Cross-species genomic and functional analyses identify a combination therapy using a CHK1 inhibitor and a ribonucleotide reductase inhibitor to treat triple-negative breast cancer

• Published in: Breast cancer research : BCR Vol. 14; no. 4; p. R109
• Main Authors: Bennett, Christina N, Tomlinson, Christine C, Michalowski, Aleksandra M, Chu, Isabel M, Luger, Dror, Mittereder, Lara R, Aprelikova, Olga, Shou, James, Piwinica-Worms, Helen, Caplen, Natasha J, Hollingshead, Melinda G, Green, Jeffrey E
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 19-07-2012; BioMed Central
• Subjects: Analysis; Animals; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Breast cancer; Cancer; Care and treatment; Cell Cycle - drug effects; Cell Line, Tumor; Cell Proliferation; Checkpoint Kinase 1; Cluster Analysis; Deoxycytidine - analogs & derivatives; Deoxycytidine - pharmacology; Disease Models, Animal; DNA damage; DNA Damage - drug effects; Dose-Response Relationship, Drug; Drug Synergism; Female; Gene Expression Profiling - methods; Gene Expression Regulation, Neoplastic; Genes; Genetic aspects; Genetic research; Humans; Inhibitory Concentration 50; Mice; Patient outcomes; Prognosis; Protein Kinase Inhibitors - pharmacology; Protein Kinases - genetics; Protein Kinases - metabolism; Retinoblastoma Protein - metabolism; Ribonucleoside Diphosphate Reductase - antagonists & inhibitors; Ribonucleoside Diphosphate Reductase - genetics; Ribonucleotide Reductases - antagonists & inhibitors; RNA Interference; RNA, Small Interfering - genetics; Staurosporine - analogs & derivatives; Staurosporine - pharmacology; Triple Negative Breast Neoplasms - drug therapy; Triple Negative Breast Neoplasms - genetics; Triple Negative Breast Neoplasms - metabolism; Triple Negative Breast Neoplasms - pathology; Tumor Burden - drug effects; Tumor Suppressor Protein p53 - metabolism; Tumor Suppressor Proteins - antagonists & inhibitors; Tumor Suppressor Proteins - genetics; Xenograft Model Antitumor Assays
• ISSN: 1465-542X; 1465-5411; 1465-542X
• DOI: 10.1186/bcr3230

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that is diagnosed in approximately 15% of all human breast cancer (BrCa) patients. Currently, no targeted therapies exist for this subtype of BrCa and prognosis remains poor. Our laboratory has previously identified a proliferation/DNA repair/cell cycle gene signature (Tag signature) that is characteristic of human TNBC. We hypothesize that targeting the dysregulated biological networks in the Tag gene signature will lead to the identification of improved combination therapies for TNBC.
Cross-species genomic analysis was used to identify human breast cancer cell lines that express the Tag signature. Knock-down of the up-regulated genes in the Tag signature by siRNA identified several genes that are critical for TNBC cell growth. Small molecule inhibitors to two of these genes were analyzed, alone and in combination, for their effects on cell proliferation, cell cycle, and apoptosis in vitro and tumor growth in vivo. Synergy between the two drugs was analyzed by the Chou-Talalay method.
A custom siRNA screen was used to identify targets within the Tag signature that are critical for growth of TNBC cells. Ribonucleotide reductase 1 and 2 (RRM1 and 2) and checkpoint kinase 1 (CHK1) were found to be critical targets for TNBC cell survival. Combination therapy, to simultaneously attenuate cell cycle checkpoint control through inhibition of CHK1 while inducing DNA damage with gemcitabine, improved therapeutic efficacy in vitro and in xenograft models of TNBC.
This combination therapy may have translational value for patients with TNBC and improve therapeutic response for this aggressive form of breast cancer.