Peritoneal Tumor Research Articles

A research of STEAP1 regulated gastric cancer cell proliferation, migration and invasion in vitro and in vivos.

Six‐Transmembrane Epithelial Antigene of the Prostate 1 (STEAP1) is associated with the occurrence and development of cancer. This study aimed to clarify the role of STEAP1 in gastric cancer tumour growth and metastasis, as well as its molecular mechanism of action.Statistical methods were used for clinical data analysis. Protein expression was detected using immunohistochemistry(IHC). The mRNA and protein expression in the cell cultures were detected using reverse transcription‐polymerase chain reaction(RT‐PCR) and western blot analysis. Overexpression and silencing models were constructed using plasmid and lentivirus transfection. To detect cell proliferation in vitro, Cell Counting Kit‐8(CCK‐8), flow cytometry and colony formation assays were used; transwell and wound healing assays were used to detect cell migration and invasion;For in vivo experiments, nude BALB/c mice were used for detecting subcutaneous tumorigenesis and intraperitoneal implantation. In the results,we found STEAP1 was overexpressed in gastric cancer tissues and cell lines. Single‐factor and Cox analyses showed that STEAP1 gene expression level correlated with poor prognosis. Up‐regulation of STEAP1 increased cell proliferation, migration and invasion, which decreased after STEAP1 was knocked down. These changes were achieved via the activation of the AKT/FoxO1 pathway and epithelial‐mesenchymal transformation (EMT). The in vivo animal experiments showed that STEAP1 knock down, resulted in a decrease in the subcutaneous tumour and peritoneal tumour formation.

Evaluation Of The Carcinoembryonic Antigen Test In Patients With Resected Colon Cancer

Abstract Introduction/Objective To determine the effectiveness of carcinoembryonic antigen (CEA) in patient with known residual disease after resection of colonic cancer Methods Serial carcinoembryonic antigen (CEA) levels were measured in 43 patients following incomplete excision of colorectal cancer. Twenty-seven patients received chemotherapy. The patients reported in this study were amongst those participating in a randomized trial of chemotherapy following palliative resection of colorectal cancer. All patients had a resection of colorectal cancer leaving behind macroscopic quantities of tumour, though of a small total residual bulk. The residual sites of tumour were recorded as: (a) local - where there was local extension of the tumour; (b) nodal - where there were clinically involved nodes remaining, with histological confirmation of involved nodes in the resected specimen; (c) hepatic - where small hepatic metastases were noted, individually not greater than 2 cm in diameter and in total representing less than 10% of the liver bulk; (d) peritoneal - where peritoneal tumour seedlings remained, with histological confirmation of at least one of the seedlings. Results Of the 43 patients studied after operation and prior to chemotherapy, the mean log CEA was 1.19 and only 3 patients exceeded 1.48, despite the fact that all patients were known to have residual tumour. Similarly, the mean log CEA at 3 months for the total group remained at 1.26 but 6 patients now had abnormal values. Thereafter the mean values of the total group exceeded the upper limit of normality and increasing numbers of patients showed elevated CEA values. About one half of the patients had levels of CEA well within the normal range during the first postoperative year despite the evidence of residual disease documented at operation. Conclusion The most appropriate application for a marker such as CEA may be as an assessment of the effect of chemotherapy in patients who have a definite, but objectively unmeasurable, tumour load.

Amido-Bridged Nucleic Acid-Modified Antisense Oligonucleotides Targeting SYT13 to Treat Peritoneal Metastasis of Gastric Cancer

Patients with peritoneal metastasis of gastric cancer have dismal prognosis, mainly because of inefficient systemic delivery of drugs to peritoneal tumors. We aimed to develop an intraperitoneal treatment strategy using amido-bridged nucleic acid (AmNA)-modified antisense oligonucleotides (ASOs) targeting synaptotagmin XIII (SYT13) and to identify the function of SYT13 in gastric cancer cells. We screened 71 candidate oligonucleotide sequences according to SYT13-knockdown efficacy, in vitro activity, and off-target effects. We evaluated the effects of SYT13 knockdown on cellular functions and signaling pathways, as well as the effects of intraperitoneal administration to mice of AmNA-modified anti-SYT13 ASOs. We selected the ASOs (designated hSYT13-4378 and hSYT13-4733) with the highest knockdown efficiencies and lowest off-target effects and determined their abilities to inhibit cellular functions associated with the metastatic potential of gastric cancer cells. We found that SYT13 interfered with focal adhesion kinase (FAK)-mediated intracellular signals. Intraperitoneal administration of hSYT13-4378 and hSYT13-4733 in a mouse xenograft model of metastasis inhibited the formation of peritoneal nodules and significantly increased survival. Reversible, dose- and sequence-dependent liver damage was induced by ASO treatment without causing abnormal morphological and histological changes in the brain. Intra-abdominal administration of AmNA-modified anti-SYT13 ASOs represents a promising strategy for treating peritoneal metastasis of gastric cancer.

