Exploring the peritoneal surface malignancy phenotype--a pilot immunohistochemical study of human pseudomyxoma peritonei and derived animal models

A Novel Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth in Mouse Models of GI Cancer

Here, we describe a novel pan-RAS inhibitor, ADT-007, that potently inhibited the growth of RAS mutant cancer cells irrespective of the RAS mutation or isozyme. RAS WT cancer cells with GTP-activated RAS from upstream mutations were equally sensitive. Conversely, RAS WT cancer cells harboring downstream BRAF mutations and normal cells were essentially insensitive to ADT-007. Sensitivity of cancer cells to ADT-007 required activated RAS and dependence on RAS for proliferation, while insensitivity was attributed to metabolic deactivation by UDP-glucuronosyltransferases expressed in RAS WT and normal cells but repressed in RAS mutant cancer cells. ADT-007 binds nucleotide-free RAS to block GTP activation of effector interactions and MAPK/AKT signaling, resulting in mitotic arrest and apoptosis. ADT-007 displayed unique advantages over mutant-specific KRAS and pan-KRAS inhibitors, as well as other pan-RAS inhibitors that could impact in vivo antitumor efficacy by escaping compensatory mechanisms leading to resistance. Local administration of ADT-007 showed robust antitumor activity in syngeneic immune-competent and xenogeneic immune-deficient mouse models of colorectal and pancreatic cancer. The antitumor activity of ADT-007 was associated with the suppression of MAPK signaling and activation of innate and adaptive immunity in the tumor immune microenvironment. Oral administration of ADT-007 prodrug also inhibited tumor growth, supporting further development of this novel class of pan-RAS inhibitors for RAS-driven cancers.

SIGNIFICANCE

ADT-007 has unique pharmacological properties with distinct advantages over other RAS inhibitors by circumventing resistance and activating antitumor immunity. ADT-007 prodrugs and analogs with oral bioavailability warrant further development for RAS-driven cancers.

Peritoneal Microenvironment Promotes Appendiceal Adenocarcinoma Growth: A Multi-omics Approach Using Patient-Derived Xenografts

Appendiceal adenocarcinoma (AA) is unique from other gastrointestinal malignancies in that it almost exclusively metastasizes to the peritoneal cavity. However, few studies have investigated the molecular interaction of the peritoneal microenvironment and AA. Here, we use a multi-omics approach with orthotopic and flank-implanted patient-derived xenografts (PDX) to study the effect of the peritoneal microenvironment on AA. AA tumors implanted in the peritoneal microenvironment tended to grow faster and displayed greater nuclear expression of Ki-67 relative to the same tumors implanted in the flank. Comparing the tumor-specific transcriptome (excluding stromal transcription), the peritoneal microenvironment relatively upregulated genes related to proliferation, including MKI67 and EXO1. Peritoneal tumors were also enriched for proliferative gene sets, including E2F and Myc Targets. Proteomic studies found a 2.5-fold increased ratio of active-to-inactive phosphoforms of the YAP oncoprotein in peritoneal tumors, indicating downregulation of Hippo signaling.

IMPLICATIONS

The peritoneal microenvironment promotes growth of appendiceal tumors and expression of proliferative pathways in PDXs.

Comparative transcriptomic analyses reveal activation of the epithelial-mesenchymal transition program in non-metastasizing low grade pseudomyxoma peritonei

