SMI of Bcl-2 TW-37 is active across a spectrum of B-cell tumors irrespective of their proliferative and differentiation status

The Bcl-2 family of proteins is critical to the life and death of malignant B-lymphocytes. Interfering with their activity using small-molecule inhibitors (SMI) is being explored as a new therapeutic strategy for treating B-cell tumors. We evaluated the efficacy of TW-37, a non-peptidic SMI of Bcl-2 against a range spectrum of human B-cell lines, fresh patient samples and animal xenograft models. Multiple cytochemical and molecular approaches such as acridine orange/ethidium bromide assay for apoptosis, co-immunoprecipitation of complexes and western blot analysis, caspase luminescent activity assay and apoptotic DNA fragmentation assay were used to demonstrate the effect of TW-37 on different B-cell lines, patient derived samples, as well as in animal xenograft models. Nanomolar concentrations of TW-37 were able to induce apoptosis in both fresh samples and established cell lines with IC50 in most cases of 165–320 nM. Apoptosis was independent of proliferative status or pathological classification of B-cell tumor. TW-37 was able to block Bim-Bcl-XL and Bim-Mcl-1 heterodimerization and induced apoptosis via activation of caspases -9, -3, PARP and DNA fragmentation. TW-37 administered to tumor-bearing SCID mice led to significant tumor growth inhibition (T/C), tumor growth delay (T-C) and Log10kill, when used at its maximum tolerated dose (40 mg/kg × 3 days) via tail vein. TW-37 failed to induce changes in the Bcl-2 proteins levels suggesting that assessment of baseline Bcl-2 family proteins can be used to predict response to the drug. These findings indicate activity of TW-37 across the spectrum of human B-cell tumors and support the concept of targeting the Bcl-2 system as a therapeutic strategy regardless of the stage of B-cell differentiation

Epigenetic control of the ubiquitin carboxyl terminal hydrolase 1 in renal cell carcinoma

<p>Abstract</p> <p>Background</p> <p>The ubiquitin carboxyl-terminal hydrolase 1 (UCHL1) gene involved in the regulation of cellular ubiquitin levels plays an important role in different cellular processes including cell growth and differentiation. Aberrant expression of UCHL1 has been found in a number of human solid tumors including renal cell carcinoma (RCC). In RCC, UCHL1 overexpression is associated with tumor progression and an altered von Hippel Lindau gene expression.</p> <p>Methods</p> <p>To determine the underlying mechanisms for the heterogeneous UCHL1 expression pattern in RCC the UCHL1 promoter DNA methylation status was determined in 17 RCC cell lines as well as in 32 RCC lesions and corresponding tumor adjacent kidney epithelium using combined bisulfite restriction analysis as well as bisulfite DNA sequencing.</p> <p>Results</p> <p>UCHL1 expression was found in all 32 tumor adjacent kidney epithelium samples. However, the lack of or reduced UCHL1 mRNA and/or protein expression was detected in 13/32 RCC biopsies and 7/17 RCC cell lines and due to either a total or partial methylation of the UCHL1 promoter DNA. Upon 2'-deoxy-5-azacytidine treatment an induction of UCHL1 mRNA and protein expression was found in 9/17 RCC cell lines, which was linked to the demethylation degree of the UCHL1 promoter DNA.</p> <p>Conclusion</p> <p>Promoter hypermethylation represents a mechanism for the silencing of the UCHL1 gene expression in RCC and supports the concept of an epigenetic control for the expression of UCHL1 during disease progression.</p

Unintended target effect of anti-BCL-2 DNAi

Abdul Shukkur Ebrahim,1 Mustapha Kandouz,2 Nada Emara,1 Amara B Sugalski,3 Leonard Lipovich,3 Ayad M Al-Katib1 1Lymphoma Research Laboratory, 2Department of Pathology, School of Medicine, 3Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI, USA Introduction: Previous research suggested that a novel compound PNT2258 inhibits B-cell lymphoma 2 (BCL-2) transcription by DNA interference (DNAi) and demonstrated its activity in preclinical xenograft models and in a pilot Phase II clinical trial in non-Hodgkin&rsquo;s lymphoma (NHL). While the drug downregulates BCL-2 at the promoter, mRNA, and protein levels, there is a significant homology (13&ndash;16 bases) between PNT100 and a number of promoters of genes involved in cell cycle regulation and survival. In this study, we identify cyclin-dependent kinase-4 (CDK4) as an unintended target gene of PNT2258 and examine its relevance to NHL.Methods: We performed a Basic Local Alignment Search Tool (BLAST) homology search using PNT100 DNAi sequences. Also, we conducted CDK4 promoter assay in K562 cells and studied the protein expression of CDK4 in Wayne State University (WSU)-follicular small cleaved cell lymphoma (FSCCL), WSU-diffuse large cell lymphoma, and WSU-Waldenstr&ouml;m&rsquo;s macroglobulinemia (WM) lymphoma cells.Results: BLAST homology search showed that PNT100 completely binds to BCL-2 gene as expected. However, there was 100% homology in a stretch of 14 bases (8&ndash;21) between PNT100 and CDK4. PNT2258 strongly inhibited CDK4 promoter activity in K562 cells. Moreover, CDK4 protein expression was significantly downregulated by PNT2258 in WSU-FSCCL and WSU-WM cell lines. Discussion: DNAi may work not only through knocking down the intended gene but also by knocking down other genes. PNT2258 affects CDK4 expression and promoter activity. Results of the present study suggest a broader mechanism of action for DNAi targeting both intended (BCL-2) and unintended (CDK4) genes. Keywords: non-Hodgkin&rsquo;s lymphoma, BCL-2, PNT2258, BLAST, CDK