Michelle M. Hess

Clonal Evolution in t(14;18)-Positive Follicular Lymphoma, Evidence for Multiple Common Pathways, and Frequent Parallel Clonal Evolution

Purpose: Follicular lymphoma typically has acquired a t(14;18) translocation, but subsequent additional cytogenetic abnormalities contribute to disease progression. The main aims of the study are to (a) identify the frequency and temporal sequence of cytogenetic events in t(14;18)-positive follicular lymphoma, (b) determine if there are specific pathways in the evolution of follicular lymphoma, (c) determine the clonal divergence in cases with sequential biopsies or multiple clones from a single biopsy, and (d) determine the association of genetic imbalances with clinical outcome. Experimental Design: All cases with a histologically confirmed diagnosis of follicular lymphoma and cytogenetic analysis showing t(14;18)(q32;q21) were included. The karyotypes were reviewed and cytogenetic data were entered into a relational database for further computational analysis; 418 biopsies from 360 follicular lymphoma patients including 43 sequential biopsies were analyzed. Results: Of the cases with only one or two genomic imbalances, the most frequent chromosomal imbalances were +7, del(6q), +der(18)t(14;18), +18, and +X. These abnormalities were also among the most frequent ones encountered when all karyotypes were analyzed. Cytogenetically abnormal clones in the same (26%) and sequential biopsies (63%) often showed divergence of genetic alterations. Balanced translocations other than the t(14;18) were uncommon events, but chromosomal breaks involving 14q32, 18q21, 1p36, 1q21, 10q22, 10q24, and a large cluster at 6q occurred relatively frequently. del(6q), +5, +19, and +20 were associated with poorer overall survival, and del(17p) was associated with poorer event-free survival. Lower-grade tumors (1 and 2) were associated with fewer imbalances. Conclusion: Our analysis suggested that +der(18)t(14;18) may be an entry point to a distinct pathway of genetic evolution in follicular lymphoma. The other common early events appeared to provide multiple entry points, and they might cooperate in the pathogenesis and progression of the follicular lymphoma. Cytogenetically abnormal clones from same patients often showed divergence of genetic alterations, suggesting that parallel evolution from precursor clones are frequent events. This study provides the framework for further analysis of genetic pathways of tumor progression.

Deletion of Cell Division Cycle 2-Like 1 Gene Locus on 1p36 in Non-Hodgkin Lymphoma

Our laboratories have documented a significantly high occurrence of chromosome 1p36 rearrangements in non-Hodgkin lymphoma (NHL). The cell division cycle 2-like 1(CDC2L1) (also known as TP58 or PITSLRE) gene, a protein kinase implicated in apoptotic signaling, is located at the very distal region of chromosome 1p36 and is likely to be disrupted by structural rearrangements involving 1p36. To determine the molecular consequences of the recurrent involvement of the 1p36 region, we examined metaphases containing 1p36 abnormalities from 31 specimens derived from 26 patients for the possible deletion of CDC2L1 by fluorescence in situ hybridization (FISH) using the TP58clk-1 DNA probe. Twenty-three cases exhibited the loss of CDC2L1 from the abnormal chromosome 1. In 2 of 26 cases, the gene locus was translocated to the partner chromosome, and in four specimens, all derived from one case, CDC2L1 was not deleted. This pilot investigation suggests that 1p36 rearrangements, and consequently the loss of the CDC2L1 gene locus, is important in NHL. This work also opens avenues for further molecular studies and prognostic correlations.

Lack of a common or characteristic cytogenetic anomaly in solitary fibrous tumor.

Solitary fibrous tumor is a mesenchymal tumor that was initially described as a pleural-based lesion, but later was discovered in many other locations. The light-microscopic appearance of solitary fibrous tumor may overlap with other diagnostic entities; however, consistent tumor cell CD34 immunoreactivity is useful in establishing the diagnosis. Limited data suggest that solitary fibrous tumors are karyotypically diverse, and no common or characteristic anomaly has yet emerged for this entity. Cytogenetic analysis of two solitary fibrous tumors, one peritoneal and the other arising in the liver, revealed predominantly structural abnormalities in the former and numerical imbalances in the latter. Clonal karyotypic abnormalities were lacking in three additional solitary fibrous tumors.

Cytogenetic findings in a primary malignant fibrous histiocytoma of bone and the lung metastasis

&NA; Cytogenetic studies were performed on a malignant fibrous histiocytoma of bone and its metastasis to lung. Numerical chromosome abnormalities were described for all chromosomes except chromosomes 2, 4 and 16. Structural abnormalities in the primary tumor involved chromosomes 1, 3, 5, 10, 11, 13, 15, 16 and 17. The chromosomal rearrangements seen both in the primary tumor and its metastasis involved chromosomes 13, 15 and 17. Two × chromosomes contained large homogeneously staining regions (HSRs) in the primary tumor which were replaced by multiple double minutes (DMs) in the metastatic tumor.

Cytogenetic Abnormalities in B-Immunoblastic Lymphoma

We have considered the cytogenetic abnormalities present in 27 unpublished cases of B-immunoblastic lymphoma. Among these 27 patients, the chromosome changes were heterogeneous and complex. The chromosomes most commonly gained were 3 (44% of cases), 18 (44%), 6 (30%) and 11 (30%). The most common structural abnormalities involved band 14q32 (26%), band 18q21 (15%) and bands 6q16-21 (19%). Study of these 27 immunoblastic lymphomas did not allow us to tentatively identify a common primary cytogenetic abnormality unique to B-immunoblastic lymphoma, however, a translocation at 14q32 may be the primary cytogenetic lesion in some of the cases. Rather, we have added to the number of abnormalities reported in immunoblastic lymphoma and in non-Hodgkins lymphoma in general.

