Establishment of a patient-derived orthotopic Xenograft (PDOX) model of HER-2-positive cervical cancer expressing the clinical metastatic pattern

Progress in building clinically relevant patient-derived tumor xenograft models for cancer research

Patient-derived tumor xenograft (PDX) models, a method involving the surgical extraction of tumor tissues from cancer patients and subsequent transplantation into immunodeficient mice, have emerged as a pivotal approach in translational research, particularly in advancing precision medicine. As the first stage of PDX development, the patient-derived orthotopic xenograft (PDOX) models implant tumor tissue in mice in the corresponding anatomical locations of the patient. The PDOX models have several advantages, including high fidelity to the original tumor, heightened drug sensitivity, and an elevated rate of successful transplantation. However, the PDOX models present significant challenges, requiring advanced surgical techniques and resource-intensive imaging technologies, which limit its application. And then, the humanized mouse models, as well as the zebrafish models, were developed. Humanized mouse models contain a human immune environment resembling the tumor and immune system interplay. The humanized mouse models are a hot topic in PDX model research. Regarding zebrafish patient-derived tumor xenografts (zPDX) and patient-derived organoids (PDO) as promising models for studying cancer and drug discovery, zPDX models are used to transplant tumors into zebrafish as novel personalized medical animal models with the advantage of reducing patient waiting time. PDO models provide a cost-effective approach for drug testing that replicates the in vivo environment and preserves important tumor-related information for patients. The present review highlights the functional characteristics of each new phase of PDX and provides insights into the challenges and prospective developments in this rapidly evolving field.

Establishment of a high-fidelity patient-derived xenograft model for cervical cancer enables the evaluation of patient's response to conventional and novel therapies

BACKGROUND

Recurrent or metastatic cervical cancer (r/m CC) often has poor prognosis owing to its limited treatment options. The development of novel therapeutic strategies has been hindered by the lack of preclinical models that accurately reflect the biological and genomic heterogeneity of cervical cancer (CC). Herein, we aimed to establish a large patient-derived xenograft (PDX) biobank for CC, evaluate the consistency of the biologic indicators between PDX and primary tumor tissues of patients, and explore its utility for assessing patient's response to conventional and novel therapies.

METHODS

Sixty-nine fresh CC tumor tissues were implanted directly into immunodeficient mice to establish PDX models. The concordance of the PDX models with their corresponding primary tumors (PTs) was compared based on the clinical pathological features, protein biomarker levels, and genomic features through hematoxylin & eosin staining, immunohistochemistry, and whole exome sequencing, respectively. Moreover, the clinical information of CC patients, RNA transcriptome and immune phenotyping of primary tumors were integrated to identify the potential parameters that could affect the success of xenograft engraftment. Subsequently, PDX model was evaluated for its capacity to mirror patient's response to chemotherapy. Finally, PDX model and PDX-derived organoid (PDXO) were utilized to evaluate the therapeutic efficacy of neratinib and adoptive cell therapy (ACT) combination strategy for CC patients with human epidermal growth factor receptor 2 (HER2) mutation.

RESULTS

We established a PDX biobank for CC with a success rate of 63.8% (44/69). The primary features of established PDX tumors, including clinicopathological features, the expression levels of protein biomarkers including Ki67, α-smooth muscle actin, and p16, and genomics, were highly consistent with their PTs. Furthermore, xenograft engraftment was likely influenced by the primary tumor size, the presence of follicular helper T cells and the expression of cell adhesion-related genes in primary tumor tissue. The CC derived PDX models were capable of recapitulating the patient's response to chemotherapy. In a PDX model, a novel therapeutic strategy, the combination of ACT and neratinib, was shown to effectively inhibit the growth of PDX tumors derived from CC patients with HER2-mutation.

CONCLUSIONS

We established by far the largest PDX biobank with a high engraftment rate for CC that preserves the histopathological and genetic characteristics of patient's biopsy samples, recapitulates patient's response to conventional therapy, and is capable of evaluating the efficacy of novel therapeutic modalities for CC.

Dissecting metastasis using preclinical models and methods

Metastasis has long been understood to lead to the overwhelming majority of cancer-related deaths. However, our understanding of the metastatic process, and thus our ability to prevent or eliminate metastases, remains frustratingly limited. This is largely due to the complexity of metastasis, which is a multistep process that likely differs across cancer types and is greatly influenced by many aspects of the in vivo microenvironment. In this Review, we discuss the key variables to consider when designing assays to study metastasis: which source of metastatic cancer cells to use and where to introduce them into mice to address different questions of metastasis biology. We also examine methods that are being used to interrogate specific steps of the metastatic cascade in mouse models, as well as emerging techniques that may shed new light on previously inscrutable aspects of metastasis. Finally, we explore approaches for developing and using anti-metastatic therapies, and how mouse models can be used to test them.

Tumor Organoid and Spheroid Models for Cervical Cancer

Cervical cancer is one of the most common malignant diseases in women worldwide. Despite the global introduction of a preventive vaccine against the leading cause of cervical cancer, human papillomavirus (HPV) infection, the incidence of this malignant disease is still very high, especially in economically challenged areas. New advances in cancer therapy, especially the rapid development and application of different immunotherapy strategies, have shown promising pre-clinical and clinical results. However, mortality from advanced stages of cervical cancer remains a significant concern. Precise and thorough evaluation of potential novel anti-cancer therapies in pre-clinical phases is indispensable for efficient development of new, more successful treatment options for cancer patients. Recently, 3D tumor models have become the gold standard in pre-clinical cancer research due to their capacity to better mimic the architecture and microenvironment of tumor tissue as compared to standard two-dimensional (2D) cell cultures. This review will focus on the application of spheroids and patient-derived organoids (PDOs) as tumor models to develop novel therapies against cervical cancer, with an emphasis on the immunotherapies that specifically target cancer cells and modulate the tumor microenvironment (TME).

Advances in the Lung Cancer Immunotherapy Approaches

Despite the progress in the comprehension of LC progression, risk, immunologic control, and treatment choices, it is still the primary cause of cancer-related death. LC cells possess a very low and heterogeneous antigenicity, which allows them to passively evade the anticancer defense of the immune system by educating cytotoxic lymphocytes (CTLs), tumor-infiltrating lymphocytes (TILs), regulatory T cells (Treg), immune checkpoint inhibitors (ICIs), and myeloid-derived suppressor cells (MDSCs). Though ICIs are an important candidate in first-line therapy, consolidation therapy, adjuvant therapy, and other combination therapies involving traditional therapies, the need for new predictive immunotherapy biomarkers remains. Furthermore, ICI-induced resistance after an initial response makes it vital to seek and exploit new targets to benefit greatly from immunotherapy. As ICIs, tumor mutation burden (TMB), and microsatellite instability (MSI) are not ideal LC predictive markers, a multi-parameter analysis of the immune system considering tumor, stroma, and beyond can be the future-oriented predictive marker. The optimal patient selection with a proper adjuvant agent in immunotherapy approaches needs to be still revised. Here, we summarize advances in LC immunotherapy approaches with their clinical and preclinical trials considering cancer models and vaccines and the potential of employing immunology to predict immunotherapy effectiveness in cancer patients and address the viewpoints on future directions. We conclude that the field of lung cancer therapeutics can benefit from the use of combination strategies but with comprehension of their limitations and improvements.

Establishment and genetically characterization of patient-derived xenograft models of cervical cancer

Purpose

Patient-derived xenograft (PDX) models were established to reproduce the clinical situation of original cancers and have increasingly been applied to preclinical cancer research. Our study was designed to establish and genetically characterize cervical cancer PDX models.