Epithelial-mesenchymal transition (EMT), angiogenesis, cell adhesion and extracellular matrix (ECM) interaction are essential for colorectal cancer (CRC) metastasis. Low grade mucinous neoplasia of the appendix (LAMN) and its advanced state low grade pseudomyxoma peritonei (lgPMP) show local aggressiveness with very limited metastatic potential as opposed to CRC. To better understand the underlying processes that foster or impede metastatic spread, we compared LAMN, lgPMP, and CRC with respect to their molecular profile with subsequent pathway analysis. LAMN, lgPMP and (mucinous) CRC cases were subjected to transcriptomic analysis utilizing Poly(A) RNA sequencing. Successfully sequenced cases (LAMN n = 10, 77%, lgPMP n = 13, 100% and CRC n = 8, 100%) were investigated using bioinformatic and statistical tests (differential expression analysis, hierarchical clustering, principal component analysis and gene set enrichment analysis). We identified a gene signature of 28 genes distinguishing LAMN, lgPMP and CRC neoplasias. Ontology analyses revealed that multiple pathways including EMT, ECM interaction and angiogenesis are differentially regulated. Fifty-three significantly differentially regulated gene sets were identified between lgPMP and CRC followed by CRC vs. LAMN (n = 21) and lgPMP vs. LAMN (n = 16). Unexpectedly, a substantial enrichment of the EMT gene set was observed in lgPMP vs. LAMN (FDR=0.011) and CRC (FDR=0.004). Typical EMT markers were significantly upregulated (Vimentin, TWIST1, N-Cadherin) or downregulated (E-Cadherin) in lgPMP. However, MMP1 and MMP3 levels, associated with EMT, ECM and metastasis, were considerably higher in CRC. We show that the different tumor biological behaviour and metastatic spread pattern of midgut malignancies is reflected in a different gene expression profile. We revealed a strong activation of the EMT program in non-metastasizing lgPMP vs. CRC. Hence, although EMT is considered a key step in hematogenous spread, successful EMT does not necessarily lead to hematogenous dissemination. This emphasizes the need for further pathway analyses and forms the basis for mechanistic and therapy-targeting research.

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.

Intraperitoneal administration of cabazitaxel-loaded nanoparticles in peritoneal metastasis models

Colorectal and ovarian cancers frequently develop peritoneal metastases with few treatment options. Intraperitoneal chemotherapy has shown promising therapeutic effects, but is limited by rapid drug clearance and systemic toxicity. We therefore encapsulated the cabazitaxel taxane in poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs), designed to improve intraperitoneal delivery. Toxicity of free and encapsulated cabazitaxel was investigated in rats by monitoring clinical signs, organ weight and blood hematological and biochemical parameters. Pharmacokinetics, biodistribution and treatment response were evaluated in mice. Biodistribution was investigated by measuring both cabazitaxel and the 2-ethylbutanol NP degradation product. Drug encapsulation was shown to increase intraperitoneal drug retention, leading to prolonged intraperitoneal drug residence time and higher drug concentrations in peritoneal tumors. As a result, encapsulation of cabazitaxel improved the treatment response in two in vivo models bearing intraperitoneal tumors. Together, these observations indicate a strong therapeutic potential of NP-based cabazitaxel encapsulation as a novel treatment for peritoneal metastases.

Alginate Microsphere Encapsulation of Drug-Loaded Nanoparticles: A Novel Strategy for Intraperitoneal Drug Delivery

Alginate hydrogels have been broadly investigated for use in medical applications due to their biocompatibility and the possibility to encapsulate cells, proteins, and drugs. In the treatment of peritoneal metastasis, rapid drug clearance from the peritoneal cavity is a major challenge. Aiming to delay drug absorption and reduce toxic side effects, cabazitaxel (CAB)-loaded poly(alkyl cyanoacrylate) (PACA) nanoparticles were encapsulated in alginate microspheres. The PACAlg alginate microspheres were synthesized by electrostatic droplet generation and the physicochemical properties, stability, drug release kinetics, and mesothelial cytotoxicity were analyzed before biodistribution and therapeutic efficacy were studied in mice. The 450 µm microspheres were stable at in vivo conditions for at least 21 days after intraperitoneal implantation in mice, and distributed evenly throughout the peritoneal cavity without aggregation or adhesion. The nanoparticles were stably retained in the alginate microspheres, and nanoparticle toxicity to mesothelial cells was reduced, while the therapeutic efficacy of free CAB was maintained or improved in vivo. Altogether, this work presents the alginate encapsulation of drug-loaded nanoparticles as a promising novel strategy for the treatment of peritoneal metastasis that can improve the therapeutic ratio between toxicity and therapeutic efficacy.

