RHOA Mutations Research Articles

Tumor-derived RHOA mutants interact with effectors in the GDP-bound state

RHOA mutations are found at diverse residues in various cancer types, implying mutation- and cell-specific mechanisms of tumorigenesis. Here, we focus on the underlying mechanisms of two gain-of-function RHOA mutations, A161P and A161V, identified in adult T-cell leukemia/lymphoma. We find that RHOAA161P and RHOAA161V are both fast-cycling mutants with increased guanine nucleotide dissociation/association rates compared with RHOAWT and show reduced GTP-hydrolysis activity. Crystal structures reveal an altered nucleotide association in RHOAA161P and an open nucleotide pocket in RHOAA161V. Both mutations perturb the dynamic properties of RHOA switch regions and shift the conformational landscape important for RHOA activity, as shown by 31P NMR and molecular dynamics simulations. Interestingly, RHOAA161P and RHOAA161V can interact with effectors in the GDP-bound state. 1H-15N HSQC NMR spectra support the existence of an active population in RHOAA161V-GDP. The distinct interaction mechanisms resulting from the mutations likely favor an RHOAWT-like “ON” conformation, endowing GDP-bound state effector binding activity.

Phase 2 trial of the farnesyltransferase inhibitor tipifarnib for relapsed/refractory peripheral T-cell lymphoma

AbstractA phase 2, international, open-label, nonrandomized, single-arm trial was conducted to evaluate the efficacy and safety of tipifarnib, a farnesyltransferase inhibitor, as monotherapy for relapsed/refractory peripheral T-cell lymphoma (PTCL) and to evaluate tumor mutation profile as a biomarker of response. Adults with relapsed/refractory PTCL received tipifarnib 300 mg orally twice daily for 21 days in a 28-day cycle. The primary end point was objective response rate (ORR); secondary end points included ORR, progression-free survival (PFS), duration of response (DOR), and adverse events (AEs) in specific subtypes. Sixty-five patients with PTCL were enrolled: n = 38 angioimmunoblastic T-cell lymphoma (AITL), n = 25 PTCL not otherwise specified, and n = 2 other T-cell lymphomas. The ORR was 39.7% (95% confidence interval [CI], 28.1-52.5) in all patients and 56.3% (95% CI, 39.3-71.8) for AITL. Median PFS was 3.5 months overall (954% CI, 2.1-4.4), and 3.6 months (95% CI, 1.9-8.3) for AITL. Median DOR was 3.7 months (95% CI, 2.0-15.3), and greatest in patients with AITL (7.8 months; 95% CI, 2.0-16.3). The median overall survival was 32.8 months (95% CI, 14.4 to not applicable). Tipifarnib-related hematologic AEs were manageable and included neutropenia (43.1%), thrombocytopenia (36.9%), and anemia (30.8%); other tipifarnib-related AEs included nausea (29.2%) and diarrhea (27.7%). One treatment-related death occurred. Mutations in RhoA, DNMT3A, and IDH2 were seen in 60%, 33%, and 27%, respectively, in the AITL tipifarnib responder group vs 36%, 9%, and 9% in the nonresponder group. Tipifarnib monotherapy demonstrated encouraging clinical activity in heavily pretreated relapsed/refractory PTCL, especially in AITL, with a manageable safety profile. This trial was registered at www.ClinicalTrials.gov as #NCT02464228.

Identification of New Pathogenic Variants of Hereditary Diffuse Gastric Cancer.

Hereditary diffuse gastric cancer (HDGC) presents a significant genetic predisposition, notably linked to mutations in the CDH1 and CTNNA1. However, the genetic basis for over half of HDGC cases remains unidentified. The aim of this study is to identify novel pathogenic variants in HDGC and evaluate their protein expression. Among 20 qualifying families, two were selected based on available pedigree and DNA. Whole genome sequencing (WGS) on DNA extracted from blood and whole exome sequencing on DNA from formalin-fixed paraffin-embedded tissues were performed to find potential pathogenic variants in HDGC. After selection of a candidate variant, functional validation, and enrichment analysis were performed. As a result of WGS, three candidate germline mutations (EPHA5, MCOA2, and RHOA) were identified in one family. After literature review and in-silico analyses, the RHOA mutation (R129W) was selected as a candidate. This mutation was found in two gastric cancer patients within the family. In functional validation, it showed RhoA overexpression and a higher GTP-bound state in the RhoaR129W mutant. Decreased phosphorylation at Ser127/397 suggested altered YAP1 regulation in the Rho-ROCK pathway. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses linked RhoaR129W overexpression to changed migration/adhesion in MKN1 cell line. However, this RHOA mutation (R129W) was not found in index patients in other families. The RHOA mutation (R129W) emerges as a potential causative gene for HDGC, but only in one family, indicating a need for further studies to understand its role in HDGC pathogenesis fully.

Genomic and Pathologic Profiling of Very Well-Differentiated Gastric Adenocarcinoma of Intestinal Type: A Study With Emphasis on Diffuse-Type Transformation.

Very well-differentiated adenocarcinoma of intestinal type is a distinct subtype of gastric cancer characterized by anastomosing glands with a hand-in-hand pattern and low-grade cytologic atypia resembling intestinal metaplasia. This is a slow-growing neoplasm with an indolent clinical course; however, a subset demonstrates transformation into adenocarcinoma with higher-grade histology, typically diffuse-type carcinoma, and behaves aggressively. This study aimed to better characterize the genomic and pathologic features, with a focus on factors associated with diffuse-type transformation. A total of 58 cases with (n=31) and without (n=27) diffuse-type transformation were analyzed for molecular and pathologic features. First, comprehensive deep DNA sequencing was conducted in 18 cases (discovery cohort), followed by a digital droplet polymerase chain reaction of hot spot RHOA mutations in 40 cases (validation cohort). In total, RHOA mutations were the most common alteration (34%), followed by loss of ARID1A (12%), p53 alterations (10%), and CLDN18 :: ARHGAP26/6 fusions (3.4%). FGFR2 amplification was identified in an advanced case with a p53 alteration. Altered p53 expression was recognized only in higher-grade components and was significantly associated with advanced disease ( P =0.0015) and diffuse-type transformation ( P =0.026). A mixed mucin phenotype was also strongly correlated with advanced disease ( P <0.001) and diffuse-type transformation ( P <0.001). Decreased E-cadherin expression was frequently observed (74%) in poorly cohesive components. This study demonstrated that a subset of RHOA -mutant diffuse-type gastric cancers develops through the transformation of very well-differentiated adenocarcinoma of intestinal type. Our observations suggest a mixed mucin phenotype as a risk factor and alterations in p53 and E-cadherin as drivers of diffuse-type transformation.

