A novel Bcl-2/Bcl-X(L)/Bcl-w inhibitor ABT-737 as therapy in multiple myeloma.

Bcl-2 or Bcl-X(L) confers resistance to chemotherapy in multiple myeloma (MM). Here we characterized the effects of ABT-737, a potent small-molecule inhibitor of antiapoptotic proteins Bcl-2, Bcl-X(L) and Bcl-w with markedly higher affinity than previously reported compounds, on human MM cells. ABT-737 induces apoptosis in MM cells, including those resistant to conventional therapy. Examination of purified patient MM cells demonstrated similar results, without significant toxicity against normal peripheral blood mononuclear cells and MM bone marrow stromal cells. Importantly, ABT-737 decreases the viability of bortezomib-, dexamethasone-(Dex) and thalidomide-refractory patient MM cells. Additionally, ABT-737 abrogates MM cell growth triggered by interleukin-6 or insulin-like growth factor-1. Mechanistic studies show that ABT-737-induced apoptosis is associated with activation of caspase-8, caspase-9 and caspase-3, followed by poly(ADP-ribose) polymerase cleavage. Combining ABT-737 with proteasome inhibitor bortezomib, melphalan or dexamethasone induces additive anti-MM activity. Taken together, our study provides the rationale for clinical protocols evaluating ABT-737, alone and together with botezomib, mephalan or dexamethasone, to enhance MM cell killing, overcome drug resistance conferred by Bcl-2 and improve patient outcome in MM.

CpG island methylator phenotype (CIMP) of colorectal cancer is best characterised by quantitative DNA methylation analysis and prospective cohort studies.

BACKGROUND: The concept of CpG island methylator phenotype (CIMP) is not universally accepted. Even if specific clinicopathological features have been associated with CIMP, investigators often failed to demonstrate a bimodal distribution of the number of methylated markers, which would suggest CIMP as a distinct subtype of colorectal cancer. Previous studies primarily used methylation specific polymerase chain reaction which might detect biologically insignificant low levels of methylation. AIM: To demonstrate a distinct genetic profile of CIMP colorectal cancer using quantitative DNA methylation analysis that can distinguish high from low levels of DNA methylation. MATERIALS AND METHODS: We developed quantitative real time polymerase chain reaction (MethyLight) assays and measured DNA methylation (percentage of methylated reference) of five carefully selected loci (promoters of CACNA1G, CDKN2A (p16), CRABP1, MLH1, and NEUROG1) in 460 colorectal cancers from large prospective cohorts. RESULTS: There was a clear bimodal distribution of 80 microsatellite instability-high (MSI-H) tumours according to the number of methylated promoters, with no tumours showing 3/5 methylated loci. Thus we defined CIMP as having >or=4/5 methylated loci, and 17% (78) of the 460 tumours were classified as CIMP. CIMP was significantly associated with female sex, MSI, BRAF mutations, and wild-type KRAS. Both CIMP MSI-H tumours and CIMP microsatellite stable (MSS) tumours showed much higher frequencies of BRAF mutations (63% and 54%) than non-CIMP counterparts (non-CIMP MSI-H (0%, p<10(-5)) and non-CIMP MSS tumours (6.6%, p<10(-4)), respectively). CONCLUSION: CIMP is best characterised by quantitative DNA methylation analysis. CIMP is a distinct epigenotype of colorectal cancer and may be less frequent than previously reported.