Investigating the possible impact of peritoneal tumor exposure amongst women with early stage cervical cancer treated with minimally invasive approach

IntroductionRecent findings show a detrimental impact of the minimally invasive approach on patients with early stage cervical cancer (ECC). Reasons beyond these results are unclear. The aim of the present article is to investigate the possible role of peritoneal contamination during intracorporeal colpotomy. Methodspatients with early stage cervical cancer were divided into 2 groups: no intraperitoneal exposure (N-IPE) intraperitoneal exposure (IPE) during minimally invasive surgery. Patients of the 2 groups were propensity-matched according to the major risk factors. Results226 cases of the IPE group had a significant worst prognosis than the 142 cases of the N-IPE group (4.5-years disease free survival: 86.6% vs 95.9% respectively, p = 0.005), while N-IPE had similar survival to open surgery (4.5-years disease free survival: 95.0% vs 90.5% respectively, p = 0.164). Distant recurrence was more frequent among IPE patients with a borderline significance (3.5% vs 0.4% among IPE and N-IPE respectively, p = 0.083). On multivariate analysis, intraperitoneal tumor exposure was an independent prognostic factors for worse survival; patients belonging to the N-IPE group had a risk of recurrence of about 3-fold lower compared to patients of the IPE group (hazard ratio: 0.37, 95% confidence interval: 0.15–0.88, p = 0.025). Conclusionit would be advisable that further prospective studies investigating the efficacy of different surgical approach in ECC take into consideration of this issue. Moreover, all other measures that could potentially prevent peritoneal exposure of tumor should be adopted during minimally invasive surgery for early stage cervical cancer to provide higher survival outcomes.

Pleuropulmonary blastoma-like peritoneal sarcoma: a newly described malignancy associated with biallelic DICER1 pathogenic variation

Since the original description of pathogenic germline DICER1 variation underlying pleuropulmonary blastoma (PPB), the spectrum of extrapulmonary neoplasms known to be associated with DICER1 has continued to expand and now includes tumors of the ovary, thyroid, kidney, eye, and brain among other sites. This report documents our experience with another manifestation: a primitive sarcoma that resembles PPB and DICER1-associated sarcoma of the kidney. These tumors are distinguished by their unusual location in the peritoneal cavity, associated with visceral and/or parietal mesothelium. A total of seven cases were identified through pathology review in children presenting at a median age of 13 years (range 3–14 years). Primary sites of origin included the fallopian tube (four cases), serosal surface of the colon (one case), and pelvic sidewall (two cases). One case had pathologic features of type I PPB, another type Ir (regressed) PPB, and the remaining five had features of type II or III PPB with a mixed primitive sarcomatous pattern with or without cystic elements. All had a pathogenic DICER1 variation identified in germline and/or tumor DNA. PPB-like peritoneal tumors represent a newly described manifestation of DICER1 pathogenic variation whose pathologic features are also recapitulated in DICER1-related renal sarcoma, cervical embryonal rhabdomyosarcoma, and some Sertoli–Leydig cell tumors with heterologous elements. Tumors arising from the fallopian tube or elsewhere in the abdomen/pelvis, especially those with heterogeneous rhabdomyosarcomatous and/or cartilaginous differentiation, should prompt consideration of germline and tumor DICER1 testing.

EP34 Ovarian cancer presenting as primary Sjögren’s syndrome: a rare but important mimic

EP34 Ovarian cancer presenting as primary Sjögren’s syndrome: a rare but important mimic

Influence of a Low-Carbohydrate High-Fat Diet on Peritoneal Inflammation, Cancer-Associated Lymphocytes, and Survival in a Murine Carcinomatous Peritonitis Model.

Low-carbohydrate high-fat diets (LCHFDs) are thought to be beneficial for metabolic support in patients with advanced cancer. However, whether LCHFDs affect the progression of carcinomatous peritonitis (CP) remains unclear. Our study examined the influence of a lard-based LCHFD on host immunity and survival in a murine CP model. Mice were fed either a normal diet (ND) or an LCHFD ad libitum. On day 7, Panc02 cancer cells were inoculated intraperitoneally. Mice were killed on days 7, 21, and 35, and cytokine levels in the peritoneal fluid, as well as the number and phenotypes of peritoneal, splenic, and tumor-infiltrating lymphocytes were measured. Survival studies were performed with both ad libitum and isocaloric feeding in other sets of mice. The levels of all cytokines significantly increased in the LCHFD group compared with those in the ND group on day 21. The tumor necrosis factor α and interleukin-10 levels were higher in the LCHFD group than in the ND group on day 35. In the LCHFD group, the regulatory T-cell (Treg) number was significantly higher in the peritoneal cavity and tumor. The survival times were worse in the LCHFD group than in the ND group. The ad libitum, lard-based LCHFD feeding of CP mice increases the peritoneal cytokine levels, which may reduce splenic, anticancer lymphocytes and increase the number of Tregs in the peritoneal cavity and tumor. The detrimental effects of LCHFD are linked to dietary composition rather than overfeeding.

