Further evidence for a pseudoautosomal gene for Hodgkin's lymphoma: Reply to ‘The familial risk of Hodgkin's lymphoma ranks among the highest in the Swedish Family-Cancer Database’ by Altieri A and Hemminki K

Sex chromosome loss and the pseudoautosomal region genes in hematological malignancies

Cytogenetic aberrations, such as chromosomal translocations, aneuploidy, and amplifications, are frequently detected in hematological malignancies. For many of the common autosomal aberrations, the mechanisms underlying their roles in cancer development have been well-characterized. On the contrary, although loss of a sex chromosome is observed in a broad range of hematological malignancies, how it cooperates in disease development is less understood. Nevertheless, it has been postulated that tumor suppressor genes reside on the sex chromosomes. Although the X and Y sex chromosomes are highly divergent, the pseudoautosomal regions are homologous between both chromosomes. Here, we review what is currently known about the pseudoautosomal region genes in the hematological system. Additionally, we discuss implications for haploinsufficiency of critical pseudoautosomal region sex chromosome genes, driven by sex chromosome loss, in promoting hematological malignancies. Because mechanistic studies on disease development rely heavily on murine models, we also discuss the challenges and caveats of existing models, and propose alternatives for examining the involvement of pseudoautosomal region genes and loss of a sex chromosome in vivo. With the widespread detection of loss of a sex chromosome in different hematological malignances, the elucidation of the role of pseudoautosomal region genes in the development and progression of these diseases would be invaluable to the field.

Risk of familial classical Hodgkin lymphoma by relationship, histology, age, and sex: a joint study from five Nordic countries

We aimed to provide the familial risk of classical Hodgkin lymphoma (HL) by relationship, histology, age at diagnosis, and sex. A cohort of 57,475 first-degree relatives of 13,922 HL patients diagnosed between 1955 and 2009 in 5 European countries was observed for HL incidence. The overall lifetime cumulative risk (CR) of HL in first-degree relatives of a patient with HL was 0.6%, which represents a threefold (standardized incidence ratio [SIR], 3.3; 95% confidence interval [CI], 2.8-3.9) increased risk over the general population risk. The risk in siblings (6.0-fold; 95% CI, 4.8- to 7.4-fold) was significantly higher than in parents and/or children (2.1-fold; 95% CI, 1.6- to 2.6-fold). Very high lifetime risk of HL was found for those with multiple affected first-degree relatives (13-fold; 95% CI, 2.8- to 39-fold) and for same-sex twins (57-fold; 95% CI, 21- to 125-fold). We found high familial risks between some concordant histologic subtypes of HL such as lymphocyte-rich (81-fold; 95% CI, 30- to 177-fold) and nodular sclerosis (4.6-fold; 95% CI, 2.9- to 7.0-fold) and also between some discordant subtypes. The familial risk in sisters (9.4-fold; 95% CI, 5.9- to 14-fold) was higher than in brothers (4.5-fold; 95% CI, 2.9- to 6.7-fold) or unlike-sex siblings (5.9-fold; 95% CI, 4.3- to 8.1-fold). The lifetime risk of HL was higher when first-degree relatives were diagnosed at early ages (before age 30 years). This study provides tangible absolute risk estimates for relatives of HL patients, which can be used as a sex-, age-, and family history-based risk calculator for classical HL by oncologists and genetic counselors.

Male-to-female sex ratios of abnormalities detected by fluorescence in situ hybridization in a population of chronic lymphocytic leukemia patients

Distorted sex ratios occur in hematologic disorders. For example, chronic lymphocytic leukemia (CLL) displays disproportionate sex ratios with a large male excess. However, the underlying genetics for these disparities are poorly understood, and gender differences for specific cytogenetic abnormalities have not been carefully investigated. We sought to provide an initial characterization of gender representation in genetic abnormalities in CLL by using fluorescence in situ hybridization (FISH). We confirm the well known skewed male-tofemale (M/F sex ratio) of ~1.5 in our CLL study population, but also determine the genotypic M/F sex ratio values corresponding to specific FISH DNA probes. Genetic changes in CLL detectable by four FISH probes were statistically compared with respect to gender. Initial FISH evaluations of 4698 CLL patients were retrospectively examined and new findings of the genotypic M/F sex ratios for these probes are reported. This study represents the largest CLL survey conducted in the United States using FISH probes. The CLL database demonstrated that FISH abnormalities (trisomy 12, 13q14.3 deletion and 17p13.1 deletion) probes had skewed M/F ratios of ~1.5. Also, by statistical analysis it was shown that ATM gene loss (11q22.3q23.1 deletion) solely or with other abnormalities was considerably higher in males with an M/F ratio of 2.5 and significantly different from M/F ratios of 1.0 or 1.5. We hypothesize that interactions involving these autosomal abnormalities (trisomy 12, and deletions of 11q22.3, 13q14.3, and 17p13.1), and the sex chromosomes may provide the genetic basis for the altered phenotypic M/F ratio in CLL.

KLHDC8B in Hodgkin lymphoma and possibly twinning

A key feature of Hodgkin lymphoma is that the malignant cells are binucleated, as a consequence of failed cytokinesis. We recently ascertained a family in which multiple cases of Hodgkin lymphoma had occurred among individuals who inherited a balanced chromosomal translocation. We cloned the translocation breakpoints and found that it disrupted a previously uncharacterized gene, KLHDC8B, encoding a Kelch family protein whose deficiency impairs cytokinesis and leads to binucleated cells. In other families we found a rare single nucleotide polymorphism affecting mitotic translation of KLHDC8B that was associated with and linked to Hodgkin lymphoma. Interestingly, the index family demonstrated an unusual frequency of twins, and there is a previously reported association between Hodgkin lymphoma and twins. Here we review the unusual genetic features of Hodgkin lymphoma, including gender concordance among siblings, and genetically test the hypothesis that KLHDC8B may participate in twinning by disrupting cytokinesis through impediment of polar body separation from oocytes.

Heritability of hematologic malignancies: from pedigrees to genomics

Many hematologic malignancies have an underlying heritable component. Although not as well characterized as the acquired genetic abnormalities that define important prognostic and therapeutic subgroups of myeloid and lymphoid neoplasms, investigations are beginning to unravel the role of germline genetic variation in the predisposition to hematologic malignancies. Information gained from the study of striking family pedigrees, epidemiologic data, and candidate genes are now being combined with unbiased genome-wide investigations to outline the network of genetic abnormalities that contribute to hematologic malignancy risk. This article reviews the current understanding of the heritability of hematologic malignancies in the genomics era.