ALBERT

Description: Introduction: Advanced follicular lymphoma (FL) is a clinically and molecularly heterogeneous disease. About 20% of patients have early progression of disease (POD) and short overall survival (OS). We have previously shown that integration of lymphoma-specific gene mutations and clinical factors improves pretreatment risk stratification (Pastore, 2015) and prediction of early POD (i.e., within 24 months, POD24; Jurinovic, 2016). Recently, we have shown that high-dose therapy (HDT) followed by autologous stem-cell transplantation (ASCT) is an effective treatment option for eligible patients with high-risk disease as defined by POD24 (Jurinovic, 2018). Here, we aimed to explore whether HDT/ASCT is an effective frontline therapy for patients identified to be high-risk by clinical (i.e., FLIPI) or clinicogenetic risk models (i.e., m7-FLIPI, POD24-PI). Methods: We performed targeted DNA deep-sequencing of 〉150 genes in available diagnostic FL biopsies from 165 patients ≤60 years with advanced FL from the GLSG2000 trial who uniformly received R-CHOP as frontline treatment. Of these, 87 patients (53%) were randomized to receive consolidative HDT/ASCT, 78 (47%) were randomized to interferon maintenance. We performed intention-to-treat (ITT) survival and regression analyses to explore whether known clinical and clinicogenetic risk factors can be overcome by ASCT. Results: The HDT/ASCT and no-HDT/ASCT cohorts were balanced regarding age (48 vs 50 years), sex (49% vs 64% male patients), high-risk FL International Prognostic Index (FLIPI; 25% vs 29%), Eastern Cooperative Oncology Group Performance Score 〉1 (6% vs 5%) and mutation status of EZH2 (23% vs 18%) and TP53 (3% vs 3%). The incidence of POD24 was not significantly lower in the HDT/ASCT cohort (8% vs 14%, p=0.32). After a median follow-up of 7.5 years, 5-year failure-free survival (FFS) rates in the HDT/ASCT and no-HDT/ASCT cohorts were 77% and 69% (HR 0.7, p=0.16), 5-year OS rates were 95% and 90% (HR 0.6, p=0.21), respectively. The high-risk cohorts identified by FLIPI, m7-FLIPI, and POD24-PI comprised 27% (n=45), 18% (n=29) and 22% (n=37) of patients, respectively (Fig. A). The m7-FLIPI reclassified 10% (n=16) of patients from high-risk FLIPI to low-risk m7-FLIPI. The POD24-PI reclassified 5% (n=9) of patients from high-risk FLIPI to low-risk POD24-PI; one patient was reclassified from low-risk FLIPI to high-risk POD24-PI. Patients identified to be high-risk by all three indices had shorter FFS (FLIPI: HR 2.8, p=0.0002; m7-FLIPI: HR 3.0, p=0.0003; POD24-PI: HR 2.5, p=0.0013), but OS was not different (FLIPI: HR 1.4, p=0.47; m7-FLIPI: HR 1.5, p=0.45; POD24-PI: HR 1.5, p=0.47). The risk to develop POD24 was increased in high-risk patients (FLIPI: OR 4.4, p=0.007; m7-FLIPI: OR 4.8, p=0.005; POD24-PI: OR 4.3, p=0.008). Consolidative HDT/ASCT did not prolong FFS in high-risk patients as defined by FLIPI (HR 1.2, p=0.67), m7-FLIPI (HR 1.2, p=0.70; Fig. B) and POD24-PI (HR 1.3, p=0.63; Fig. B). Similarly, OS was not significantly improved in all three high-risk cohorts (FLIPI: HR 0.2, p=0.13; m7-FLIPI: HR n/a, p〉0.99; and POD24-PI: HR 0.3, p=0.22). In low-risk patients, HDT/ASCT was associated with a non-significant trend towards prolonged FFS (FLIPI: HR 0.5, p=0.061; m7-FLIPI: HR 0.6, p=0.16; POD24-PI: HR 0.5, p=0.068; Fig. B), but again OS was not significantly different (FLIPI: HR 0.8, p=0.69; m7-FLIPI: HR 0.8, p=0.66; and POD24-PI: HR 0.7, p=0.52). Conclusions: Our ITT-analysis confirms that consolidative HDT/ASCT should not be offered to unselected cohorts of patients with previously untreated, advanced FL after R-CHOP. Also, our current clinicogenetic risk models are not optimized to select high-risk patients who may benefit from frontline HDT/ASCT. The fraction of patients identified to be high-risk by FLIPI, m7-FLIPI and POD24-PI is low when applied to younger, medically fit patients. Moreover, the fraction of patients being reclassified by integrating gene mutation data is low in this patient cohort. Therefore, we are developing specific stratification algorithms for younger, medically fit patients who are eligible for dose-intensified approaches. Figure. Figure. Disclosures Klapper: