title: Oral silibinin inhibits lung tumor growth in athymic nude mice and forms a novel chemocombination with doxorubicin targeting nuclear factor kappaB-mediated inducible chemoresistance.
abstract: The acute and cumulative dose-related toxicity and drug resistance, mediated via nuclear factor kappaB (NFkappaB), of anthracycline anticancer drugs pose a major problem in cancer chemotherapy. Here, we report that oral silibinin (a flavanone) suppresses human non-small-cell lung carcinoma A549 xenograft growth (P = 0.003) and enhances the therapeutic response (P < 0.05) of doxorubicin in athymic BALB/c nu/nu mice together with a strong prevention of doxorubicin-caused adverse health effects. Immunohistochemical analyses of tumors showed that silibinin and doxorubicin decrease (P < 0.001) proliferation index and vasculature and increase (P < 0.001) apoptosis; these effects were further enhanced (P < 0.001) in combination treatment. Pharmacologic dose of silibinin (60 mumol/L) achieved in animal study was biologically effective (P < 0.01 to 0.001, growth inhibition and apoptosis) in vitro in A549 cell culture together with an increased efficacy (P < 0.05 to 0.001) in doxorubicin (25 nmol/L) combination. Furthermore, doxorubicin increased NFkappaB DNA binding activity as one of the possible mechanisms for chemoresistance in A549 cells, which was inhibited by silibinin in combination treatment. Consistent with this, silibinin inhibited doxorubicin-caused increased translocation of p65 and p50 from cytosol to nucleus. Silibinin also inhibited cyclooxygenase-2, an NFkappaB target, in doxorubicin combination. These findings suggest that silibinin inhibits in vivo lung tumor growth and reduces systemic toxicity of doxorubicin with an enhanced therapeutic efficacy most likely via an inhibition of doxorubicin-induced chemoresistance involving NFkappaB signaling.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
authors.forename: Rana P
authors.initials: RP
authors.lastname: Singh
authors.forename: G U
authors.initials: GU
authors.lastname: Mallikarjuna
authors.forename: Girish
authors.initials: G
authors.lastname: Sharma
authors.forename: Sivanandhan
authors.initials: S
authors.lastname: Dhanalakshmi
authors.forename: Anil K
authors.initials: AK
authors.lastname: Tyagi
authors.forename: Daniel C F
authors.initials: DC
authors.lastname: Chan
authors.forename: Chapla
authors.initials: C
authors.lastname: Agarwal
authors.forename: Rajesh
authors.initials: R
authors.lastname: Agarwal
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000473:pathology / Q000517:prevention & control; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism; D004317:Doxorubicin / Q000008:administration & dosage; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007124:Immunoenzyme Techniques; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000517:prevention & control; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D020944:Silybum marianum; D016328:NF-kappa B / Q000378:metabolism*; D021381:Protein Transport; D015398:Signal Transduction; D000077385:Silybin; D012838:Silymarin / Q000008:administration & dosage; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
chemical_list: D016328:NF-kappa B; D012838:Silymarin; D000077385:Silybin; D004317:Doxorubicin