It is well known that myelodysplastic syndromes are very heterogeneous entities, characterized by accelerated rates of apoptosis in early stages and higher proliferation, accumulation of less differentiated cells, with high genomic instability in the advanced phases.
Consequently, it is really difficult to derive any conclusive results from the gene expression profiling of few MDS patients. Moreover, molecular studies performed in patients receiving ATO that could increase the knowledge about real mechanisms of its action are still lacking, thus a homogenously treated series of patients, even if small, could represent a good opportunity in this field.
Here, we evaluated 12 patients affected by advanced and resistant MDS receiving ATO and Ascorbic Acid for 16 weeks. The aim was to assess ex vivo what was previously observed in vitro by our group also, with particular interest in the apoptotic pathways.
Thus, we evaluated by quantitative real-time PCR the expression of 93 genes involved in apoptosis in a “test patient” (who was analyzed just before and soon after treatment), and in other 3 patients affected by RA, 4 by RAEB1, and 4 by RAEB2.
As reported in the result section, in 4 of 6 cases with stable disease the gene expression profile did not significantly change. Two patients achieved a major response: in the patient with RA the treatment with ATO and Ascorbic Acid down-regulated about 60% of the pro-apoptotic genes, whereas, in the patient affected by RAEB, 91% of the pro-apoptotic genes were up-regulated. This observation could have a clinical impact, if we consider that in the early phases of MDS the goal of treatment would be the reduction of apoptosis and inflammatory status, whereas in the more advanced phases a perfect drug would exert principally an anti-proliferative effect.
Another interesting result from the present study is the demonstration that among principal targets for ATO there are genes belonging to the BCL2 family, analogously to that already observed in vitro. Interestingly, responsive patients showed a higher induction of BAD than those with stable disease. High expression of the pro-apoptotic BCL2-family proteins (BAK, BAD, BCL-XS, as well the apoptosis facilitator BCL2L14) has been previously associated with longer survival and decreased risk of leukemic transformation . In our series, BCL2L14 expression was significantly increased by ATO and Ascorbic Acid, both in the “test patient” and in responsive cases. On the other hand, the expression of BCL2L10, an anti-apoptotic gene, resulted significantly down-regulated in 4 cases, as observed in the “test patient”.
Moreover, the expression of ICEBERG was significantly reduced in 8 cases; this gene physiologically inhibits caspase-1 activity. Caspase-1 is able to activate the IL-1β precursor; this could be interesting, because various myelosuppressive and pro-inflammatory cytokines have been implicated in the high rates of apoptosis and hematopoietic suppression seen in MDS [17, 18]. Thus, decreased expression of ICEBERG could be a relevant target for new therapeutic strategies in early MDS.
Another gene that was significantly up-regulated after treatment is the TNFRSFA1 (Tumor necrosis factor receptor super family member 1A); its protein is one of the major receptors for the TNFα, and it is physiologically able to mediate apoptosis . Consequently, its up-regulation could be another interesting target for treatments in advanced MDS.
Finally, a significant association between low WT1 levels and good response was found, in line with the negative prognostic role of WT1 in MDS progression previously shown .
Recently, immunological approaches to inactivate WT1 in acute leukemia and high-risk MDS have been proposed: these studies provided preliminary evidences of potential clinical efficacy in these patients .