Abstract 4388: Tumor-associated RhoA mutants interact with effectors in both GDP- and GTP-bound states

Abstract RhoA is the founding member of the Ras-homology (Rho) small GTPase family and is a master regulator for multiple cell functions. Recurrent RhoA mutations have been identified in several human cancers, particularly in leukemia/lymphoma and gastric cancer. Intriguingly, both gain-of-function and loss-of-function mutations of RhoA are present, suggesting that RhoA GTPase may have a more sophisticated role in cancer and requires more rigorous investigations. Here, we have focused on two of the gain-of-function RhoA mutations identified in Adult T cell Leukemia/lymphoma (ATLL) at residue A161 (A161P and A161V) and aim to reveal the underlying mechanistic basis for their function by biochemical and structural analyses. We found that in contrast to conventional gain-of-function RhoA mutants such as RhoAG14V and RhoAQ63L which affect the GTP-hydrolysis activity, RhoAA161P and RhoAA161Vare both fast-cycling with drastically increased nucleotide dissociation and association rates, but only slightly reduced GTP-hydrolysis activity. We solved the crystal structures of GDP-bound RhoAA161P and RhoAA161V and saw that while RhoAA161P displays impaired solvent-mediated interactions to the bound nucleotide, RhoAA161V has a more exposed nucleotide binding pocket compared to RhoAWT and RhoAA161P. Interestingly, RhoAA161P and RhoAA161Vcan interact with effector targets in the GDP-bound states. Further 1H-15N HSQC NMR study provides evidence of the active population in GDP-bound RhoAA161V. Molecule dynamics (MD) simulations show that the dynamic properties of RhoA switch regions are affected differently by the two mutations. Thus, RhoAA161V and RhoAA161P are fast-cycling mutants with distinct mechanisms, and both likely endow their GDP-bound state towards an active conformation. These findings provide a better understanding of the oncogenic role of RhoA mutations in cancer and shine light on how changes in RhoA protein dynamic properties caused by mutations may affect its function. Citation Format: Yuan Lin, Theresa A. Ramelot, Simge Senyuz, Attila Gursoy, Hyunbum Jang, Ruth Nussinov, Ozlem Keskin, Yi Zheng. Tumor-associated RhoA mutants interact with effectors in both GDP- and GTP-bound states [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4388.

Abstract 7506: Comprehensive mutational profile of true single circulating tumor cells compared with CtDNA in advanced pancreatic adenocarcinoma

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is aggressive malignancy characterized by 5-year survival rate of &amp;lt;10%. Comprehending PDAC's mutational landscape through NGS-based assays, acquiring representative tumor tissue biopsies remains arduous. Single circulating tumor cell (sCTC) genomics could provide clinically relevant personalized diagnostics. Here we demonstrate comparative analysis of sCTCs genomics and ctDNA outcomes in paired advanced PDAC patients. Methods: Retrospectively, 25 live sCTCs and sCTC clusters were isolated from 10 advanced PDAC patients' blood using OncoRadar platform consisting glass beads conjugated with antiEPCam antibodies, tuned for releasing CTCs, without cell fixing, an assay in 96 well plate. Whole genomes from sCTCs were amplified using random degenerate primer-based PCR. Amplified genomes and paired ctDNA were subjected to CGP using clinical assay OncoIndx® to identify patient-specific genomic alterations in sCTC and paired ctDNA samples. The raw sequence alignment and variant calling was performed using iCare software®. Results: Live 25 sCTCs and 8 CTC clusters were isolated (≥2 CTCs). Mutational profiling revealed multiple pathogenic (P) and likely pathogenic (LP) variants. sCTCs exhibited at least twice as many P variants compared to paired ctDNA samples, with CHD4, FGFR2, and HNF1α being the most common. The mutational profile of sCTCs showed concordance with at least one variant in paired ctDNA, and was enriched in dysregulated cytoskeleton and cell migration machinery. Specifically, COL7A, KIF5B, and RHOA mutations were prevalent in almost all sCTCs, with exclusive mutations (KIF5B and RHOA) in some cases. KRAS P variants were exclusive to 50% of ctDNA samples, paired sCTCs exhibited NRAS P variants. RAS isoforms were observed in 70% of sCTCs. Gene amplification occurred in CCND1/2, FGFR2, and ERBB2 in 90% of sCTCs, with CCND1 amplification more prevalent in sCTC clusters. Mutations in epigenetic repressors (HDAC1, KDM2B) were ubiquitous in sCTCs, co-occurring with DDR pathway mutations (F test, P 0.003, OR 11). Loss-of-function BRCA mutations were detected in 60% of sCTCs, and were absent in paired ctDNA. Additionally, 70% of sCTCs exhibited therapy-resistant variants (NF1, STK11, ARID1A, and PIK3CA), contrasting with a 10% frequency in paired ctDNA. Conclusions: Genomic profile of sCTCs in advanced PDAC patients revealed a complex mutational landscape, providing additional clinically relevant insights that complemented ctDNA findings. sCTCs exhibited greater tumor mutational heterogeneity compared to paired ctDNA samples, and detected additional actionable pathogenic variants. Results suggest that sCTCs may offer therapeutically relevant molecular information for advanced PDAC patients for whom tissue is unavailable and ctDNA fails to provide actionable therapy options. Citation Format: Jayant Khandare, Atul Bharde, Ganesh Khutale, Saloni Andhari, Richa Deshpande, Kanchan Hariramani, Madhura Basavalingegowda, Vikas Jadhav, Mohan Uttarwar, Gowhar Shafi. Comprehensive mutational profile of true single circulating tumor cells compared with CtDNA in advanced pancreatic adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7506.

