosis is commonly found in aggressive cancers such as the triple negative breast cancer (TNBC) subtype, and can limit drug delivery to the tumour fuelling treatment resistance, as well as enabling cancer cell invasion and metastasis. In TNBC, the predominant treatment strategy is systemic taxane-based chemotherapy; however, this approach often shows only modest efficacy and can further advance the fibrotic response. The use of anti-fibrotic therapies to target the ECM has therefore gained significant momentum for improving therapy efficacy and extending patient survival.
Our laboratory and others have shown that targeting fibrosis and the Rho-associated protein kinase 1/2 (ROCK1/2) signalling pathway in a range of cancer types can impair cancer spread and improve response to standard-of-care chemotherapy; however, poor specificity and drug toxicity of ROCK inhibitors has limited successful translation into the clinic. Here, we assess the anti-fibrotic efficacy of a novel, highly specific and clinically relevant ROCK2 inhibitor (ROCK2i).
Using publicly available BC patient cohorts, we show that high ROCK2 expression significantly correlates with poorer patient survival. Furthermore, single-cell RNA sequencing data reveals increased expression of ROCK2 in cancer-associated fibroblasts (CAFs), a key stromal cell type involved in ECM production and remodelling. We also show in organotypic contraction assays that ROCK2i decreases the ability of CAFs to contract a collagen matrix. Here second harmonic generation (SHG) and collagen birefringence imaging reveals that there is a significant decrease in collagen I cross-linking and fibrillar collagen I/III maturation, respectively in ROCK2i treated matrices.
In future, this project will interrogate the role that ROCK2 plays in BC progression, invasion and metastasis in vivo. Here, we will use innovative intravital imaging techniques, including optical imaging windows, which will be placed above the live mammary tumour or lung to track tumour growth or metastasis, respectively. Finally, we will use patient derived xenografts to assess if ROCK2i can be used in a human personalised medicine setting to improve survival in this deadly disease.