Methods

A total of 91 fresh fragments obtained from 22 surgically resected cervical cancer tissues were subcutaneously engrafted into female NOD-SCID mice. Hematoxylin and eosin (H&E) staining was performed to assess whether the established PDX models conserved the histological features of original patient cervical cancer tissues. Moreover, a Venn diagram was applied to display the overlap of all mutations detected in whole-genome sequencing (WGS) data from patient original cervical cancer (F0) and F2-, F3-PDX models. The whole exome sequencing (WES) and the “maftools” package were applied to determine the somatic mutations among primary cervical cancers and the established PDX models.

Results

Our study successfully developed a panel of cervical cancer PDX models and the latency time of cervical cancer PDX model establishment was variable with a progressive decrease as the passage number increased, with a mean time to initial growth of 94.71 days in F1 engraftment to 40.65 days in F3 engraftment. Moreover, the cervical cancer PDX models preserved the histological features of their original cervical cancer. WGS revealed that the genome of original cervical cancer was preserved with high fidelity in cervical cancer PDX models throughout the xenografting and passaging process. Furthermore, WES demonstrated that the cervical cancer PDX models maintained the majority somatic mutations of original cervical cancer, of which the KMT2D, LRP1B, NAV3, TP53, FAT1, MKI67 and PKHD1L1 genes were identified as the most frequently mutated genes.

Conclusions

The cervical cancer PDX models preserved the histologic and genetic characteristics of their original cervical cancer, which helped to gain a deeper insight into the genetic alterations and lay a foundation for further investigation of the molecular targeted therapy of cervical cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01342-5.

Review: Precise sarcoma patient-derived orthotopic xenograft (PDOX) mouse models enable identification of novel effective combination therapies with the cyclin-dependent kinase inhibitor palbociclib: A strategy for clinical application

Introduction

Sarcomas are rare heterogeneous malignant tumors that originate and develop in soft tissue or bone. Effective treatment for sarcomas is still limited to traditional chemotherapy and surgery that are often ineffective for recurrent disease. Cyclin-dependent kinases (CDKs) promote abnormal cell cycling and cell division in many cancers including sarcomas. Therefore, our hypothesis was that CDK inhibitors may be useful candidates for sarcoma treatment. Patient-derived orthotopic xenograft (PDOX) mouse models mimic the clinical disease for all major cancer types and have identified effective treatments that hold much clinical promise. The present report reviews sarcoma PDOX models that we have established for their potential to discover effective combination treatments based on CDK inhibitors for recalcitrant sarcoma.

Methods

We have previously reported six sarcoma PDOX studies evaluating the CDK inhibitor palbociclib on sarcoma, including osteosarcoma, Ewing sarcoma, de-differentiated liposarcoma, and peritoneal metastatic leiomyosarcoma.

Results

Palbociclib monotherapy significantly inhibited, but not regressed, the PDOX growth of osteosarcoma, Ewing sarcoma, de-differentiated liposarcoma, and peritoneal metastatic leiomyosarcoma. A combination of palbociclib and a mammalian target of rapamycin (mTOR) inhibitor, everolimus, significantly inhibited, but did not regress, the PDOX growth of osteosarcoma. Combinations of palbociclib with a multikinase inhibitor, sorafenib, and palbociclib combined with recombinant methioninase were effective and regressed the osteosarcoma and de-differentiated liposarcoma PDOX models, respectively.

Conclusions

Novel effective drug combinations using the CDK inhibitor palbociclib were identified in PDOX models of the major types of sarcomas. Methionine restriction effected by methioninase increased the efficacy of palbociclib. Combination therapy with palbociclib is a promising future strategy for improved sarcoma therapy in the clinic.

Validation of a Patient-Derived Xenograft Model for Cervical Cancer Based on Genomic and Phenotypic Characterization

Simple Summary

The rate of total tumor engraftment of patient-derived xenografts is 50% in cervical cancer. These cancers retain their histopathological characteristics. The gene mutations and expression patterns associated with carcinogenesis and infiltration and the expression levels of genes in extracellular vesicles released from the tumors are similar between patient-derived xenograft models and primary tumors. Patient-derived xenograft models of cervical cancer could be potentially useful tools for translational research.

Abstract

Patient-derived xenograft (PDX) models are useful tools for preclinical drug evaluation, biomarker identification, and personalized medicine strategies, and can be developed by the heterotopic or orthotopic grafting of surgically resected tumors into immunodeficient mice. We report the PDX models of cervical cancer and demonstrate the similarities among original and different generations of PDX tumors. Fresh tumor tissues collected from 22 patients with primary cervical cancer were engrafted subcutaneously into NOD.CB17-PrkdcSCID/J mice. Histological and immunohistochemical analyses were performed to compare primary and different generations of PDX tumors. DNA and RNA sequencing were performed to verify the similarity between the genetic profiles of primary and PDX tumors. Total RNA in extracellular vesicles (EVs) released from primary and PDX tumors was also quantified to evaluate gene expression. The total tumor engraftment rate was 50%. Histologically, no major differences were observed between the original and PDX tumors. Most of the gene mutations and expression patterns related to carcinogenesis and infiltration were similar between the primary tumor and xenograft. Most genes associated with carcinogenesis and infiltration showed similar expression levels in the primary tumor and xenograft EVs. Therefore, compared with primary tumors, PDX models could be potentially more useful for translational research.

Patient-Derived Xenograft Models in Cervical Cancer: A Systematic Review

BACKGROUND

Patient-derived xenograft (PDX) models have been a focus of attention because they closely resemble the tumor features of patients and retain the molecular and histological features of diseases. They are promising tools for translational research. In the current systematic review, we identify publications on PDX models of cervical cancer (CC-PDX) with descriptions of main methodological characteristics and outcomes to identify the most suitable method for CC-PDX.

METHODS

We searched on PubMed to identify articles reporting CC-PDX. Briefly, the main inclusion criterion for papers was description of PDX created with fragments obtained from human cervical cancer specimens, and the exclusion criterion was the creation of xenograft with established cell lines.

RESULTS

After the search process, 10 studies were found and included in the systematic review. Among 98 donor patients, 61 CC-PDX were established, and the overall success rate was 62.2%. The success rate in each article ranged from 0% to 75% and was higher when using severe immunodeficient mice such as severe combined immunodeficient (SCID), nonobese diabetic (NOD) SCID, and NOD SCID gamma (NSG) mice than nude mice. Subrenal capsule implantation led to a higher engraftment rate than orthotopic and subcutaneous implantation. Fragments with a size of 1-3 mm3 were suitable for CC-PDX. No relationship was found between the engraftment rate and characteristics of the tumor and donor patient, including histology, staging, and metastasis. The latency period varied from 10 days to 12 months. Most studies showed a strong similarity in pathological and immunohistochemical features between the original tumor and the PDX model.

CONCLUSION

Severe immunodeficient mice and subrenal capsule implantation led to a higher engraftment rate; however, orthotopic and subcutaneous implantation were alternatives. When using nude mice, subrenal implantation may be better. Fragments with a size of 1-3 mm3 were suitable for CC-PDX. Few reports have been published about CC-PDX; the results were not confirmed because of the small sample size.

Inhibition of Orthotopic Genital Cancer Induced by Subcutaneous Administration of Human Papillomavirus Peptide Vaccine with CpG Oligodeoxynucleotides as an Adjuvant in Mice

Purpose

Persistent high-risk human papillomavirus (HPV) infection is the most common cause of cervical cancer and its precursor lesions. Although prophylactic HPV vaccines have been applied in the general population for the prevention of HPV infections, no licensed therapeutic HPV vaccine is currently available to treat preexisting HPV infections or HPV-associated diseases, including cervical cancer.