Mutational, immune microenvironment, and clinicopathological profiles of diffuse large B-cell lymphoma and follicular lymphoma with BCL6 rearrangement.

BCL6-rearrangement (BCL6-R) is associated with a favorable prognosis of follicular lymphoma (FL), but the mechanism is unknown. We analyzed the clinicopathological, immune microenvironment (immune checkpoint, immuno-oncology markers), and mutational profiles of 10 BCL6-R-positive FL, and 19 BCL6-R-positive diffuse large B-cell lymphoma (DLBCL) cases (both BCL2-R and MYC-R negative). A custom-made panel included 168 genes related to aggressive B-cell lymphomas and FL. FL cases were nodal, histological grade 3A in 70%, low Ki67; and had a favorable overall and progression-free survival. DLBCL cases were extranodal in 60%, IPI high in 63%, non-GCB in 60%, EBER-negative; and had a progression-free survival comparable to that of DLBCL NOS. The microenvironment had variable infiltration of M2-like tumor-associated macrophages (TAMs) that were CD163, CSF1R, LAIR1, PD-L1, and CD85A (LILRB3) positive; but had low IL10 and PTX3 expression. In comparison to FL, DLBCL had higher TAMs, IL10, and PTX3 expression. Both lymphoma subtypes shared a common mutational profile with mutations in relevant pathogenic genes such as KMT2D, OSBPL10, CREBBP, and HLA-B (related to chromatin remodeling, metabolism, epigenetic modification, and antigen presentation). FL cases were characterized by a higher frequency of mutations of ARID1B, ATM, CD36, RHOA, PLOD2, and PRPRD (p < 0.05). DLBCL cases were characterized by mutations of BTG2, and PIM1; and mutations of HIST1H1E and MFHAS1 to disease progression (p < 0.05). Interestingly, mutations of genes usually associated with poor prognosis, such as NOTCH1/2 and CDKN2A, were infrequent in both lymphoma subtypes. Some high-confidence variant calls were likely oncogenic, loss-of-function. MYD88 L265P gain-of-function was found in 32% of DLBCL. In conclusion, both BCL6-R-positive FL and BCL6-R-positive DLBCL had a common mutational profile; but also, differences. DLBCL cases had a higher density of microenvironment markers.

Oncogenic aberrations in primary gastric cancer tumors to predict metachronous peritoneal metastasis.

392 Background: Peritoneal metastases (PM) in gastric cancer (GC) portend a poor prognosis. Yet, there are a paucity of data on underlying genomic alterations predictive of GCPM. Methods: Two-hundred and nine patients who underwent primary tumor (PT) surgical resection were included in the prospective cohort. Whole exome sequencing (WES) of these resected PT GC specimens (average coverage 129X for tumor samples, 70X coverage for matched normal/blood controls) were undertaken. Participants were followed-up longitudinally for peritoneal metastases. Results: Fifty-one (51/209, 24.4%) patients developed PM after a median follow-up duration of 87.0 months and had poorer survival outcomes compared to patients without metastasis (log-rank, p&lt;0.001). Patients with bulkier and more advanced tumors were at increased hazard of PM (T-stage and N-stage stratified analysis, log-rank, p&lt;0.0001). Consistent with known clinical outcomes, The Cancer Genome Atlas (TCGA) genomically stable (GS) subtype (log-rank, p=0.0059) and mesenchymal subtype GC were associated with a higher proclivity for peritoneal organotropism (log-rank, p=0.020). Among patients who developed PM, TP53 was the most commonly altered driver mutation (25/51, 49.0%), followed by ARID1A (9/51, 17.6%), CDH1 (8/51, 15.7%), PIK3CA (6/51, 11.8%). Comparing the PTs of patients with PM against those PTs without PM, ELF3, CDH1 and PIGR were significantly associated with PM (all adjusted p&lt;0.05). Amongst TCGA GS tumors, ARID1A mutations (p=0.018) were significantly associated with PM compared to patients with GS tumors with no metastasis. CDH1 mutations were found to significantly co-occur with PIGR and RHOA mutations and was mutually exclusive to TP53. ARID1A mutations were also found to significantly co-occur with multiple other mutations such as PTEN, PIK3CA, ERBB2, and KRAS. Conclusions: CDH1, PIGR, ELF3 mutations in primary GC tumors were found to be significantly associated with metachronous PM.

RHOA drivers take alternate routes in gastric cancer.

Oncogenic small guanosine triphosphatases (GTPases) are often characterized by a limited set of activating mutations that affect their intrinsic biochemical function, but RHOA-which is frequently mutated in gastric cancer-appears not to have read the instruction manual. Having previously characterized the Y42C RHOA mutation in gastric cancer, in this issue of Science Signaling, Schaefer et al. take on the slightly less common L57V mutation and find that individual RHOA mutations can have different and unpredictable signaling outcomes.

RHOAL57V drives the development of diffuse gastric cancer through IGF1R-PAK1-YAP1 signaling.

