Composite and sequential lymphoma between classical Hodgkin lymphoma and primary mediastinal lymphoma/diffuse large B-cell lymphoma, a clinico-pathological series of 25 cases

Composite and sequential lymphomas involving both classical Hodgkin lymphoma (CHL) and primary mediastinal B-cell lymphoma (PMBCL) are rare phenomena. Beyond the relevant biological interest raised by these cases, treatments and outcome data are poorly covered in the recent literature. This retrospective analysis describes the pathological and clinical characteristics of 10 composite and 15 sequential cases included after a central pathological review. At diagnosis, 70% of the composite lymphomas presented a disseminated and extranodal disease. Among the 15 sequential lymphomas, 12 were CHL at first occurrence and three were PMBCL. Based on their clinical evolution, these sequential lymphomas could be divided into early (i.e., diagnosis of second lymphoma within a year) and late [(i.e., a second lymphoma occurrence occurring after a long period of complete remission]). All composite cases were alive in complete remission after a median follow-up of 34 months. If the early sequential lymphoma presented a particularly poor outcome with a median overall survival shorter than one year, the late cases were efficiently salvaged. Further molecular studies are needed to describe the underlying biology of these rare diseases, possibly representing the extreme of tumour cell plasticity found in grey-zone lymphoma.

Abstract P2-05-06: Identification of specific gene signatures and alternative splice variants using exon array in Inflammatory breast Cancer

Inflammatory Breast Cancer (IBC) is a rare form of breast cancer with a particular phenotype and aggressiveness. Although significant progress has been made in the management of IBC, the prognosis remains poor. Intensive research on IBC has allowed identification of several candidate genes and pathways, but molecular findings unique to IBC have yet to be identified to improve treatment and survival. Transcriptomic studies have revealed a marked heterogeneity of IBC with limited gene overlap between studies, preventing the identification of a sensitive and specific signature in IBC.

In order to detect both gene expression levels and alternate RNA splice isoforms, we chose to perform splice-sensitive array profiling using Affymetrix Exon Array in a well-defined series of 33 IBC (core biopsies from previously untreated T4d carcinomas) compared with 28 stage I to non-inflammatory stage III breast cancers.

Gene expression analysis allowed the identification of classical molecular subtypes in both IBC and non-IBC, with overrepresentation of basal-like (17/33 vs 9/28) but no luminal A in IBC (vs 11/28). Based on Fold-Change (FC) > 1.5 and p-value < 0.05, 495 genes were significantly dysregulated between IBC and non-IBC, including in particular up-regulated hemoglobin genes and down-regulated ER-related genes in IBC compared to non-IBC. Most activated pathways were hematopoeitic cell lineage, cytokine-cytokine receptor interaction, chemokine signalling pathway and complement and coagulation cascade. We defined a 21-gene signature discriminating IBC from non-IBC with 8% error rate. To get rid of genes associated with molecular subtypes like ER-related genes, an analysis restricted to basal-like BC (17 IBC compared to 9 non-IBC) was performed allowing the definition of a 29-gene signature discriminating the whole groups of IBC from non-IBC with 3.3% error rate. Validation of this signature in the gene expression datasets from the World IBC Consortium will be presented.

Specific exon expression analysis revealed that when based on FC splicing-index and p-value, 266 exons representing 177 distinct genes were differentially regulated between IBC and non-IBC. After manually curation of results, 13 splice events representing 12 distinct genes were retained as good candidates for alternative splicing in IBC (EVL, RPL10, MYH10, HSPA8, DOCK7, DIDO1, RPL4, TRAK1, RGS1, LMO4, SMARCA4, ZNF337).

To confirm gene-signatures specific to IBC, altered pathways and major splice variants, we are performing a validation study using quantitative RT-PCR in the screening set (n=33) and in an independent series of 140 IBC compared to 200 non-stage-matched non-IBC. Finally the most dysregulated genes will also be studied at the protein level using immunohistochemistry.

Citation Format: Florence Lerebours, Sophie Vacher, Marie Le Cann, Sophie Rondeau, David Gentien, Steven Van Laere, François Bertucci, Pierre de la Grange, Ivan Bieche. Identification of specific gene signatures and alternative splice variants using exon array in Inflammatory breast Cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-05-06.

A yeast-based assay identifies drugs that interfere with immune evasion of the Epstein-Barr virus

Epstein-Barr virus (EBV) is tightly associated with certain human cancers, but there is as yet no specific treatment against EBV-related diseases. The EBV-encoded EBNA1 protein is essential to maintain viral episomes and for viral persistence. As such, EBNA1 is expressed in all EBV-infected cells, and is highly antigenic. All infected individuals, including individuals with cancer, have CD8(+) T cells directed towards EBNA1 epitopes, yet the immune system fails to detect and destroy cells harboring the virus. EBV immune evasion depends on the capacity of the Gly-Ala repeat (GAr) domain of EBNA1 to inhibit the translation of its own mRNA in cis, thereby limiting the production of EBNA1-derived antigenic peptides presented by the major histocompatibility complex (MHC) class I pathway. Here we establish a yeast-based assay for monitoring GAr-dependent inhibition of translation. Using this assay we identify doxorubicin (DXR) as a compound that specifically interferes with the GAr effect on translation in yeast. DXR targets the topoisomerase-II-DNA complexes and thereby causes genomic damage. We show, however, that the genotoxic effect of DXR and various analogs thereof is uncoupled from the effect on GAr-mediated translation control. This is further supported by the observation that etoposide and teniposide, representing another class of topoisomerase-II-DNA targeting drugs, have no effect on GAr-mediated translation control. DXR and active analogs stimulate, in a GAr-dependent manner, EBNA1 expression in mammalian cells and overcome GAr-dependent restriction of MHC class I antigen presentation. These results validate our approach as an effective high-throughput screening assay to identify drugs that interfere with EBV immune evasion and, thus, constitute candidates for treating EBV-related diseases, in particular EBV-associated cancers.

Polyunsaturated fatty acids inhibit PI3K activity in a yeast-based model system

The phosphatidylinositol 3-kinase (PI3K) pathway controls the regulation of cell growth, proliferation, migration and apoptosis. In many tumors, the PI3K gene is mutated or overexpressed, and/or the PI3K pathway is hyperactive. PI3K is therefore a potential pharmacological target for the development of anti-tumor drugs. Some polyunsaturated fatty acids (PUFA), when given in the diet, may lead to a decrease in PI3K activity. We used a yeast-based model to reconstitute the PI3K/PTEN/Akt pathway to study the effects of long-chain polyunsaturated n-3 fatty acids on PI3K, and found that various PUFA were able to alleviate toxicity induced by overexpression of PI3K. The various PUFA had no significant effect on the steady-state level of PI3K catalytic subunit proteins (p110alpha) in yeast. However, depletion of phosphatidylinositol 4,5-bisphosphate due to overexpression of the p110alpha subunit was significantly reduced by treating the yeast cells with the various PUFA. The inhibition of mammalian PI3K, expressed in an exogenous cellular context in yeast, is likely to be a direct effect of these PUFA on PI3K rather than on other mammalian endogenous or environmental factors. These results are particularly promising given the abundance of active PUFA in marine foodstuffs and especially fish oils.