Activation of EGFR signaling in CD44 positive cells promotes aggressive behavior and progression of breast cancer.

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #5056 Ductal carcinoma in situ (DCIS) of the breast is a pre-invasive tumor stage with a hallmark of filling the breast ducts with tumor cells. At present, the mechanism of progression of DCIS to invasive breast cancer is poorly defined. Understanding the molecular events controlling this process should allow for the development of biomarkers for personalized medicine. Increasing evidence suggests that breast cancer is initiated from a few transformed cells that are capable of self-renewal, which is the feature of stem cells. The presence of cancer stem cells in the CD44+/CD24- cells is demonstrated in human breast cancer tissues. We found that 3 to 4% of cells in a human breast cancer cell line, MCF-10DCIS.com (MCF-10DCIS), strongly express CD44. Although MCF-10DCIS cells give rise to DCIS lesions at the early stage which progresses to invasive tumors at a later stage after injection into nude mice, injection of 500 to 5000 of the CD44+ DCIS cells produced predominantly invasive tumors in a short time. However, the CD44 - cells did not produce any tumors even at 100 fold higher cell numbers. We have previously shown that EGFR activated HIF-1α upregulates the anti-apoptotic protein survivin. Our current results show that EGFR-activated HIF-1α plays an important role in the aggressive behavior of CD44+ cells and promotes DCIS progression. Several studies demonstrated that HIF-1α also increases the levels of the genes related to invasion and metastasis, such as uPAR and CXCR4. Histological examination of MCF-10DCIS tumor xenografts shows high levels of CD44, EGFR, HIF-1α and survivin are co-localized at the macroinvasive areas and basal layer of DCIS lesions. Furthermore, invaisve tumor cells are heterogeneous with a high percentage of EGFR+, CD44+, and Her-2 - cells and a low percentage of CD44+, EGFR- and Her-2 + cells. Therefore, this orthotopic model provides an excellent tumor model for identifying biomarkers that promote DCIS invasion. Recent studies have shown that breast cancers with a triple negative phenotype (ER, PR- and Her-2-) are very aggressive and significant less numbers of the cancer patients are found in the DCIS stage compared to other breast cancer types. A high percentage of triple negative cancer tissues also expresses EGFR. We found that CD44 and survivin are expressed in 60 to 70% of the triple negative invasive cancer and in 100% of triple negative DCIS tissues. CD44 and EGFR were detected in triple negative DCIS tumor cells located at the luminal, basal and microinvasive DCIS areas, while in the ER+ DCIS type, CD44 and EGFR are found in the tumor cells at the basal layer and microinvasive foci, suggesting the role of CD44 +, EGFR and survivin expressing tumor cells in progression of DCIS to invasive breast cancer. Since MCF-10DCIS cells are negative for ER and PR, this tumor model provides a great opportunity to investigate signal pathways for triple negative breast cancer as well as the development of novel therapeutics for the treatment of this aggressive cancer type. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5056.