Materials and Methods

The most common murine cervical cancer model used for the evaluation of the efficacy of a therapeutic HPV vaccine in preclinical studies is the ectopic model, which is established by the subcutaneous inoculation of tumor cells, such as TC-1 cells, into the flank of an animal. We have previously demonstrated the efficacy of a therapeutic HPV peptide vaccine adjuvanted with unmethylated cytosine-phosphate-guanosine oligodeoxynucleotide in the clearance of ectopic subcutaneous tumors in C57BL/6 mice after vaccination. In the current study, we established orthotopic genital tumors by injecting TC-1 cells into the vaginal submucosa close to the cervix and assessed whether the subcutaneous administration of the therapeutic vaccine could inhibit the growth of genital tumors. Additionally, we evaluated the effect of the vaccination on the tumor microenvironment.

Results

The results showed that the vaccination induced an increase in infiltrating CD4+ and CD8+ T cells, a decrease in myeloid-derived suppressor cells and cancer-associated fibroblasts, as well as the differential expression of a panel of cytokines, chemokines, and matrix metalloproteinases within the tumor microenvironment.

Conclusion

The administration of the vaccine resulted in the inhibition of established implanted orthotopic genital tumors by inducing strong antitumor immune responses and reversed tolerogenic local immunosuppression in a mouse model of orthotopic genital cancer.

Vaginal drug delivery approaches for localized management of cervical cancer

Cervical cancer or cervical intraepithelial neoplasia (CIN) remain a major public health problem among women globally. Traditional methods such as surgery are often associated with possible complications which may impact future pregnancies and childbirth especially for young female patients. Vagina with a high contact surface is a suitable route for the local and systemic delivery of drugs but its abundant mucus in continuous exchange presents a barrier for the popularization of conventional vaginal formulations including suppositories, gel, patch, creams and so on. So the development of new pharmaceutical forms based on nanotechnology became appealing owing to its several advantages such as mucosa penetration, bioadhesion, controlled drug release, and decreased adverse effects. This review provided an overview of the development of topical treatment of cervical cancer or CIN through vaginal drug delivery ranging from conventional vaginal formulations to new nanocarriers to the newly developed phototherapy and gene therapy, analyzing the problems faced by current methods used, and advising the developing trend in future. The methods of establishing preclinical animal model are also discussed.

An mTOR and VEGFR inhibitor combination arrests a doxorubicin resistant lung metastatic osteosarcoma in a PDOX mouse model

In order to identify more effective therapy for recalcitrant osteosarcoma, we evaluated the efficacy of an mTOR-VEGFR inhibitor combination on tumor growth in a unique osteosarcoma patient-derived orthotopic xenograft (PDOX) mouse model derived from the lung metastasis of an osteosarcoma patient who failed doxorubicin therapy. We also determined the efficacy of this inhibitor combination on angiogenesis using an in vivo Gelfoam fluorescence angiogenesis mouse model implanted with osteosarcoma patient-derived cells (OS-PDCs). PDOX models were randomly divided into five groups of seven nude mice. Group 1, control; Group 2, doxorubicin (DOX); Group 3, everolimus (EVE, an mTOR and VEGF inhibitor); Group 4, pazopanib (PAZ, a VEGFR inhibitor); Group 5, EVE-PAZ combination. Tumor volume and body weight were monitored 2 times a week. The in vivo Gelfoam fluorescence angiogenesis assay was performed with implanted OS-PDCs. The nude mice with implanted Gelfoam and OSPDCs also were divided into the four therapeutic groups and vessel length was monitored once a week. The EVE-PAZ combination suppressed tumor growth in the osteosarcoma PDOX model and decreased the vessel length ratio in the in vivo Gelfoam fluorescent angiogenesis model, compared with all other groups (p < 0.05). There was no significant body-weight loss in any group. Only the EVE-PAZ combination caused tumor necrosis. The present study demonstrates that a combination of an mTOR-VEGF inhibitor and a VEGFR inhibitor was effective for a DOX-resistant lung-metastatic osteosarcoma PDOX mouse model, at least in part due to strong anti-angiogenesis efficacy of the combination.

Oral recombinant methioninase combined with paclitaxel arrests recalcitrant ovarian clear cell carcinoma growth in a patient-derived orthotopic xenograft (PDOX) nude-mouse model

PURPOSE

Advanced ovarian clear cell carcinoma (OCCC) is a recalcitrant disease, often resistant to the first-line platinum-based therapy. Using a novel patient-derived orthotopic xenograft (PDOX) nude-mouse model of OCCC, we tested whether oral-recombinant methioninase (o-rMETase) could enhance the efficacy of paclitaxel (PTX).

METHODS

The OCCC PDOX model was established and passaged in nude mice. The OCCC PDOX models were randomized into 5 groups. G1: untreated control; G2: paclitaxel (PTX) (20 mg/kg, intraperitoneal (i.p.) injection, weekly); G3: o-rMETase (100 units, oral, daily); G4: PTX (20 mg/kg, i.p. injection, weekly) + carboplatinum (CBDCA) (40 mg/kg, i.p. injection weekly); G5: PTX (20 mg/kg, i.p. injection, weekly) + o-rMETase (100 units, oral, daily). The treatment period was 2 weeks.

RESULTS

The combination of PTX and o-rMETase arrested OCCC tumor growth (relative tumor volume: 1.09 ± 0.63 (mean ± SD)) compared with the untreated control (relative tumor volume: 3.92 ± 1.04 (mean ± SD)) (p < 0.0001). There was no significant difference in relative tumor volume between PTX plus o-rMETase and PTX plus CBDCA (relative tumor volume: 1.39 ± 0.37 (mean ± SD)) (p = 0.93).

CONCLUSION

PTX plus o-rMETase arrested the OCCC tumor growth. o-rMETase is readily administered and can greatly enhance first-line therapy of a recalcitrant cancer. The novel and effective treatment strategy in the present report has future clinical potential for patients with OCCC, especially for patients who cannot well tolerate platinum-based therapy.

Application of Animal Models in Cancer Research: Recent Progress and Future Prospects

Animal models refers to the animal experimental objects and related materials that can simulate human body established in medical research. As the second-largest disease in terms of morbidity and mortality after cardiovascular disease, cancer has always been the focus of human attention all over the world, which makes it a research hotspot in the medical field. At the same time, more and more animal models have been constructed and used in cancer research. With the deepening of research, the construction methods of cancer animal models are becoming more and more diverse, including chemical induction, xenotransplantation, gene programming, and so on. In recent years, patient-derived xenotransplantation (PDX) model has become a research hotspot because it can retain the microenvironment of the primary tumor and the basic characteristics of cells. Animal models can be used not only to study the biochemical and physiological processes of the occurrence and development of cancer in objects but also for the screening of cancer drugs and the exploration of gene therapy. In this paper, several main tumor animal models and the application progress of animal models in tumor research are systematically reviewed. Finally, combined with the latest progress and development trend in this field, the future research of tumor animal model was prospected.

The antitumor capacity of mesothelin-CAR-T cells in targeting solid tumors in mice

Since the approval of chimeric antigen receptor (CAR) T cell therapy targeting CD19 by the FDA, CAR-T cell therapy has received increasing attention as a new method for targeting tumors. Although CAR-T cell therapy has a good effect against hematological malignancies, it has been less effective against solid tumors. In the present study, we selected mesothelin (MSLN/MESO) as a target for CAR-T cells because it is highly expressed by solid tumors but only expressed at low levels by normal tissues. We engineered a third generation MSLN-CAR comprising a single-chain variable fragment (scFv) targeting MSLN (MSLN-scFv), a CD8 transmembrane domain, the costimulatory domains from CD28 and 4-1BB, and the activating domain CD3ζ. In vitro, MSLN-CAR-T cells killed various solid tumor cell lines, demonstrating that it could specifically kill MSLN-positive cells and release cytokines. In vivo, we investigated the effects of MSLN-CAR-T cell therapy against ovarian, breast, and colorectal cancer cell-line-derived xenografts (CDX) and MSLN-positive colorectal and gastric cancer patient-derived xenografts (PDX). MSLN-CAR decreased the growth of MSLN-positive tumors concomitant with significantly increased T cells and cytokine levels compared to the control group. These results indicated that modified MSLN-CAR-T cells could be a promising therapeutic approach for solid tumors.