Cancer-associated mutations in the guanosine triphosphatase (GTPase) RHOA are found at different locations from the mutational hotspots in the structurally and biochemically related RAS. Tyr42-to-Cys (Y42C) and Leu57-to-Val (L57V) substitutions are the two most prevalent RHOA mutations in diffuse gastric cancer (DGC). RHOAY42C exhibits a gain-of-function phenotype and is an oncogenic driver in DGC. Here, we determined how RHOAL57V promotes DGC growth. In mouse gastric organoids with deletion of Cdh1, which encodes the cell adhesion protein E-cadherin, the expression of RHOAL57V, but not of wild-type RHOA, induced an abnormal morphology similar to that of patient-derived DGC organoids. RHOAL57V also exhibited a gain-of-function phenotype and promoted F-actin stress fiber formation and cell migration. RHOAL57V retained interaction with effectors but exhibited impaired RHOA-intrinsic and GAP-catalyzed GTP hydrolysis, which favored formation of the active GTP-bound state. Introduction of missense mutations at KRAS residues analogous to Tyr42 and Leu57 in RHOA did not activate KRAS oncogenic potential, indicating distinct functional effects in otherwise highly related GTPases. Both RHOA mutants stimulated the transcriptional co-activator YAP1 through actin dynamics to promote DGC progression; however, RHOAL57V additionally did so by activating the kinases IGF1R and PAK1, distinct from the FAK-mediated mechanism induced by RHOAY42C. Our results reveal that RHOAL57V and RHOAY42C drive the development of DGC through distinct biochemical and signaling mechanisms.

Angioimmunoblastic T-Cell Lymphoma with Concurrent EBV Viremia: A Challenging Case

Abstract Introduction/Objective Angioimmunoblastic T-cell lymphoma (AITL) represents only 1-2% of all non-Hodgkin lymphomas but is one of the most common non-cutaneous T-cell lymphomas. Although typically associated with latent Epstein Barr Virus (EBV) infection, recent studies have demonstrated the presence and prognostic impact of EBV viremia at the time of diagnosis. Here, we present a case of AITL in which the diagnosis was complicated by EBV viremia. Methods/Case Report A 41-year-old male presented to our hospital with generalized abdominal pain, diffuse lymphadenopathy, hepatomegaly, ascites, and diffuse body wall edema. A recent retroperitoneal lymph node biopsy reportedly demonstrated features suggesting an infectious process, and EBV PCR revealed a viral load of 141,050 copies/mL. A left axillary lymph node was excised, which demonstrated vascular proliferation and diffuse architectural effacement by a polymorphous infiltrate including variably sized lymphocytes with moderate to abundant clear cytoplasm, and occasional admixed neutrophils, plasma cells, and eosinophils. Immunohistochemical staining demonstrated an atypical CD4-positive, CD7-negative T-cell population in a vaguely nodular distribution, expressing Bcl-6, PD-1, ICOS, and CXCL13 without definite CD10 expression. CD21 immunostaining demonstrated markedly expanded follicular dendritic cell meshworks in a distribution similar to the atypical T-cell population. No B-cell or cytotoxic T-cell proliferation was seen, and in situ hybridization for EBV-encoded RNA (EBER ISH) demonstrated only scattered EBV- positive cells. Taken together, these findings supported a diagnosis of AITL over an atypical reaction to EBV infection. Next-generation sequencing demonstrated mutations in TET2, IDH2, and RHOA, further confirming the diagnosis. Results (if a Case Study enter NA) NA Conclusion AITL manifests with a diverse range of clinical symptoms and pathological features and may mimic infection. Additionally, acute EBV infection is well-known to mimic various lymphomas and has rarely been reported to mimic AITL. We present this case to raise awareness of the concurrent presentation of AITL with EBV viremia and to highlight features that may be helpful in distinguishing between the two.

Anti-PD-1 Antibody (Tislelizumab) Combined with R-CHOP for the Treatment of Previously Untreated Primary Mediastinal B-Cell Lymphoma: A Prospective Phase II Study

Background: Primary mediastinal B-cell lymphoma (PMBCL) is a rare aggressive B-cell lymphoma of thymic origin. Due to the low incidence rate of PMBCL, there is currently no internationally accepted standard first-line treatment regimen. Dose-adjusted (DA) EPOCH-R which is the more commonly used first-line therapy plan is not so effective because patients usually cannot tolerate it. The R-CHOP regimen is comparable to the R-DA-EPOCH for the first-line treatment of PMBCL in terms of survival and has a better safety profile (Bhatt, V.R. et al, Cancer Treat Rev 2015; Iwanicka el al., Curr Hematol Malig Rep 2014). Meanwhile, patients with PMBCL usually have alterations of 9p24.1, leading to overexpression of PDL-1/2. Previous studies have found that PD-1 monoclonal antibody shows good efficacy in recurrent and refractory PMBCL (Steidl et al., Blood 2011; Zinzani et al., Blood 2017). Tislelizumab, a humanized IgG4 antibody that binds PD-1 with high affinity, minimizes binding to Fcγ receptor 1 (FcγRI) on macrophages by the genetic engineering of Fc segment, abrogating antibody-dependent phagocytosis (ADCP)-induced T-cell clearance. The efficacy and safety of its combination with R-CHOP in previously untreated PMBCL is not yet clear. We speculate that the combination of both may be a new option for the first-line therapy for PMBCL patients with good efficacy and low toxicity. Methods: This is a single-arm, multi-center, phase II clinical study (ChiCTR2100044313). Patients aged 18 years or older with a diagnosis of PMBCL and previously untreated were eligible. Eligible patients received 6 cycles of Tislelizumab (200 mg D1), Rituximab (375 mg/m 2 D1), Cyclophosphamide (750 mg/m 2 D2), Pirarubicin (50 mg/m 2 D2), Vincristine (1.4 mg/m 2, maximum dose 2 mg, D2), Prednisone (100 mg/d D2-6), every 21 days for 1 cycle. Disease response assessments were performed by positron emission tomography and computed tomography (PET-CT) or enhanced CT every two cycles, meanwhile peripheral blood ctDNA was monitored, and treatment-related adverse effects were assessed and recorded. The primary endpoint was objective remission rate (ORR). The secondary endpoints included treatment safety, progression-free survival (PFS) and overall survival (OS), and the exploratory analyses of the correlation between PD-L1 expression in tumor tissues, tumor-associated macrophages (TAM) phenotype in tumor microenvironment and efficacy. Results: From June 2020 to June 2023, 12 patients were enrolled and 9 patients had evaluable efficacy with the median age of 34 years, 3 males and 6 females, all patients had large mediastinal mass at initial diagnosis. 7 patients had PD-L1 expression (VENTANA SP263) above 80% and 2 cases could not be further tested due to insufficient tissue specimens. The ORR was 100%, and the CR rate was 77.8% (7/9) after 6 cycles of treatment. The 5 th and 9 th patient reached PR after 6 cycles of treatment due to irregular hospitalization. And CR was achieved after 2 cycles of regular treatment for the 5 th patient. NGS from formalin-fixed paraffin-embedded (FFPE) and circulating tumor DNA (ctDNA) evaluation from blood were performed across all patients before treatment. 5 patients underwent end of treatment-ctDNA test. Median follow-up 15m (6.8m-26.3m), the third patient was lost to follow-up at 9m. The other patients who achieved CR are still at complete remission. Moreover, we found SOCS1, TNFAIP3 are the most frequently mutated genes in biopsies of PMBCL and only the 5th patient had RHOA mutation which is highly related to PMBCL. The PET-CT and ctDNA assessments were negative in three patients at the end of 6 cycles with 60% concordance, and the 5 th and 9 th patient achieved PR on PET-CT, but the ctDNA assessments were negative. The most common adverse events (AEs) were gastrointestinal reactions, 2 patients experienced grade IV myelosuppression and 1 patient had grade I hyperthyroidism. No treatment-related deaths occurred. Conclusion: Tislelizumab combined with R-CHOP for the treatment of previously untreated PMBCL had good efficacy and sustained response with low toxicity. Longer follow-up is required to access the survival benefit of this regimen. Figure 1: Disease Remission in the Included Patients

