ABSTRACT
Intratumor heterogeneity is a major clinical problem because tumor cell subtypes display variable sensitivity to therapeutics and may play different roles in progression. We previously characterized 2 cell populations in human breast tumors with distinct properties: CD44+CD24- cells that have stem cell-like characteristics, and CD44-CD24+ cells that resemble more differentiated breast cancer cells. Here we identified 15 genes required for cell growth or proliferation in CD44+CD24- human breast cancer cells in a large-scale loss-of-function screen and found that inhibition of several of these (IL6, PTGIS, HAS1, CXCL3, and PFKFB3) reduced Stat3 activation. We found that the IL-6/JAK2/Stat3 pathway was preferentially active in CD44+CD24- breast cancer cells compared with other tumor cell types, and inhibition of JAK2 decreased their number and blocked growth of xenografts. Our results highlight the differences between distinct breast cancer cell types and identify targets such as JAK2 and Stat3 that may lead to more specific and effective breast cancer therapies.
Subject(s)
Breast Neoplasms/pathology , CD24 Antigen/metabolism , Hyaluronan Receptors/metabolism , Janus Kinase 2/metabolism , STAT3 Transcription Factor/metabolism , Signal Transduction/physiology , Stem Cells/physiology , Animals , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , CD24 Antigen/genetics , Cell Line, Tumor , Female , Gene Expression Profiling , Humans , Hyaluronan Receptors/genetics , Interleukin-6/genetics , Interleukin-6/metabolism , Janus Kinase 2/antagonists & inhibitors , Janus Kinase 2/genetics , Mice , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , STAT3 Transcription Factor/genetics , Stem Cells/cytology , Transplantation, HeterologousABSTRACT
The karyotypic chaos exhibited by human epithelial cancers complicates efforts to identify mutations critical for malignant transformation. Here we integrate complementary genomic approaches to identify human oncogenes. We show that activation of the ERK and phosphatidylinositol 3-kinase (PI3K) signaling pathways cooperate to transform human cells. Using a library of activated kinases, we identify several kinases that replace PI3K signaling and render cells tumorigenic. Whole genome structural analyses reveal that one of these kinases, IKBKE (IKKepsilon), is amplified and overexpressed in breast cancer cell lines and patient-derived tumors. Suppression of IKKepsilon expression in breast cancer cell lines that harbor IKBKE amplifications induces cell death. IKKepsilon activates the nuclear factor-kappaB (NF-kappaB) pathway in both cell lines and breast cancers. These observations suggest a mechanism for NF-kappaB activation in breast cancer, implicate the NF-kappaB pathway as a downstream mediator of PI3K, and provide a framework for integrated genomic approaches in oncogene discovery.