F.Hoffman-La Roche: Honoraria, Research Funding; HTG Molecular Diagnostics, Inc.: Research Funding; Regeneron: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Takeda: Honoraria, Research Funding. Schmitz:Riemser: Honoraria, Other: Travel grants; Kite/Gilead: Honoraria, Other: Travel grants; Novartis: Honoraria, Other: Travel grants; Celgene: Other: Travel grants; Roche: Honoraria. Hess:CTI: Research Funding; Celgene: Consultancy, Honoraria, Other: travel expenses, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Unterhalt:F. Hoffman-La Roche: Other: Travel support. Dreyling:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sandoz: Membership on an entity's Board of Directors or advisory committees. Schmidt:Gilead: Honoraria, Other: Travel Grants; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grants; Celgene: Honoraria. Hoster:F. Hoffman-La Roche: Other: Travel support, Research Funding; Roche Pharma AG: Other: Travel support, Research Funding. Hiddemann:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffman-La Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Research Funding. Weigert:Roche: Research Funding; Novartis: Research Funding.

Description: The highly variable clinical course of follicular lymphoma (FL) is determined by the molecular heterogeneity of the tumor cells and complex interactions with the microenvironment. The underlying molecular mechanisms and therapeutic vulnerabilities are not well understood. IL-4 producing follicular helper T cells (TFH) have been identified as a key component of the malignant B-cell niche. IL-4 activates paracrine signaling via STAT6. In a cohort of 258 patients with advanced stage FL, we identified STAT6 mutations in 13% of diagnostic biopsies (n=33). All mutations were clustered within the DNA binding domain, mostly at D419, and included a polymorphic variant (rs11172102). Gene set enrichment analysis (GSEA) revealed that STAT6 mutant cases were significantly enriched for two distinct IL-4 gene expression signatures. Gene expression data and immunohistochemistry of primary FL samples showed significant up-regulation of IL-4/STAT6 target genes in STAT6 mutant cases, including FCER2, which encodes for CD23. We stably expressed wild type STAT6 or mutant STAT6 (D419G, N421K, and D519V) in two B-cell lymphoma lines (OCI-Ly1, OCI-Ly8), both harboring the FL hallmark translocation t(14;18). Upon IL-4 stimulation, cells expressing mutant STAT6 had significantly increased FCER2 transcript levels. Similarly, IL-4 induced expression of membrane-bound as well as soluble CD23 was significantly increased in STAT6 mutant cells. Cells expressing mutant STAT6 showed significantly increased nuclear accumulation of pSTAT6 following IL-4 stimulation. Of note, we did not observe any effect of STAT6 mutations in the absence of IL-4. RNA sequencing of IL-4-stimulated lymphoma cell lines (STAT6 mutant versus wild type) identified PARP14 -a known transcriptional co-activator of STAT6- among the top differentially expressed genes. Bioinformatics and functional experiments demonstrated that PARP14 per se is a novel STAT6 target gene. Furthermore, reporter assays showed increased transactivation activity of mutant STAT6 at the PARP14 promotor, suggesting a regulatory feed-forward loop. Pharmacological inhibition of PARP and knock-down of PARP14 completely abrogated the mutant STAT6 gain-of-function phenotype. In summary, our results suggest that PARP14 is a novel target in STAT6 mutant FL. Our data also imply that the biological and clinical impact of STAT6 mutations will heavily depend on the (targetable) upstream activation of the IL-4 signaling cascade, including the abundance of IL-4 / TFH cells in the microenvironment of FL. Disclosures Richter: HTG Molecular Diagnostics, Inc.: Research Funding. Klapper:Amgen: Honoraria, Research Funding; F.Hoffman-La Roche: Honoraria, Research Funding; HTG Molecular Diagnostics, Inc.: Research Funding; Takeda: Honoraria, Research Funding; Regeneron: Honoraria, Research Funding. Hiddemann:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffman-La Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Research Funding. Weigert:Novartis: Research Funding; Roche: Research Funding.