Significance of the Rhoa G17V Mutation Detected By Ddpcr in Diagnostic and Monitor of Angioimmunoblastic T-Cell Lymphoma

Introduction Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma (PTCL) that originates from T follicular helper cells (TFH). RHOA G17V mutation is the most common hotspot locus which could be detected in 50%-70% of cases, showing its potential value for the diagnosis and clinical monitor of this disease. Methods RHOA G17V mutation were detected by Droplet digital PCR (ddPCR) in available samples from PTCL patients, at baseline and before every cycle. Response assessments were done by PET/CT and evaluated according to Lugano criteria after 3 cycles and end of first line chemotherapy(EOT), or at suspicious of disease progression. All data analyses were performed using SPSS 20.0 software (SPSS, Inc.) and GraphPad Prism 9.0 software (GraphPad software). p-Value &amp;lt; 0.05 was considered statistically significant. Results 30 patients with PTCL were included in our center from 2021-01-01 to 2023-07-01,21 were confirmed as AITL and 9 were PTCL-NOS by pathologist review. In whole cohort, RHOA G17V mutation could be detected in 46.7%(14/30) of all patients, also was positive in 61.9%(13/21) and negative in 38.1% (9/21) of patients with AITL. The sensitivity and specificity of RHOA G17V mutation in AITL by ddPCR is 61.9% and 88.9%, with a positive predictive value of 92.9%, and a negative predictive value of 50%. Hyperglobulinemia, positive direct Coombs test, elevated LDH, elevated β2-MG were founded in 76.9%(10/13),61.5%(8/13) ,61.5%(8/13) and 76.9% (10/13) of AITL patients with RHOA G17V mutation, which were significantly higher than those without RHOA G17V mutation(P=0.002,0.019,0.019,0.026). Furthermore, all of the of RHOA G17V mutated AITL patients were in clinical stage III or IV(100%, 13/13), 76.9%(10/13) of them with detectable whole-blood EBV-DNA(≥500 copies/mL) and all have three or more TFH markers(100%,13/13). We next evaluated the baseline and dynamical changes in RHOA G17V VAF-positive patients with AITL. Pretreatment VAF was significantly lower for patients who achieved complete remission or partial remission at EOT compared with that of patients with progressive disease or stable disease (mean VAF, 20.75% vs. 4.31%, p = 0.0028). (Figure 1). In addition, the median PFS in AITL patients with and without RHOA G17V mutation was 9.157 months and 15.154 months respectively(P=0.32).Finally, in 10 AITL patients with dynamic results of RHOA G17V mutation (Figure 2) , a good correlation was found in between dynamic changes of VAF of RHOA G17V mutation and response assessment by PET/CT, rerise of RHOA G17V mutation VAF could be detected prior to clinical progression in two patients，showing for the its protentional value for disease monitor. Conclusions Our study first reported the diagnostic value of single hotspot detection of G17V RHOA mutation by ddPCR in PTCL. Monitoring of G17V RHOA mutation in AITL has predictive value of assess tumor burden and response, also can complement the longitudinal supervise of disease.

Phase 1 Pharmacodynamic and Pharmacokinetic Study of the Geranylgeranyltransferase I Inhibitor PTX-100 (GGTI-2418) in Patients with Advanced Malignancies

