title: Evaluating TBK1 as a therapeutic target in cancers with activated IRF3.
abstract: TBK1 (TANK-binding kinase 1) is a noncanonical IκB protein kinase that phosphorylates and activates downstream targets such as IRF3 and c-Rel and, mediates NF-κB activation in cancer. Previous reports demonstrated synthetic lethality of TBK1 with mutant KRAS in non-small cell lung cancer (NSCLC); thus, TBK1 could be a novel target for treatment of KRAS-mutant NSCLC. Here, the effect of TBK1 on proliferation in a panel of cancer cells by both genetic and pharmacologic approaches was evaluated. In KRAS-mutant cancer cells, reduction of TBK1 activity by knockdown or treatment with TBK1 inhibitors did not correlate with reduced proliferation in a two-dimensional viability assay. Verification of target engagement via reduced phosphorylation of S386 of IRF3 (pIRF3(S386)) was difficult to assess in NSCLC cells due to low protein expression. However, several cell lines were identified with high pIRF3(S386) levels after screening a large panel of cell lines, many of which also harbor KRAS mutations. Specifically, a large subset of KRAS-mutant pancreatic cancer cell lines was uncovered with high constitutive pIRF3(S386) levels, which correlated with high levels of phosphorylated S172 of TBK1 (pTBK1(S172)). Finally, TBK1 inhibitors dose-dependently inhibited pIRF3(S386) in these cell lines, but this did not correlate with inhibition of cell growth. Taken together, these data demonstrate that the regulation of pathways important for cell proliferation in some NSCLC, pancreatic, and colorectal cell lines is not solely dependent on TBK1 activity.
  
  
  CONCLUSIONS
  TBK1 has therapeutic potential under certain contexts and phosphorylation of its downstream target IRF3 is a biomarker of TBK1 activity.
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science; asli_muvaffak@dfci.harvard.edu ywang@tesarobio.com.
authors.forename: Asli
authors.initials: A
authors.lastname: Muvaffak
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Qi
authors.initials: Q
authors.lastname: Pan
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Haiyan
authors.initials: H
authors.lastname: Yan
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Rafael
authors.initials: R
authors.lastname: Fernandez
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Jongwon
authors.initials: J
authors.lastname: Lim
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Brian
authors.initials: B
authors.lastname: Dolinski
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Thi T
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Peter
authors.initials: P
authors.lastname: Strack
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Stephen
authors.initials: S
authors.lastname: Wu
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Rossana
authors.initials: R
authors.lastname: Chung
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Weiqun
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Chris
authors.initials: C
authors.lastname: Hulton
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Steven
authors.initials: S
authors.lastname: Ripley
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Heather
authors.initials: H
authors.lastname: Hirsch
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Nagashima
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science; Department of Medical Oncology, Dana-Farber Cancer Institute; and.
authors.forename: Kwok-Kin
authors.initials: KK
authors.lastname: Wong
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science; Department of Medical Oncology, Dana-Farber Cancer Institute; and.
authors.forename: Pasi A
authors.initials: PA
authors.lastname: Jánne
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Seidel-Dugan
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Leigh
authors.initials: L
authors.lastname: Zawel
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Paul T
authors.initials: PT
authors.lastname: Kirschmeier
authors.affiliation: Authors' Affiliations: Belfer Institute for Applied Cancer Science;
authors.forename: Richard E
authors.initials: RE
authors.lastname: Middleton
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts.
authors.forename: Erick J
authors.initials: EJ
authors.lastname: Morris
authors.affiliation: Merck Research Laboratories, Boston, Massachusetts asli_muvaffak@dfci.harvard.edu ywang@tesarobio.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics / Q000628:therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000628:therapy*; D058990:Molecular Targeted Therapy; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human