Eribulin Regresses a Doxorubicin-resistant Dedifferentiated Liposarcoma in a Patient-derived Orthotopic Xenograft Mouse Model

BACKGROUND/AIM

Dedifferentiated liposarcoma (DDLPS) is recalcitrant type of sarcoma. DDLPS has a low survival rate with high recurrence and metastasis. In the present study, we evaluated the efficacy of several drugs against doxorubicin-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) model for precision oncology. To establish the PDOX model, a tumor from a patient who had recurrent high-grade DDLPS from the retroperitoneum was previously grown orthotopically in the retroperitoneum of nude mice.

MATERIALS AND METHODS

We randomized DDLPS PDOX models into 8 treatment groups when tumor volume became approximately 100 mm³: control, no treatment; G2, doxorubicin (DOX); G3, pazopanib (PAZ); G4, gemcitabine (GEM) combined with docetaxel (DOC); G5, trabectedin (YON); G6, temozolomide (TEM); G7, palbociclib (PAL); G8, eribulin (ERB). Tumor length and width were measured both at the beginning and at the end of treatment.

RESULTS

At the end of treatment (day 14), all treatments significantly inhibited DDLPS PDOX tumor growth compared to the untreated control, except DOX. ERB was significantly more effective and regressed tumor volume compared to other treatments on day 14 after initiation of treatment. No significant differences were found in the relative body weight on day 14 compared to day 0 in any group.

CONCLUSION

The clinical potential of ERB against DDLPS is herein presented in a PDOX model.

Real-Time Fluorescence Image-Guided Oncolytic Virotherapy for Precise Cancer Treatment

Oncolytic virotherapy is one of the most promising, emerging cancer therapeutics. We generated three types of telomerase-specific replication-competent oncolytic adenovirus: OBP-301; a green fluorescent protein (GFP)-expressing adenovirus, OBP-401; and Killer-Red-armed OBP-301. These oncolytic adenoviruses are driven by the human telomerase reverse transcriptase (hTERT) promoter; therefore, they conditionally replicate preferentially in cancer cells. Fluorescence imaging enables visualization of invasion and metastasis in vivo at the subcellular level; including molecular dynamics of cancer cells, resulting in greater precision therapy. In the present review, we focused on fluorescence imaging applications to develop precision targeting for oncolytic virotherapy. Cell-cycle imaging with the fluorescence ubiquitination cell cycle indicator (FUCCI) demonstrated that combination therapy of an oncolytic adenovirus and a cytotoxic agent could precisely target quiescent, chemoresistant cancer stem cells (CSCs) based on decoying the cancer cells to cycle to S-phase by viral treatment, thereby rendering them chemosensitive. Non-invasive fluorescence imaging demonstrated that complete tumor resection with a precise margin, preservation of function, and prevention of distant metastasis, was achieved with fluorescence-guided surgery (FGS) with a GFP-reporter adenovirus. A combination of fluorescence imaging and laser ablation using a KillerRed-protein reporter adenovirus resulted in effective photodynamic cancer therapy (PDT). Thus, imaging technology and the designer oncolytic adenoviruses may have clinical potential for precise cancer targeting by indicating the optimal time for administering therapeutic agents; accurate surgical guidance for complete resection of tumors; and precise targeted cancer-specific photosensitization.

A novel patient-derived orthotopic xenograft (PDOX) mouse model of highly-aggressive liver metastasis for identification of candidate effective drug-combinations

Liver metastasis is a recalcitrant disease that usually leads to death of the patient. The present study established a unique patient-derived orthotopic xenograft (PDOX) nude mouse model of a highly aggressive liver metastasis of colon cancer. The aim of the present study was to demonstrate proof-of-concept that candidate drug combinations could significantly inhibit growth and re-metastasis of this recalcitrant tumor. The patient’s liver metastasis was initially established subcutaneously in nude mice and the subcutaneous tumor tissue was then orthotopically implanted in the liver of nude mice to establish a PDOX model. Two studies were performed to test different drugs or drug combination, indicating that 5-fluorouracil (5-FU) + irinotecan (IRI) + bevacizumab (BEV) and regorafenib (REG) + selumetinib (SEL) had significantly inhibited liver metastasis growth (p = 0.013 and p = 0.035, respectively), and prevented liver satellite metastasis. This study is proof of concept that a PDOX model of highly aggressive colon-cancer metastasis can identify effective drug combinations and that the model has future clinical potential.

Thermosensitive Exosome-Liposome Hybrid Nanoparticle-Mediated Chemoimmunotherapy for Improved Treatment of Metastatic Peritoneal Cancer

Metastatic peritoneal carcinoma (mPC) is a deadly disease without effective treatment. To improve treatment of this disease, a recently developed hyperthermic intraperitoneal chemotherapy (HIPEC) has emerged as the standard of care. However, the efficacy of this approach is limited by inefficient drug penetration and rapidly developed drug resistance. Herein, a nanotechnology approach is reported that is designed to improve drug delivery to mPC and to augment the efficacy of HIPEC through delivery of chemoimmunotherapy. First, the drug delivery efficiency of HIPEC is determined and it is found that chemotherapy agents cannot be efficiently delivered to large tumors nodules. To overcome the delivery hurdle, genetically engineered exosomes-thermosensitive liposomes hybrid NPs, or gETL NPs, are then synthesized, and it is demonstrated that the NPs after intravenous administration efficiently penetrates into mPC tumors and releases payloads at the hypothermia condition of HIPEC. Last, it is shown that, when granulocyte-macrophage colony-stimulating factor (GM-CSF) and docetaxel are co-delivered, gETL NPs effectively inhibit tumor development and the efficacy is enhanced when HIPEC is co-administered. The study provides a strategy to improve drug delivery to mPCs and offers a promising approach to improve treatment of the disease through combination of locoregional delivery of HIPEC and systemic delivery of chemoimmunotherapy via gETL NPs.

The Application of Patient-Derived Xenograft Models in Gynecologic Cancers

Recently, due to the limitations of cell line models and animal models in the preclinical research with insufficient reflecting the physiological situation of humans, patient-derived xenograft (PDX) models of many cancers have been widely developed because of their better representation of the tumor heterogeneity and tumor microenvironment with retention of the cellular complexity, cytogenetics, and stromal architecture. PDX models now have been identified as a powerful tool for determining cancer characteristics, developing new treatment, and predicting drug efficacy. An increase in attempts to generate PDX models in gynecologic cancers has emerged in recent years to understand tumorigenesis. Hence, this review summarized the generation of PDX models and engraftment success of PDX models in gynecologic cancers. Furthermore, we illustrated the similarity between PDX model and original tumor, and described preclinical utilization of PDX models in gynecologic cancers. It would help supply better personalized therapy for gynecologic cancer patients.

A fast, simple, and cost-effective method of expanding patient-derived xenograft mouse models of pancreatic ductal adenocarcinoma

BACKGROUND

Patient-derived xenograft (PDX) mouse models of cancer have been recognized as better mouse models that recapitulate the characteristics of original malignancies including preserved tumor heterogeneity, lineage hierarchy, and tumor microenvironment. However, common challenges of PDX models are the significant time required for tumor expansion, reduced tumor take rates, and higher costs. Here, we describe a fast, simple, and cost-effective method of expanding PDX of pancreatic ductal adenocarcinoma (PDAC) in mice.