Prognostic significance of CEA, Ki67 and p53 in pseudomyxoma peritonei of appendiceal origin

Objective

To determine the levels of carcinoembryonic antigen (CEA), proliferating nuclear antigen Ki67 and p53 in pseudomyxoma peritonei (PMP) of appendiceal origin and to correlate the levels with clinicopathological characteristics and overall survival.

Methods

This retrospective study collected data on clinicopathological features and immunohistochemical staining of CEA, Ki67 and p53 in patients with PMP of appendiceal origin. Overall survival was evaluated using Kaplan–Meier plots. Median survival time was estimated by Log-rank tests. Potential prognostic factors were evaluated by Cox proportional hazards regression models.

Results

A total of 141 patients with PMP of appendiceal origin were enrolled in the study with a median age of 54 years. Of these, 93 (66.0%) were diagnosed with low-grade mucinous carcinoma, 43 (30.5%) with high-grade mucinous carcinoma and five (3.5%) with high-grade with signet ring cells. CEA exhibited ubiquitous immunopositivity in most cases and was not associated with overall survival. Ki67 labelling index (LI) and p53 status were related to histological grade and overall survival. The main pathological indicators affecting survival included histological grade, lymph node involvement, angiolymphatic invasion, Ki67 LI and p53.

Conclusion

Combined analysis of high Ki67 LI and aberrant p53 may provide the basis for evaluating the biological behaviour of PMP and predicting clinical outcome.

Anti-Angiogenic Treatment in Pseudomyxoma Peritonei-Still a Strong Preclinical Rationale

Simple Summary

Patients with pseudomyxoma peritonei that are not cured by the standard treatment (cytoreductive surgery and hyperthermic intraperitoneal chemotherapy) have no efficacious treatment options. Drugs that inhibit formation of new vessels (anti-angiogenic drugs) could be a therapeutic option for these patients. Using patient samples and animal models we show that angiogenesis is important in pseudomyxoma peritonei and that anti-angiogenic drugs may indeed have an effect. Our results support continued efforts to determine the role of anti-angiogenic treatment in pseudomyxoma peritonei.

Abstract

Pseudomyxoma peritonei (PMP) is a rare, slow-growing cancer characterized by progressive accumulation of intraperitoneal mucinous tumor deposits. Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) cures approximately 50% of patients, but in unresectable and recurrent cases, treatment options are limited. Anti-angiogenic treatment is being explored as a potential therapeutic option. Using PMP patient samples, microvessel densities (immunostaining for CD31 and CD105) and pro-angiogenic factors were analyzed, and the proliferative response upon incubation with human umbilical cord vascular endothelial cells (HUVEC) was determined. Growth inhibition by anti-angiogenic drugs was analyzed in patient-derived xenograft models of PMP. PMP tumor tissues were found to be highly vascularized and contained key pro-angiogenic factors, in particular related to vascular endothelial growth factor (VEGF) signaling, but interestingly, high levels of fibroblast growth factor 2 were also detected. HUVEC proliferation was stimulated upon incubation with fresh tumor samples and the observed proliferation could be inhibited by VEGF pathway inhibitor bevacizumab. In xenograft models the two VEGF pathway inhibitors, bevacizumab and aflibercept, inhibited tumor growth. This work reemphasizes the importance of angiogenesis as a major driver in PMP and strengthens the preclinical rationale for continued exploration of angiogenesis inhibition in the hope of providing novel treatment to a group of patients that have few other treatment options.