High-Grade Serous Carcinoma of Ovary With Choriocarcinomatous Differentiation: A Case Report and Review of Literature

Non-gestational choriocarcinoma (NGC) of the ovary is a rare, highly malignant neoplasm usually of germ cell origin. Rarely, NGC has been observed in association with ovarian epithelial neoplasms. So far 11 cases of NGC with choriocarcinomatous differentiation have been described in the relevant literature. Here we describe a case of NGC differentiation in a high-grade serous carcinoma of the ovary. A 53-year-old nulliparous, postmenopausal woman presented with abdominal pain and vaginal bleeding. Abdominal imaging revealed a complex pelvic mass and carcinomatosis. The patient underwent a total abdominal hysterectomy with bilateral salpingo-oophorectomy and peritoneal tumor debulking. Microscopic examination of the bilateral ovarian mass tissue revealed a high-grade serous carcinoma with a distinct component of choriocarcinomatous differentiation. The presence of choriocarcinomatous differentiation in epithelial malignancy is associated with a very poor prognosis. Our patient succumbed to disease within 2 months of diagnosis. J Clin Gynecol Obstet. 2020;9(3):53-59 doi: https://doi.org/10.14740/jcgo669

The role of palliative radiation therapy in treating pleural or peritoneal disseminated tumors: 22 cases and a review of the literature.

Local radiation therapy (RT) can provide pain relief and reduce bleeding resulting from pleural or peritoneal dissemination of primary tumors. However, the optimal RT exposure dose for such tumors is unclear and the response rate is unknown. In this study, we examined the effectiveness of palliative RT for pleural or peritoneal disseminated tumors to determine the optimal dose in these patients. The data of 22 patients with pleural- or peritoneal-disseminated tumors who were treated with local RT at our institution between 2011 and 2019 were retrospectively reviewed. Among these patients, 9 (40.9%) had pleural tumors, 13 (59.1%) had peritoneal tumors and 2 had tumors in the peritoneum and umbilicus. The most common primary tumors were lung (22.8%) and pancreatic cancer (18.2%). RT was mainly administered for pain alleviation (72.7%). Three patients (13.6%) received RT for hemostasis. Thirteen patients (59.1%) received a regimen of 30 Gy/10 fractions (fr), with the total dosage for all patients ranging from 27 to 56 Gy. No grade 2 or higher RT-related adverse events occurred. Three and four patients obtained complete and partial responses, respectively. The timing of the measurement of response to pain relief ranged from 0 to 232 (median, 21) days upon completion of RT. Overall response to pain relief occurred in nine of 16 patients (56.3%) with pain before RT. Hemostasis was confirmed in 2 of the 3 patients (66.7%) with bleeding before RT. Twelve of 20 (60%) patients with symptoms before RT responded to RT. Disease-specific survival (DSS) time after RT ranged from 1 to 656 (median, 106) days. Prompt palliative administration of RT to patients with advanced disease to alleviate pain from disseminated tumors may achieve therapeutic efficacy.

Peritoneal Lavage Tumor DNA as a Novel Biomarker for Predicting Peritoneal Recurrence in Pancreatic Ductal Adenocarcinoma.

The clinical role of peritoneal lavage cytology (CY) in pancreatic ductal adenocarcinoma (PDAC) remains controversial, partly due to its low sensitivity. This study aimed to develop a new biomarker, defined as peritoneal lavage tumor DNA (ptDNA), using DNAs extracted from peritoneal lavage samples from patients with PDAC. Samples were collected intraoperatively from 89 PDAC patients who underwent pancreatectomy between 2012 and 2017. Droplet digital polymerase chain reaction (PCR) was used to measure ptDNA for detection of KRAS mutations. The ptDNA status and clinical characteristics were retrospectively evaluated. Positive ptDNA was found in 41 patients, including all 9 patients positive for CY (CY+) and 32 patients negative for CY (CY-). The mutant allele frequency was significantly higher in the CY+ patients than in the CY- patients. The disease-free survival (DFS) and overall survival (OS) were significantly poorer in the high-ptDNA group than in the low-ptDNA group (median DFS, 11.0 vs. 18.8months; p = 0.007; median OS, 28.7 vs not reached; p = 0.001). The survival curves of DFS and OS in the CY+ group were almost equal to those in the CY- and high-ptDNA group. In a multivariable analysis, ptDNA was an independent predictive factor for DFS (p = 0.025) and OS (p = 0.047). The estimated cumulative incidence of peritoneal recurrence was 45.5% in the high-ptDNA group. The ptDNA biomarker had a much higher sensitivity for peritoneal recurrence than CY, whereas CY had higher specificity. As a promising biomarker, ptDNA may predict poor prognosis and peritoneal recurrence in PDAC, resolving the controversy surrounding CY.