Description: Introduction : We have previously shown that a clinicogenetic risk model called the m7- Follicular Lymphoma (FL) International Prognostic Index (m7-FLIPI), which includes the mutation status of 7 genes (EZH2, ARID1A, MEF2B, EP300, FOXO1, CREBBP, and CARD11), the FLIPI, and the ECOG performance status improves risk stratification in patients with advanced stage FL receiving frontline immunochemotherapy (Pastore, 2015). The m7-FLIPI was trained on a group of patients treated with R-CHOP and validated on an independent cohort treated with R-CVP. The aim of this study was to test the prognostic utility of the m7-FLIPI in patients treated within the GALLIUM trial. The GALLIUM trial enrolled 1202 patients with FL randomized to either receive Rituximab (R)- or Obinutuzumab (GA101, G)-based frontline treatment (Marcus, 2017). The chemotherapy consisted either of CHOP, CVP or Bendamustine and was allocated by the treating study center. All patients had previously untreated FL, advanced stage disease (stage III/IV or stage II with bulky disease) and ECOG performance status 0-2. All patients required treatment according to the GELF criteria. Methods: We performed targeted DNA sequencing of recurrently mutated genes, including the m7-FLIPI genes from diagnostic FL biopsies. We excluded cases with no available biopsies, insufficient DNA quantity/quality, or if patients did not sign informed consent for molecular studies. 418 patients were available for evaluation of the m7-FLIPI. The m7-FLIPI was calculated as previously described (http://www.glsg.de/m7-flipi/). Investigator-assessed progression-free survival (PFS), the primary endpoint in the GALLIUM trial, was the primary endpoint of this analysis. We performed Kaplan-Meier estimation and Cox proportional hazards regression to test the prognostic utility of the m7-FLIPI. The median follow up in the evaluable cohort was 4.7 years. 283 patients (68%) received Bendamustine (140 R, 143 G), 111 (27%) received CHOP (52 R, 59 G), and 24 (6%) received CVP (12 R, 12 G). Results : 104 patients (25%) had high-risk m7-FLIPI. 90 out of 194 patients with high-risk FLIPI (46%) were reclassified as low-risk by the m7-FLIPI. High-risk m7-FLIPI was associated with shorter PFS in the overall cohort (HR 1.52, P=0.030). Likewise, the m7-FLIPI was prognostic in patients treated with R-based regimens (HR 1.67, P=0.037). However, it was not prognostic in patients treated with G-based regimens (HR 1.24, P=0.49). When analyzed by different chemotherapy regimens, the m7-FLIPI was prognostic in patients receiving CHOP/CVP-based treatment (HR 2.05, P=0.013), validating the results from our original publication. The m7-FLIPI outperformed the FLIPI (HR 1.34, P=0.31) and had a significantly higher C-index (m7-FLIPI C=0.69, FLIPI C=0.57, P=0.021). However, the m7-FLIPI was not prognostic in patients receiving Bendamustine-based treatment (HR 1.23, P=0.42). Within the m7-FLIPI, mutations in EZH2 have the highest weight of all gene mutations. In this study, we found EZH2 mutations in 93 cases (22%). EZH2 mutations were associated with longer PFS (HR 0.25, P=0.0036) in CHOP/CVP-treated patients, but not in Bendamustine-treated patients (HR 1.11, P=0.71). Interaction analysis between the chemotherapy regimen and EZH2 mutation status showed a significant interaction term of 1.49 (P=0.011) for EZH2 mutations and Bendamustine. This increased the previously favorable HR in EZH2 unmutated patients (HR 0.55 for Bendamustine vs CHOP/CVP) to an unfavorable HR of 2.42 in EZH2 mutated patients. Overall, patients with EZH2 mutant FL appeared to benefit more from CHOP/CVP, whereas patients without EZH2 mutations had longer PFS with Bendamustine-based regimens, regardless whether chemotherapy was combined with R or G (see Figure). Conclusions: Here, we validated the prognostic utility of the m7-FLIPI for patients treated with R-CHOP/CVP. However, the m7-FLIPI was not prognostic in patients treated with Bendamustine-based regimens. While EZH2 mutation status was associated with longer PFS in patients receiving CHOP/CVP regimens (with either R or G), it did not impact treatment outcome of patients treated with Bendamustine, suggesting that EZH2 mutation status is a predictive marker for differential efficacy of the chemotherapy regimen. If confirmed, the EZH2 mutation status might be a highly useful biomarker to guide the selection of the preferred upfront chemotherapy. Figure Disclosures Oestergaard: F. Hoffmann-La Roche: Employment. Knapp:F. Hoffmann-La Roche Ltd: Employment. Mundt:F. Hoffmann-La Roche: Employment. Fitzgibbon:Gilead: Speakers Bureau; Epizyme: Membership on an entity's Board of Directors or advisory committees, Research Funding. Klapper:Roche, Takeda, Amgen, Regeneron: Honoraria, Research Funding. Marcus:Roche / Genentech: Honoraria, Speakers Bureau; Gilead: Consultancy. Davies:Karyopharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Research Funding; Acerta Pharma: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; GSK: Research Funding; MorphoSys AG: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; ADCT Therapeutics: Honoraria, Research Funding; BioInvent: Research Funding. Herold:Roche: Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Gilead: Honoraria; Celgene: Honoraria. Hiddemann:F. Hoffmann-La Roche: Research Funding. Unterhalt:F. Hoffmann-La Roche: Research Funding. Hoster:Roche Pharma AG: Other: Travel support; Janssen: Research Funding. Weigert:Novartis: Research Funding; F. Hoffmann-La Roche: Research Funding.

