Intraperitoneal Paclitaxel Is a Safe and Effective Therapeutic Strategy for Treating Mucinous Appendiceal Adenocarcinoma

Appendiceal adenocarcinomas (AA) are a rare and heterogeneous mix of tumors for which few preclinical models exist. The rarity of AA has made performing prospective clinical trials difficult, which has partly contributed to AA remaining an orphan disease with no chemotherapeutic agents approved by the FDA for its treatment. AA has a unique biology in which it frequently forms diffuse peritoneal metastases but almost never spreads via a hematogenous route and rarely spreads to lymphatics. Given the localization of AA to the peritoneal space, intraperitoneal delivery of chemotherapy could be an effective treatment strategy. Here, we tested the efficacy of paclitaxel given by intraperitoneal administration using three orthotopic patient-derived xenograft (PDX) models of AA established in immunodeficient NSG mice. Weekly intraperitoneal paclitaxel treatment dramatically reduced AA tumor growth in all three PDX models. Comparing the safety and efficacy of intravenous with intraperitoneal administration, intraperitoneal delivery of paclitaxel was more effective, with reduced systemic side effects in mice. Given the established safety record of intraperitoneal paclitaxel in gastric and ovarian cancers, and lack of effective chemotherapeutics for AA, these data showing the activity of intraperitoneal paclitaxel in orthotopic PDX models of mucinous AA support the evaluation of intraperitoneal paclitaxel in a prospective clinical trial.

SIGNIFICANCE

The activity and safety of intraperitoneal paclitaxel in orthotopic PDX models of mucinous appendiceal adenocarcinoma supports the evaluation of intraperitoneal paclitaxel in a prospective clinical trial of this rare tumor type.

Antitumor activity of intraperitoneal paclitaxel in orthotopic patient-derived xenograft models of mucinous appendiceal adenocarcinoma

Appendiceal adenocarcinomas (AAs) are a rare and heterogeneous mix of tumors for which few preclinical models exist. The rarity of AA has made performing prospective clinical trials difficult, and in part because of this AA remains an orphan disease with no chemotherapeutic agents approved by the FDA for its treatment. AA has a unique biology in which it frequently forms diffuse peritoneal metastases, but almost never spreads via a hematogenous route and rarely spreads to lymphatics. Given its localization to the peritoneal space we hypothesized that intraperitoneal (IP) delivery of chemotherapy could be an effective treatment strategy. Here we tested the efficacy paclitaxel given by IP administration using three orthotopic PDX models of AA established in NSG mice. Weekly treatment of 25.0 mg/kg of IP paclitaxel dramatically reduced AA tumor growth in TM00351 (81.9% reduction vs. control), PMP-2 (98.3% reduction vs. control), and PMCA-3 (71.4% reduction vs. control) PDX models. Comparing the safety and efficacy of intravenous (IV) to IP administration in PMCA-3, neither 6.25 nor 12.5 mg/kg of IV paclitaxel significantly reduced tumor growth. These results suggest that IP administration of paclitaxel is favorable to IV administration. Given the established safety record of IP paclitaxel in gastric and ovarian cancers, and lack of effective chemotherapeutics for AA, these data showing the activity of IP paclitaxel in orthotopic PDX models of mucinous AA support the evaluation of IP paclitaxel in a prospective clinical trial.

Abstract 2467: SPECT-imaging guided development and evaluation of targeted alpha therapy (TAT) for colorectal liver metastasis

BACKGROUND: Only a small fraction of patients with colorectal liver metastases (CLM) is eligible for curative resection, and novel treatment options are highly needed. The high linear-energy transfer of short-ranged alpha particles can induce complex double-stranded DNA breaks, leading to cell death. With no known resistance mechanism, alpha-particle emitting isotopes represent a promising tool in cancer management. In targeted alpha therapy (TAT), an alpha-particle emitting isotope is attached to a tumor-targeting antibody (hereafter TAT antibody), ensuring specific delivery to the tumor. By substituting the alpha-particle emitting isotope (Actinium-225, 225Ac) with a diagnostic isotope (Zirconium-89, 89Zr), the in-vivo distribution of the TAT antibody can be monitored using PET/SPECT/CT. The aim of this work was to set up robust labeling and PET/SPECT protocols to evaluate TAT in CLM using novel experimental models.

