Resistance to Selumetinib (AZD6244) in colorectal cancer cell lines is mediated by p70S6K and RPS6 activation.
Selumetinib (AZD6244, ARRY-142886) is a MEK1/2 inhibitor that has gained interest as an anti-tumour agent. We have determined the degree of sensitivity/resistance to Selumetinib in a panel of colorectal cancer cell lines using cell proliferation and soft agar assays. Sensitive cell lines underwent G1 arrest, whereas Selumetinib had no effect on the cell cycle of resistant cells. Some of the resistant cell lines showed high levels of ERK1/2 phosphorylation in the absence of serum. Selumetinib inhibited phosphorylation of ERK1/2 and RSK and had no effect on AKT phosphorylation in both sensitive and resistant cells. Furthermore, mutations in KRAS, BRAF, or PIK3CA were not clearly associated with Selumetinib resistance. Surprisingly, Selumetinib was able to inhibit phosphorylation of p70 S6 kinase (p70S6K) and its downstream target ribosomal protein S6 (RPS6) in sensitive cell lines. However, p70S6K and RPS6 phosphorylation remained unaffected or even increased in resistant cells. Moreover, in some of the resistant cell lines p70S6K and RPS6 were phosphorylated in the absence of serum. Interestingly, colorectal primary cultures derived from tumours excised to patients exhibited the same behaviour than established cell lines. Pharmacological inhibition of p70S6K using the PI3K/mTOR inhibitor NVP-BEZ235, the specific mTOR inhibitor Rapamycin and the specific p70S6K inhibitor PF-4708671 potentiated Selumetinib effects in resistant cells. In addition, biological inhibition of p70S6K using siRNA rendered responsiveness to Selumetinib in resistant cell lines. Furthermore, combination of p70S6K silencing and PF-47086714 was even more effective. We can conclude that p70S6K and its downstream target RPS6 are potential biomarkers of resistance to Selumetinib in colorectal cancer.
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain.
Silvina
S
Grasso
Unidad AECC de Investigación Traslacional en Cáncer, Hospital Clínico Universitario Virgen de la Arrixaca, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain.
Elena
E
Tristante
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain ; Unidad de Investigación, Hospital General Universitario de Elche, 03203 Elche (Alicante), Spain.
Miguel
M
Saceda
Centro de Bioquímica y Genética Clínica, Hospital Clínico Universitario Virgen de la Arrixaca, 30120 Murcia, Spain.
Pablo
P
Carbonell
Unidad AECC de Investigación Traslacional en Cáncer, Hospital Clínico Universitario Virgen de la Arrixaca, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain.
Leticia
L
Mayor-López
Unidad AECC de Investigación Traslacional en Cáncer, Hospital Clínico Universitario Virgen de la Arrixaca, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain.
Mar
M
Carballo-Santana
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain.
Estefanía
E
Carrasco-García
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain.
Lourdes
L
Rocamora-Reverte
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain ; Unidad de Investigación, Hospital General Universitario de Elche, 03203 Elche (Alicante), Spain.
Pilar
P
García-Morales
Unidad AECC de Investigación Traslacional en Cáncer, Hospital Clínico Universitario Virgen de la Arrixaca, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain ; Servicio de Gastroenterología, Hospital Clínico Universitario Virgen de la Arrixaca, 30120 Murcia, Spain.
Fernando
F
Carballo
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain.
José A
JA
Ferragut
Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain ; Unidad AECC de Investigación Traslacional en Cáncer, Hospital Clínico Universitario Virgen de la Arrixaca, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain.
Isabel
I
Martínez-Lacaci
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D058990:Molecular Targeted Therapy; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D011804:Quinolines / Q000494:pharmacology; D038601:Ribosomal Protein S6 / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics
C517975:AZD 6244; D001562:Benzimidazoles; D007093:Imidazoles; C117307:KRAS protein, human; C552719:PF-4708671; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011804:Quinolines; D038601:Ribosomal Protein S6; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; C531198:dactolisib
CRC, colorectal cancer; ERK, extracellular signal-regulated kinase; MEK, mitogen-activated protein kinase; RPS6, ribosomal protein S6; RSK, p90 ribosomal S6 kinase; p70S6K, p70 S6 kinase