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.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
This combination therapy may have translational value for patients with TNBC and improve therapeutic response for this aggressive form of breast cancer.
Christina N
CN
Bennett
Christine C
CC
Tomlinson
Aleksandra M
AM
Michalowski
Isabel M
IM
Chu
Dror
D
Luger
Lara R
LR
Mittereder
Olga
O
Aprelikova
James
J
Shou
Helen
H
Piwinica-Worms
Natasha J
NJ
Caplen
Melinda G
MG
Hollingshead
Jeffrey E
JE
Green
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000071877:Checkpoint Kinase 1; D016000:Cluster Analysis; D004249:DNA Damage / Q000187:drug effects; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020128:Inhibitory Concentration 50; D051379:Mice; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D016160:Retinoblastoma Protein / Q000378:metabolism; D012262:Ribonucleoside Diphosphate Reductase / Q000037:antagonists & inhibitors / Q000235:genetics; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D047368:Tumor Burden / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D003841:Deoxycytidine; C054852:7-hydroxystaurosporine; D012264:Ribonucleotide Reductases; C093713:ribonucleotide reductase M2; C475286:RRM1 protein, human; D012262:Ribonucleoside Diphosphate Reductase; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse; D019311:Staurosporine; D000093542:Gemcitabine