METHODS

We used two established frozen PDAC PDX tissues (derived from two different patients) and implanted them subcutaneously into SCID mice. After tissues reached 10-20 mm in diameter, we performed survival surgery on each mouse to harvest 90-95% of subcutaneous PDX (incomplete resection), allowing the remaining 5-10% of PDX to continue growing in the same mouse.

RESULTS

We expanded three consecutive passages (P1, P2, and P3) of PDX in the same mouse. Comparing the times required for in vivo expansion, P2 and P3 (expanded through incomplete resection) grew 26-60% faster than P1. Moreover, such expanded PDX tissues were successfully implanted orthotopically into mouse pancreases. Within 20 weeks using only 14 mice, we generated sufficient PDX tissue for future implantation of 200 mice. Our histology study confirmed that the morphologies of cancer cells and stromal structures were similar across all three passages of subcutaneous PDX and the orthotopic PDX and were reflective of the original patient tumors.

CONCLUSIONS

Taking advantage of incomplete resection of tumors associated with high local recurrence, we established a fast method of PDAC PDX expansion in mice.

Temozolomide and Pazopanib Combined with FOLFOX Regressed a Primary Colorectal Cancer in a Patient-derived Orthotopic Xenograft Mouse Model

Purpose: The goal of the present study was to determine the efficacy of temozolomide (TEM) and pazopanib (PAZ) combined with FOLFOX (oxaliplatin, leucovorin and 5-fluorouracil) on a colorectal cancer patient-derived orthotopic xenograft (PDOX) mouse model. Materials and Methods: A colorectal cancer tumor from a patient previously established in non-transgenic nude mice was implanted subcutaneously in transgenic green fluorescence protein (GFP)-expressing nude mice in order to label the tumor stromal cells with GFP. Then labeled tumors were orthotopically implanted into the cecum of nude mice. Mice were randomized into four groups: Group 1, untreated control; group 2, TEM + PAZ; group 3, FOLFOX; group 4, TEM + PAZ plus FOLFOX. Tumor width, length, and mouse body weight were measured weekly. The Fluor Vivo imaging System was used to image the GFP-lableled tumor stromal cells in vivo. H&E staining and immunohistochemical staining were used for histological analysis. Results: All three treatments inhibited tumor growth as compared to the untreated control group. The combination of TEM + PAZ + FOLFOX regressed tumor growth significantly more effectively than TEM + PAZ or FOLFOX. Only the combination of TEM + PAZ + FOLFOX group caused a decrease in body weight. PAZ suppressed lymph vessels density in the colorectal cancer PDOX mouse model suggesting inhibition of lymphangiogenesis. Conclusion: Our results suggest that the combination of TEM + PAZ + FOLFOX has clinical potential for colorectal cancer patient.

Regorafenib regresses an imatinib-resistant recurrent gastrointestinal stromal tumor (GIST) with a mutation in exons 11 and 17 of c-kit in a patient-derived orthotopic xenograft (PDOX) nude mouse model

Gastrointestinal stromal tumor (GIST) with a mutation in exons 11 and 17 of c-kit is a rare type of sarcoma. The aim of this study was to determine drug sensitivity for a regionally-recurrent case of GIST using a patient-derived orthotopic xenograft (PDOX) model. The PDOX model was established in the anterior wall of the stomach. GIST PDOX models were randomized into 5 groups of 6 mice each when the tumor volume reached 60 mm³: G1, control group; G2, imatinib group (oral administration (p.o.), daily, for 3 weeks); G3, sunitinib group (p.o., daily, for 3 weeks); G4, regorafenib (p.o., daily, for 3 weeks); G5, pazopanib (p.o., daily, for 3 weeks). All mice were sacrificed on day 22. Tumor volume was evaluated on day 0 and day 22 by laparotomy. Body weight were measured 2 times per week. Though regorafenib is third-line therapy for GIST, it was the most effective drug and regressed the tumor significantly (p < 0.001). Sunitinib suppressed tumor growth compared to the control group (p = 0.002). Imatinib, first-line therapy for GIST, and pazopanib did not have significant efficacy compared to the control group (p = 0.886, p = 0.766). The implications of this result is discussed for GIST patients.

Pazopanib regresses a doxorubicin-resistant synovial sarcoma in a patient-derived orthotopic xenograft mouse model

Synovial sarcoma (SS) is an aggressive subgroup of soft tissue sarcoma (STS) with high grade and high risk of metastasis. However, there are no systemic therapies available that target SS. Therefore, transformative therapy is needed for SS. To establish a patient-derived orthotopic xenograft (PDOX) model, a patient tumor with high grade SS from a lower extremity was grown orthotopically in the right biceps femoris muscle of mice. To test the efficacy of drugs, the PDOX models were randomized into five groups: Group 1 (G1), control-without treatment; Group 2 (G2), doxorubicin (DOX); Group 3 (G3), temozolomide (TEM); Group 4 (G4), gemcitabine (GEM) combined with docetaxel (DOC); and Group 5 (G5), pazopanib (PAZ). Tumor size and body weight were measured twice a week for each treatment group. A significant growth inhibition was found on day 14 in each treatment group compared to the untreated control, except for DOX. However, PAZ was significantly more effective than both TEM and GEM + DOC. In addition, PAZ significantly regressed the tumor volume on day 14 compared to day 0. No change was found in body weight on day 14 compared to day 0 in any treatment group. The present study demonstrated the precision of the SS PDOX models for individualizing SS therapy.

Efficacy of Recombinant Methioninase (rMETase) on Recalcitrant Cancer Patient-Derived Orthotopic Xenograft (PDOX) Mouse Models: A Review

An excessive requirement for methionine (MET), termed MET dependence, appears to be a general metabolic defect in cancer and has been shown to be a very effective therapeutic target. MET restriction (MR) has inhibited the growth of all major cancer types by selectively arresting cancer cells in the late-S/G₂ phase, when they also become highly sensitive to cytotoxic agents. Recombinant methioninase (rMETase) has been developed to effect MR. The present review describes the efficacy of rMETase on patient-derived orthotopic xenograft (PDOX) models of recalcitrant cancer, including the surprising result that rMETase administrated orally can be highly effective.

Temozolomide targets and arrests a doxorubicin-resistant follicular dendritic-cell sarcoma patient-derived orthotopic xenograft mouse model

Follicular dendritic cell sarcoma (FDCS) is a very rare and highly recalcitrant disease. A patient's doxorubicin-resistant FDCS was previously established orthotopically on the right high thigh into the biceps femoris of mice to establish a patient-derived orthotopic xenograft (PDOX) model. The aim of the present manuscript was to identify an effective drug for this recalcitrant tumor. Here, we evaluated the efficacy of temozolomide (TMZ), trabectedin (TRAB) and pazopanib (PAZ) on the FDCS PDOX model. PDOX mouse models were randomized into five groups of eight to nine mice, respectively. Group 1, untreated control with PBS, i.p.; Group 2, treated with doxorubicin (DOX), 2.4 mg/kg, i.p., weekly for 3 weeks; Group 3, treated with PAZ, 50 mg/kg, oral gavage, daily for 3 weeks; Group 4, treated with TMZ, 25 mg/kg, oral gavage, daily for 3 weeks; Group 5, treated with TRAB, 0.15 mg/kg, i.v., weekly for 3 weeks. Body weight and tumor volume were assessed 2 times per week. TMZ arrested the FDCS PDOX model compared to the control group (p < 0.05). PAZ and TRAB did not have significant efficacy compared to the control group (p = 0.99, p = 0.69 respectively). The PDOX tumor was resistant to DOX (p= 0.99). as was the patient. The present study demonstrates that TMZ is effective for a PDOX model of FDCS established from a patient who failed DOX treatment, further demonstrating the power of PDOX to identify effective therapy including for tumors that failed first line therapy.