Proliferative Fraction and DNA Content are Lower in B-Cell Non-Hodgkin's Lymphomas with the (t14; 18)

The t(14;18), which juxtaposes the immunoglobulin enhancer region from chromosome 14 to the bcl-2 gene on chromosome 18, is a recurrent cytogenetic abnormality in the majority of follicular lymphomas (FL). This translocation results in overexpression of bcl-2, which increases cellular life span of the mutated cells by decreasing apoptosis. The t(14;18) also occurs in a subgroup of diffuse large cell lymphomas (DLCL), and current thought is that the majority of these represent transformation of FL. Low grade FL are characterized by low proliferation, and diploid/peridiploid DNA content. In this study, we compared proliferative activity (PF) and DNA content (DI) in FL containing the t(14;18) to DLCL with and without the t(14;18). The mean PF and DI were lower in the NHL containing t(14;18) irregardless of histologic subtype. We conclude that increased life span due to the presence of t(14;18) provides the conditions for accumulation of a different set of mutations as compared to those NHL developing from mutations in more rapidly proliferating precursors. This has implications for prognosis of patients with DLCL depending upon the presence or absence of t(14;18).

Comparison of DNA content in non-Hodgkin's lymphoma as measured by flow cytometry and cytogenetics

Specific cytogenetic changes such as t(14;18) and t(8;14) are associated with specific histologic subtypes of non-Hodgkins lymphoma (NHL) and may predict disease outcome. Nonspecific cytogenetic changes include other structural rearrangements or numerical changes such as monosomies and trisomies, which may cause changes in total cellular DNA content. In many solid tumors, the presence of abnormal DNA content may be predictive of clinical behavior. NHL biopsies, however, contain normal (diploid) as well as abnormal cells, and DNA changes in the peridiploid range are detectable by cytogenetic analysis, but not consistently by flow cytometry. In the present study, we performed flow cytometric and cytogenetic analysis of DNA on biopsies from 129 patients with non-Hodgkins lymphoma (NHL). Cytogenetic studies were successful on 88 (68%) of the samples. There was 55% concordance between flow cytometric and cytogenetic techniques in detecting aneuploid DNA content, with the majority of discrepancies occurring in the peridiploid range. We also detected six samples which were aneuploid by flow cytometry, but diploid by cytogenetics. We suggest that a reasonable approach to determine DNA content, as it relates to prediction of outcome in NHL, would be to combine data from both of these techniques and analyze the results in terms of ranges of DNA rather than by categorizing as diploid versus aneuploid.

Is a Duplication of 14q32 a New Recurrent Chromosomal Alteration in B-Cell Non-Hodgkin Lymphoma?

Identification of clonal chromosomal abnormalities involving 14q32 and its association with specific histological subtypes of non-Hodgkin lymphoma (NHL) has provided substantial insight to the genetic events leading to the disease. However, in some cases with inferior morphology of tumor cell chromosomes, the additional segment on chromosome 14 remains unidentified by cytogenetic banding techniques alone. To elucidate the origin of the additional chromosomal segment and to correlate the newly determined alterations with histology, metaphases from 15 NHL patients with add(14)(q32) were examined using fluorescence in situ hybridization (FISH) techniques after cytogenetic analysis had been performed. We found the duplication of 14q involving the q32 region in 6 cases with a dup(14) (q32) in 4 cases and a dup(14)(q24q32) in 2 cases. In 8 cases, FISH unveiled known NHL associated translocations; a t(14;18)(q32;q21) in 4 cases, a t(11;14)(q13;q32) in 2 cases, a t(8;14)(q24;q32) and a t(9;14)(p13;q32) in 1 case each. We also noted a t(14;17)(q32;q21) in 1 case. The use of FISH was a valuable asset in determining the origin of the additional material on chromosome 14q32, and helped resolve a group of B-cell NHLs with involvement of a duplicated 14q32 region.

SEARCHING FOR ELECTRICAL PROPERTIES, PHENOMENA AND MECHANISMS IN THE CONSTRUCTION AND FUNCTION OF CHROMOSOMES

Our studies reveal previously unidentified electrical properties of chromosomes: (1) chromosomes are amazingly similar in construction and function to electrical transformers; (2) chromosomes possess in their construction and function, components similar to those of electric generators, conductors, condensers, switches, and other components of electrical circuits; (3) chromosomes demonstrate in nano-scale level electromagnetic interactions, resonance, fusion and other phenomena similar to those described by equations in classical physics. These electrical properties and phenomena provide a possible explanation for unclear and poorly understood mechanisms in clinical genetics including: (a) electrically based mechanisms responsible for breaks, translocations, fusions, and other chromosomal abnormalities associated with cancer, intellectual disability, infertility, pregnancy loss, Down syndrome, and other genetic disorders; (b) electrically based mechanisms involved in crossing over, non-disjunction and other events during meiosis and mitosis; (c) mechanisms demonstrating heterochromatin to be electrically active and genetically important.