Abstract PO-20: Molecular characterization of a mouse model of peripheral T-cell lymphoma with Tfh and Th2 features

Peripheral T-cell lymphomas (PTCLs) comprise a heterogeneous group of malignancies with an aggressive clinical course. Molecular and immunophenotypic analysis have linked PTCL subgroups to derivation from differentiated T cells, including T follicular helper (Tfh), Th1, and Th2 cells. Effective therapies for these PTCLs are undefined and tumor models are limited. We developed a novel mouse model of PTCL and applied it to evaluate responses to therapy. An in vivo transplantable cell line was isolated by passaging a splenic lymphoma arising from a mouse with B cell-specific Blimp1-deletion (Cγ1-Cre Blimp1fl/fl) into C57bl/6J mice. Lymphomas were profiled by flow cytometry, immunohistochemistry, RNA, and exome sequencing. Mice intravenously inoculated with lymphoma cells developed disseminated disease affecting primarily lymphoid tissues and the liver. Model latency to welfare endpoint was 3-4 weeks. Transplantable cells expressed multiple T-cell lineage markers, were CD8 negative and CD4 positive, but gradually downregulated CD4 with passaging. Lymphoma cells (“mPTCL”) also expressed a single TCRvβ chain, suggesting origin from a T helper cell clone. Immunophenotypically, mPTCL stably expressed Tfh markers ICOS, PD-1, CD40L, and low BCL6, and thus was potentially classifiable as a surrogate PTCL of Tfh phenotype. However, the transcriptome of purified mPTCL or spleens indicated a resemblance to Th2 cells and corresponding PTCL-GATA3 subtype (a PTCL-not otherwise specified). In accord with Tfh and Th2 helper function, B cells in the tumor microenvironment had an activated phenotype but were nonexpansive. Investigation into oncogenic pathways in mPTCL revealed a predicted deleterious mutation in Ctnnb1 (β-catenin) and enrichment for Myc-activated, cell cycle regulation, and DNA damage response genes. In vivo, mPTCL progression was significantly and potently delayed by monotherapy inhibition of ataxia telangiectasia and Rad3-related (ATR), a kinase central to resolving replication stress. Taken together, we established a novel model of PTCL with overlapping Tfh and Th2 features. Our findings in this model suggest the use of a DNA damage response inhibitor as a potential treatment strategy for aggressive PTCL-GATA3 lymphomas.

Citation Format: Elizabeth Kuczynski, Giulia Morlino, Alison Peter, Dinis Calado, Charles Sinclair, Larissa Carnevalli. Molecular characterization of a mouse model of peripheral T-cell lymphoma with Tfh and Th2 features [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-20.

Abstract B17: FOXO1 is transcriptional regulator of malignant B-cell surface antigen CD20, the target for therapeutic monoclonal antibodies

Rituximab, a therapeutic anti-CD20 monoclonal antibody, is effective against B-cell malignancies, when combined with chemotherapy, such as cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP therapy). However, in case of 30-40% patients the resistance to rituximab-based therapy appears to be a serious concern. One of the major mechanisms of resistance relies on the reduced level of CD20 antigen on the surface of tumor B-cells.

While exploring the molecular mechanisms affecting the level of CD20, we found that transcription factor FOXO1 is a negative regulator of MS4A1 expression, the gene encoding CD20 antigen. Using the CRISPR/Cas9 genome-editing technology, we disrupted the loci of FOXO genes in lymphoma cell lines and discovered that ablation of FOXO1 (but not FOXO3) was sufficient for upregulation of the surface level of CD20 by 3-fold. Consistently, the complement-dependent cytotoxicity (CDC), induced by rituximab, was significantly improved in cell clones with abrogated expression of FOXO1, but not FOXO3. Importantly, the treatment with pharmacological inhibitor of FOXO1 activity, AS1842856, resulted in increased levels of CD20 on the surface of both lymphoma cell lines and patients-derived chronic lymphocytic leukemia (CLL) cells cultured ex vivo.

In order to verify our findings in the animal model, we inoculated SCID mice intravenously with Raji cells, what resulted in the development of lymphoma-like tumors. We demonstrated that mice treated systemically with rituximab, administered at a dose of 10 mg/kg, survived longer when inoculated with sgFOXO1-transduced Raji cells as compared with mice inoculated with control Raji cells (median survival 49 days versus 29 days, respectively). These results confirmed that FOXO1 ablation in lymphoma cells resulted in higher efficacy of rituximab treatment in vivo.

Taken together, these results establish FOXO1 as an important determinant of cell response to complement-dependent rituximab-induced cytotoxicity and indicate that FOXO1 inhibitors could be exploited for the therapeutic purposes, in combination with anti-CD20 monoclonal antibodies. Novel FOXO1 inhibitors with improved potency and selectivity are however urgently needed for further exploration of our discoveries in the near future.

Acknowledgments: NCN, Poland (grant no: 2013/11/B/NZ5/03240) and H2020 (STREAM project, CSA action, grant no: 692180).

Citation Format: Beata Pyrzynska, Abdessamad Zerrouqi, Michal Dwojak, Giulia Morlino, Piotr Zapala, Nina Miazek, Agnieszka Zagozdzon, Kamil Bojarczuk, Malgorzata Bobrowicz, Marta Siernicka, Marcin M. Machnicki, Joanna Barankiewicz, Ewa Lech-Maranda, Przemyslaw Juszczynski, Dinis Calado, Jakub Golab, Magdalena Winiarska. FOXO1 is transcriptional regulator of malignant B-cell surface antigen CD20, the target for therapeutic monoclonal antibodies [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B17.

