Kolluri, Aarti

Background and Aims: Efficacy of chimeric antigen receptor (CAR) T cells for treating solid tumors, including HCC, remains a challenge. Nanobodies are emerging building blocks of CAR T cells due to their small size and high expression. Membrane proximal sites have been shown as attractive epitopes of CAR T cells. However, current CAR formats are not tailored toward nanobodies or targeting membrane distal epitopes. Approach and Results: Using hYP7 Fv (membrane proximal) and HN3 VH nanobody (membrane distal) as GPC3 targeting elements, we sought to determine how hinges and transmembrane portions of varying structures and sizes affect CAR T-cell function. We generated multiple permutations of CAR T cells containing CD8, CD28, IgG4, and Fc domains. We show that engineered HN3 CAR T cells can be improved by 2 independent, synergistic changes in the hinge and transmembrane domains. The T cells expressing the HN3 CAR which contains the hinge region of IgG4 and the CD28 transmembrane domain (HN3-IgG4H-CD28TM) exhibited high cytotoxic activity and caused complete HCC tumor eradication in immunodeficient mice. HN3-IgG4H-CD28TM CAR T cells were enriched for cytotoxic-memory CD8+ T cells and NFAT signals, and reduced β catenin levels in HCC cells. Conclusion: Our findings indicate that altering the hinge and transmembrane domains of a nanobody-based CAR targeting a distal GPC3 epitope, in contrast to a membrane proximal epitope, lead to robust T-cell signaling and induce swift and durable eradication of HCC tumors.

e14512 Background: Glypican 3 (GPC3), a cell surface protein associated with early development, is an established biomarker of hepatocellular carcinoma (HCC). In a vast compendium of work, HN3, a human GPC3 nanobody (VH) isolated from a phage library, was shown to abrogate HCC tumors and block the distally located Wnt binding domain of GPC3. To date, it remains challenging how to precisely engineer CAR T cells for improved efficacy in solid tumors. In the context of hepatocellular carcinoma, we determined how hinges and transmembrane portions of varying structures and sizes affect CAR T cell function. Here, we show how rationally designed, engineered Chimeric Antigen Receptor (CAR) T cells containing HN3, demonstrate enhanced CAR T activity in HCC. Methods: We generated and compared multiple permutations of GPC3 targeted CAR T cells containing HN3, CD8, CD28, IgG4 and Fc domains. Incorporation of HN3, into multiple CAR formats yielded nine constructs, which were screened for antigen-specific and antigen-independent signaling using a luciferase reporter system in Hep3B, Huh7 and HepG2 cell lines. For in vivo assessment, immunodeficient NSG mice were intraperitonially injected with Hep3B or Huh7 cells and treated with a single dose (5 or 15 million) of engineered HN3 CAR T cells. Blood was collected at 2, 4 and 5 weeks to assess proliferation, T cell subtypes and exhaustion. Results: In vitro, the HN3-IgG4H-CD28TM CAR T cells induced high specificity and cytotoxic activity. HN3-IgG4H-CD28TM CAR T cells markedly improved HN3 cell killing activity by 30-40% in low (1.6:1) and high (25:1) effector to target ratios. Similarly, in vivo, in a high antigen environment, two determinative changes in the hinge region and transmembrane domains led to complete tumor eradication in immunodeficient mice bearing HCC tumors within 7-10 days. Moreover, HN3-IgG4H-CD28TM CAR T cells maintained specific tumor killing and averted exhaustion by producing a clear T cell response signature of enriched cytotoxic-memory (Temra) CD8+ along with a subset of naïve T cells. Conclusions: Engineered nanobody based CAR T cells containing the appropriate hinge and transmembrane domains can lead to determinative T cell signaling capable of inducing swift and durable eradication of HCC tumors. Altogether, we show that engineered HN3 CAR T cell therapy demonstrates strong potential for treatment of aggressive HCCs enabled by Wnt dysregulation.

Abstract Background: Pancreatic cancer (PC) ranks among the top causes of cancer mortality. Risk stratification is an important step toward prevention and early detection. Prior work has shown that ABO blood type (non-O) and first-degree family history of PC are associated with increased PC risk. Individuals with first-degree family history of PC have a 2- to 3-fold increased risk, but it is unclear if ABO blood type plays a role in the familial aggregation of PC. We investigated PC risk among first-degree relatives (FDRs) of PC probands based on the probands' serologic blood type (O vs non-O). Methods: A total of 702 probands sequentially enrolled in the Mayo Clinic Pancreas Research Registry from 2000-2016 with serologic ABO blood type provided information on family history of cancer for 5,178 FDRs. FDRs were grouped based on their related probands' blood type as type O (n=242; 1,768 FDRs) vs non-O (n=460; 3,410 FDRs). Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated by comparing the number of PC cases observed among FDRs to those expected using data from the Surveillance, Epidemiology and End Results (SEER) Program as the reference population. SIRs for PC risk were calculated separately for FDRs of probands with type O vs FDRs of probands with non-O blood, and stratified by sex of FDRs and relationship to proband (parent, sibling, or offspring). Results: Compared to the SEER reference, PC risk was nearly 2-fold higher among FDRs of PC probands (SIR=1.76; 95%CI: 1.35-2.26). When stratified by probands' ABO type, risk for PC was higher among FDRs of probands with non-O blood (SIR=1.94; 95%CI: 1.41-2.60), compared to FDRs of probands with O blood (SIR=1.42; 95%CI: 0.83-2.28). Parents of probands with non-O blood had increased PC risk (SIR=3.28; 95%CI: 2.18-4.74, n=920), but not parents of probands with O blood (SIR=1.75; 95%CI: 0.75-3.45, n=484), p-value for between-group difference=0.10. Among FDRs of probands with O blood, female FDRs had increased PC risk (SIR=2.12; 95%CI: 1.06-3.79), but male FDRs did not (SIR=0.86; 95%CI: 0.31-1.88). Higher PC risk was observed among female FDRs of probands with non-O blood (SIR=2.28; 95%CI: 1.44-3.41) than male FDRs of probands with non-O blood (SIR=1.62; 95%CI: 1.00-2.48). Mothers of probands with O blood had increased PC risk (SIR=2.89; 95%CI: 1.05-6.28) compared to fathers (SIR=0.79; 95%CI: 0.09-2.84). Both mothers (SIR=3.60; 95%CI: 1.96-6.03) and fathers (SIR=2.95; 95%CI: 1.61-4.95) of probands with non-O blood had increased PC risk. No major findings were observed among probands' siblings or offspring. Conclusions: PC risk is greater among FDRs of PC probands with non-O blood than among FDRs of probands with type O. PC risk is higher among parents of probands with non-O blood, and female FDRs and mothers of probands with non-O blood. Possible clustering of non-O blood type in families may contribute to increased PC risk. Citation Format: Aarti Kolluri, Samuel O. Antwi, Sarah E. Fagan, Kari G. Chaffee, Brendan T. Broderick, William R. Bamlet, Ann L. Oberg, Robert R. McWilliams, Gloria M. Petersen. Risk of pancreatic cancer is increased among first-degree relatives of pancreatic cancer probands who have non-O ABO blood type [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1239.