Functional Studies On Multiple Myeloma Tumor-associated Gene HMMTAG2

Multiple myeloma (MM) is a hematological malignancy characterized by the uncontrolled proliferation of monoclonal plasma cells in post-germinal center. Multiple myeloma cells posses extreme genetic instability, induce number and structure abnormalities in MM cells. Chromosome 1 aberrations are very common in most hematologic malignancies and constitute the most common structural aberration in MM, characterized as chromosome 1p delete and 1q gain/amplification.We have identified a novel multiple myeloma tumor-associated gene from ARH-77 cell line cDNA gene pool which named as hMMTAG2 by expression cloning (Genbank accession Number: AY137773). The hMMTAG2 gene is located at chromosome 1 q42.13. The full length of hMMTAG2 cDNA is 1300bp, which contain 8 exons and encode a 29kD protein. The studies showed that hMMTAG2 can induce NIH3T3 cells transformation. The encoded products of hMMTAG2 are located at cell nuclus.We have constructed the pLXSN/TAG2 retroviral recombinant, and then transfected the package cell PA317, established the stable expressed cell line PA317/TAG2. The supernatant from the cell line PA317/TAG2 culture was harvested to infect NIH3T3 cells. 6 cell clones of stable expression hMMTAG2 gene were acquired by G418 selection. Cell growth curve analysis, MTT analysis, flow cytometry (FCM) and soft agar clone forming method were adopted to examine the biology activity of the transfected cells. The results showed that the hMMTAG2 could induce cell growth and cell proliferation, drive cell through G1 phase and induce S phase entry. Then, the NIH3T3/TAG2 cells were injected i.h. into BALB/c nude mice to understand whether they could form the implanted tumor. The results showed that hMMTAG2 has the ability of tumorgenesis. Bioinformatics analysis showed that MMTAG2 has a similar structure with transcrtipt factor. Meanwhile, we have found that the expression of c-myc mRNA and protein were upregulated in NIH3T3/TAG2 cells, whereas not in NIH3T3 cells.These data indicate that overexpression of hMMTAG2 induce cell proliferation and tumor formation. The overexpression of hMMTAG2 can upregulate the expression level of c-myc. The evidence suggest that MMTAG2 may play a role in inducing transcription and regulation as a nuclear transcript factor through c-myc dependent pathway.