Differential expansion of human breast cancer stem cells in culture
The regulation of the development of humans and cancer are closely related. Small differences in the rate of self renewal, expansion and differentiation of tissues can provide premalignant cells a selective advantage resulting in tumors. As cancers progress they may accumulate additional mutations that result in increasingly divergent behavior and opportunities of evading host defenses and therapeutic intervention. Differential killing of the early stages of cancer is difficult because of collateral damage. However, an opportunity of significantly impacting breast cancer mortality may reside in instructing early stage disease to adopt a normal tissue fate instead of progressing to invasive and metastatic stages of the disease. The demonstration that only some, and perhaps very few, of the cells of some breast cancers are responsible for both perpetuating the tumor and generating the diversity of cell types within the tumor, has defined a breast cancer stem cell as one that has the capacity to self renew but also retains the potential to differentiate to a more specialized state. These cancer stem cells present the opportunity of differentiation therapy as an alternative or adjuvant to cytoxic therapies. One proven way to identify new compounds that might direct the differentiation of cancer stem cells requires testing thousands of chemicals. To use automated methods of screening candidate chemicals that makes this strategy feasible, suitable cell lines are needed. Nearly all of the cancer cell lines currently used were isolated under conditions selective for growth but not necessarily differentiation potential. By starting with conditions that inhibit the differentiation of mouse mammary cancer stem cells and promote their self renewal in cell culture, we have improved the culture conditions necessary to isolate breast cancer stem cells that retain the potential to differentiate. We have successfully propagated mouse cancer stem cells and similar cells from human tumor surgical. We propose to extend our efforts to isolate a larger number human cancer stem cell lines from representative types of early and late stage disease for eventual use in identifying new therapeutic candidates for differentiation therapy. We will characterize these cell lines with regard to their tumorigenicity, behavior in culture, gene expression profile and sensitivity to a panel of chemical compounds. The selective propagation, amplification and characterization of human cancer stem cell lines from representative types of early and late stage disease will provide the necessary tools to use current screening methods to identify new drugs that may significantly decrease the incidence of late stage breast cancer.
Breast cancer afflicts nearly one in ten women during their lifetime. While progress is being made in certain targeted therapies, major advances in treating very early stage disease could have a great impact on preventing the progression of the disease to stages that are difficult to cure. In some cancers like colorectal cancer, stem cells are clearly the target of genetic changes that accumulate and cause the progressive loss of cellular control. In breast cancer there is increasing evidence for cancer stem cells that are responsible for the propagation of the disease but also retain the potential to differentiate to a benign fate. It is the stem cell characteristic of breast cancer stem cells that is the opportunity for the development of an alternative to cytotoxic cancer therapies. The differential killing of cancer cells with minimum impact on normal cells is the difficult requirement that leads to the well know adverse side effects of radiation and cytotoxic chemotherapy. Differentiation therapy uses the alternative strategy of inducing cancer stem cells to adopt a benign fate. However the search for chemicals and biologics that might efficiently instruct breast cancer stem cells to adopt a benign fate has been restricted by the availability of representative breast cancer stem cell cultures. Our goal is to amplify the breast cancer stem cells of representative human tumors for use in identifying compounds and gene targets that regulate their differentiation to benign cell fates. Periodic treatment of women at very early stages of disease who are at increased risk of the disease with therapeutics that instruct breast cancer stem cells to differentiate to a benign fate could greatly diminish invasive breast cancer incidence and progression. Our proposal would provide new tools to discover therapeutics for differentiation therapy. In part this proposal is facilitated by the Athena Project that coordinates clinical research activities across the multiple campuses of the University of California and by CIRM support of a Stem Cell Laboratory that provides equipment for expanding the culture of cells in low oxygen environments. Citizens of the California will benefit from this research by accelerating progress in substantially decreasing the incidence of invasive breast cancer.