Introduction: The RAS superfamily of small GTPases mediate hallmarks of cancer cell proliferation, viability, migration, invasion and metastasis. Several GTPases such as RAL, RHO and RAC are required for RAS to induce malignant transformation. RAS post-translational modification (PTM) by farnesyltransferase (FT) as well as RAL, RHO and RAC PTM by geranylgeranyltransferase 1 (GGT-1) are critical for the membrane localization and oncogenicity of these GTPases. Mutations in HRAS, NRAS, KRAS and RHOA are prevalent in solid tumors as well as T-cell lymphomas (TCL) such as peripheral T-cell lymphoma (PTCL), angioimmunoblastic T-cell lymphoma (AITL), PTCL-not otherwise specified and cutaneous T-cell lymphoma (CTCL). PTX-100 is a small molecule inhibitor of GGT-1 that disrupts the oncogenic activity by inhibiting RAL, RHO and RAC PTM. Methods: This ongoing phase 1 study (NCT03900442) in 2 Australian sites, consists of a 3+3 dose escalation with an expansion phase. The aim is to evaluate the pharmacodynamic (PD), pharmacokinetics (PK), preliminary efficacy and safety of 500, 1000 and 2000 mg/m 2 PTX-100 in patients (pts) with advanced malignancies. PTX-100 is administered by IV infusion over 60 minutes days 1 to 5 of a 14 day cycle for 4 cycles. Disease response is assessed via CT, MRI or PET-CT or per SOC after 4 cycles. Pts with a complete response (CR), partial response (PR) or stable disease (SD) may be eligible for continued treatment with PTX 100, dosed in 21 day cycles with response assessment every 3 months. Results: The first pt was enrolled in October 2019 and enrollment is nearly completed in the expansion cohort. The data cutoff was 10 th July 2023. Ten pts were enrolled into Part 1 with 3 dosed at 500 mg/m 2, 3 at 1000 mg/m 2 and 4 at 2000 mg/m 2. The expansion cohort at 2000 mg/m 2 began in May 2022 and there have been 10/15 enrolled to date. Positive long-term responses (32 and 13.8 months) were observed for 2 TCL pts in Part 1 so the decision was made to enroll TCL pts into the expansion cohort. The median age was 67 years (44 to 81), the median number of prior lines was 3 (1-6). The TCL subtypes were PCTL NOS (n=6), AITL (n=3), and CTCL (n=5). Of the 14 enrolled TCL pts, 10 pts had response assessments after 4 cycles, with an overall response rate (ORR) of 40% (4pts), including 10% (1 pt) CR, 30% (3pts) PR. Two CTCL pts (20%) had durable SD &amp;gt;6 months, contributing to a 60% Disease Control Rate. The median Progression Free Survival (PFS) for all TCL pts was 5.3 mos, CTCL pts 13.6 mos and PTCL pts 2.5 mos. No responses were observed in the 5 solid tumor pts. There were 23 Grade ≥3 adverse events in 8 pts including laboratory neutropenia in 2 pts with 1 deemed possibly related. Neutrophil count decreased in 2 pts with 1 deemed possibly related and the platelet count decreased in 2 pts with 1 deemed possibly related. Grade 1-2 adverse events deemed possibly related included, nausea reported in 4 pts and diarrhea in 3 pts. For the PD studies, we determined the effects of PTX-100 on the geranylgeranylation (GG) of the small GTPase RAP1 in peripheral blood monocytes (PBMCs) isolated from pts on cycle 1, day 1 (prior to treatment) and subsequently on days 2, 3, 4, 5, and 8. PTX-100 inhibited GG of RAP1A as early as 1 day after treatment, and with the majority of the pts, the inhibition of RAP1A GG persisted three days after the last dose of PTX-100. Inhibition of RAP1 GG was observed with all doses including the lowest dose of 500 mg/m 2. PK analysis is underway at the time of abstract preparation and the PK parameters will be presented at the meeting. Conclusions: Preliminary data from this phase 1 dose escalation study of PTX-100 indicates promising safety profile in this difficult to treat pt population. PTX-100 demonstrated clinical activity in TCL with an ORR of 40%, and a median PFS for all TCL pts of 5.3 months. PD studies demonstrated that the GGT-1 target was engaged with sustained inhibition of RAP1 GG.

Validation of Circulating Tumor DNA As an Alternative to Tumor Tissue Biopsy in Genotyping across Multiple Lymphoma Subtypes

Introduction Genotyping plays an important role in the diagnosis, risk stratification and treatment response surveillance of lymphoma, a disease with considerable heterogeneity in clinical and pathological characteristics. To date, tumor tissue biopsy based genotyping is still considered as gold standard in lymphoma, but its application is hampered by the invasive nature and imperfect performance in capturing spatial and temporal tumor heterogeneity. Circulating tumor DNA (ctDNA), which is shed into peripheral blood by apoptotic or necrotic tumor cells, has shown the potential as a noninvasive alternative to tumor tissue DNA (tDNA) for molecular profiling. Many efforts have been made to investigate the feasibility of ctDNA based on next-generation sequencing (NGS) in lymphoma, but most of the studies were conducted in Caucasian population and limited to B-cell lymphoma patients. In the present study, we evaluated the performance of plasma-derived ctDNA against tDNA based genotyping across multiple lymphoma subtypes. Methods Between 4/2021 and 5/2023, a total of 110 patients were enrolled in this study. Matched tumor tissue biopsies and peripheral blood were collected at diagnosis. Both tDNA and ctDNA were extracted and subjected to a targeted capture NGS assay covering the entire coding region or recurrently mutated region of 196 genes. The mean coverage depth was 2431x and 2513x for tDNA and ctDNA, respectively. The limit of detection (LOD) was 1% and 0.5% for tDNA and ctDNA, respectively. Results The enrolled cohort comprised of 63 (57.3%) male and 47(42.7%) female patients, with a median age of 58 years old (range 1.25-89). Among the 110 patients, the most prevalent subtype is diffuse large B-cell lymphoma (DLBCL，n=45), following by angioimmunoblastic T-cell lymphoma (AITL, n=16), anaplastic large cell lymphoma (ALCL, n=13) , mantle cell lymphoma (MCL, n=10), follicular lymphoma (FL, n=9), primary mediastinal large B-cell lymphoma (PMBL, n=9), extranodal natural killer/T cell lymphoma (ENKTL, n=4), and peripheral T-cell lymphoma not otherwise specified (PTCL-NOS, n=4). For further analysis, DLBCL, MCL, FL and PMBL were categorized as B-cell lymphoma group (n=73), while AITL, ALCL, ENKTL and PTCL-NOS were categorized as T-cell lymphoma group (n=37). Mutations were detected in 109（99.10%）tDNA and 110（100%）ctDNA, respectively. A total of 1586 mutations involving 177 genes were detected in tDNA, and the median number of mutations per sample was 12 (range 0-62), with KMT2D (39.09%), KMT2C (30.90%), IGLL5 (30.00%), TET2 (25.45%) and TP53 (20.90%) being the top 5 mutated genes. For ctDNA, a total of 1750 mutations involving 178 genes were detected and the median number of mutations per sample was 14 (range 2-63), with KMT2D (37.27%), KMT2C (29.09%), IGLL5 (27.27%), TET2 (25.45%) and DNMT3A (27.27%) being the top 5 mutated genes. To determine the concordance of mutations detected in tDNA and ctDNA, sensitivity was calculated utilizing tDNA as gold standard. The overall sensitivity of ctDNA based genotyping was 85.39% (95%CI: 82.36%-88.41%), with B-cell lymphoma showing a slightly higher sensitivity than T-cell lymphoma (86.17%, 95%CI: 83.51%-88.83% vs. 83.84%, 95%CI: 76.30%-91.32%). In terms of subtypes, PTCL-NOS exhibited the highest sensitivity (89.58%, 95%CI: 56.43%-122.73%, while AITL exhibited the lowest sensitivity (78.53%, 95%CI: 64.09%-92.97%) (Figure 1A). In addition, the difference of mutational spectrum between B-cell lymphoma and T-cell lymphoma was precisely depicted by ctDNA based genotyping. We discovered mutations in TET2, RHOA, and PLCG1 were significantly present in T-cell lymphoma, while mutations in MYD88, CD79B, CARD11, CREBBP, MYC, PIM1, IGLL5, ATM, SOCS1 and HIST1HIE were significantly enriched in B-cell lymphoma (Figure 1B). Conclusion In the present study, recurrent mutations across a variety of lymphoma subtypes were identified by ctDNA based genotyping, which were in high concordance with tDNA based genotyping. These data demonstrated that ctDNA based genotyping is a reliable noninvasive alternative to tumor tissue biopsy for molecular profiling of lymphoma patients, especially for patients whose tissues are not accessible for genotyping.