Role of Epithelial-Mesenchymal Plasticity in Pseudomyxoma Peritonei: Implications for Locoregional Treatments

The mechanisms by which neoplastic cells disseminate from the primary tumor to metastatic sites, so-called metastatic organotropism, remain poorly understood. Epithelial-mesenchymal transition (EMT) plays a role in cancer development and progression by converting static epithelial cells into the migratory and microenvironment-interacting mesenchymal cells, and by the modulation of chemoresistance and stemness of tumor cells. Several findings highlight that pathways involved in EMT and its reverse process (mesenchymal-epithelial transition, MET), now collectively called epithelial-mesenchymal plasticity (EMP), play a role in peritoneal metastases. So far, the relevance of factors linked to EMP in a unique peritoneal malignancy such as pseudomyxoma peritonei (PMP) has not been fully elucidated. In this review, we focus on the role of epithelial-mesenchymal dynamics in the metastatic process involving mucinous neoplastic dissemination in the peritoneum. In particular, we discuss the role of expression profiles and phenotypic transitions found in PMP in light of the recent concept of EMP. A better understanding of EMP-associated mechanisms driving peritoneal metastasis will help to provide a more targeted approach for PMP patients selected for locoregional interventions involving cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

Experimental Treatment of Mucinous Peritoneal Metastases Using Patient-Derived Xenograft Models

Mucinous peritoneal metastases (PM) generally respond poorly to systemic treatment, and there is a clear unmet need for new treatment strategies to improve survival and quality of life for patients with PM. In this work, the growth inhibitory effect of five drugs (oxaliplatin (OXA; 5 mg/kg), irinotecan (IRI; 60 mg/kg), cabazitaxel (CBZ; 15 or 30 mg/kg), regorafenib (REG; 10, 30 or 60 mg/kg), and capecitabine (CAP; 359 or 755 mg/kg) was investigated in three orthotopic patient-derived xenograft models that mimic mucinous PM. Drugs were administered intraperitoneally (i.p.) as monotherapy weekly for 4 weeks (OXA, IRI), as one single i.p. injection (CBZ), or orally (REG, CAP) daily 5 of 7 days per week for four weeks, and i.p. tumor growth and survival were monitored and compared between treatment groups. The i.p. administered drugs (OXA, IRI, CBZ) had the strongest growth inhibitory effect, with OXA being most efficacious, completely inhibiting tumor growth in the majority of the animals. CBZ and IRI also strongly inhibited tumor growth, but with more variation in efficacy between the models. A moderate reduction in tumor growth was observed in all models treated with REG, while CAP had little to no growth inhibitory effect. Targeted next-generation-sequencing has identified mutational profiles typically associated with PM (mutations in KRAS, GNAS, and BRAF oncogenes), supporting the representativeness of the models. The results presented in this work support the continued exploration of i.p. treatment protocols for PM, with OXA remaining and CBZ emerging as particularly interesting candidates for further studies.

The biological basis and function of GNAS mutation in pseudomyxoma peritonei: a review

Purpose

Pseudomyxoma peritonei (PMP) is a rare clinical malignancy syndrome characterized by the uncontrollable accumulation of copious mucinous ascites in the peritoneal cavity, resulting in “jelly belly”. The mechanism of tumor progression and mucin hypersecretion remains largely unknown, but GNAS mutation is a promising contributor. This review is to systemically summarize the biological background and variant features of GNAS, as well as the impacts of GNAS mutations on mucin expression, tumor cell proliferation, clinical-pathological characteristics, and prognosis of PMP.

Methods

NCBI PubMed database (in English) and WAN FANG DATA (in Chinese) were used for literature search. And NCBI Gene and Protein databases, Ensembl Genome Browser, COSMIC, UniProt, and RCSB PDB database were used for gene and protein review.

Results

GNAS encodes guanine nucleotide-binding protein α subunit (Gsα). The mutation sites of GNAS mutation in PMP are relatively stable, usually at Chr20: 57,484,420 (base pair: C-G) and Chr20: 57,484,421 (base pair: G-C). Typical GNAS mutation results in the reduction of GTP enzyme activity in Gsα, causing failure to hydrolyze GTP and release phosphoric acid, and eventually the continuous binding of GTP to Gsα. The activated Gsα could thus continuously promote mucin secretion through stimulating the cAMP-PKA signaling pathway, which is a possible mechanism leading to elevated mucin secretion in PMP.

