For general info: A likely target or trigger of breast cancer is the phosphorylation of the enzyme tyrosine kinase, as seen here:


A cascade of events through phosphorylation of intracellular proteins that ultimately transmit ("transduce") the extracellular signal to the nucleus, causing changes in gene expression. Many RTKs are involved in oncogenesis, either by gene mutation, or chromosome translocation,[14] or simply by over-expression. In every case, the result is a hyper-active kinase, that confers an aberrant, ligand-independent, non-regulated growth stimulus to the cancer cells.

tyrosine kinase is an enzyme that can transfer a phosphate group from ATPto a protein in a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases are a subclass of protein kinase.
https://en.m.wikipedia.org/wiki/Tyrosine_kinase