The RHOA Mutation G17V Does Not Lead to Increased Migration of Human Malignant T Cells but Is Associated with Matrix Remodelling

Nodal T-follicular helper cell lymphoma, angioimmunoblastic-type (AITL), is characterized by constitutional symptoms, advanced-stage disease, and generalized lymphadenopathy. A genetic hallmark of this lymphoma is the frequent occurrence of the RHOA mutation G17V in neoplastic cells, which is observed in around 60% of patients. Because RHOA is involved in both T-cell receptor downstream signalling and cell migration, we hypothesized that the characteristic presentation of AITL could be the result of enhanced tumor cell migration. Therefore, this study aimed to elucidate the impact of the RHOA variant G17V on the migration of neoplastic T cells. We transfected the T-cell lymphoma cell lines HH and HuT78 to stably express the RHOA-G17V variant. RHOA-G17V-expressing T cells did not exhibit enhanced motility compared to empty-vector-transfected cells in microchannels, a 3D collagen gel, or primary human lymphatic tissue. Cells of the HH cell line expressing RHOA-G17V had an increased number of cells with cleaved collagen compared with the empty-vector-transfected cells. Therefore, we hypothesized that the early spread of AITL tumor cells may be related to remodelling of the extracellular matrix. Accordingly, we observed a significant negative correlation between the relative area of collagen in histological sections from 18 primary AITL and the allele frequency of the RHOA-G17V mutation. In conclusion, our results suggest that the characteristic presentation of AITL with early, widespread dissemination of lymphoma cells is not the result of an enhanced migration capacity due to the RHOA-G17V mutation; instead, this feature may rather be related to extracellular matrix remodelling.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Background: Emerging evidence suggests the prognostic impact of the tumor microenvironment (TME) in peripheral T-cell lymphomas (PTCLs). To better understand PTCL pathobiology, we performed an integrative multi-omics study to explore the genetic subtypes and the TME signatures of PTCLs, especially nodal T-follicular helper T-cell lymphomas (nTFHLs) and PTCL, not otherwise specified (PTCL-NOS). Method: We performed whole-exome sequencing of 92 nTFHLs and 37 PTCL-NOSs, a total of 129 cases. Ninety-two nTFHLs included 85 angioimmunoblastic T-cell lymphomas (AITLs), four nPTCL with TFH phenotypes, two follicular T-cell lymphomas, and one unclassifiable nTFHL. Genetic drivers were integrated using non-negative matrix factorization consensus clustering (NMF). We estimated the proportion of immune cell fractions from bulk RNA sequencing data (n = 57) using CIBERSORTx and classified the TME signatures using hierarchical clustering. Results: NMF clustering analysis revealed three genetic subtypes within our cohort, except for 10 cases lacking recurrent genetic abnormalities (denoted as cluster 0). C2 was characterized by TP53 mutation, CDKN2A loss, PTEN loss, and chromosomal instability, corresponding to the previously described GATA3-PTCL subtype. C1 and C3 shared TFH-related genomic alterations, but C3 had significantly higher frequencies of chromosome (Chr) 5 gain, Chr 21 gain, RHOA, IDH2, and CD28 mutations. A higher frequency of rash and higher C-reactive protein levels than the other AITLs characterized C3-AITL. Pairwise association analysis of genomic alterations revealed that multiple TET2 mutations, rather than a single TET2 mutation, significantly co-occurred with IDH2 and RHOA mutations. A Bradley-Terry model estimated that the first TET2 and DNMT3A mutations occurred earlier, and the second or later TET2, RHOA, and IDH2 mutations occurred later. Compared to C1, significantly inferior survival was observed in C2 (hazard ratio (HR), 2.52; 95% CI, 1.37–4.63) and C3(HR, 2.14; 95% CI, 1.17–3.89; Figure A). The TME signatures were divided into TME1 (B-cells and follicular helper T-cells), TME2 (activated memory CD4 T-cells, M2 macrophages, and CD8 T-cells), and TME3 (naïve CD4 T-cells and activated mast cells). mTORC1 signaling was enriched in the TME2 signature compared to TME1 and TME3 signatures. The TME2 signature was significantly associated with shorter survival than the TME3 signature (HR: 3.4, 95% CI 1.6–7.5; Figure B). C2 had significantly more TME2 signature than C1 (64.3% vs. 7.7%), while C1 had significantly more TME3 signature than C2 (80.8% vs. 28.6%, p = 0.006; Figure C). Keywords: genomics, epigenomics, and other -omics, microenvironment Encore Abstract—previously submitted to EHA 2023 The research was funded by: Japan Society for the Promotion of Science KAKENHI grants (grant numbers: 19K23879, 22K19451, and 21H02945) and Japan Agency for Medical Research and Development (AMED) grants (20ck0106544 and 21ck0106644)