Conclusion

GNAS mutation is one of the most important molecular biological features in PMP, with major functions to promote mucin hypersecretion.

Intraperitoneal mitomycin C improves survival compared to cytoreductive surgery alone in an experimental model of high-grade pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a rare cancer commonly originating from appendiceal neoplasms that presents with mucinous tumor spread in the peritoneal cavity. Patients with PMP are treated with curative intent by cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). The value of adding HIPEC to CRS has not been proven in randomized trials, and the objective of this study was to investigate the efficacy of intraperitoneal mitomycin C (MMC) and regional hyperthermia as components of this complex treatment. Xenograft tissue established from a patient with histologically high-grade PMP with signet ring cell differentiation was implanted intraperitoneally in 65 athymic nude male rats and the animals were stratified into three treatment groups; the cytoreductive surgery group (CRSG, CRS only), the normothermic group (NG, CRS and intraperitoneal chemotherapy perfusion (IPEC) with MMC at 35 ºC), and the hyperthermic group (HG, CRS and IPEC at 41 ºC). The main endpoints were survival and tumor weight at autopsy. Adequate imitation of the clinical setting and treatment approach was achieved. The median survival was 31 days in the CRSG, 60 days in NG and 67 days in HG. The median tumor weights at autopsy were 34 g in CRSG, 23 g NG and 20 g in HG. In conclusion, the addition of IPEC with MMC after CRS doubled the survival time and reduced tumor growth compared to CRS alone. Adding regional hyperthermia resulted in a modest improvement of treatment outcome.

CLDN1 induces autophagy to promote proliferation and metastasis of esophageal squamous carcinoma through AMPK/STAT1/ULK1 signaling

Tight junction is a structural constitution in cell-cell adhesion and play an important role in the maintenance of permeability and integrity of normal epithelial cell barrier. The protein encoded by Claudin 1 (CLDN1), a member of the claudin family, is an integral membrane protein and a component of tight junction strands. CLDN1 has been proved to regulate the proliferation and metastasis of multiple tumors, but little is known about its role in esophageal squamous cell carcinoma (ESCC). Here, we found that CLDN1 was aberrantly increased in ESCC tissues and cell lines, and mainly distributed in the nucleus of tumor cells. Furthermore, we confirmed that CLDN1 promoted the proliferation and metastasis of ESCC by triggering autophagy both in vitro and in vivo. Mechanically, we validated that CLDN1-induced autophagy via increasing Unc-51 like autophagy activating kinase 1 (ULK1) expression through AMP-activated protein kinase (AMPK)/signal transducer and activator of transcription 1 (STAT1) signaling pathway in ESCC cells. Taken together, our findings demonstrated that aberrant expression and distribution of CLDN1 promoted the proliferation and metastasis of esophageal squamous carcinoma by triggering autophagy through AMPK/STAT1/ULK1 signaling pathway.

MOC31PE immunotoxin - targeting peritoneal metastasis from epithelial ovarian cancer

Peritoneal metastasis (PM) is an important feature of epithelial ovarian cancer (EOC) and is a frequent site of drug resistant disease recurrence, identifying PM-EOC an important clinical challenge. The MOC31PE immunotoxin targets and kills tumor cells expressing the epithelial cell adhesion molecule (EpCAM), which is highly expressed in EOC, and MOC31PE is being investigated for use in treatment of PM-EOC.

The efficacy of MOC31PE treatment alone and in combination with cytotoxic drugs was investigated in two human EpCAM expressing EOC cell lines, B76 and MDHA-2774, in vitro and in corresponding mouse models mimicking PM-EOC. MOC31PE efficaciously killed tumor cells alone and showed equal or superior activity in vitro (paclitaxel, cisplatin, carboplatin) and in vivo (paclitaxel, mitomycin C) compared to the investigated cytotoxic drugs. Additive, or importantly, no antagonistic effects were observed in combination experiments.