METHODS: For SPECT-imaging of 225Ac daughter isotopes, the combined gamma emission spectra were gated at 218 keV ± 20% and 440 keV ± 20% for Francium-221 and Bismuth-213, respectively. 89Zr was labeled to a desferrioxamine* (DFO*) conjugated TAT antibody, which recognizes both the murine and human antigen. Indium-111 (111In) labeling was performed through diethylenetriaminepentaacetic acid (DTPA) conjugated to an isotype antibody. Radiochemical purity and protein integrity were assessed by size exclusion HPLC, iTLC and SDS-PAGE. For orthotopic CLM model development, 106 cells of human colorectal cancer cell lines HT-55 or LS1034 were injected in the spleen of female Rj:NMRI-Foxn1nu mice, followed by splenectomy. Tumor growth was monitored by T2-weighted MR-imaging. Non-tumor bearing mice (n = 12, 3 per group) were injected with 4 MBq of 10, 20, 50 or 100 µg 89Zr-TAT antibody to evaluate biodistribution and the mice scanned on day 2, 4 and 6 after iv injection.

RESULTS: Francium-221 and Bismuth-213 could be separately visualized after free Actinium-225 administration (i.v.). 89Zr and 111In were routinely labeled to their respective antibody with up to 500 MBq/mg with >95% radiochemical purity. 89Zr-DFO*-TAT antibody showed >95% radiochemical purity and >95% protein integrity after 7 days stability test in serum, shown by iTLC and SDS-PAGE. SPECT/CT of 89Zr-DFO*-TAT antibody in non-tumor bearing mice showed little uptake in healthy tissues apart from the liver due to hepatic antibody clearance. Orthotopic models of CLM show reproducible development of metastases for HT-55 and LS1034 within 3 weeks.

CONCLUSION: Robust labeling methods, PET/SPECT imaging protocols and suitable animal models of CLM were established. Results of our dual-isotope SPECT/CT imaging of our 89Zr-DFO*-TAT antibody in comparison with an 111In-labeled isotype antibody, together with efficacy data of the TAT, will be presented at the meeting.

Citation Format: Frans V. Suurs, Alexander Kristian, Gebregziabher Petros, Yuan Zeng Feng, Karianne G. Fleten, Roger M. Bjerke, Alan Cuthbertson, Kjersti Flatmark. SPECT-imaging guided development and evaluation of targeted alpha therapy (TAT) for colorectal liver metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2467.

Peptide vaccine targeting mutated GNAS: a potential novel treatment for pseudomyxoma peritonei

Background

Pseudomyxoma peritonei (PMP) is a rare, slow-growing abdominal cancer with no efficacious treatment options in non-resectable and recurrent cases. Otherwise, rare activating mutations in the GNAS oncogene are remarkably frequent in PMP and the mutated gene product, guanine nucleotide-binding protein α subunit (Gsα), is a potential tumor neoantigen, presenting an opportunity for targeting by a therapeutic cancer vaccine.

Methods

Tumor and blood samples were collected from 25 patients undergoing surgery for PMP (NCT02073500). GNAS mutation analysis was performed by next-generation targeted sequencing or digital droplet PCR. Responses to stimulation with Gsα mutated (point mutations R201H and R201C) 30 mer peptides were analyzed in peripheral blood T cells derived from patients with PMP and healthy donors. Fresh PMP tumor samples were analyzed by mass cytometry using a panel of 35 extracellular markers, and cellular subpopulations were clustered and visualized using the visual stochastic network embedding analysis tool.

Results

GNAS mutations were detected in 22/25 tumor samples (88%; R201H and R201C mutations detected in 16 and 6 cases, respectively). Strong T cell proliferation against Gsα mutated peptides was observed in 18/24 patients with PMP. Mass cytometry analysis of tumor revealed infiltration of CD3 +T cells in most samples, with variable CD4+:CD8 + ratios. A large proportion of T cells expressed immune checkpoint molecules, in particular programmed death receptor-1 and T cell immunoreceptor with Ig and ITIM, indicating that these T cells were antigen experienced.

