CTLA4 haploinsufficiency as a predisposition to classical Hodgkin lymphoma

Role of non-chromosomal birth defects on the risk of developing childhood Hodgkin lymphoma: A Children's Oncology Group study

BACKGROUND

Non-chromosomal birth defects are an important risk factor for several childhood cancers. However, these associations are less clear for Hodgkin lymphoma (HL). Therefore, we sought to more fully elucidate the association between non-chromosomal birth defects and HL risk.

PROCEDURE

Information on cases (n = 517) diagnosed with HL (ages of 0-14) at Children's Oncology Group Institutions for the period of 1989-2003 was obtained. Control children without a history of cancer (n = 784) were identified using random digit dialing and individually matched to cases on sex, race/ethnicity, age, and geographic location. Parents completed comprehensive interviews and answered questions including whether their child had been born with a non-chromosomal birth defect. To test the association between birth defects and HL risk, conditional logistic regression was applied to generate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

RESULTS

Children born with any non-chromosomal birth defect were not more likely to be diagnosed with HL at 0-14 years of age (aOR: 0.91; 95% CI: 0.69-1.21). No associations were detected between major or minor birth defects and HL (aOR: 1.34; 95% CI: 0.67-2.67 and aOR: 0.88; 95% CI: 0.57-1.34, respectively). Similarly, no association was observed for children born with any birth defect and EBV-positive HL (aOR: 0.57; 95% CI: 0.25-1.26).

CONCLUSIONS

Previous assessments of HL in children with non-chromosomal birth defects have been limited. Using data from the largest case-control study of HL in those <15 years of age, we did not observe strong associations between being born with a birth defect and HL risk.

A significant proportion of classic Hodgkin lymphoma recurrences represents clonally unrelated second primary lymphoma

Despite high cure rates in classic Hodgkin lymphoma (cHL), relapses are observed. Whether relapsed cHL represents second primary lymphoma or an underlying T-cell lymphoma (TCL) mimicking cHL is underinvestigated. To analyze the nature of cHL recurrences, in-depth clonality testing of immunoglobulin (Ig) and T-cell receptor (TCR) rearrangements was performed in paired cHL diagnoses and recurrences among 60 patients, supported by targeted mutation analysis of lymphoma-associated genes. Clonal Ig rearrangements were detected by next-generation sequencing (NGS) in 69 of 120 (58%) diagnoses and recurrence samples. The clonal relationship could be established in 34 cases, identifying clonally related relapsed cHL in 24 of 34 patients (71%). Clonally unrelated cHL was observed in 10 of 34 patients (29%) as determined by IG-NGS clonality assessment and confirmed by the identification of predominantly mutually exclusive gene mutations in the paired cHL samples. In recurrences of >2 years, ∼60% of patients with cHL for whom the clonal relationship could be established showed a second primary cHL. Clonal TCR gene rearrangements were identified in 14 of 125 samples (11%), and TCL-associated gene mutations were detected in 7 of 14 samples. Retrospective pathology review with integration of the molecular findings were consistent with an underlying TCL in 5 patients aged >50 years. This study shows that cHL recurrences, especially after 2 years, sometimes represent a new primary cHL or TCL mimicking cHL, as uncovered by NGS-based Ig/TCR clonality testing and gene mutation analysis. Given the significant therapeutic consequences, molecular testing of a presumed relapse in cHL is crucial for subsequent appropriate treatment strategies adapted to the specific lymphoma presentation.

Heterozygous CTLA4 splice site mutation c.458-1G > C presenting with immunodeficiency and variable degree of immune dysregulation in three generation kindred of Caribbean descent

Cytotoxic T-lymphocyte-associated protein 4 (CTLA4) is an immune checkpoint, which downregulates T cell activation and T regulatory cell function. CTLA4 haploinsufficiency (CTLA4 HI) leads to T cell hyperactivation, immunodeficiency and variable degree of immune dysregulation. Furthermore, CTLA4 HI predisposes affected individuals to development of various cancers. Less well understood is the penetrance and expressivity of CTLA4 mutations. We describe five members of a single family with heterozygous CTLA4 splice site mutation c.458-1G > C, previously shown to result in CTLA-4 HI, who presented with immunodeficiency and variable degree of immune dysregulation. The host, environmental and the epigenetic factors affecting the penetrance and expressivity of CTLA4 mutations merits further investigation.