In ex vivo cell culture, the cytotoxic effect of MOC31PE was studied on freshly isolated surgical EOC samples. All investigated fresh EOC samples expressed EpCAM and MOC31PE effectively reduced cell viability in ex vivo cultures.

In conclusion, these results, together with our previous preclinical and clinical experience, support development of MOC31PE for treatment of PM-EOC in combination with currently used cytotoxic drugs.

Pathology of Mucinous Appendiceal Tumors and Pseudomyxoma Peritonei

Neoplasms of the appendix are rare, but because of their unusual presentation and unpredictable biologic behavior, it is important to diagnose them correctly. Mucinous tumors account for 58 % of malignant tumors of appendix in SEER database and the remaining are carcinoids. The mucinous appendiceal tumors have a potential to spread to the peritoneum and viscera in the form of gelatinous material with or without neoplastic cells resulting in Pseudomyxoma peritonei. (PMP) PMP is a clinical entity that has a unique biological behavior and can arise from seemingly benign tumors to frankly malignant ones. Several classifications exist for PMP of which Ronnet's classification has been the most popular. In 2010, the WHO proposed a 2 tier classification that classified PMP as either low grade or high grade based on the presence of mucin, cytological and architectural features. According to this classification when the underlying cause for PMP is an appendiceal tumor it is always a mucinous adenocarcinoma rather than a mucocoele or adenoma and these terms should no longer be used. This system of classification helps in predicting the behavior of the tumor and proper treatment strategies. The understanding of the pathogenesis of the disease has also improved with identification of newer biomarkers and molecular genetic alterations. IHC markers CK 20, CDX2 and MUC2 are found to be positive in these tumors in addition to KRAS mutation and loss of heterozygosity in some gene loci. Proper histopathologic classification and predicting the tumor behavior requires a close interaction between the pathologist and the surgeon. The use of the combined modality treatment of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has led to a 5-year survival ranging from 62.5 % to 100 % for low grade, and 0 %-65 % for high grade disease. This article focuses on the etiopathogenesis, clinical behavior, diagnosis and classification of mucinous tumors of the appendix and pseudomyxoma peritonei.

Animal models of colorectal peritoneal metastasis

Colorectal cancer remains an important cause of mortality worldwide. The presence of peritoneal carcinomatosis (PC) causes significant symptoms and is notoriously difficult to treat. Therefore, informative preclinical research into the mechanisms and possible novel treatment options of colorectal PC is essential in order to improve the prognostic outlook in these patients. Several syngeneic and xenograft animal models of colorectal PC were established, studying a wide range of experimental procedures and substances. Regrettably, more sophisticated models such as those giving rise to spontaneous PC or involving genetically engineered mice are lacking. Here, we provide an overview of all reported colorectal PC animal models and briefly discuss their use, strengths, and limitations.

Global gene expression in pseudomyxoma peritonei, with parallel development of two immortalized cell lines

Pseudomyxoma peritonei (PMP) is a rare tumor of appendiceal origin. Treatment is major cytoreductive surgery but morbidity is high. PMP is considered chemo-resistant; its molecular biology is understudied; and presently, there is no platform for pre-clinical drug testing. Here, we performed exon array analysis from laser micro-dissected PMP tissue and normal colonic epithelia. The array analysis identified 27 up-regulated and 34 down-regulated genes: candidate up-regulated genes included SLC16A4, DSC3, Aldolase B, EPHX4, and ARHGAP24; candidate down-regulated genes were MS4A12, TMIGD1 and Caspase-5. We confirmed differential expression of the candidate genes and their protein products using in-situ hybridization and immuno-histochemistry. In parallel, we established two primary PMP cell lines, N14A and N15A, and immortalized with an SV40 T-antigen lentiviral vector. We cross-checked for expression of the candidate genes (from the array analyses) using qPCR in the cell lines and demonstrated that the gene profiles were distinct from those of colorectal tumor libraries and commonly used colon cell lines. N14A and N15A were responsiveness to mitomycin and oxaliplatin. This study characterizes global gene expression in PMP, and the parallel development of the first immortalized PMP cell lines; fit for pre-clinical testing and PMP oncogene discovery.

