title: Co-administration phenoxodiol with doxorubicin synergistically inhibit the activity of sphingosine kinase-1 (SphK1), a potential oncogene of osteosarcoma, to suppress osteosarcoma cell growth both in vivo and in vitro.
abstract: Elucidation of the mechanisms of chemo-resistance and implementation of strategies to overcome it will be pivotal to improve the survival for osteosarcoma (OS) patients. We here suggest that sphingosine kinase-1 (SphK1) might be the key factor contributing to chemo-resistance in OS. Our Western-blots and immunohistochemistry results showed that SphK1 is over-expressed in multiple clinical OS tissues. Over-expression of SphK1 in OS cell line U2OS promoted its growth and endorsed its resistance against doxorubicin, while knocking-down of SphK1 by shRNA inhibited U2OS cell growth and increased its sensitivity to doxorubicin. Co-administration phenoxodiol with doxorubicin synergistically inhibited SphK1 activity to trigger cellular ceramide accumulation, and achieved synergistic anti-OS growth effect, accompanied with a significant increased of apoptosis and cytotoxicity. Increased cellular level of ceramide by the co-administration induced the association between Akt and Protein Phosphatase 1 (PP1) to dephosphorylate Akt, and to introduce a constitutively active Akt (CA-Akt) restored Akt activation and diminished cell growth inhibition. Further, phenoxodiol and doxorubicin synergistically activated apoptosis signal-regulating kinase 1(ASK1)/c-jun-NH2-kinase (JNK) signaling, which also contributed to cell growth inhibition. Significantly, the role of SphK1 in OS cell growth and the synergistic anti-OS effect of phenoxodiol and doxorubicin were also seen in a mice OS xenograft model. In conclusion, our data suggest that SphK1 might be a critical oncogene of OS and co-administration phenoxodiol with doxorubicin synergistically inhibited the activity of SphK1 to suppress osteosarcoma cell growth both in vivo and in vitro.
authors.affiliation: Department of Orthopedics, BenQ Medical Center, Nanjing Medical University, Nanjing, Jiangsu 210019, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Yao
authors.forename: Sujia
authors.initials: S
authors.lastname: Wu
authors.forename: Dong
authors.initials: D
authors.lastname: Li
authors.forename: Huimin
authors.initials: H
authors.lastname: Ding
authors.forename: Zuyu
authors.initials: Z
authors.lastname: Wang
authors.forename: Yongjiang
authors.initials: Y
authors.lastname: Yang
authors.forename: Shichang
authors.initials: S
authors.lastname: Yan
authors.forename: Zhangping
authors.initials: Z
authors.lastname: Gu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism; D004317:Doxorubicin / Q000008:administration & dosage / Q000494:pharmacology*; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007529:Isoflavones / Q000008:administration & dosage / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D051379:Mice; D016513:Mice, SCID; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009857:Oncogenes / Q000235:genetics*; D012516:Osteosarcoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D000099157:Sphingosine Kinase
chemical_list: D002518:Ceramides; D004317:Doxorubicin; D007529:Isoflavones; D048031:JNK Mitogen-Activated Protein Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D000099157:Sphingosine Kinase; C471183:phenoxodiol