Description: Although recent advances in molecular genetics have enabled improved risk classification of follicular lymphoma (FL) using, for example, the m7-FLIPI score, the impact on treatment has been limited. We aimed to assess the prognostic significance of copy-number aberrations (CNAs) and copy-neutral loss of heterozygosity (cnLOH) identified by chromosome genomic-array testing (CGAT) at FL diagnosis using prospectively collected clinical trial specimens from 255 patients enrolled in the SWOG study S0016. The impact of genomic aberrations was assessed for early progression (progressed or died within 2 years after registration), progression-free survival (PFS), and overall survival (OS). We showed that increased genomic complexity (ie, the total number of aberration calls) was associated with poor outcome in FL. Certain chromosome arms were critical for clinical outcome. Prognostic CNAs/cnLOH were identified: whereas early progression was correlated with 2p gain (P = .007; odds ratio [OR] = 2.55 [1.29, 5.03]) and 2p cnLOH (P = .005; OR = 10.9 [2.08, 57.2]), 2p gain specifically encompassing VRK2 and FANCL predicted PFS (P = .01; hazard ratio = 1.80 [1.14, 2.68]) as well as OS (P = .005; 2.40 [1.30, 4.40]); CDKN2A/B (9p) deletion correlated with worse PFS (P = .004, 3.50 [1.51, 8.28]); whereas CREBBP (16p) (P 〈 .001; 6.70 [2.52, 17.58]) and TP53 (17p) (P 〈 .001; 3.90 [1.85, 8.31]) deletion predicted worse OS. An independent cohort from the m7-FLIPI study was explored, and the prognostic significance of aberration count, and TP53 and CDKN2A/B deletion were further validated. In conclusion, assessing genomic aberrations at FL diagnosis with CGAT improves risk stratification independent of known clinical parameters, and provides a framework for development of future rational targeted therapies.

Description: The highly variable clinical course of follicular lymphoma (FL) is determined by the molecular heterogeneity of the tumor cells and complex interactions with the microenvironment. Here, we provide biochemical, structural, functional and clinical evidence that aberrant Cathepsin S (CTSS) activity induces a supportive immune microenvironment in FL. By targeted DNA sequencing of 305 diagnostic FL biopsies, we identified somatic mutations of CTSS in 8% of cases (24/305), mostly clustered at Y132 (19/24) converting Y to D (16/19). A subset of CTSS Y132 mutations (N=5) occurred at lower variant allele frequencies (5-10%), indicating subclonality. Another 13% of FL had CTSS amplifications (37/286). CTSS Y132 mutations and CTSS amplifications were mutually exclusive. In a cohort of 51 FL, CTSS amplifications were associated with higher CTSS expression (P=0.05). Of note, a subset of FL without CTSS amplifications also had higher CTSS expression, suggesting additional mechanisms of transcriptional dysregulation. CTSS is a cysteine protease that is highly expressed in endolysosomes of antigen presenting cells and malignant B-cells. CTSS is involved in proteolytical processing of antigenic peptides for presentation on MHC-II to be recognized by antigen specific CD4+ T-cells. CTSS is synthesized as an inactive zymogen, which is converted to its active form by autocatalytic cleavage of the autoinhibitory propeptide (pro-CTSS). We used CRISPR/Cas9 to introduce CTSS Y132D into Karpas422, a B-cell lymphoma cell line that harbors the FL hallmark translocation t(14;18). Single-cell derived Y132D mutant clones showed 〉3-fold higher ratios of active CTSS to pro-CTSS (N=4, P=0.0003). Immunoprecipitated CTSS Y132D had 〉3-fold higher in vitro substrate cleavage activity compared to CTSS wild type (WT) (N=6, P=0.001). We purified pro-CTSS WT and Y132D and assayed their in vitro autocatalytic cleavage over time. The time required to convert 50% of pro-CTSS decreased from 17 minutes for WT to 11 minutes for Y132D (N=3, P=0.04). In contrast, purified active CTSS WT and Y132 had similar in vitro cleavage activities. Molecular dynamics simulations showed that the