Chromosomal aberrations in follicular non-Hodgkin lymphomas of Japanese patients, detected with comparative genomic hybridization and polymerase chain reaction analysis

Integrated immunohistochemical and DNA copy number profiling analysis provides insight into the molecular pathogenesis of canine follicular lymphoma

Follicular lymphomas (FLs) typically exhibit a chromosome translocation that induces constitutive expression of the anti-apoptotic bcl2 protein and accumulation of additional molecular defects. This rearrangement offers a promising therapeutic target, but its nature as a fundamental driver of FL pathogenesis remains unclear as 15% of cases lack the translocation. We performed an integrated immunohistochemical and genomic investigation of 10 naturally occurring FL cases from domestic dogs, showing that, as with human tumours, they exhibit marked heterogeneity in the frequency and intensity of bcl2 protein expression. Genomic copy number aberrations were infrequent and broadly consistent with those of other canine B-cell lymphoma subtypes. None of the canine FL specimens exhibited a rearrangement consistent with the hallmark translocation of human FL, despite their remarkable histomorphologic similarity. Parallel exploration of canine and human cases may reveal alternative tumour-initiating mechanisms other than BCL2 disruption, yielding a more complete definition of the molecular pathogenesis of FL.

Comparative genomic hybridization in detection of DNA changes in canine lymphomas

In this study, chromosomal imbalances in tumor tissues (lymphomas) and nucleotide changes in tumor suppressor TP53 were studied in a Bernese Mountain dog bitch and a cross breed bitch. Using comparative genomic hybridization, numerous chromosomal rearrangements were detected, which indicated the heterogeneity in tumor growth: in the cross breed bitch, a deletion on the chromosome 9, and duplications on chromosomes 5, 8 and 17 have been found. In the Bernese Mountain Dog bitch, losses on chromosomes 1, 5, 8, 12, 18, 22, 27, 29 and gains on chromosomes 1, 2, 9, 11, 15, 16, 18, 20, 23, 24, 25, 28, 29, 30, 34, 36, 37 and 38 were identified. With the sequencing of the TP53 gene, one silent mutation, transition A/G at position 138 in exon 5 was detected, without changing the amino acid.

Aberrant somatic hypermutations in thyroid lymphomas

To determine a possible role of aberrant somatic hypermutation (ASHM) in the pathogenesis of thyroid lymphoma (TL), mutational status of genes affected by ASHM, including c-MYC, PIM-1, PAX-5 and RhoH/TTF, was analyzed. Tumor specimens from 33 patients with thyroid B-cell lymphoma and 14 with chronic lymphocytic thyroiditis (CLTH), an autoimmune thyroiditis known to provide a basis for TL development, was examined. Mutations of at least one of these genes was detected in 16 of 33 (48.5%) patients with TL and in 2 of 14 (14.3%) CLTH. Occurrence of ASHM in PIM-1, RhoH/TTF, and c-MYC was a constant finding in follicular lymphoma (FL) (all of 11 cases) but not so frequent in diffuse large B-cell lymphoma (DLBCL) (4 (33.3%) of 12 cases) and Marginal zone B-cell lymphoma (MZBCL) (1 (10.0%) of 10 cases). ASHM activity is ongoing in most of FL and DLBCL because intraclonal variants were found. FL was also unique in its lower expression level of activation-induced cytidine deaminase, a main player in DNA-modifying processes during SHM, compare to DLBCL and MZBCL.

