PCDH10Gene Promotes Apoptosis Of Multiple Myeloma Cells And Its Related Mechanisms

Objective Protocadherin-10(PCDH10) belongs to the δ2subgroup ofthe protocadherin subfamily, and recent studies indicated PCDH10asa tumor suppressor gene (TSG). Re-expression of PCDH10genesuppresses the cell growth, migration, invasion and colony formationof tumor cells. Multiple myeloma (MM) is a hematologicalmalignancy characterized by neoplastic proliferation of monoclonalplasma cells in bone marrow. Activation of nuclear factor-κB (NF-κB)is crucial for apoptosis of myeloma cells. Our preliminary resultsshowed PCDH10gene inhibits the function of the MM. However, theexact role mechanisms and of PCDH10in multiple myeloma islargely unknown. This study was purposed to investigate theapoptosis-inducing effect of Protocadherin10gene (PCDH10) onmultiple myeloma (MM) cells and its mechanisms.Methods The human MM cell line RPMI8226and KM3were stablytransfected with pcDNA3.1(+)PCDH10or pcDNA3.1(+) bylipofectamine. For the following experiments, untransfected andpcDNA3.1(+) plasmid transfected cells were used as control. The expressions of PCDH10mRNA and protein in thePCDH10-tansfected cells were detected by real-time PCR and westernblot. The cell apoptotic rate was assayed by flow cytometry, andtransmission electron microscopy (TEM) was employed to observethe ultra-structure of cells. The expressions of apoptosis-relatedprotein, IKKs, pIκBα and NF-κB regulated gene protein levels in thecytoplasm, phospho-p65in the nucleus were detected by western blot.We observed the intracellular distribution of p65in RPMI8226andKM3cells after PCDH10-transfection by immunofluorescence.Results After transfection with PCDH10, it was showed thatover-expression of PCDH10gene resulted in obviously increasedexpressions of PCDH10gene and protein. The flow cytometry assayrevealed increased apoptosis of KM3cell line transfected withPCDH10gene (P<0.05). TEM displayed that the PCDH10-tansfectedKM3cells had cytoplasmic cavities, karyopyknosis and obviousapoptotic bodies. But no such change was found in the control group.At the same time PCDH10-tansfected KM3cells resulted indown-regulation the expression of anti-apoptotic proteins andinhibited expression of activated caspase-3, PARP (P<0.05). Thenucleus distribution of p65in MM cells after PCDH10-transfection byimmunofluorescence was declined. We also discovered that PCDH10suppressed the activation of NF-κB through repression the expression of IKK and IκBα phosphorylation. The expressions of NF-κBregulated gene products COX-2, VEGF and ICAM-1weredown-regulated by PCDH10gene (P<0.05).Conclusion The PCDH10gene plays a promoting role in apoptosis ofMM cells．These results suggest that PCDH10induces myeloma cellapoptosis probably by suppressing NF-κB pathway.