Controlling the microenvironmental pH to affect breast precancer invasiveness

A long-standing and central challenge in cancer research is preventing the progression of early precancer lesions to invasive and metastatic cancer. The breast precancer stage is termed ductal carcinoma in situ (DCIS). In DCIS, the epithelial cells of the milk duct become cancerous but are still confined in the duct lumen. DCIS will not necessarily develop into invasive breast cancer and theoretically does not always require treatment. Approximately 40% of DCIS cases, however, do develop into invasive ductal carcinoma (IDC), in which the cancer cells penetrate the surrounding tissue and lymph nodes and may metastasize to distant organs. The genetic events that lead to the progression from precancer to invasive cancer are yet unknown. Accumulating evidence suggests that the extracellular matrix (ECM) can affect tumor progression from precancer to invasive and that increased acidity might contribute to that progression. Controlling the ECM pH may allow us to decrease the invasiveness of the precancer cells. We study how the tumor microenvironment`s pH affects the invasiveness of breast precancer cells in an in vitro 3D tumor model. Our model consists of multicellular precancer DCIS spheroids that develop in suspension. We manipulate the microenvironmental pH and control the ECM acidity in two ways: by changing the pH of the culture media and by using liposomes that contain alkaline solution. To measure the local acidity changes in the spheroids in response to manipulating the ECM pH, we use live-cell imaging confocal microscopy with a pH probe to distinguish between adjacent regions of different acidity spatially. We investigate the precancer cell phenotype as a response to changes in the ECM pH to detect markers for cell alteration from DCIS to IDC. This methodology allows us to link local ECM pH changes to the invasiveness of precancer cells. Potentially, this approach may affect disease progression by manipulating the ECM pH.