TCL1A gene involvement in T-cell prolymphocytic leukemia in Japanese patients

Exploring the molecular pathogenesis associated with T-cell prolymphocytic leukemia based on a comprehensive bioinformatics analysis

As a rare hematological malignancy, T-cell prolymphocytic leukemia (T-PLL) has a high mortality rate. However, the comprehensive mechanisms of the underlying pathogenesis of T-PLL are unknown. The purpose of the present study was to investigate the pathogenesis of T-PLL based on a comprehensive bioinformatics analysis. The differentially expressed genes (DEGs) between T-PLL blood cell samples and normal peripheral blood cell samples were investigated using the GSE5788 Affymetrix microarray data from the Gene Expression Omnibus database. To investigate the functional changes associated with tumor progression, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were used on the identified DEGs, followed by protein-protein interaction (PPI) and sub-PPI analysis. Transcription factors and tumor-associated genes (TAGs) were investigated further. The results identified 84 upregulated genes and 354 downregulated genes in T-PLL samples when compared with healthy samples. These DEGs featured in various functions including cell death and various pathways including apoptosis. The functional analysis of DEGs revealed 17 dysregulated transcription factors and 37 dysregulated TAGs. Furthermore, the PPI network analysis based on node degree (a network topology attribute) identified 61 genes, including the core downregulated gene of the sub-PPI network, signal transducer and activator of transcription 3 (STAT3; degree, 13) and the core upregulated gene, insulin receptor substrate-1 (IRS1; degree, 5), that may have important associations with the progression of T-PLL. Alterations to cell functions, including cell death, and pathways, including apoptosis, may contribute to the process of T-PLL. Candidate genes identified in the present study, including STAT3 and IRS1, should be targets for additional studies.

Comparison of karyotyping, TCL1 fluorescence in situ hybridisation and TCL1 immunohistochemistry in T cell prolymphocytic leukaemia

Aims

T cell prolymphocytic leukaemia (T-PLL) is defined as an aggressive T cell leukaemia composed of small to medium-sized lymphocytes with a mature T cell immunophenotype. Most of these cases are known to be associated with inv(14q11q32)/t(14;14)(q11;q32) or rarely t(X;14)(q28;q11). However, T-PLL can show variations in clinical presentation, morphology or immunophenotype that can make a diagnosis of T-PLL challenging. We aim to explore the value of ancillary testing in the diagnosis of T-PLL.

Methods

With this large cohort of 69 patients with T-PLL, we compared the diagnostic utility of conventional cytogenetics, TCL1 rearrangement by fluorescence in situ hybridisation (FISH) and TCL1 expression by immunohistochemistry (IHC).

Results

Conventional karyotyping was performed in all 69 patients and was abnormal in 44 (65%), showing 14q32 abnormalities in 31 (43%) and t(X;14) (MTCP) in 2 (3%). TCL1 rearrangement was assessed by FISH in 26 cases and was positive in 23 (85%). All cases with 14q32 abnormalities shown by karyotype were positive for TCL1 rearrangement by FISH, whereas 12/15 (80%) cases without 14q32 abnormalities were also positive. TCL1 overexpression by IHC was detected in 51/64 (81%), including 40/42 (95%) cases with TCL1/14q32 rearrangement, and 3 cases without, showing a concordance of 89%. TCL1 IHC was negative in both cases with t(X;14)(q28;q11).

Conclusions

Our study shows that TCL1 by IHC is a convenient test, positive in >80% T-PLL. Conventional cytogenetics is insensitive in the detection of 14q32/TCL1 rearrangements but provides more complete information of the chromosomal landscape of T-PLL. FISH for TCL1 rearrangement is very valuable in diagnostic challenging cases.

Discovery of novel drug sensitivities in T-PLL by high-throughput ex vivo drug testing and mutation profiling

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive neoplasm of mature T-cells with an urgent need for rationally designed therapies to address its notoriously chemo-refractory behavior. The median survival of T-PLL patients is <2 years and clinical trials are difficult to execute. Here we systematically explored the diversity of drug responses in T-PLL patient samples using an ex vivo drug sensitivity and resistance testing platform and correlated the findings with somatic mutations and gene expression profiles. Intriguingly, all T-PLL samples were sensitive to the cyclin-dependent kinase inhibitor SNS-032, which overcame stromal-cell-mediated protection and elicited robust p53-activation and apoptosis. Across all patients, the most effective classes of compounds were histone deacetylase, phosphoinositide-3 kinase/AKT/mammalian target of rapamycin, heat-shock protein 90 and BH3-family protein inhibitors as well as p53 activators, indicating previously unexplored, novel targeted approaches for treating T-PLL. Although Janus-activated kinase-signal transducer and activator of transcription factor (JAK-STAT) pathway mutations were common in T-PLL (71% of patients), JAK-STAT inhibitor responses were not directly linked to those or other T-PLL-specific lesions. Overall, we found that genetic markers do not readily translate into novel effective therapeutic vulnerabilities. In conclusion, novel classes of compounds with high efficacy in T-PLL were discovered with the comprehensive ex vivo drug screening platform warranting further studies of synergisms and clinical testing.

Epigenetic therapy overcomes treatment resistance in T cell prolymphocytic leukemia

T cell prolymphocytic leukemia (T-PLL) is a rare, mature T cell neoplasm with distinct features and an aggressive clinical course. Early relapse and short overall survival are commonplace. Use of the monoclonal anti-CD52 antibody alemtuzumab has improved the rate of complete remission and duration of response to more than 50% and between 6 and 12 months, respectively. Despite this advance, without an allogeneic transplant, resistant relapse is inevitable. We report seven complete and one partial remission in eight patients receiving alemtuzumab and cladribine with or without a histone deacetylase inhibitor. These data show that administration of epigenetic agents can overcome alemtuzumab resistance. We also report epigenetically induced expression of the surface receptor protein CD30 in T-PLL. Subsequent treatment with the anti-CD30 antibody-drug conjugate brentuximab vedotin overcame organ-specific (skin) resistance to alemtuzumab. Our findings demonstrate activity of combination epigenetic and immunotherapy in the incurable illness T-PLL, particularly in the setting of previous alemtuzumab therapy.