High Oncolytic Activity of a Double-Deleted Vaccinia Virus Copenhagen Strain against Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a cancer of the pleura that lacks efficient treatment. Oncolytic immunotherapy using oncolytic vaccinia virus (VV) may represent an alternative therapeutic approach for the treatment of this malignancy. Here, we studied the oncolytic activity of VV thymidine kinase (TK)-ribonucleotide reductase (RR)-/green fluorescent protein (GFP) against MPM. This virus is a VV from the Copenhagen strain that is deleted of two genes encoding the TK (J2R) and the RR (I4L) and that express the GFP. First, we show in vitro that VVTK-RR-/GFP efficiently infects and kills the twenty-two human MPM cell lines used in this study. We also show that the virus replicates in all eight tested MPM cell lines, however, with approximately a 10-fold difference in the amplification level from one cell line to another. Then, we studied the therapeutic efficiency of VVTK-RR-/GFP in non-obese diabetic (NOD) severe combined immunodeficient (SCID) mice that bear peritoneal human MPM tumors. One intraperitoneal infection of VVTK-RR-/GFP reduces the tumor burden and significantly increases mice survival compared to untreated animals. Thus, VVTK-RR- may be a promising oncolytic virus (OV) for the oncolytic immunotherapy of MPM.

Extracellular Vesicles from Cancer-Associated Fibroblasts Containing Annexin A6 Induces FAK-YAP Activation by Stabilizing β1 Integrin, Enhancing Drug Resistance.

Extracellular vesicles (EV) from cancer-associated fibroblasts (CAF) are composed of diverse payloads. Although CAFs impact the aggressive characteristics of gastric cancer cells, the contribution of CAF-EV to gastric cancer progression has not been elucidated. Here, we investigated the molecular mechanism of the changes in gastric cancer characteristics induced by CAF-EV. CAF abundance in gastric cancer tissues was associated with poor prognosis of patients with gastric cancer receiving chemotherapy. Moreover, CAF-EV induced tubular network formation and drug resistance of gastric cancer cells in the extracellular matrix (ECM). Comprehensive proteomic analysis of CAF-EV identified that Annexin A6 plays a pivotal role in network formation and drug resistance of gastric cancer cells in the ECM via activation of β1 integrin-focal adhesion kinase (FAK)-YAP. A peritoneal metastasis mouse model revealed that CAF-EV induced drug resistance in peritoneal tumors, and inhibition of FAK or YAP efficiently attenuated gastric cancer drug resistance in vitro and in vivo. These findings demonstrate that drug resistance is conferred by Annexin A6 in CAF-EV and provide a potential avenue for overcoming gastric cancer drug resistance through the inhibition of FAK-YAP signaling in combination with conventional chemotherapeutics. SIGNIFICANCE: This study elucidates a novel molecular mechanism through which Annexin A6 in CAF-EV activates FAK-YAP by stabilizing β1 integrin at the cell surface of gastric cancer cells and subsequently induces drug resistance. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/16/3222/F1.large.jpg.

Abstract 2838: Peritoneal immune evasion can be overcome with STING agonist treatment in peritoneal carcinomatosis of colon cancer

Abstract Introduction: Peritoneal immune system plays an important role during the peritoneal dissemination of colon cancers. Therefore, tumor-induced T cell anergy in peritoneal cavity could lead to immune evasion and the progression of peritoneal carcinomatosis. Here, we aimed to reverse the immune evasion in peritoneal cavity and effectively suppress the peritoneal carcinomatosis of colon cancer by STING-based immunotherapy. Methods: We established an animal model of peritoneal carcinomatosis by intraperitoneal injection of MC38 colon cancer cells to C57BL/6 mice. Temporal changes in peritoneal immune microenvironment during peritoneal tumor dissemination were first characterized by analyzing tumor nodules, malignant ascites, and peritoneum lavage by flow cytometry. Then, tumor-bearing mice were treated with either STING agonist (ADU-S100), and/or anti-PD-1 antibody. Tumor burden and the volume of ascites were assessed after the treatment. The tumors were analyzed with flow cytometric, histologic, and RNA sequencing analyses. Results: The intraperitoneal inoculation of MC38 colon cancer cells led to dramatic immune cell changes in peritoneal cavity. While the number of myeloid-derived suppressor cells (MDSCs) were markedly increased, the number of CD8+ T cells and dendritic cells gradually decreased after initial influx in the peritoneal cavity. Treatment with STING agonist remarkably suppressed the growth of peritoneal seeding nodules (75%). Moreover, normalization and reduction of peritoneal tumor blood vessels resulted in an overt decrease in malignant ascites (85%) in the peritoneal cavity after STING agonist treatment. In addition, the number of dendritic cells and CD8+ T cells had markedly increased, but that of MDSCs was decreased in the peritoneal cavity. Moreover, the number of IFN-gamma-secreting cytotoxic T cells were increased in tumor nodules and peritoneal cavity after STING agonist treatment. Finally, the combination immunotherapy of STING agonist and anti-PD1 antibody induced stronger adaptive immunity against peritoneal carcinomatosis than monotherapy and showed potent anti-cancer activity with reduced ascites formation. Conclusion: STING immunotherapy can normalize peritoneal tumor vasculature and immune system, and synergize with immune checkpoint blockade to control peritoneal carcinomatosis of colon cancer. Citation Format: Hannah Yang, Seung Jun Lee, Yu Seong Lee, Won Suk Lee, So Jung Kong, Beodeul Kang, Hong Jae Chon, Chan Kim. Peritoneal immune evasion can be overcome with STING agonist treatment in peritoneal carcinomatosis of colon cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2838.