Conclusion

These findings point to the existence of a pre-existing immunity in patients with PMP towards mutated Gsα, which has been insufficient to control tumor growth, possibly because of inhibition of antitumor T cells by upregulation of immune checkpoint molecules. The results form a rationale for exploring peptide vaccination with Gsα peptides in combination with immune checkpoint inhibiton as a possible curative treatment for PMP and other GNAS mutated cancers.

Abstract 4705: The novel oncolytic peptide, DTT-304, induces regression of colorectal cancer tumors in vivo

Colorectal cancer (CRC) is the third most common cancer in the world, and approximately 50% of the patients develop liver metastasis, which is a major cause of disease mortality. New drugs and treatment options are therefore necessary to improve the survival of these patients. Lately, different types of immunotherapy, such as check point inhibitors, have shown great promise in the treatment of metastatic cancer, although for most patients with CRC the efficacy has been restricted to cases with microsatellite instable disease. Another novel immunotherapeutic strategy is oncolytic immunotherapy, which has been shown to cause immunogenic cancer cell death. Following cancer cell lysis, damage associated molecular patterns (DAMPs) are released, which are recognized by immune cell receptors. Pro-inflammatory responses will then be triggered to induce release of tumor specific antigens that are presented to the immune system, leading to tumor-specific immune responses.

In the present study, we have investigated the efficacy of a novel oncolytic peptide, DTT-304, using two mouse models. Subcutaneous tumors were established in Balb c mice using the cell line CT26 and in C57Bl6 mice using the cell line MC38, both murine CRC cell lines. In both models, intra-tumoral injection of the peptide induced tumor necrosis and complete regression a few days after initiation of treatment, thus showing the potential of this peptide for use in colorectal cancer.

In ongoing experiments we are investigating if the peptide has the potential to induce long lasting protective tumor-specific immune responses by re-challenging previously treated mice with the same cell line in a liver metastasis model. In addition, the possibility of treating liver tumors by direct peptide injection will be investigated.

Citation Format: Karianne G. Fleten, Johannes J. Eksteen, Brynjar Mauseth, Ketil Camilio, Øystein Rekdal, Meng Yu Wang, Gunhild M. Mælandsmo, Kjersti Flatmark. The novel oncolytic peptide, DTT-304, induces regression of colorectal cancer tumors in vivo [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 4705.

hvTRA, a novel TRAIL receptor agonist, induces apoptosis and sustained growth retardation in melanoma

In recent years, new treatment options for malignant melanoma patients have enhanced the overall survival for selected patients. Despite new hope, most melanoma patients still relapse with drug-resistant tumors or experience intrinsic resistance to the therapy. Therefore, novel treatment modalities beneficial for subgroups of patients are needed. TRAIL receptor agonists have been suggested as promising candidates for use in cancer treatment as they preferentially induce apoptosis in cancer cells. Unfortunately, the first generation of TRAIL receptor agonists showed poor clinical efficacy. hvTRA is a second-generation TRAIL receptor agonist with improved composition giving increased potency, and in the present study, we showed hvTRA-induced activation of apoptosis leading to an efficient and sustained reduction in melanoma cell growth in cell lines and xenograft models. Furthermore, the potential of hvTRA in a clinical setting was demonstrated by showing efficacy on tumor cells harvested from melanoma patients with lymph node metastasis in an ex vivo drug sensitivity assay. Inhibition of mutated BRAF has been shown to regulate proteins in the intrinsic apoptotic pathway, making the cells more susceptible for apoptosis induction. In an attempt to increase the efficacy of hvTRA, combination treatment with the mutated BRAF inhibitor vemurafenib was investigated. A synergistic effect by the combination was observed for several cell lines in vitro, and an initial cytotoxic effect was observed in vivo. Unfortunately, the initial increased reduction in tumor growth compared with hvTRA mono treatment was not sustained, and this was related to downregulation of the DR5 level by vemurafenib. Altogether, the presented data imply that hvTRA efficiently induce apoptosis and growth delay in melanoma models and patient material, and the potential of this TRAIL receptor agonist should be further evaluated for treatment of subgroups of melanoma patients.