Methioninase Cell-Cycle Trap Cancer Chemotherapy

Cancer cells are methionine (MET) dependent compared to normal cells as they have an elevated requirement for MET in order to proliferate. MET restriction selectively traps cancer cells in the S/G₂ phase of the cell cycle. The cell cycle phase can be visualized by color coding with the fluorescence ubiquitination-based cell cycle indicator (FUCCI). Recombinant methioninase (rMETase) is an enzyme that effectively degrades MET. rMETase induces S/G₂-phase blockage of cancer cells which is identified by the cancer cells' green fluorescence with FUCCI imaging. Cancer cells in G₁/G₀ are the majority of the cells in solid tumors and are resistant to the chemotherapy. Treatment of cancer cells with standard chemotherapy drugs only led to the majority of the cancer cell population being arrested in G₀/G₁ phase, identified by the cancer cells' red fluorescence in the FUCCI system. The G₀/G₁-phase cancer cells are chemo-resistant. Tumor targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) was used to decoy quiescent G₀/G₁ stomach cancer cells growing in nude mice to cycle, with subsequent rMETase treatment to selectively trap the decoyed cancer cells in S/G₂ phase, which made them highly sensitive to chemotherapy. Subsequent cisplatinum (CDDP) or paclitaxel (PTX) chemotherapy was then administered to kill the decoyed and trapped cancer cells, which completely prevented or regressed tumor growth. In a subsequent experiment, a patient-derived orthotopic xenograft (PDOX) model of recurrent CDDP-resistant metastatic osteosarcoma was eradicated by the combination of Salmonella typhimurium A1-R decoy, rMETase S/G₂-phase cell cycle trap, and CDDP cell kill. Salmonella typhimurium A1-R and rMETase pre-treatment thereby overcame CDDP resistance. These results demonstrate the effectiveness of the new chemotherapy paradigm of "decoy, trap, and kill" chemotherapy.

Afterword: Oral Methioninase-Answer to Cancer and Fountain of Youth?

The elevated methionine (MET) requirement of cancer cells is termed MET dependence and is possibly the only known general metabolic defect in cancer. Targeting MET by recombinant methioninase (rMETase) can arrest the growth of cancer cells in vitro and in vivo due to their elevated requirement for MET. rMETase can also potentiate chemotherapy drugs active in S phase due to the selective arrest of cancer cells in S/G₂ phase during MET restriction (MR). We previously reported that rMETase, administrated by intraperitoneal injection (ip-rMETase), could inhibit tumor growth in mouse models of cancer including patient-derived orthotopic xenograft (PDOX) mouse models. We subsequently compared ip-rMETase and oral rMETase (o-rMETase) on a melanoma PDOX mouse model. o-rMETase was significantly more effective than ip-rMETase to inhibit tumor growth without overt toxicity. The combination of o-rMETase+ip-rMETase was significantly more effective than either monotherapy and completely arrested tumor growth. Thus, o-rMETase is effective as an anticancer agent with the potential of clinical development for chronic cancer therapy as well as for cancer prevention. o-rMETase may also have potential as an antiaging agent for healthy people, since MR has been shown to extend the life span of a variety of different organisms.

Metabolic targeting with recombinant methioninase combined with palbociclib regresses a doxorubicin-resistant dedifferentiated liposarcoma

Liposarcoma is the most common type of soft tissue sarcoma. Among the subtypes of liposarcoma, dedifferentiated liposarcoma (DDLPS) is recalcitrant and has the lowest survival rate. The aim of the present study is to determine the efficacy of metabolic targeting with recombinant methioninase (rMETase) combined with palbociclib (PAL) against a doxorubicin (DOX)-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) model. A resected tumor from a patient with recurrent high-grade DDLPS in the right retroperitoneum was grown orthotopically in the right retroperitoneum of nude mice to establish a PDOX model. The PDOX models were randomized into the following groups when tumor volume reached 100 mm³: G1, control without treatment; G2, DOX; G3, PAL; G4, recombinant methioninase (rMETase); G5, PAL combined with rMETase. Tumor length and width were measured both pre- and post-treatment. On day 14 after initiation, all treatments significantly inhibited tumor growth compared to the untreated control except DOX. PAL combined with rMETase was significantly more effective than both DOX, rMETase alone, and PAL alone. Combining PAL and rMETase significantly regressed tumor volume on day 14 after initiation of treatment and was the only treatment to do so. The relative body weight on day 14 compared with day 0 did not significantly differ between each treatment group. The results of the present study indicate the powerful combination of rMETase and PAL should be tested clinically against DDLPS in the near future.

A patient derived xenograft model of cervical cancer and cervical dysplasia

Aim

To develop a patient derived xenograft (PDX) model of cervical cancer and cervical dysplasia using the subrenal capsule.

Methods

Cervical cancer (12 Squamous Cell Carcinoma, 1 Adenocarcinoma, 1 Adenosquamous Carcinoma), 7 cervical dysplasia biopsy and normal cervical tissues were transplanted beneath the renal capsule of immunocompromised NOD/SCID/gamma mice. Resulting tumours were harvested and portions serially transplanted into new recipient mice for up to three in vivo passages. Parent and xenograft tumours were examined by immunohistochemistry for p16^INK41, HPV, and CD-45. Single cell suspensions of mixed mouse and human, or human only cell populations were also transplanted.

Results

The overall engraftment rate for the primary cervical cancer PDX model was 71.4 ±12.5% (n = 14). Tumours maintained morphological, histoarchitecture and immunohistochemical features of the parent tumour, and demonstrated invasiveness into local tissues. Single cell suspensions did not produce tumour growth in this model. Mean length of time (32.4 +/- 3.5 weeks) for the transplanted tissue to generate a tumour in the animal was similar between successive transplantations. Three of four xenografted cervical dysplasia tissues generated microscopic cystic structures resembling dysplastic cervical tissue. Normal cervical tissue (4 of 5 xenografted) also developed microscopic cervical tissue grafts.

Conclusion

The subrenal capsule can be used for a PDX model of human cervical cancer with a good engraftment rate and the ability to model in vivo characteristics of cervical cancer. For the first time we have demonstrated that cervical dysplasia and normal cervical tissue generated microscopic tissues in a PDX model.

A combination of irinotecan/cisplatinum and irinotecan/temozolomide or tumor-targeting Salmonella typhimurium A1-R arrest doxorubicin- and temozolomide-resistant myxofibrosarcoma in a PDOX mouse model

Myxofibrosarcoma (MFS) is the most common sarcomas in elderly patients and is either chemo-resistant or recurs with metastasis after chemotherapy. This recalcitrant cancer in need of improved treatment. We have established a patient-derived orthotopic xenograft (PDOX) of MFS. The MFS PDOX model was established in the biceps femoris of nude mice and randomized into 7 groups of 7 mice each: control; doxorubicin (DOX); pazopanib (PAZ); temozolomide (TEM); Irinotecan (IRN); IRN combined with TEM; IRN combined with cisplatinum (CDDP) and Salmonella typhimurium A1-R (S. typhimurium A1-R). Treatment was evaluated by relative tumor volume and relative body weight. The MFS PDOX models were DOX, PAZ, and TEM resistant. IRN combined with TEM and IRN combined with CDDP were most effective on the MFS PDOX. S. typhimurium A1-R arrested the MFS PDOX tumor. There was no significant body weight loss in any group. The present study suggests that the combination of IRN with either TEM or CDDP, and S. typhimurium have clinical potential for MFS.

