Identification and expression of MMSA-8, and its clinical significance in multiple myeloma

In our previous studies, we identified 12 multiple myeloma (MM)-associated antigens by serological analysis of tumor-associated antigens with a recombinant cDNA expression library (SEREX) on MM. MM-associated antigen-8 (MMSA-8) was one of the new antigens identified. We determined the 3'- and 5'-ends of MMSA-8 using SMART-rapid amplification of cDNA ends (RACE) and then cloned its full-length cDNA in the U266 cell line. The full cDNA sequence revealed that MMSA-8 is RPS27A-related transcript variant 1 that is specifically associated with MM. We examined its prognostic significance for the first time, by investigating the correlations between MMSA-8 expression and definite clinicopathological features. We quantitatively assessed MMSA-8 expression using qRT-PCR and western blot analysis in healthy donors and MM patients. The expression levels of MMSA-8 were upregulated with statistical significance in MM patients in contrast to those in healthy donors. The expression of MMSA-8 was also upregulated in relapsed patients compared with that in the complete remission (CR) group. Contrasting MMSA-8 expression levels in different patients with definite clinicopathological features suggested an association between MMSA-8 with unfavorable clinicopathological characteristics, such as international staging system (ISS) stage III, higher lactate dehydrogenase (LDH) levels and higher C-reactive protein (CRP) levels. The expression of MMSA-8 was also increased in patients with unfavorable cytogenetic and genetic abnormalities, including the presence of t(11;14), t(4;14), t(14;16), del(17p), del(13q) and p53 deletion, which was statistically significant. The expression of MMSA-8 exhibited significant variance in the treatment responses of the CR, PR, progression and relapse groups. Univariate and multivariate analyses revealed that high MMSA-8 values were associated with poorer progression-free survival (PFS) and overall survival (OS) in MM patients independently. In conclusion, our data indicated that MMSA-8 is an independent and unfavorable prognostic risk factor in MM; MMSA-8 is also a promising diagnostic and therapeutic target in MM patients, but further validation is needed.