Frequency of t(14;18) in follicular lymphoma patients: geographical or technical variation

The t(14;18) translocation is the most distinguishing molecular finding in follicular lymphoma (FL). However, the reported frequencies of t(14;18) in FL show significant variation, which is often attributed to geographical and/or methodological factors. The methods used to detect t(14;18) include Southern blotting, conventional cytogenetics, fluorescent in situ hybridization, and polymerized chain reaction (PCR). Because of its practicality and superior sensitivity, PCR is becoming the more commonly used method in clinical laboratories. The identification of the main breakpoint regions on chromosome 18, including the major breakpoint region (MBR), the minor cluster region (mcr), and the newly defined intermediate cluster region (icr), increased the detection frequency of PCR. In our study, using a highly sensitive nested PCR strategy with primers for MBR, mcr and icr regions, we were able to detect t(14;18) in 95% of FL patients, which is one of the highest reported frequencies using PCR. We screened 58 FL patient samples collected retrospectively from different hospitals in Jordan. DNA was extracted from archival paraffin-embedded samples, some of which were >10 years old. The respective breakpoint distributions were, 47 for MBR (81%), two for mcr (3.5%) and six for icr (10.3%). In this report, we analyze this high frequency of t(14;18) detection in a general review of the recent literature, in an attempt to assess the geographical vs. methodological influences on the reported frequencies.

Correlation of EGFR mutations with chromosomal alterations and expression of EGFR, ErbB3 and VEGF in tumor samples of lung adenocarcinoma patients

INTRODUCTION

Mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) are frequently detected in lung adenocarcinomas with bronchioloalveolar (BAC) differentiation and have been associated with increased response to small molecule EGFR inhibitors in some clinical studies. However, further molecular characterization of tumor cells carrying EGFR mutations (EGFR-mut) is warranted.

METHODS

By DNA sequencing, 120 patients with lung adenocarcinomas (70 tumors with BAC components) were screened for EGFR mutations within exons 18-21. Performing comparative genomic hybridization (CGH) and immunohistochemistry, chromosomal imbalances and protein expression levels of EGFR, ErbB3 and VEGF (vascular endothelial growth factor) were analyzed, respectively.

RESULTS

EGFR mutations were detected in 20/120 tumors. Tumors with BAC components carried more frequently EGFR mutations compared to adenocarcinomas without BAC histology (17/70=24% vs 3/50=6.0%; p=0.012). In a subsequent matched-pair analysis, CGH-analysis demonstrated similar mean numbers of chromosomal imbalances for EGFR mutated and wild-type tumors (8.6 vs 7.8 gains; 2.4 vs 2.7 losses), respectively. Furthermore, tumors with mutated EGFR demonstrated gains in chromosomes 7p, 16p and 20q and losses in chromosome 8p. Interestingly, EGFR mutated tumors showed higher VEGF expression (p=0.03) while differences in EGFR expression were not statistically significant.

CONCLUSION

EGFR gene mutations are frequently seen in lung adenocarcinomas with BAC differentiation and can be linked to chromosomal imbalances and increased VEGF expression.

CD26, together with cell surface adenosine deaminase, is selectively expressed on ALK-positive, but not on ALK-negative, anaplastic large cell lymphoma and Hodgkin's lymphoma

CD26/dipeptidyl peptidase IV is a cell surface antigen with multiple biological functions. Although its involvement in tumor biology has been suggested, the significance of its expression in malignant lymphoma has not been clarified in detail. This study examined the expression of CD26 and cell surface adenosine deaminase (ADA) in 42 cases of Hodgkin's lymphoma (HL) and T-cell lymphoma by immunohistochemistry on frozen sections. CD26 was expressed in three of 14 cases of HL, in four of eight cases of anaplastic large cell lymphoma (ALCL), in two of nine cases of peripheral T-cell lymphoma, in one of six cases of lymphoblastic lymphoma and in none of three cases of adult T-cell lymphoma/leukemia. Expression of cell surface ADA was fully correlated with the expression of CD26 and expression of CD26/ADA in ALCL and HL was also completely correlated with the expression of p80 and epithelial membrane antigen. Of 10 CD26-positive patients, seven had fever and elevated CRP at initial diagnosis and over a median follow-up of 61 months (range, 7 - 152 months) only three survived. This study suggested that CD26 is selectively expressed on ALK-positive, but not on ALK-negative, ALCL and HL. This is also the first report to demonstrate that ADA is coexpressed with CD26 on the cell surface of malignant neoplasms in vivo.