Poster Presentation 32nd Lorne Cancer 2020

BMP4 inhibits breast cancer metastasis independent of tumour SMAD4 expression (#138)

Lap Hing Chi 1 2 , Allan D Burrows 1 2 , Robin L Anderson 1 2 3 4
  1. Translational Breast Cancer Programme, Olivia Newton-John Cancer Research Institute, Heidelberg, VIC, Australia
  2. School of Cancer Medicine, La Trobe University, Bundoora, VIC, Australia
  3. Department of Clinical Pathology, the University of Melbourne, Parkville, VIC, Australia
  4. Sir Peter MacCallum Department of Oncology, the University of Melbourne, Parkville, VIC, Australia

Localised breast cancer is largely curable, however, due to a lack of effective therapies, patients with tumours that have spread (metastasised) have a poor 5-year survival rate at 27%. We have previously identified an anti-metastatic protein, bone morphogenetic protein-4 (BMP4)1. Aggressive breast cancer cells lack BMP4 proteins.

However, BMP4 can promote the progression of colorectal and pancreatic cancers2, where a critical mediator of canonical BMP signalling, mothers against decapentaplegic-4 (SMAD4), is frequently lost3. We aim to understand how this disparity has arisen, so that patients who will benefit from BMP4 can be distinguished from those who may have an adverse response. We hypothesised that the anti-metastatic effect of BMP4 is dependent on SMAD4, and BMP4 induces detrimental effects in the absence of SMAD44.

In human breast cancer MDA-MB-231-HM cells and mouse mammary cancer 4T1.2 cells, SMAD4 was reduced with short hairpin RNA or knockded out. In SMAD4-null MDA-MB-468 cells, SMAD4 was ectopically restored. BMP4 was then ectopically expressed in these metastatic lines. We confirmed that the induction of canonical BMP4 target genes (Id1, Id2 and Smad7) is dependent on SMAD4 (P<0.05).

Orthotopic tumours were established via injection into the 4th mammary fat pad of mice. Tumours were monitored and resected at 400 mm3, and subsequent development of metastasis was characterised. Consistent with our hypothesis, BMP4 accelerated the growth of tumours with low or no SMAD4 expression (P<0.05). This was potentially due to increased angiogenesis, and no difference in the proportion of Ki67+ tumour cells was found (P>0.4). This suggests that BMP4 agonists are not an appropriate therapy for patients whose tumours express low levels of SMAD4.

Surprisingly, BMP4 markedly inhibited metastasis regardless of SMAD4 expression in tumours (P<0.01), indicating that downstream signalling can be targeted to reduce cancer spread. We are currently investigating mediators of this anti-metastatic effect and testing small molecules that activate BMP4 signalling as a potential therapy to treat metastatic breast cancer.

  1. Cao, Y., C. Y. Slaney, B. N. Bidwell, B. S. Parker, C. N. Johnstone, J. Rautela, B. L. Eckhardtet al., 2014. “BMP4 Inhibits Breast Cancer Metastasis by Blocking Myeloid-Derived Suppressor Cell Activity.” Cancer Research 74 (18): 5091–5102.
  2. Zhang, L., Y. Ye, X. Long, P. Xiao, X. Ren, and J. Yu. 2016. “BMP Signaling and Its Paradoxical Effects in Tumorigenesis and Dissemination.” Oncotarget 7 (47): 78206–78218.
  3. Sanchez-Vega, F., M. Mina, J. Armenia, W. K. Chatila, A. Luna, K. C. La, S. Dimitriadoy, et al. 2018. “Oncogenic Signaling Pathways in the Cancer Genome Atlas.” Cell 173 (2): 321.
  4. Chi, L.H., A. D. Burrows, and R. L. Anderson. 2019. "Bone morphogenetic protein signaling in breast cancer progression." Growth Factors 37:1-2, 12-28.