Y132D mutation shortens the distances by ~2Å between the catalytic triad of active CTSS (C139, H278, N298) and a stretch of amino acids from the proform (L80, G81, D82, S94), which may facilitate intramolecular cleavage. By mass spectrometry we could indeed detect novel intermediate-sized CTSS fragments. Thus, Y132D does not increase the activity of the mature enzyme but is a gain-of-function mutation by accelerating the conversion from pro-CTSS to catalytically active CTSS. CD74 (invariant chain) is a physiologic CTSS substrate that plays critical roles in the assembly, trafficking and stabilization of peptide-free MHC-II. CTSS cleaves CD74, thereby allowing binding and presentation of antigens on MHC-II to antigen specific CD4+ T-cells. We could show that CTSS Y132D enhanced CD74 cleavage in Karpas422 cells. We then tested the impact of CTSS on antigen specific CD4+ T-cell activation in co-culture assays. CTSS knock-out lymphoma cells were broadly incapable of activating CD4+ T-cells. Overexpression of CTSS WT activated CD4+ T-cells more efficiently compared to empty vector control. CTSS Y132 had the highest capacity to stimulate antigen specific CD4+ T-cell responses. Furthermore, in primary FL biopsies (N=51) CTSS Y132 mutations had gene expression profiles linked with antigen-processing and chemokine perturbation, including CXCL13, a B-cell chemoattractant produced by activated CD4+ T-follicular helper cells. Lastly, we aimed to correlate CTSS aberrations with clinical outcome in patients who received standard immunochemotherapy (R-CHOP) for advanced FL (N=51 with available CTSS mutation and gene expression data). Compared to all other patients (N=34), patients with CTSS Y132 mutations or CTSS overexpression (N=17) had longer failure free survival (P=0.012) and overall survival (P=0.041). In summary, we propose that aberrant CTSS activity - even if only present in a FL subclone - can elicit a CD4+ T-cell driven tumor-promoting immune response, which could be amplified within the microenvironment via pro-inflammatory and chemotactic cytokines and substantially impact the biology and clinical course of the disease. Thus, aberrant CTSS activity is a promising biomarker and therapeutic target in FL and potentially also other tumors. Disclosures Klapper: Roche, Takeda, Amgen, Regeneron: Honoraria, Research Funding. Hiddemann:Bayer: Research Funding; Roche: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Vector Therapeutics: Consultancy, Honoraria. Steidl:Juno Therapeutics: Consultancy; Bristol-Myers Squibb: Research Funding; Nanostring: Patents & Royalties: Filed patent on behalf of BC Cancer; Roche: Consultancy; Tioma: Research Funding; Seattle Genetics: Consultancy; Bayer: Consultancy. Kridel:Gilead Sciences: Research Funding. Weinstock:Celgene: Research Funding; Verastem Oncology: Research Funding. Weigert:Novartis: Research Funding; Roche: Research Funding.

Description: Cancer cells often harbor chromosomes in abnormal numbers and with aberrant structure. The consequences of these chromosomal aberrations are difficult to study in cancer, and therefore several model systems have been developed in recent years. We show that human cells with extra chromosome engineered via microcell-mediated chromosome transfer often gain massive chromosomal rearrangements. The rearrangements arose by chromosome shattering and rejoining as well as by replication-dependent mechanisms. We show that the isolated micronuclei lack functional lamin B1 and become prone to envelope rupture, which leads to DNA damage and aberrant replication. The presence of functional lamin B1 partly correlates with micronuclei size, suggesting that the proper assembly of nuclear envelope might be sensitive to membrane curvature. The chromosomal rearrangements in trisomic cells provide growth advantage compared to cells without rearrangements. Our model system enables to study mechanisms of massive chromosomal rearrangements of any chromosome and their consequences in human cells.