No abstract

Follicle center lymphoma (FCL) is an indolent B cell non-Hodgkin's lymphoma (NHL) characterized genetically by the t(14;18) translocation. Histological transformation and clinical progression of FCLs are frequently associated with secondary genetic alterations at both nucleic acid and chromosomal levels. To determine the type and pattern of genomic instability occurring in histological transformation of FCLs and the role of DNA mismatch repair defects in this procedure, we have performed microsatellite analysis, comparative genomic hybridization (CGH) and mutational analysis of hMLH1 and hMSH2 genes on serial biopsy specimens from patients with FCL transformed to diffuse large cell lymphoma (DLCL). Paired biopsy samples of eight patients were analyzed for microsatellite instability and structural alterations for hMLH1 and hMSH2 genes, and tumor samples of five patients were subjected to CGH analysis. A high level of microsatellite instability was associated with histological transformation of two cases of FCL, but no mutations of the hMLH1 and hMSH2 genes were detected in any of the lymphoma samples. In the five cases subjected to CGH analysis, the histological transformation of FCLs was associated with genomic imbalances at 21 chromosomal regions. The genomic abnormalities found were rather heterogeneous and none of the genetic changes were overrepresented in the transformed DLCLs. These data suggest that histological transformation of FCLs to DLCL is frequently associated with genome wide instability at both nucleic acid and chromosomal levels, although mutations of the hMSH1 and hMLH2 genes are not involved in this process. Leukemia (2000) 14, 2142-2148.

Follicular lymphoma (FL) is a B cell non-Hodgkin's lymphoma (NHL) that frequently displays a t(14;18) translocation. Clonal evolution and histological transformation of FL is frequently associated with the accumulation of secondary genetic alterations. It has been demonstrated that the BCL-6 gene can be altered by chromosomal rearrangements and by mutations clustering in its 5' noncoding region in a significant fraction of FL and diffuse large cell lymphoma (DLCL). To elucidate the role of the BCL-6 gene alterations in the histological transformation and clonal progression of FL, we analyzed serial biopsy specimens from 12 patients with FL. Two cases of FL showed no histological alteration in the second biopsy, and 10 cases of FL showed morphological transformation to DLCL in the second biopsy. Southern blot analysis was used to detect rearrangement of the BCL-6 gene, polymerase chain reaction-single strand conformation polymorphism and sequence analysis were performed for identification of mutations in the 5' noncoding region of the BCL-6 gene, and immunohistochemical analysis was applied to reveal the BCL-6 protein expression. No BCL-6 gene rearrangement was detected in any of the samples, but a total of 58 mutations were found in the 5' noncoding region of the BCL-6 gene in seven cases. In five cases, both the FL and the clonally related FL or DLCL, and in two cases only the DLCL samples were mutated. The mutations were identical in multiple biopsy specimens of FL that did not show morphological transformation. In six patients where FL cells underwent morphological transformation, considerable intraclonal sequence heterogeneity was observed, indicating an ongoing type of somatic mutation. Based on the pattern of shared and nonshared mutations, the genealogical relationship of neoplastic clones could be established. In all of these cases, the histological transformation of FL was associated with the emergence of a subpopulation marked by new sites of mutations in the BCL-6 5' noncoding sequences. In three of these six cases, the histological transformation is also associated with the reduced expression of the BCL-6 protein. These findings demonstrate that mutation of the 5' noncoding region of the BCL-6 gene developed in the clonal evolution of FL, and at different time points in the lymphoma evolution different clonotypes dominate.

Some brain tumours, such as glioblastomas express high levels of receptors for bombesin/gastrin releasing peptide. We investigated whether bombesin/gastrin releasing peptide receptors found in glioblastoma cell lines can be utilised for targeting of a cytotoxic bombesin analogue, AN-215 consisting of a potent derivative of doxorubicin, 2-pyrrolino-doxorubicin (AN-201) linked to a bombesin-like peptide carrier. This study reports the effect of AN-215 on the growth of U-87MG human glioblastomas xenografted into nude mice. High affinity binding of AN-215 to U-87MG tumours was characterised by an IC 50 value of 4.0+0.1 nM, as determined by radioreceptor assays. mRNA analyses revealed the presence of mRNA for BN receptor subtypes 1 and 2. Treatment with AN-215 significantly (P50.05) extended tumour doubling time from 4.54+0.2 days to 8.18+1.8 days and inhibited tumour growth as demonstrated by a 69.6% reduction in final tumour volume (P50.001) and a 64.6% decrease in tumour weight as compared to controls. Cytotoxic radical AN-201 at the same dose was ineffective. The antitumour effect of AN-215 could be blocked by pretreatment with an excess of a bombesin antagonist, indicating that the action of this cytotoxic analogue is receptor-mediated. Our results suggest that patients with inoperable brain tumours such as malignant gliomas may benefit from targeted chemotherapy based on cytotoxic bombesin analogue AN-215.