Tumor targeting Salmonella typhimurium A1-R in combination with gemcitabine (GEM) regresses partially GEM-resistant pancreatic cancer patient-derived orthotopic xenograft (PDOX) nude mouse models

Gemcitabine (GEM) is first-line therapy for pancreatic cancer but has limited efficacy in most cases. Nanoparticle-albumin bound (nab)-paclitaxel is becoming first-line therapy for pancreatic cancer, but also has limited efficacy for pancreatic cancer. Our goal was to improve the treatment outcome in patient-like models of pancreatic cancer. We previously established patient-derived orthotopic xenografts (PDOX) pancreatic cancers from two patients. The pancreatic tumor was implanted orthotopically in the pancreatic tail of nude mice to establish the PDOX models. Five weeks after implantation, 50 PDOX mouse models were randomized into five groups of 10 mice for each pancreatic cancer PDOX: untreated control; GEM (100 mg/kg, i.p., once a week for 2 weeks); GEM + nab-PTX (GEM: 100 mg/kg, i.p., once a week for 2 weeks, nab-PTX: 10 mg/kg, i.v., twice a week for 2 weeks); S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks); GEM + S. typhimurium A1-R (GEM: 100 mg/kg, i.p., once a week for 2 weeks, S. typhimurium A1-R; 5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks). GEM + nab-PTX was significantly more effective than GEM alone in one PDOX model (p = 0.0004), but there was no significant difference in the other PDOX model. The combination of GEM + S. typhimurium A1-R regressed both PDOX models. These results show S. typhimurium A1-R can overcome the ineffectiveness or partial effectiveness of GEM in patient-like models of pancreatic cancer and demonstrate clinical potential for this combination.

Tumor-targeting Salmonella typhimurium A1-R overcomes partial carboplatinum-resistance of a cancer of unknown primary (CUP)

Cancer of unknown primary (CUP) is metastatic disease without a known primary and therefore very difficult to identify effective therapy. Previously, we demonstrated partial efficacy of Salmonella typhimurium A1-R (S. typhimurium A1-R) alone and carboplatinum alone (CAR) on a CUP patient tumor in the patient-derived xenograft (PDOX) model. The aim of the present study was to investigate the efficacy of S. typhimurium A1-R combined with CAR on the CUP PDOX model. The CUP tumors were implanted orthotopically into the left supraclavicular fossa of nude mice to match the site from which they were resected from the patient. CUP PDOX models were divided randomly into the following 4 groups after the tumor volume reached 100 mm³: G1: untreated group; G2: CAR (30 mg/kg, i.p., weekly, 2 weeks); G3: S. typhimurium A1-R (5x10⁷ CFU/body, i.v., weekly, 2 weeks).; G4: S. typhimurium A1-R combined with CAR (S. typhimurium A1-R; 5x10⁷ CFU/body, i.v., weekly, 2 weeks; CAR, 30 mg/kg, i.p., weekly, 2 weeks). Each group comprised 7 mice. All mice were sacrificed on day 15. Tumor volume and body weight were measured twice a week. S. typhimurium A1-R and CAR moderately inhibited tumor growth compared to the untreated group on day 15 (P < 0.001 and P < 0.001, respectively). S. typhimurium A1-R combined with CAR inhibited the tumor growth significantly more compared to S. typhimurium A1-R monotherapy or CAR monotherapy on day 15 (P = 0.004 and P = 0.001, respectively). The present report demonstrates that S. typhimurium A1-R can increase the efficacy of a standard drug used for CUP in a PDOX model.

Patterns of sensitivity to a panel of drugs are highly individualised for undifferentiated/unclassified soft tissue sarcoma (USTS) in patient-derived orthotopic xenograft (PDOX) nude-mouse models

Undifferentiated/unclassified soft tissue sarcoma (USTS) is a recalcitrant disease; therefore, precise individualised therapy is needed. Toward this goal, we previously established patient-derived orthotopic xenograft (PDOX) models of USTS in nude mice. Here, we determined the extent of uniqueness of drug response in a panel on USTS PDOX models from 5 different patients. We previously showed that 3 of the 5 patients were resistant to doxorubicin (DOX) despite DOX being first-line therapy. Two weeks after orthotopic tumour implantation, PDOX mouse models were randomised into five groups: untreated control, DOX, gem-citabine/docetaxel (GEM/DOC), pazopanib (PAZ), temozolomide (TEM). Three PDOX cases were completely resistant to DOX. TEM had high efficacy for 4 USTS PDOX models, including DOX-resistant cases. GEM/DOC and PAZ were effective in three USTS PDOX. One case was completely resistant to TEM. Two cases were completely resistant to PAZ. The results showed the drug sensitivity pattern for each USTS PDOX was highly individualised and that at least one effective drug could be found for each. The PDOX model could be effective in precise individualised drug sensitivity testing which is especially important for heterogeneous cancers such as USTS, and can give the patient a greater chance to be treated with an effective drug.

Trabectedin arrests a doxorubicin-resistant PDGFRA-activated liposarcoma patient-derived orthotopic xenograft (PDOX) nude mouse model

BACKGROUND

Pleomorphic liposarcoma (PLPS) is a rare, heterogeneous and an aggressive variant of liposarcoma. Therefore, individualized therapy is urgently needed. Our recent reports suggest that trabectedin (TRAB) is effective against several patient-derived orthotopic xenograft (PDOX) mouse models. Here, we compared the efficacy of first-line therapy, doxorubicin (DOX), and TRAB in a platelet-derived growth factor receptor-α (PDGFRA)-amplified PLPS.

METHODS

We used a fresh sample of PLPS tumor derived from a 68-year-old male patient diagnosed with a recurrent PLPS. Subcutaneous implantation of tumor tissue was performed in a nude mouse. After three weeks of implantation, tumor tissues were isolated and cut into small pieces. To match the patient a PDGFRA-amplified PLPS PDOX was created in the biceps femoris of nude mice. Mice were randomized into three groups: Group 1 (G1), control (untreated); Group 2 (G2), DOX-treated; Group 3 (G3), TRAB-treated. Measurement was done twice a week for tumor width, length, and mouse body weight.

RESULTS

The PLPS PDOX showed resistance towards DOX. However, TRAB could arrest the PLPS (p < 0.05 compared to control; p < 0.05 compared to DOX) without any significant changes in body-weight.

CONCLUSIONS

The data presented here suggest that for the individual patient the PLPS PDOX model could specifically distinguish both effective and ineffective drugs. This is especially crucial for PLPS because effective first-line therapy is harder to establish if it is not individualized.

Tumor-targeting Salmonella typhimurium A1-R arrests a doxorubicin-resistant PDGFRA-amplified patient-derived orthotopic xenograft mouse model of pleomorphic liposarcoma

Pleomorphic liposarcoma (PLPS) is a recalcitrant soft-tissue sarcoma (STS) subtype in need of transformative therapy. We have previously established a patient-derived orthotopic xenograft (PDOX) model, of PLPS with PDGFRA amplification, using surgical orthotopic implantation. In the current study, the PLPS PDOX model was randomized into 3 groups of 7 mice each: untreated control; doxorubicin (DOX)-treated; and treated with Salmonella typhimurium A1-R (S. typhimurium A1-R) expressing green fluorescent protein (GFP). Tumor volume and body weight were monitored during the treatment period. The PLPS PDOX was resistant to DOX. In contrast, the PLPS PDOX was highly sensitive to S. typhimurium A1-R. There was no significant body-weight loss among these 3 groups. Fluorescence imaging demonstrated that S. typhimurium A1-R-GFP was very effective to target the PLPS PDOX tumor. The current study demonstrates that a PLPS PDOX, resistant to first-line therapy DOX, was highly sensitive to tumor targeting S. typhimurium A1-R.

