ZHX2, CHC1L and RAN Gene Expression Levels Determine Different Prognosis Groups in Multiple Myeloma (MM) Patients.

Gene Expression Profiling through RNA arrays has provided new clues to Multiple Myeloma pathogenesis and prognostic pattern evaluation. Recently, ZHX2, CHC1L & RAN expression have been highlighted as key elements in MM. In the present paper, we have evaluated theses genes by real time quantitative RT-PCR (RQ-PCR) in purified plasma cells from 74 patients with plasma cell discrasias.

MATERIAL AND METHODS: Purified Bone Marrow cells were obtained from the following patients: 6 MGUS, 7 smoldering MM, 59 newly diagnosed symptomatic MM patients and 2 Plasma cell leukemia (PCL). After RNA extraction, RQ-PCR of CHC1L(C), RAN(R) and ZHX2 (Z) genes was carried out using the standard protocol from TaqMan^® gene expression Assays-on-Demand in an ABI-PRISM 7700 Sequence Detection System (Applied Biosystems, Foster City, CA, USA).

Expression levels were normalized with ABL gene and expressed in n-fold times compared to the expression in a pool of RNA from mononuclear cells from healthy donors. The expression level of the different genes was evaluated for correlation with the diagnosis, clinical characteristics and prognosis of the patients.

RESULT AND CONCLUSIONS: None of these genes displayed a clear relationship with the different stages of disease pathogenesis, although ZHX2 gene was slightly more expressed in the indolent forms of the proliferative disorders (MGUS and SMM). Within symptomatic MM patients, several interesting associations were observed. Thus, in hyperdiploid MM cases, CHC1L expressions observed were fewer than in those with a normal DNA index, confirming the participation of the gene product in chromosomal condensation during the mitosis. No other important associations were observed for this gene, although patients with the lowest expression displayed a very good prognosis, but without reaching statistically significant differences. As expected, RAN expression was related to S-Phase PC, since patients with high S phase values (>1.8 %) displayed higher levels of RAN transcripts. This, however, only resulted in a marginal impact on survival. ZHX2 provided the most interesting results, whereby decreased levels of ZHX2 were related to unfavorable prognostic indicators such as B2 microglobulin >4 mg/L and Hemoglobin levels <10.5 g/dl. This was significantly associated with a shorter survival. As such, patients with a level of ZHX2 expression lower than twice the expression of controls were associated with a very low survival (median of 6 months vs not reached, p=0.019). If we take into account the survival prediction value of these three genes, the following prognosis groups were defined: very good prognosis (Z+ C−), poor prognosis (Z− C+) and intermediate (the remaining patients).

SUMMARY: From this study we can confirm that RAN, CHC1L and especially ZHX2 genes play a role in the pathogenesis and behavior of MM, this could be helpful in predicting survival of patients.