Phosphoproteomic Analysis Identifies Focal Adhesion Kinase 2 (FAK2) as a Potential Therapeutic Target for Tamoxifen Resistance in Breast Cancer.
Tamoxifen, an estrogen receptor-α (ER) antagonist, is an important agent for the treatment of breast cancer. However, this therapy is complicated by the fact that a substantial number of patients exhibit either de novo or acquired resistance. To characterize the signaling mechanisms underlying this resistance, we treated the MCF7 breast cancer cell line with tamoxifen for over six months and showed that this cell line acquired resistance to tamoxifen in vitro and in vivo. We performed SILAC-based quantitative phosphoproteomic profiling on the tamoxifen resistant and vehicle-treated sensitive cell lines to quantify the phosphorylation alterations associated with tamoxifen resistance. From >5600 unique phosphopeptides identified, 1529 peptides exhibited hyperphosphorylation and 409 peptides showed hypophosphorylation in the tamoxifen resistant cells. Gene set enrichment analysis revealed that focal adhesion pathway was one of the most enriched signaling pathways activated in tamoxifen resistant cells. Significantly, we showed that the focal adhesion kinase FAK2 was not only hyperphosphorylated but also transcriptionally up-regulated in tamoxifen resistant cells. FAK2 suppression by specific siRNA knockdown or a small molecule inhibitor repressed cellular proliferation in vitro and tumor formation in vivo. More importantly, our survival analysis revealed that high expression of FAK2 is significantly associated with shorter metastasis-free survival in estrogen receptor-positive breast cancer patients treated with tamoxifen. Our studies suggest that FAK2 is a potential therapeutic target for the management of hormone-refractory breast cancers.
From the ‡McKusick-Nathans Institute of Genetic Medicine and Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
Xinyan
X
Wu
From the ‡McKusick-Nathans Institute of Genetic Medicine and Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
Muhammad Saddiq
MS
Zahari
§Institute of Bioinformatics, International Technology Park, Bangalore, 560066 India;
Santosh
S
Renuse
§Institute of Bioinformatics, International Technology Park, Bangalore, 560066 India;
Raja Sekhar
RS
Nirujogi
From the ‡McKusick-Nathans Institute of Genetic Medicine and Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
Min-Sik
MS
Kim
§Institute of Bioinformatics, International Technology Park, Bangalore, 560066 India;
Srikanth S
SS
Manda
¶Department of Oncology;
Vered
V
Stearns
‖Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231.
Edward
E
Gabrielson
¶Department of Oncology;
Saraswati
S
Sukumar
From the ‡McKusick-Nathans Institute of Genetic Medicine and Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; ¶Department of Oncology; ‖Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231 pandey@jhmi.edu.
Akhilesh
A
Pandey
D000230:Adenocarcinoma / Q000235:genetics* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D049109:Cell Proliferation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D051418:Focal Adhesion Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007553:Isotope Labeling; D061986:MCF-7 Cells; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016019:Survival Analysis; D013629:Tamoxifen / Q000494:pharmacology*; D015533:Transcriptional Activation; D047368:Tumor Burden; D023041:Xenograft Model Antitumor Assays
D018931:Antineoplastic Agents, Hormonal; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D020543:Proteome; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen; D013629:Tamoxifen; D051418:Focal Adhesion Kinase 2; C103547:PTK2B protein, human