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Introduction: TFH lymphomas (TFHL) commonly harbor mutations in TET2, RHOA, DNMT3A and IDH2. While RHOA and IDH2 appear restricted to the neoplastic cells, TET2 and DNMT3A mutations occur in a significant proportion of cases in a hematopoietic progenitor cell and can also be detected in B or myeloid cells. Cell-free DNA (cfDNA) sequencing allows the detection of circulating tumor DNA in solid cancers or B-cell lymphomas, with predictive value, but few data exist on cfDNA sequencing in TFHL. Methods: In the frame of the ORACLE study, a phase 3 trial comparing oral azacitidine to investigator choice treatment in relapsed or refractory TFHL patients, we collected tumor biopsies and plasma in streck tube at inclusion, after 3 cycles, and at progression. Tumour and cfDNA were sequenced by NGS using 9 genes, amplicon-based libraries. Median sequencing depth was 2386X in tumor and 3519X in cfDNA. Results: Among patients with confirmed TFHL treated in LYSA centers, we collected 45 samples at inclusion, 16 after cycle 3, and 14 at progression. The median cfDNA concentration at each time point was respectively 7507 (IQR 3418–19414), 5182 (3438–12429), and 15750 (7316–26953) hEG/mL. Results of cfDNA at inclusion and tumor sequencing were compared in 43 patients. Common TET2 mutations were detected in the tumor of 36/43 (84%) and in cfDNA of 33/43 (77%) patients, with a median variant allele frequency (VAF) of 17.75% vs. 9.8% respectively. RHOAG17V was detected in 29/43 (67%, VAF 10%) and in 24/43 (59%, VAF 4.4%), DNMT3A in 13/43 (30%, VAF 17.9%) and 15/73 (35%, VAF 17.9%), and IDH2 in 12/43 (28%, VAF 5.9%) and 8/43 (19%, VAF 5.4%) of tumor biopsies and cfDNA samples respectively. Only one patient had detectable TET2, DNMT3A, IDH2, and RHOA mutations in the cfDNA and not in the tumor biopsy, corresponding to a tumor with low neoplastic cell content. By contrast, 3 patients had DNMT3A mutations, not affecting the R882 residue, detected in the cfDNA but not in the tumor likely corresponding to clonal hematopoiesis not related to the TFHL. We also compared 25 paired cfDNA samples collected at inclusion and after cycle 3 (including progression sample if occurring at cycle 3 or before). In all but one patient, we observed the persistence of TET2 and DNMT3A mutations, even in responding patients, confirming that these mutations are not restricted to neoplastic cells, and suggesting that treatment, especially with 5-azacitidine, does not affect the clonal hematopoiesis. By contrast, among the 14/25 patients with a detectable RHOA mutation in cfDNA at inclusion, progression-free survival was longer in the 4 patients with the disappearance of the RHOA mutations in cfDNA at cycle 3 than in the 10 others (median 29 vs. 3 months, p = 0.01). The research was funded by: BMS Force Hémato Keywords: Aggressive T-cell non-Hodgkin lymphoma, Liquid biopsy, Minimal residual disease No conflicts of interests pertinent to the abstract.

Molecular profile of poorly cohesive gastric carcinoma with special reference to survival.

Patients with poorly cohesive gastric carcinoma (PCC) are known to have poor survival. However, detailed molecular biology of PCC has not been elucidated, except for mutations in CDH1 and RHOA. Additionally, the molecular profiles of signet-ring cell carcinoma (SRC) have not been fully investigated. We aimed to investigate the association between molecular profiles and survival in PCC and PCC subtypes. The present study included 455 patients with gastric adenocarcinoma underwent radical gastrectomy. Whole-exome sequencing and gene expression profiling were conducted. Patients were classified according to the WHO classification as PCC or non-PCC, with PCC being further classified into SRC, combined, and PCC not-otherwise-specified (NOS). Clinicopathological factors and survival were compared with molecular profiles. Of the patients, 159 were classified with PCC, while 296 were classified with non-PCC. Among PCC, 44 were classified with SRC, 64 with combined, and 51 with PCC-NOS. Mutations in CDH1 and RHOA were remarkably more frequent in PCC than in non-PCC. PCC had worse overall survival (OS) and disease-specific survival (DSS) compared to non-PCC. For PCC, the SRC group had good OS and DSS, whereas PCC-NOS classification with CDH1 mutations was associated with extremely poor survival. In the PCC-NOS and combined groups, patients with mutations in the extracellular domain 1 of CDH1 had poor survival. Our findings suggest that PCC has poorer survival than non-PCC. Accumulation of CDH1 and RHOA mutations are unique profiles in PCC. Among PCC, CDH1 mutations may play a crucial role in the survival of non-SRC PCC.

Multiancestry genomic and transcriptomic analysis of gastric cancer.

Gastric cancer is among the most common malignancies worldwide, characterized by geographical, epidemiological and histological heterogeneity. Here, we report an extensive, multiancestral landscape of driver events in gastric cancer, involving 1,335 cases. Seventy-seven significantly mutated genes (SMGs) were identified, including ARHGAP5 and TRIM49C. We also identified subtype-specific drivers, including PIGR and SOX9, which were enriched in the diffuse subtype of the disease. SMGs also varied according to Epstein-Barr virus infection status and ancestry. Non-protein-truncating CDH1 mutations, which are characterized by in-frame splicing alterations, targeted localized extracellular domains and uniquely occurred in sporadic diffuse-type cases. In patients with gastric cancer with East Asian ancestry, our data suggested a link between alcohol consumption or metabolism and the development of RHOA mutations. Moreover, mutations with potential roles in immune evasion were identified. Overall, these data provide comprehensive insights into the molecular landscape of gastric cancer across various subtypes and ancestries.