Patient-derived xenograft mouse models of pseudomyxoma peritonei recapitulate the human inflammatory tumor microenvironment

Pseudomyxoma peritonei (PMP) is a neoplastic syndrome characterized by peritoneal tumor implants with copious mucinous ascites. The standard of care for PMP patients is aggressive cytoreductive surgery performed in conjunction with heated intraperitoneal chemotherapy. Not all patients are candidates for these procedures and a majority of the patients will have recurrent disease. In addition to secreted mucin, inflammation and fibrosis are central to PMP pathogenesis but the molecular processes that regulate tumor-stromal interactions within the peritoneal tumor microenvironment remain largely unknown. This knowledge is critical not only to elucidate PMP pathobiology but also to identify novel targets for therapy. Here, we report the generation of patient-derived xenograft (PDX) mouse models for PMP and assess the ability of these models to replicate the inflammatory peritoneal microenvironment of human PMP patients. PDX mouse models of low- and high-grade PMP were generated and were of a similar histopathology as human PMP. Cytokines previously shown to be elevated in human PMP were also elevated in PDX ascites. Significant differences in IL-6 and IL-8/KC/MIP2 were seen between human and PDX ascites. Interestingly, these cytokines were mostly secreted by mouse-derived, tumor-associated stromal cells rather than by human-derived PMP tumor cells. Our data suggest that the PMP PDX mouse models are especially suited to the study of tumor-stromal interactions that regulate the peritoneal inflammatory environment in PMP as the tumor and stromal cells in these mouse models are of human and murine origins, respectively. These mouse models are therefore, likely to be useful in vivo surrogates for testing and developing novel therapeutic treatment interventions for PMP.

Secreted mucins in pseudomyxoma peritonei: pathophysiological significance and potential therapeutic prospects

Pseudomyxoma peritonei (PMP, ORPHA26790) is a clinical syndrome characterized by progressive dissemination of mucinous tumors and mucinous ascites in the abdomen and pelvis. PMP is a rare disease with an estimated incidence of 1-2 out of a million. Clinically, PMP usually presents with a variety of unspecific signs and symptoms, including abdominal pain and distention, ascites or even bowel obstruction. It is also diagnosed incidentally at surgical or non-surgical investigations of the abdominopelvic viscera. PMP is a neoplastic disease originating from a primary mucinous tumor of the appendix with a distinctive pattern of the peritoneal spread. Computed tomography and histopathology are the most reliable diagnostic modalities. The differential diagnosis of the disease includes secondary peritoneal carcinomatoses and some rare peritoneal conditions. Optimal elimination of mucin and the mucin-secreting tumor comprises the current standard of care for PMP offered in specialized centers as visceral resections and peritonectomy combined with intraperitoneal chemotherapy. This multidisciplinary approach has reportedly provided a median survival rate of 16.3 years, a median progression-free survival rate of 8.2 years and 10- and 15-year survival rates of 63% and 59%, respectively. Despite its indolent, bland nature as a neoplasm, PMP is a debilitating condition that severely impacts quality of life. It tends to be diagnosed at advanced stages and frequently recurs after treatment. Being ignored in research, however, PMP remains a challenging, enigmatic entity. Clinicopathological features of the PMP syndrome and its morbid complications closely correspond with the multifocal distribution of the secreted mucin collections and mucin-secreting implants. Novel strategies are thus required to facilitate macroscopic, as well as microscopic, elimination of mucin and its source as the key components of the disease. In this regard, MUC2, MUC5AC and MUC5B have been found as the secreted mucins of relevance in PMP. Development of mucin-targeted therapies could be a promising avenue for future research which is addressed in this article.

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.