title: MKK4 suppresses metastatic colonization by multiple highly metastatic prostate cancer cell lines through a transient impairment in cell cycle progression.
abstract: Metastatic dissemination in prostate cancer is often early, but not all cancer cells form clinical metastases. Map kinase kinase 4 (MKK4) suppresses metastasis in a preclinical prostate cancer model. We hypothesize that MKK4 will specifically inhibit metastatic colonization through impaired proliferation. Three highly metastatic rat prostate cancer cell lines (AT6.1, Mat-Lu and AT3.1) were employed. Stably over-expressing HA-MKK4 or vector control lines were injected into immunocompromised mice. These experiments validated that HA-MKK4 specifically affects metastatic colonization and increases survival. Median survival (days) with HA-MKK4 vs. vector was 42 vs. 28 (p < 0.0001) for AT6.1, 25 vs. 19 (p < 0.0001) for Mat-Lu and 27 vs. 20 (p < 0.0001) for AT3.1. HA-MKK4 suppresses colonization within 14 days post dissemination, after which exponential proliferation resumes. Although overt metastases retain HA-MKK4, it is inactive within these lesions. Nonetheless, metastasis-derived cell lines were shown to retain functional HA-MKK4 and like their parental HA-MKK4 line are suppressed for experimental metastasis formation in vivo. Disseminated AT6.1-HA-MKK4 cells were analyzed and were found to have an alteration in cell cycle. Specifically, there was an accumulation of cells in G1-phase (p = 0.024) and decrease in S-phase (p = 0.037) compared with vector. In multiple prostate cancer lines, HA-MKK4 suppresses an early step in metastatic colonization. These data support a model in which MKK4 activation at the metastatic site causes a cell-cycle arrest, which is eventually overcome despite presence of functional HA-MKK4. Further studies will specifically interrogate the regulation of MKK4 activation within the metastatic microenvironment and the down-stream molecular events critical for metastasis suppression.
authors.affiliation: Department of Medicine, Section of Hematology/Oncology, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: Russell Z
authors.initials: RZ
authors.lastname: Szmulewitz
authors.forename: Robert
authors.initials: R
authors.lastname: Clark
authors.forename: Tamara
authors.initials: T
authors.lastname: Lotan
authors.forename: Kristen
authors.initials: K
authors.lastname: Otto
authors.forename: Jennifer
authors.initials: J
authors.lastname: Taylor Veneris
authors.forename: Kay
authors.initials: K
authors.lastname: Macleod
authors.forename: Carrie
authors.initials: C
authors.lastname: Rinker-Schaeffer
mesh_terms: D000818:Animals; D059447:Cell Cycle Checkpoints / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016193:G1 Phase / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000556:secondary; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D051381:Rats; D047368:Tumor Burden / Q000235:genetics
chemical_list: D048670:MAP Kinase Kinase 4