Abstract 6597: Highly localized, inducible interleukin-12 release augments ICAM-1 CAR T cell activity against solid tumors

Abstract Background: Chimeric antigen receptor (CAR) T cells have demonstrated continued success in the treatment of hematological malignancies. By contrast, limited efficacy of CAR T cells has been seen in solid tumors due to multiple obstacles including impaired T cell infiltration and immune suppressive tumor environment, resulting in lack of proliferation and function. Previously, we have developed a micromolar affinity tuned CAR T cells targeting overexpressed ICAM-1 against a variety of tumors. To combat the immunosuppressive microenvironment in solid tumors, we developed a novel lentivirus vector that incorporates expression cassettes for CAR, somatostatin receptor 2 (SSTR2) for PET/CT imaging of T cells, and CAR-activation dependent release of IL-12. Inducible IL-12 (iIL-12) expression was enabled by a synthetic promoter containing both NFkB and NFAT promoter elements by T cells to leverage IL-12's ability to promote Th1 response and at the same time to minimize systemic toxicity of IL-12. The iIL-12 CAR T exhibited much more robust killing of subcutaneous and peritoneal tumors, which showed partial to limited response to conventional CAR T cells without inducible cytokines. Methods: CAR T cells were generated by double lentiviral transduction of primary human T cells at 24 and 48 hours after activation with anti-CD3/CD28 Dynabeads. NSG mice inoculated with subcutaneous anaplastic thyroid cancer cells (8505c) and triple negative breast cancer cells (MDA-MB-468), and intraperitoneal gastric cancer cells (MKN28) were treated with with or without iIL-12 CAR T cells. Tumor growth was monitored regularly by bioluminescence imaging. PET/CT imaging was implemented to monitor T cell localization and biodistribution using 18F-NOTA-octreotide, a radiotracer targeting SSTR2. Results: Jurkat cells expressing iIL-12 ICAM-1 CAR produced IL-12 in an antigen density dependent manner when co-incubated with ICAM-1 positive tumor cells or HEK 293T cells transduced to express human ICAM-1. In in vitro cytotoxicity assay, iIL-12 CAR T cells exhibited significantly augmented tumor-lytic activity than conventional ICAM-1 CAR T cells. In striking contrast to conventional ICAM-1 CAR T cells which did not control tumor growth, iIL-12 CAR T cells mediated complete regression of various solid tumors and prolonged mouse survival significantly. Based on PET/CT imaging, both conventional and iIL-12 CAR T cells showed high levels of T cell infiltration and localization in tumor lesions. These results suggest that conventional CAR T cells quickly exhausted and lost function after penetration, while locally released IL-12 played an important role in improving anti-tumor responses. Furthermore, serum levels of IL-12 in mice treated with iIL-12 CAR T cells were not detectable, indicating that IL-12 secretion was tightly controlled and limited to tumor sites. Conclusions: These findings demonstrate that local release of inducible IL-12 can help overcome hostile tumor microenvironment and augment anti-tumor immune responses. Studies are underway to evaluate the feasibility of inducible IL-12 armored ICAM-1 CAR T cells as a potential therapy with favorable safety and efficacy profiles. Citation Format: Yanping Yang, Jaclyn E. McCloskey, Yogindra Vedvyas, Irene M. Min, Eric von Hofe, Moonsoo M. Jin. Highly localized, inducible interleukin-12 release augments ICAM-1 CAR T cell activity against solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6597.

