Date of Award

January 2015

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Robert Tigelaar

Second Advisor

Michael Girardi

Subject Area(s)

Medicine, Oncology

Abstract

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous group of skin-homing neoplasms of memory CD4+ T cells. Disease presentation can mimic benign dermatoses, often leading to delayed diagnosis and treatment. Diagnosis and monitoring peripheral blood involvement in CTCL is also challenging as there is no single sensitive and specific marker of disease. Utilizing comparative genomic hybridization (CGH) array and full exome sequencing, the Girardi lab previously identified a set of genetic drivers advanced CTCL characterized by blood involvement. Towards improving our understanding of the pathogenesis of CTCL and the development of a sensitive and specific test for blood and early tissue involvement, we created a Yale CTCL FISH panel including ten probes of the most frequently altered genes by copy number. Cytometric flow sorted malignant and normal T cell populations from eleven CTCL patients with peripheral blood involvement and used our novel CTCL FISH panel to compare the gene copy number alterations in both populations. We then applied our FISH panel to paraffin embedded tissue to explore the feasibility of this strategy for early tissue diagnosis. We also explored genetic alterations occurring in CTCL and CLL dual malignancies in order to begin to study whether if these malignancies might originate from a common malignant precursor cell. Additionally, we undertook a retrospective analysis of 161 patients seen at Yale to (1) identify superior elements of current ISCL-B2 criteria (CD4/CD8 ratio ≥10, %CD4+/CD26- ≥ 30%, %CD4+/CD7- ≥ 40%, TCR gene rearrangement via PCR), (2) study the potential role of TCR-Vβ testing in improving this staging, and (3) explore alternative immunophenotypic criteria for B1 staging (CD4/CD8 ratio ≥5, %CD4+/CD26- ≥ 20%, %CD4+/CD7- ≥ 20%). Peripheral blood FISH demonstrated TP53 and STAT3/5B as the most common alterations. Nine samples showed FISH abnormalities and 8 of these 9 (89%) had ≥3 abnormalities. The comparison populations had lower quantities of defects proportionally to purity in these samples. FISH on tissue samples was successful and identified abnormalities in a tumor sample, demonstrating the feasibility of this technique for early tissue diagnosis. Two patients with concurrent CTCL and CLL were identified and analyzed; only one sample had a TP53 deletion in both isolated B and T cells. In our retrospective analysis, we found loss of CD26 to be the most sensitive marker for blood involvement; changing the criteria to include CD4+CD26-> 25% increased this marker’s sensitivity without a large effect on its specificity. Current ISCL B1 criteria did not capture five patients with immunophenotypic abnormalities who later had disease progression. We found Vβ testing to have superior specificity as compared to PCR; there appears to be a role for TCR-Vβ testing in patients who meet B2 or modified B1 criteria in order to detect clonality and possibly upstage patients.. In conclusion, our study demonstrates the feasibility of FISH for CTCL in both peripheral blood and tissue samples and argues that CTCL patients should be genotyped in order to correlate genetic alterations to prognosis and potential therapies. The utilization of FISH in CTCL could usher in a new age of precision medicine. Further, in patients where a TCR- Vβ clone is detectable, it may be useful to continue to monitor tumor burden based on TCR-Vβ expression

Share

COinS