Immune thrombocytopenic purpura (ITP) is an autoimmune disease related to the presence of elevated levels of platelet-associated immunoglobulin, or autoantibodies. In recent years the importance of macrophage Fcγ receptors in the uptake of platelets in ITP has been confirmed. Although in patients with ITP the platelet destruction occurs in liver and spleen, in this present experimental mouse model the liver was the principal organ of sequestration of sensitized platelets. The uptake in the spleen, bone marrow, lung, and kidneys was negligible and not different from that in control animals. In addition, the trapped platelets did not return to circulation, and new cells derived from the platelet-storage pool or new thrombocytogenesis were necessary to restore the platelet count. The depletion of splenic and hepatic murine macrophages by liposome-encapsulated clodronate (lip-clod) was studied as a new strategy for ITP treatment. Lip-clod inhibits, in a dose-dependent manner, the antibody-induced thrombocytopenia. Moreover, lip-clod treatment rapidly restored (24 hours) the platelet count in thrombocytopenic animals to hematologic safe values, and despite additional antiplatelet antiserum treatment, mice were able to maintain this level of platelets at least up to 48 hours. The bleeding times in lip-clod–treated animals was not different from those in controls, demonstrating that the hemostasis was well controlled in these animals. The results presented in this study demonstrate that lip-clod treatment can be effective in the management of experimental ITP.

Aberrant DNA methylation is considered an important epigenetic mechanism for gene inactivation. Monoclonal gammopathy of undetermined significance (MGUS) is believed to be a precursor of multiple myeloma (MM). We have analyzed methylation status of p15 INK4B , p16 INK4A , ARF, SOCS-1, p27 KIP1 , RASSF1A, and TP73 genes in bone marrow DNA samples from 21 MGUS and 44 MM patients, in order to determine the role of aberrant promoter methylation as one of the steps involved in the progression of MGUS to MM. Methylation specific polymerase chain reaction assay followed by DNA sequencing of the resulting product was performed. SOCS-1 gene methylation was significantly more frequent in MM (52%) than in MGUS (14%; p=0,006). Methylation frequencies of TP73, ARF, p15 INK4B , p16 INK4A , and RASSF1A were comparable in MGUS: 33%, 29%, 29%, 5%, and 0%, to that observed in MM: 45%, 29%, 32%, 7%, and 2%. All patients lacked methylation at p27 KIP1 gene. In both entities, a concurrent methylation of p15 INK4B and TP73 was observed. The mean methylation index of MGUS was lower (0.16) than that of MM (0.24; p<0.05). Correlations with clinicopathologic characteristics showed a higher mean age in MGUS patients with SOCS-1 methylated (p<0.001); meanwhile in MM, methylation of p15 INK4B was more frequent in males (p=0.009) and IgG isotype (p=0.038). Our findings suggest methylation of TP73, ARF, p15 INK4B , and p16 INK4A as early events in the pathogenesis and development of plasma cell disorders; meanwhile, SOCS-1 methylation would be an important step in the clonal evolution from MGUS to MM.

Mantle cell lymphoma (MCL) is an aggressive lymphoid neoplasm with poor prognosis. Acquired telomerase reverse transcriptase gene promoter (TERTp) mutations are among the most frequent somatic non-coding mutations in cancers. In this study, the prevalence of TERTp mutations in 24 MCL and 21 other lymphoid neoplasias (oLN) was investigated. Eight MCL samples (33%) carried TERTp mutations, two homozygous and six heterozygous (seven C228T and one C250T), which directly correlated with higher TERT transcription, mitochondrial DNA copy number, and IGHV mutational status in MCL neoplastic cells. TERTp mutations were not found in oLN. TERTp mutations correlated with more lymphoma proliferation and tumor burden, as suggested by the higher number of lymphoma cells circulating in peripheral blood, and tended to associate with longer MCL telomeres, especially in homozygous mutants, although not statistically significant. Telomere-biology genes were overexpressed in MCL cells in comparison to healthy lymphocytes, but were not influenced by mutation status. The findings described for the first time that acquired TERTp mutations are common in MCL but not in other lymphoid neoplasms. It was also demonstrated that TERTp mutations are associated with higher TERT mRNA expression in MCL cells in vivo and higher tumor burden, suggesting these mutations as a driver event in MCL development and progression.

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