Abstract 4246: SENTI-101, a novel genetically modified allogeneic cell product expressing IL12 and IL21, elicits a tumor-localized, robust, and multimodal immune response in preclinical models of solid tumors

Abstract While immunotherapies based on single recombinant cytokines such as IL12 and IL21 have shown great promise in preclinical models of solid tumors, clinical translation has proven challenging due to limited mechanisms of action, narrow therapeutic windows upon systemic administration, and short half-lives resulting in poor pharmacokinetics and distribution. Thus, there is a need for tumor-localized cytokine therapies capable of driving sustained efficacy with a wide therapeutic window. SENTI-101 is a cell-based immunotherapy comprising allogeneic bone marrow-derived mesenchymal stromal cells (BM-MSCs) genetically modified to express IL12 and IL21. Consistent with prior studies, we demonstrated that SENTI-101 innately homes to disseminated tumors in the peritoneal cavity and induces durable anti-tumor responses and immune memory in various preclinical models of peritoneal tumors. In this study, we investigated the mechanisms of action of SENTI-101. Our results demonstrate that the IL12 and IL21 combination elicits pleiotropic and complementary effects that drive a multi-modal immune response across various steps of the cancer immunity cycle. Treatment of preclinical murine models of peritoneal tumors (e.g., CT26 and B16F10) with SENTI-101 significantly increased the local production of IFNg by more than 40-fold (p<0.02). Concurrently, mice treated with SENTI-101 had significantly increased levels of cytokines and chemokines such as CXCL9 (p<0.02), which have previously been associated with better prognosis and response to immunotherapy in multiple cancer types. We used flow cytometry and multiplexed IHC to characterize the immune landscape in response to SENTI-101. The number of antigen-presenting cells (F4/80negCD11c+MHC-II+CD103+) more than doubled in peritoneal lymph nodes 72 h after treatment with SENTI-101 (p=0.016). We also observed an increase in pSTAT1 positivity in the myeloid compartment, indicating a favorable immune phenotype. This change was accompanied by an increase in T-cell infiltrates into tumors (p=0.0003) that were in close proximity with B-cells and that were organized in tertiary lymphoid structures, which are known to correlate with improved prognosis in cancer patients. T-cell activation markers (CD38, CD25, IFNg, GranzymeB) also increased by more than 6 times (p=0.015) in the tumor microenvironment (TME) and peritoneal fluid after treatment with SENTI-101. In accordance with increased T-cell infiltration and activation in the TME, SENTI-101 showed a synergistic anti-tumor effect when combined with checkpoint inhibitor anti-PD1. Overall, our preclinical studies show that SENTI-101 modulates the tumor immune landscape via multiple complementary modes of action, resulting in long-term anti-tumor immunity. Furthermore, this work demonstrates the therapeutic potential of tumor-localized cell therapies armed with gene circuits expressing combinatorial immune effectors to trigger a multi-factorial anti-tumor response. Citation Format: Alba Gonzalez, Frances D. Liu, Archana Nagaraja, Alyssa Mullenix, Russell M. Gordley, Daniel O. Frimannsson, Anissa Benabbas, Chen-Ting Lee, Tiffany A. Truong, Allison Quach, Mengxi Tian, Rowena Martinez, Rishi Savur, Alyssa Perry-McNamara, Don-Hong Wang, Ori Maller, Dharini Iyer, Ashita Magal, Sravani Mangalampalli, Christina J. Huynh, Carmina C. Blanco, Jack T. Lin, Brian S. Garrison, Philip Lee, Timothy K. Lu, Gary Lee. SENTI-101, a novel genetically modified allogeneic cell product expressing IL12 and IL21, elicits a tumor-localized, robust, and multimodal immune response in preclinical models of solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4246.

Abstract 3145: Clinical impact of new liquid biopsy using modified telomerase-specific adenovirus-based identification for viable-peritoneal tumor cells in peritoneal lavage fluid in resectable pancreatic cancer

