Isolation of Cancer Precursors from Normal Human Breasts
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: My mentor’s lab (Dr. Thea Tlsty, UCSF) is focused on understanding the earliest events of breast cancer development, specifically those that can cause normal cells to become malignant. We employ a cell culture model system of growing normal human mammary epithelial cells (HMEC) to identify early transformation. From normal HMEC, we have identified a rare population of cells that have abnormal growth control and malignant characteristics; we refer to these cells as “variant” HMEC (vHMEC). vHMEC do not express a tumor suppressor gene, called p16INK4a, due to hypermethylation of the p16INK4a promoter. The p16INK4 gene, which produces a physiological inhibitor of the cyclin D-CDK4 complex, is considered as an important tumor suppressor gene. Thus, alterations in p16INK4 functions, or gene regulation, are thought to lead to a variety of changes associated with early tumor formation. For example, the loss of p16INK4a is sufficient to induce centrosomal abnormalities leading to genomic instability in the vHMEC. Also, vHMEC overexpress cyclooxygenase-2 (COX-2), which can provide vHMEC with the ability to undergo angiogenesis and acquire invasive properties. Our lab has also shown that there are cells with hypermethylated p16INK4a promoter (i.e., an epigenetic change) and COX-2 overexpression in normal breast tissues from diseasefree women.
 
 
 
 
 
 
 
 Given these observations, we hypothesize that vHMEC exist in normal mammary tissue, and that these cells are likely candidates to be breast cancer precursors in vivo.
 
 To test this hypothesis, I have identified cell surface markers (CD73+CD90-) that facilitated the prospective isolation of a subpopulation of cells from normal mammary reduction tissues having extended growth characteristics similar to that of cultured
 
 
 
 
 
 
 
 vHMEC. Therefore, my overall aims are to:
 
 
 
 1) test whether the expression of p16INK4a is silenced in the CD73+CD90-subpopulation;
 
 
 
 2) determine the cell of origin of the CD73+CD90- subpopulation in the mammarytissue; and
 
 
 
 3) assess whether the frequency of CD73+CD90- cells is correlated with humanbreast cancer progression.
 
 
 
 
 
 
 
 These aims will be addressed with combinations of techniques from cell biology (fluorescent-activated cell sorting, immunocytochemistry, confocal microscopy, and tissue culturing of primary mammary cells), molecular biology (immunoblot analysis and methylation specific PCR), and clinical pathology (immunohistochemistry). Since we believe that cells with early malignant characteristics exist in normal breast tissues of health women, we hypothesize that all women have the potential to develop breast cancer due to activation and progression of these pre-malignant cells. We may be able to use markers, CD73 and CD90, to detect these pre-malignant cells in vivo. These markers may also be important therapeutic targets for the elimination of these pre-malignant cells.