Use of non-invasive imaging to monitor response to aflibercept treatment in murine models of colorectal cancer liver metastases

The liver is the most frequent metastatic site in colorectal cancer (CRC), and relevant orthotopic in vivo models are needed to study the efficacy of anticancer drugs in the metastatic setting. A challenge when utilizing such models is monitoring tumor growth during the experiments. In this study, experimental liver metastases were established in nude mice by splenic injection of the CRC cell lines HT29 and HCT116, and the mice were treated with the antiangiogenic drug aflibercept. Tumor growth was monitored using magnetic resonance imaging (MRI) and bioluminescence imaging (BLI). Aflibercept treatment was well tolerated and resulted in increased animal survival in HCT116, but not in HT29, while inhibited tumor growth was observed in both models. Treatment efficacy was monitored with high precision using MRI, while BLI detected small-volume disease with high sensitivity, but was less accurate in end-stage disease. Apparent diffusion coefficient (ADC) values obtained by diffusion weighted MRI (DW-MRI) were highly predictive of treatment response, with increased ADC corresponding well with areas of necrosis observed by histological evaluation of aflibercept-treated xenografts. The results showed that the efficacy of the antiangiogenic drug aflibercept varied between the two models, possibly reflecting unique growth patterns in the liver that may be representative of human disease. Non-invasive imaging, especially MRI and DW-MRI, can be used to effectively monitor tumor growth and treatment response in orthotopic liver metastasis models.

Abstract 4218: Diffusion-weighted MRI can predict response to aflibercept in in vivo models

BACKGROUND: The liver is the most frequent metastatic site in colorectal cancer (CRC), and relevant in vivo models are needed to study the efficacy of anticancer drugs in this setting. Aflibercept, targeting vascular endothelial growth factors A and B and placental growth factor, is one of the most recently approved antiangiogenic agents for treatment of metastatic CRC. In the present work, the efficacy of aflibercept was investigated in experimental models of liver metastases in nude mice and growth progression was monitored using non-invasive imaging.

METHODS: Liver metastases were established in mice by intrasplenic injection of CRC cell lines HCT116 and HT29 transfected with luciferase. Magnetic resonance imaging (MRI) (7T) and bioluminescent imaging (IVIS spectrum) were used to monitor tumor growth. Aflibercept was delivered intraperitoneally. To further characterize treatment response in metastatic tumors, diffusion-weighted (DW)-MR images were obtained. At termination tumors were sampled for histopathologic analysis.

RESULTS: Mice bearing HCT116 xenografts responded well to treatment and a significant increase in survival compared to vehicle treated animals was observed (p< 0.001), in addition to decreased tumor burden. No increase in survival was observed upon aflibercept treatment in HT29 xenografts (p = 0.155), whereas in one of two experiments performed a significant reduction in tumor volume was observed, suggesting that there was a slight response to treatment.

T2-weighted MRI was used to quantify tumor volume by manual delineation using the OsiriX software. MRI-assessed tumor volumes correlated well with tumor weight at the time of termination, while for bioluminescence measurements no such correlation was observed. In contrast, bioluminescence was a sensitive detection method early in the experiments when MRI did not show liver tumor.

DW-MRI was obtained and apparent diffusion coefficient (ADC) tumor maps were calculated using the nordicIce software. A slight increase in ADC values was observed for HT29 tumors while there was a large increase in ADC values for HCT116 tumors after treatment with aflibercept. This corresponded well with histologic evaluation of tumors, showing increased necrosis in HCT116 tumors, but not in HT29 tumors.

CONCLUSION: Our results demonstrate efficacy of aflibercept in an orthotopic model of liver metastases in CRC. MRI could be used to monitor treatment efficacy with high precision, while bioluminescence measurement could detect small-volume disease with high sensitivity, but was less specific in high-volume disease. Interestingly, ADC values obtained from DW-MRI were highly predictive of treatment response by clearly visualizing and quantifying tumor necrosis.

Citation Format: Karianne G. Fleten, Kine M. Bakke, Andreas Abildgaard, Gunhild M. Mælandsmo, Katrine Røe Redalen, Kjersti Flatmark. Diffusion-weighted MRI can predict response to aflibercept in in vivo models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4218.

