High Expression of NEK2 Induces Drug Resistance by Inhibiting Premature Senescence Through Activation of the PI3K/Akt Pathway in Myeloma and Other Cancers,

Autologous transplantation in combination with the newer drugs has significantly prolonged survival of patients with myeloma (MM). However, the majority of patients still relapses. Our previous study has shown that NEK2, a chromosomal instability (CIN) gene, is up-regulated in many types of cancer cells and is highly related to drug resistance. Recently, premature senescence has been determined to be an indicator of the efficacy of anti-cancer drugs. In this study, we investigate the correlation between the inhibition of premature senescence and NEK2 induced drug resistance.

Four MM cell lines (Δ47, KMS28PE, ARP1 and U266) and 2 other cancer cell lines (MCF7, H1299) over- and under-expressing NEK2 using a lentiviral delivery system were studied. NEK2 induced drug resistance was evaluated by colonogenic and standard apoptotic assays. The phenotypic changes of premature senescence were determined by using SA β-galactosidase (SA β-gal) staining. The mechanisms of NEK2-induced anti-senescence activity were studied in vitro and in the 5TGM1 murine MM mouse model.

Over-expression of NEK2 stimulated cancer cells into increased S and G2/M phase, resulting in polyploidy. All NEK2 over-expressing cancer cells were able to override doxorubicin-induced premature senescence and to maintain their proliferative potential. Mechanistic studies revealed that NEK2 activated the PI3K/Akt pathway. This was confirmed by the use of a specific PI3K/Akt inhibitor, KP372-1, which abrogated NEK2-induced drug resistance by decreasing clonogenicity of NEK2 over-expressing cells and by decreasing tumor burden and extending mouse survival in the 5TGM1 myeloma mouse model even better than bortezomib. In contrast, knockdown NEK2 by shRNA also induced premature senescence. We determined that NEK2 activates PI3K/Akt pathway by directly interacting with pp1. And the Akt down-stream targets GSK-3, MDM2, NF-kB and the tumor suppressor genes p53, p21, p27, the pro-apoptotic and pro-survival genes of the Bcl-2 family as well as the ABC transporters that related to drug resistance were identified to contribute to the inhibition of premature senescence resulting in drug resistance.

NEK2 inhibits doxorubicin-induced premature senescence, resulting in increased drug resistance by activating the PI3K/Akt pathway. Alternatively, down regulation of NEK2 by shRNA inhibits cell proliferation and decreases drug resistance. Thus, targeting PI3K/Akt pathway should eliminate NEK2 induced drug resistance by re-establishing drug-induced premature senescence.

No relevant conflicts of interest to declare.