Abstract Pancreatic cancer (PC) is one of the leading causes of cancer-related mortality worldwide. Although surgical resection is the only curable option, less than 20% of the patients diagnosed with localized disease are resectable. The prognosis of these patients after complete resection is extremely poor due to local and systemic recurrence. Peritoneal recurrence is a major recurrence pattern after surgery for PC. Peritoneal lavage cytology (CY) is used widely in the diagnosis and staging of gastric and pancreatic cancer to rule out patients with occult peritoneal metastasis. For gastric cancer, positive cytology (CY+), even in the absence of visible peritoneal metastasis, represents stage IV disease. However, the prognostic significance of CY+ in potentially resectable PC is controversial. We rise the question of whether CY+ status in PC has predictive value for survival and early peritoneal recurrence. Therefore, we conducted this study to evaluate use of a new genetically modified telomerase-specific replication-selective adenovirus, expressing GFP (TelomeScan F35) in rapid detection of viable peritoneal tumor cell (v-PTC) dissemination of PC. This human clinical trial sought to determine if the presence of virally-detected, rare v-PTC predict peritoneal recurrence and patient outcome. This study was approved by the IRB in Osaka Police Hospital and Rinku General Medical Center. Patients with resectable cytologically or histologically proven ductal adenocarcinoma of the pancreas were enrolled. Peritoneal lavage fluid was harvested just after a laparotomy in 53 patients with PC. Half of the fluid was examined by cytology with papanicolau staining and MOC-31 immunostaining and the remaining half was analyzed to detect v-PTC with TelomeScan F35. To distinguish between leucocyte and cells with epithelial origin, cells were stained with anti-CD45 Ab. To further distinguish cells with primary tumor origin, cells were labeled with anti-CEA, anti-CA19-9 and EpCAM Abs. GFP-positive and CD45-negative, and either CEA-, CA19-9 or EpCAM-positive cells were counted as v-PTC by automatic detection system using NIS Elements imaging software. Patients were followed after surgery to evaluate its clinical significance. Among 53 patients aged 53-87 years (30 males and 23 females), 6 were cytologically positive (CY+), other 12 were virally positive by TelomeScan F35 (v-PTC+). All 53 patients underwent a surgical resection (PD/DP/TP=32/14/7). 2 patients were double positive (CY+/v-PTC+), and peritoneal recurrence early occurred at 7 month after surgery despite adjuvant chemotherapy. 4 were CY+, but v-PTC-, and no peritoneal recurrence were observed (0%). On the other hand, other 10 were CY-, but v-PTC+, and 4 of these 10 patients occurred peritoneal recurrence (40%). Remaining 37 patients were double negative (CY-/v-PTC-), peritoneal recurrence were observed in only 4 patients. In conclusion, the TelomeScan F35-based v-PTC(+) status was associated with a significantly increased incidence of peritoneal recurrence in patients with resectable PC, resulting in impaired survival. Citation Format: Masahiro Tanemura, Kenta Furukawa, Manabu Mikamori, Tadafumi Asaoka, Yasuo Urata, Kentaro Kishi. Clinical impact of new liquid biopsy using modified telomerase-specific adenovirus-based identification for viable-peritoneal tumor cells in peritoneal lavage fluid in resectable pancreatic cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3145.

Peritoneal Metastatic Cancer Stem Cells of Gastric Cancer with Partial Mesenchymal-Epithelial Transition and Enhanced Invasiveness in an Intraperitoneal Transplantation Model.

Objectives This preliminary study is aimed at enriching and isolating peritoneal metastatic cancer stem cells (pMCSCs) of gastric cancer and assessing their epithelial-mesenchymal transition (EMT) phenotype and invasiveness. Methods Cancer stem cells of human gastric cancer (CSC-hGC) were previously isolated and transfected with green fluorescent protein and luciferase genes to validate the mouse model of peritoneal metastasis established via transplantation. The first and second generations ([G1] and [G2], respectively) of pMCSCs were isolated from intraperitoneally transplanted CSC-hGC (pMCSC-tGC) by spherical culture. CSC and EMT-related markers and regulators in the two generations of intraperitoneally transplanted tumors were examined by immunohistochemistry, immunofluorescence staining, and quantitative PCR. Cell mobility was examined by a transwell assay. Results The nude mouse model of intraperitoneally transplanted CSC-hGC was successful in establishing sequential formation of peritoneal tumors and enrichment of pMCSCs. CD44 and CD54 were consistently expressed in the two generations of transplanted tumors. In vitro cell (migration) assays and immunocytofluorescence assays showed that in pMCSC-tGC[G2], E-cad, Survivin, and Vimentin expression was stable; α-SMA expression was decreased; and OVOL2, GRHL2, and ZEB1 expression was increased. PCR analysis indicated that in pMCSC-tGC[G2], the mRNA expression of E-cad, α-SMA, MMP9, MMP2, and Vimentin was downregulated, while that of ZEB1, OVOL2, and GRHL2 was upregulated. In vivo tumor (homing) assays and immunohistochemical assays demonstrated that in pMCSC-tGC[G2], E-cad and Snail were upregulated, while α-SMA was downregulated. The numbers of migrated and invaded pMCSC-tGC[G1] and pMCSC-tGC[G2] were significantly higher than those of CSC-hGC in migration and invasion assays. Conclusions pMCSCs might be a specific subpopulation that can be sequentially enriched by intraperitoneal transplantation. pMCSCs exhibited a tendency towards partial mesenchymal-epithelial transition, enhancing their invasiveness during homing and the formation of peritoneal tumors. However, these preliminary findings require validation in further experiments.

Role of prophylactic hyperthermic intraperitoneal chemotherapy in patients with locally advanced gastric cancer.