Fibroblast-induced switching to the mesenchymal-like phenotype and PI3K/mTOR signaling protects melanoma cells from BRAF inhibitors

The knowledge on how tumor-associated stroma influences efficacy of anti-cancer therapy just started to emerge. Here we show that lung fibroblasts reduce melanoma sensitivity to the BRAF inhibitor (BRAFi) vemurafenib only if the two cell types are in close proximity. In the presence of fibroblasts, the adjacent melanoma cells acquire de-differentiated mesenchymal-like phenotype. Upon treatment with BRAFi, such melanoma cells maintain high levels of phospho ribosomal protein S6 (pS6), i.e. active mTOR signaling, which is suppressed in the BRAFi sensitive cells without stromal contacts. Inhibitors of PI3K/mTOR in combination with BRAFi eradicate pS6high cell subpopulations and potentiate anti-cancer effects in melanoma protected by the fibroblasts. mTOR and BRAF co-inhibition also delayed the development of early-stage lung metastases in vivo. In conclusion, we demonstrate that upon influence from fibroblasts, melanoma cells undergo a phenotype switch to the mesenchymal state, which can support PI3K/mTOR signaling. The lost sensitivity to BRAFi in such cells can be overcome by co-targeting PI3K/mTOR. This knowledge could be explored for designing BRAFi combination therapies aiming to eliminate both stroma-protected and non-protected counterparts of metastases.

Targeted Cancer Therapy with a Novel Anti-CD37 Beta-Particle Emitting Radioimmunoconjugate for Treatment of Non-Hodgkin Lymphoma

177Lu-DOTA-HH1 (177Lu-HH1) is a novel anti-CD37 radioimmunoconjugate developed to treat non-Hodgkin lymphoma. Mice with subcutaneous Ramos xenografts were treated with different activities of 177Lu-HH1, 177Lu-DOTA-rituximab (177Lu-rituximab) and non-specific 177Lu-DOTA-IgG1 (177Lu-IgG1) and therapeutic effect and toxicity of the treatment were monitored. Significant tumor growth delay and increased survival of mice were observed in mice treated with 530 MBq/kg 177Lu-HH1 as compared with mice treated with similar activities of 177Lu-rituximab or non-specific 177Lu-IgG1, 0.9% NaCl or unlabeled HH1. All mice injected with 530 MBq/kg of 177Lu-HH1 tolerated the treatment well. In contrast, 6 out of 10 mice treated with 530 MBq/kg 177Lu-rituximab experienced severe radiation toxicity. The retention of 177Lu-rituximab in organs of the mononuclear phagocyte system was longer than for 177Lu-HH1, which explains the higher toxicity observed in mice treated with 177Lu-rituximab. In vitro internalization studies showed that 177Lu-HH1 internalizes faster and to a higher extent than 177Lu-rituximab which might be the reason for the better therapeutic effect of 177Lu-HH1.

Immunotoxin targeting EpCAM effectively inhibits peritoneal tumor growth in experimental models of mucinous peritoneal surface malignancies

Cytoreductive surgery and intraperitoneal (i.p.) chemotherapy constitute a curative treatment option in mucinous peritoneal surface malignancies of intestinal origin, but treatment outcome is highly variable and the search for novel therapies is warranted. Immunotoxins are attractive candidates for targeted therapy in the peritoneal cavity because of direct cytotoxicity, distinct mechanisms of action and tumor cell selectivity. The MOC31PE immunotoxin targets the tumor-associated adhesion protein EpCAM (Epithelial Cell Adhesion Molecule), and has been administered safely in early clinical trials. In our work, the efficacy of i.p. administration of MOC31PE alone and together with mitomycin C (MMC) was investigated in unique animal models of human mucinous peritoneal surface malignancies. In initial model validation experiments, clear differences in efficacy were demonstrated between MMC and oxaliplatin, favoring MMC in five investigated tumor models. Subsequently, MOC31PE and MMC were given as single i.p. injections alone and in combination. In the PMCA-2 model, moderate growth inhibition was obtained with both drugs, while the combination resulted in at least additive effects; whereas the PMP-2 model was highly sensitive to both drugs separately and in combination and intermediate sensitivity was found for the PMCA-3 model. Furthermore, results from ex vivo experiments on freshly obtained mucinous tumor tissue from animals and patients suggested that classic mechanisms of immunotoxin activity were involved, i.e., inhibition of protein synthesis and induction of apoptosis. The present results suggest that adding MOC31PE to MMC-based i.p. chemotherapy should be further explored for EpCAM-expressing peritoneal surface malignancies, and a phase I trial is in preparation.