BCL11A interacts with SOX2 to control the expression of epigenetic regulators in lung squamous carcinoma

Patients diagnosed with lung squamous cell carcinoma (LUSC) have limited targeted therapies. We report here the identification and characterisation of BCL11A, as a LUSC oncogene. Analysis of cancer genomics datasets revealed BCL11A to be upregulated in LUSC but not in lung adenocarcinoma (LUAD). Experimentally we demonstrate that non-physiological levels of BCL11A in vitro and in vivo promote squamous-like phenotypes, while its knockdown abolishes xenograft tumour formation. At the molecular level we found that BCL11A is transcriptionally regulated by SOX2 and is required for its oncogenic functions. Furthermore, we show that BCL11A and SOX2 regulate the expression of several transcription factors, including SETD8. We demonstrate that shRNA-mediated or pharmacological inhibition of SETD8 selectively inhibits LUSC growth. Collectively, our study indicates that BCL11A is integral to LUSC pathology and highlights the disruption of the BCL11A-SOX2 transcriptional programme as a novel candidate for drug development.

FOXO1 promotes resistance of non-Hodgkin lymphomas to anti-CD20-based therapy

Diminished overall survival rate of non-Hodgkin lymphoma (NHL) patients treated with a combination regimen of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) has been recently linked to recurrent somatic mutations activating FOXO1. Despite of the clinical relevance of this finding, the molecular mechanism driving resistance to R-CHOP therapy remains largely unknown. Herein, we investigated the potential role of FOXO1 in the therapeutic efficacy of rituximab, the only targeted therapy included in the R-CHOP regimen. We found CD20 transcription is negatively regulated by FOXO1 in NHL cell lines and in human lymphoma specimens carrying activating mutations of FOXO1. Furthermore, both the expression of exogenous mutants of FOXO1 and the inhibition of AKT led to FOXO1 activation in lymphoma cells, increased binding to MS4A1 promoter and diminished CD20 expression levels. In contrast, a disruption of FOXO1 with CRISPR/Cas9 genome-editing (sgFOXO1) resulted in CD20 upregulation, improved the cytotoxicity induced by rituximab and the survival of mice with sgFOXO1 tumors. Accordingly, pharmacological inhibition of FOXO1 activity in primary samples upregulated surface CD20 levels. Importantly, FOXO1 was required for the downregulation of CD20 levels by the clinically tested inhibitors of BTK, SYK, PI3K and AKT. Taken together, these results indicate for the first time that the AKT-unresponsive mutants of FOXO1 are important determinant of cell response to rituximab-induced cytotoxicity, and suggest that the genetic status of FOXO1 together with its transcriptional activity need further attention while designing anti-CD20 antibodies based regimens for the therapy of pre-selected lymphomas.

Morphological characterization of insect galls and new records of associated invertebrates in a Cerrado area in Bahia State, Brazil

In this study, we report the first records and morphological characterization of galls in a Cerrado area in western Bahia, Brazil. The data were collected monthly over two hours between March and September 2015. Fifteen gall morphotypes were found in twelve plant species distributed among seven families. The plant family with the greatest richness of galls was Fabaceae (n = 8). The following gall morphologies were found: globoid, lenticular, marginal leaf roll, conical, cylindrical, fusiform, spherical and pocket shaped. Cecidomyiidae induced globoid, lenticular, conical, fusiform, spherical and cylindrical morphotypes. In addition, species of microhymenoptera belonging to the Eulophidae, Eurytomidae and Encyrtidae families were found. Marginal leaf roll and pocket-shaped galls induced by Thysanoptera were also verified. Springtails were also identified as a successor. Undescribed species of Schizomyia and Lopesia were recorded in B. cupulata and Andira humilis, respectively.

miRNAs Are Essential for the Regulation of the PI3K/AKT/FOXO Pathway and Receptor Editing during B Cell Maturation

B cell development is a tightly regulated process dependent on sequential rearrangements of immunoglobulin loci that encode the antigen receptor. To elucidate the role of microRNAs (miRNAs) in the orchestration of B cell development, we ablated all miRNAs at the earliest stage of B cell development by conditionally targeting the enzymes critical for RNAi in early B cell precursors. Absence of any one of these enzymes led to a block at the pro- to pre-B cell transition due to increased apoptosis and a failure of pre-B cells to proliferate. Expression of a Bcl2 transgene allowed for partial rescue of B cell development, however, the majority of the rescued B cells had low surface immunoglobulin expression with evidence of ongoing light chain editing. Our analysis revealed that miRNAs are critical for the regulation of the PTEN-AKT-FOXO1 pathway that in turn controls Rag expression during B cell development.

Retro-umbilical ectopic testicle: report of a case

A case of a retro-umbilical ectopic testicle in a 13-year-old cryptorchid boy is reported. To our knowledge this has not been reported previously. There is no definite explanation for this highly aberrant ectopia. During the neonatal period the boy had an umbilical suppuration that required drainage. This may offer a possible explanation since the consequent healing process could have pulled the peritoneum upwards, dragging the testicle with it. Despite the high position of this testicle (and previous operation on the other side) it was easy to cross over both testes successfully to the heterolateral scrotum.