The novel kinesin spindle protein (KSP) inhibitor SB-743921 exhibits marked activity in in vivo and in vitro models of aggressive large B-cell lymphoma.

The kinesin spindle protein (KSP) is a mitotic protein essential for cell cycle control and motility. SB-743921 (hereafter SB-921) is an inhibitor that selectively targets the ATP-binding domain of the KSP. The preclinical activity of SB-921 was evaluated in models of diffuse large B-cell lymphoma (DLBCL). The cytotoxicity of SB-921 was evaluated in a series of germinal center (GC-DLBCL) and post-germinal center (ABC-DLBCL) DLBCL cell lines and a murine lymphoma xenograft model. GC-DLBCL lines generally demonstrated greater sensitivity to SB-921. IC50 values ranged between 1 nM and 900 nM for GC-DLBCL compared to 1 nM to 10 µM for ABC lines. SB-921 demonstrated marked activity in a xenograft model of Ly-1 (GC-DLBCL). While SB-921 was relatively more active in GC derived cell lines, ABC-derived lines still underwent apoptosis at higher concentrations. These results demonstrate that SB-921 inhibits proliferation and induces apoptosis in both GC-DLBCL and ABC-DLBCL.

Oncogenic Adenomatous polyposis coli mutants impair the mitotic checkpoint through direct interaction with Mad2.

The majority of colorectal tumors are aneuploid because of the underlying chromosome instability (CIN) phenotype, in which a defective mitotic checkpoint is implicated. Adenomatous polyposis coli (APC), a tumor suppressor gene that is commonly mutated in colon cancers, has been suggested in causing CIN; however, the molecular mechanism remains unresolved. In this study, we report an interaction of tumor-associated N-terminal APC fragments (N-APC) with Mad2, an essential mitotic checkpoint protein, providing a direct molecular support for linking APC mutations to the generation of CIN. N-APC interacts with Mad2 in Xenopus egg extracts, colon cancer cells, and in vitro with purified components. The interaction between N-APC and Mad2 decreases the soluble pool of Mad2, which is essential for Mad2 cycling and releasing from unattached kinetochores to produce a diffusible |P;wait anaphase|P' signal. Addition of such an N-APC mutant of egg extracts inactivates the mitotic checkpoint. Expressing a tumor-associated N-APC mutant in mammalian cells with an intact mitotic checkpoint produces premature anaphase onset with missegregated chromosomes.

Identification of two novel female-specific non-major histocompatibility complex loci regulating collagen-induced arthritis severity and chronicity, and evidence of epistasis.

OBJECTIVE: To identify additional sex-specific and epistatic quantitative trait loci (QTL) regulating collagen-induced arthritis (CIA) severity overall, as well as within different stages during the disease course, in an intercross between major histocompatibility complex-identical inbred rat strains DA/Bkl (susceptible) and ACI/Hsd (resistant). METHODS: Arthritic male (DA x ACI)F2 intercross offspring (n = 143) were analyzed separately from the females (n = 184). Phenotypic extremes (maximum arthritis scores [MAS]) were genotyped and used for QTL analysis. All 327 rats were genotyped with the simple sequence-length polymorphism (SSLP) markers closest to the peak of Cia7 and Cia10, the major loci previously identified in this intercross, and with SSLPs covering chromosomes 12 and 18. Phenotypes studied were disease onset, arthritis severity scores on days 14-39, MAS, mean and cumulative arthritis scores, delayed-type hypersensitivity, and antibody responses to rat type II collagen. RESULTS: A new female-specific arthritis-severity recessive locus was identified on rat chromosome 12 (Cia25), with a maximum effect observed on day 28 (logarithm of odds [LOD] 4.7). The homozygous DA genotype at Cia25 was associated with a 45% higher median arthritis score in females. Sequencing analyses of the Cia25 candidate gene Ncf1 revealed polymorphisms between DA and ACI. The previously identified locus, Cia10, was found to be male-specific. A 2-locus interaction model analysis identified a novel recessive chromosome 18 QTL, Cia26, which was dependent on Cia7, with its maximum effect observed at later stages during the disease course (peak LOD score of 3.6 for arthritis scores on day 39). CONCLUSION: This study identified 2 novel female-specific loci, and 1 male-specific locus. Cia25 regulates MAS and disease severity during the mid-to-late stages of the disease course and may be accounted for by Ncf1 polymorphisms. Cia26 is in epistasis with Cia7 and regulates later stages of disease, suggesting an involvement in disease perpetuation and/or chronicity.