BACKGROUNDGastric cancer is the second most common malignant tumor in China, ranking third among all malignant tumor mortality rates. Hyperthermic intraperitoneal chemotherapy (HIPEC) has been shown to increase significantly the effectiveness of intraperitoneal chemotherapeutic drugs, prolong the action time of these drugs on intraperitoneal tumor cells, and enhance their diffusion in tumor tissues. HIPEC may be one of the best choices for the eradication of residual cancer cells in the abdominal cavity.AIMThe aim of this study was to study the role of preventive HIPEC after radical gastrectomy.METHODSA prospective analysis was performed with patients with cT4N0-3M0 gastric cancer to compare the effects of postoperative prophylactic HIPEC plus intravenous chemotherapy with those of routine adjuvant chemotherapy. Patients’ medical records were analyzed, and differences in the peritoneal recurrence rate, disease-free survival time, and total survival time between groups were examined.RESULTSThe first site of tumor recurrence was the peritoneum in 11 cases in the conventional adjuvant chemotherapy group and in 2 cases in the HIPEC group (P = 0.020). The 1-year and 3-year disease-free survival rates were 91.9% and 60.4%, respectively, in the conventional adjuvant chemotherapy group and 92.1% and 63.0%, respectively, in the HIPEC group. The 1-year and 3-year overall survival rates were 95.2% and 66.3%, respectively, in the conventional adjuvant chemotherapy group and 96.1% and 68.6%, respectively, in the HIPEC group. No significant difference in postoperative or chemotherapy complications was observed between groups.CONCLUSIONIn patients with cT4N0-3M0 gastric cancer, prophylactic HIPEC after radical tumor surgery is beneficial to reduce peritoneal tumor recurrence and prolong survival.

Peritoneal Cell-Free Tumor DNA as Biomarker for Peritoneal Surface Malignancies.

Disease burden in patients with peritoneal carcinomatosis (PC) is difficult to estimate. We evaluate whether peritoneal cell-free tumor DNA can be used as a measure of disease burden. Malignant ascites or peritoneal lavage fluids were collected from patients with PC under approved IRB protocol. Cell-free DNA was extracted from peritoneal fluid. Droplet digital PCR (ddPCR) was performed using a commercially available KRAS G12/G13 screening kit. Mutant allele frequency (MAF) was calculated based on the numbers of KRAS wild-type and mutant droplets. Clinicopathological, treatment and outcome data were abstracted and correlated with MAF of cell-free KRAS mutant DNA. Cell-free KRAS mutant DNA was detected in 15/37 (40%) malignant peritoneal fluids with a MAF of 0.1% to 26.2%. While peritoneal cell-free KRAS mutant DNA was detected in all the patients with KRAS mutant tumors (N = 10), 3/16 (19%) patients with KRAS wild-type tumors also had peritoneal cell-free KRAS mutant DNA. We also found that 71% (5/7) of patients with disease amenable to cytoreductive surgery (CRS) had a MAF of < 1% (median: 0.5%, range: 0.1-4.7%), while 75% (6/8) of patients with unresectable disease had a MAF of > 1% (median: 4.4%, range: 0.1-26.2%). This pilot proof-of-principle study suggests that peritoneal cell-free tumor DNA detected by ddPCR may enable prediction of disease burden and a measure of disease amenable to CRS in patients with PC.

Personalized Identification of Optimal HIPEC Perfusion Protocol in Patient-Derived Tumor Organoid Platform.

Chemotherapy dosing duration and perfusion temperature vary significantly in HIPEC protocols. This study investigates patient-derived tumor organoids as a platform to identify the most efficacious perfusion protocol in a personalized approach. Peritoneal tumor tissue from 15 appendiceal and 8 colon cancer patients who underwent CRS/HIPEC were used for personalized organoid development. Organoids were perfused in parallel at 37 and 42°C with low- and high-dose oxaliplatin (200mg/m2 over 2h vs. 460mg/m2 over 30min) and MMC (40mg/3L over 2h). Viability assays were performed and pooled for statistical analysis. An adequate organoid number was generated for 75% (6/8) of colon and 73% (11/15) of appendiceal patients. All 42°C treatments displayed lower viability than 37°C treatments. On pooled analysis, MMC and 200mg/m2 oxaliplatin displayed no treatment difference for either appendiceal or colon organoids (19% vs. 25%, p = 0.22 and 27% vs. 31%, p = 0.55, respectively), whereas heated MMC was superior to 460mg/m2 oxaliplatin in both primaries (19% vs. 54%, p < 0.001 and 27% vs. 53%, p = 0.002, respectively). In both appendiceal and colon tumor organoids, heated 200mg/m2 oxaliplatin displayed increased cytotoxicity as compared with 460mg/m2 oxaliplatin (25% vs. 54%, p < 0.001 and 31% vs. 53%, p = 0.008, respectively). Organoids treated with MMC or 200mg/m2 heated oxaliplatin for 2 h displayed increased susceptibility in comparison with 30-min 460mg/m2 oxaliplatin. Optimal perfusion protocol varies among patients, and organoid technology may offer a platform for tailoring HIPEC conditions to the individual patient level.