Expression of PRAME and WT1 in Multiple Myeloma Patients during High Dose Chemotherapy and Auto-SCT

High dose therapy enables further improvement in the outcome of multiple myeloma (MM) patients. However, it is still necessary to determine prognostic factors that may influence treatment results and provide additional criteria for the precise selection of treatment approaches. There are several tumor associated genes (MAGE, LAGE, GAGE, PRAME) that are over-expressed in different malignancies including MM. These genes are believed to modulate cancer properties and should be taken into account during treatment. Their significance as prognostic factors is under investigation. The aim of our study was to analyze the expression levels of PRAME and WT1 genes in MM patients during high dose chemotherapy following by auto-SCT. After having informed consent 25 primary MM patients were included into this study. The median age was 48 years (range, 31–62). All patients were treated by 3 cycles of VAD, Cyclophosphamide 6g/m² + G-CSF to mobilize Stem cells, EDAP, melphalan 200 mg/m² followed by auto-SCT. As second line therapy we used bortezomib+dexamethasone. Quantitative PRAME and WT1 gene expression analysis was performed by means of RQ-PCR. Results were normalized against expression of ABL gene which was used as internal control. Investigation was performed before treatment (n=25), after three VAD cycles (n=12), and before (n=5) and after auto-SCT (n=4). In primary MM patients: PRAME gene expression was found in 68% (n=17), WT1 in 24% (n=6) of patients, all of whom were PRAME-positive. Median expression levels were 0.1% (0.001–132%) for PRAME and 0.01% (0.002–0.07%) for WT1. PRAME and WT1 expression did not correlate with tumor bulk and was independent of the levels of M-protein, beta-2M and albumin. The expression of PRAME significantly decreased after 3 VAD cycles to 0.001–207% (n=8), at the moment of auto-SCT it was 0.05–6.1% (n=3) and after auto-SCT it was 0.013–4.9% (n=3). However for WT1, we observed increased of WT1 expression after 3 VAD cycles to 0.004-0.05% (n=4)and at the moment of auto-SCT it was 0.035–0.4% (n=3) and after auto-SCT – 0.019–2.03% (n=3). In the patients with high primary PRAME expression (>median expression) the frequency of CR+PR was significantly lower then in PRAME-negative primary patients and in patients with low (<median expression) primary PRAME expression (55% vs 84, p = 0.04). It was found also that WT1-positive primary patients were bad responders and they achieved only minimal response after 3 VAD cycles. It should be stressed that during treatment in a small number of initially negative PRAME and WT1 gene patients, we demonstrated detection by PCR. We detected the appearance of gene expression at low levels in 1 of 8 initially negative PRAME (6.1%) and in 5 of 19 initially negative WT1 (range of level 0.01–0.4%). The detection of gene expression did not correlate with disease status. All these patients achieve CR+ VGPR. In one of these secondary positive patients (acquired PRAME and WT1) relapse occurred.

Conclusion: Expression of PRAME gene was found in 68% primary patients and the level of PRAME decreased with tumor reduction. High expression level of PRAME turned out to be a factor of unfavorable prognosis. Expression of WT1 was found in 24% of MM patients all of whom were PRAME-positive. WT1 expression increased during treatment in a small group of pts. Some initially negative pts acquired PRAME and WT1 expression during treatment, but clinical relevance of it is not clear so far.