Metastasis – the process where cancer spreads to other tissues – is a complex, multi-step process. Most cancer cells do not survive the journey. Those that do, and form new tumors at a different site, are the leading cause of breast cancer deaths.
In an article published in the journal Nature, BCRF investigator and a Play for P.I.N.K. Award recepient Dr. Andrew Ewald made a stunning discovery that may aid in our understanding of metastasis. The BCRF-supported study explained how cancer cells survive with the help of a protein called E-cadherin. Dr. Ewald describes how E-cadherin, which is known to suppress cancer cell invasion – the first step in metastasis – actually promotes the survival of cancer cells that do invade.
“We had a hunch that E-cadherin was playing a role in promoting metastasis, in spite of the fact that it suppresses cancer cell invasion,” Dr. Ewald explained. “This exploratory work could not have been done without BCRF support. It’s an example of how BCRF allows investigators to pursue high-risk, high-reward research and to expand into new directions.”
Dr. Ewald’s intuition was based on the observation that E-cadherin is found on the cancer cells in the primary tumor – as well as those in the metastases.
What is E-cadherin?
E-cadherin is the “glue” that helps maintain tissue structure. It is also the glue that holds tumors together. Loss of E-cadherin in cancer cells allows the cells to break away from the tumor and invade tissue around the tumor, an important first step in metastasis. Because of this, loss of E-cadherin was believed to be a requirement of metastasis.
Dr. Ewald employed sophisticated laboratory technologies to control the expression of E-cadherin in breast cancer cells and tumors. As expected, when E-cadherin was suppressed, tumor cells spread from all borders of the tumor. His experiments went on to show, however, that those tumor cells were less likely to survive afterwards.
Conversely, while the presence of E-cadherin suppressed the cell spreading, it did not completely eliminate it. Furthermore, those cells that did spread, survived and formed new tumors. His experiments further showed that E-cadherin blocked signals that caused tumor cells to die, thereby promoting cancer cell survival and metastasis.
Why is this finding important?
The most common form of invasive breast cancer – invasive ductal carcinoma – retains E-cadherin even when it has metastasized. Understanding how E-cadherin works to promote metastasis could lead to targeted treatment and prevention strategies with the potential to dramatically reduce deaths from metastasis.
What’s next?
Dr. Ewald is not stopping here. He’s now exploring the role of E-cadherin in other aspects of metastasis such as tumor cell dormancy – a state where tumor cells lie sleeping undetectable by current screening methods. These tumor cells can wake up, sometimes many years after treatment has ended, and form a new tumor.
“Our future research aims to understand how to target the survival signals related to E-cadherin and prevent metastases from forming, thereby saving patients’ lives,” he says.
Metastasis is the leading cause of breast cancer deaths. This year BCRF is committing $27 million, more than one-third of our annual research investment, in projects aimed at improving outcomes for patients with metastatic breast cancer and developing strategies to prevent it.
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