Tumor-targeting Salmonella typhimurium A1-R suppressed an imatinib-resistant gastrointestinal stromal tumor with c-kit exon 11 and 17 mutations

Gastrointestinal stromal tumor (GIST) is a refractory disease in need of novel efficacious therapy. The aim of our study was to evaluate the effectiveness of tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) using on a patient derived orthotopic xenograft (PDOX) model of imatinib-resistant GIST. The GIST was obtained from a patient with regional recurrence, and implanted in the anterior gastric wall of nude mice. The GIST PDOX mice were randomized into 3 groups of 6 mice each when the tumor volume reached 60 mm3: G1, control group; G2, imatinib group (oral administration [p.o.], daily, for 3 weeks); G3, S. typhimurium A1-R group (intravenous [i.v.] injection, weekly, for 3 weeks). All mice from each group were sacrificed on day 22. Relative tumor volume was estimated by laparotomy on day 0 and day 22. Body weight of the mouse was evaluated 2 times per week. We found that S. typhimurium A1-R significantly reduced tumor growth in contrast to the untreated group (P = 0.001). In addition, we found that S. typhimurium A1-R was more effective compared to imatinib (P = 0.013). Furthermore, Imatinib was not significantly effective compared to the control group (P = 0.462). These results indicate that S. typhimurium A1-R may be new effective therapy for imatinib-resistant GIST and therefore a good candidate for clinical development of this disease.

Doxorubicin-resistant pleomorphic liposarcoma with PDGFRA gene amplification is targeted and regressed by pazopanib in a patient-derived orthotopic xenograft mouse model

Pleomorphic liposarcoma (PLPS) is a heterogeneous resistant group of tumors. Complete surgical resection is the only known way to treat PLPS. PLPS is reristant to both radiation and chemotherapy. Therefore, precise individualized therapy is needed to improve outcome of advanced PLPS patients. In this study, a patient-derived orthotopic xenograft (PDOX) model of a PDGFRA-amplified PLPS was established in the biceps femoris of nude mice by surgical orthotopic implantation (SOI) in order to match the patient. The PLPS PDOX was treated with pazopanib (PAZ) which targets PDGFRA, as well as with temozolomide (TEM) and first-line therapy doxorubicin (DOX). The PLPS PDOX was resistant to DOX and responded very well to PAZ as well as TEM. The tumor volume on treatment day-14 relative to day-1 was as follows: DOX (4.50 ± 2.6, p = 0.8087); PAZ (1.29 ± 0.9, p = 0.0008 compared to the control, p = 0.0167 compared to DOX); TEM (1.07 ± 0.8, p = 0.0079 compared to the control, p = 0.0079 compared to DOX). There was no significant difference in body weight between any treated group or control. The PAZ- and TEM-treated tumors showed extensive necrosis compared to the DOX-treated and untreated PDOX tumors. The present study showed that PDGFRA amplification could be effectively targeted by PAZ. The PLPS PDOX model also identified the efficacy of TEM which does not target PDGFRA, indicating that the PDOX model can identify effective targeted therapy as well as standard therapy and at the same time, identify ineffective drugs, even if they are first-line.

Targeting altered cancer methionine metabolism with recombinant methioninase (rMETase) overcomes partial gemcitabine-resistance and regresses a patient-derived orthotopic xenograft (PDOX) nude mouse model of pancreatic cancer

Pancreatic cancer is a recalcitrant disease. Gemcitabine (GEM) is the most widely-used first-line therapy for pancreatic cancer, but most patients eventually fail. Transformative therapy is necessary to significantly improve the outcome of pancreatic cancer patients. Tumors have an elevated requirement for methionine and are susceptible to methionine restriction. The present study used a patient-derived orthotopic xenograft (PDOX) nude mouse model of pancreatic cancer to determine the efficacy of recombinant methioninase (rMETase) to effect methionine restriction and thereby overcome GEM-resistance. A pancreatic cancer obtained from a patient was grown orthotopically in the pancreatic tail of nude mice to establish the PDOX model. Five weeks after implantation, 40 pancreatic cancer PDOX mouse models were randomized into four groups of 10 mice each: untreated control (n = 10); GEM (100 mg/kg, i.p., once a week for 5 weeks, n = 10); rMETase (100 units, i.p., 14 consecutive days, n = 10); GEM+rMETase (GEM: 100 mg/kg, i.p., once a week for 5 weeks, rMETase: 100 units, i.p., 14 consecutive days, n = 10). Although GEM partially inhibited PDOX tumor growth, combination therapy (GEM+rMETase) was significantly more effective than mono therapy (GEM: p = 0.0025, rMETase: p = 0.0010). The present study is the first demonstrating the efficacy of rMETase combination therapy in a pancreatic cancer PDOX model to overcome first-line therapy resistance in this recalcitrant disease.

Temozolomide regresses a doxorubicin-resistant undifferentiated spindle-cell sarcoma patient-derived orthotopic xenograft (PDOX): precision-oncology nude-mouse model matching the patient with effective therapy

Undifferentiated spindle-cell sarcoma (USCS) is a recalcitrant cancer, resistant to conventional chemotherapy. A patient with high-grade USCS from a striated muscle was implanted orthotopically in the right biceps femoris muscle of mice to establish a patient-derived orthotopic xenograft (PDOX) model. The PDOX models were randomized into the following groups when tumor volume reached 100 mm³ : G1, control without treatment; G2, doxorubicin (DOX) (3 mg/kg, intraperitoneal [i.p.] injection, weekly, for 2 weeks); G3, temozolomide (TEM) (25 mg/kg, p.o., daily, for 14 days). Tumor size and body weight were measured with calipers and a digital balance twice a week. TEM significantly inhibited tumor volume growth compared to the untreated control and the DOX-treated group on day 14 after treatment initiation: control (G1): 343 ± 78 mm³ ; DOX (G2): 308 ± 31 mm³ , P = 0.272; TEM (G3): 85 ± 21 mm³ , P < 0.0001. TEM significantly regressed the tumor volume compared to day 0 (P = 0.019). There were no animal deaths in any group. The body weight of treated mice was not significantly different in any group. Tumors treated with DOX were comprised of spindle-shaped viable cells without apparent necrosis or inflammatory changes. In contrast, tumors treated with TEM showed extensive tumor necrosis. The present study demonstrates the potential power of matching the patient with an effective drug and saving the patient needless toxicity from ineffective drugs.

MEK inhibitors cobimetinib and trametinib, regressed a gemcitabine-resistant pancreatic-cancer patient-derived orthotopic xenograft (PDOX)

A pancreatic ductal adenocarcinoma (PDAC), obtained from a patient, was grown orthotopically in the pancreatic tail of nude mice to establish a patient-derived orthotopic (PDOX) model. Seven weeks after implantation, PDOX nude mice were divided into the following groups: untreated control (n = 7); gemcitabine (100 mg/kg, i.p., once a week for 2 weeks, n = 7); cobimetinib (5 mg/kg, p.o., 14 consecutive days, n = 7); trametinib (0.3 mg/kg, p.o., 14 consecutive days, n = 7); trabectedin (0.15 mg/kg, i.v., once a week for 2 weeks, n = 7); temozolomide (25 mg/kg, p.o., 14 consecutive days, n = 7); carfilzomib (2 mg/kg, i.v., twice a week for 2 weeks, n = 7); bortezomib (1 mg/kg, i.v., twice a week for 2 weeks, n = 7); MK-1775 (20 mg/kg, p.o., 14 consecutive days, n = 7); BEZ-235 (45 mg/kg, p.o., 14 consecutive days, n = 7); vorinostat (50 mg/kg, i.p., 14 consecutive days, n = 7). Only the MEK inhibitors, cobimetinib and trametinib, regressed tumor growth, and they were more significantly effective than other therapies (p < 0.0001, respectively), thereby demonstrating the precision of the PDOX models of PDAC and its potential for individualizing pancreatic-cancer therapy.

Increasing aggressiveness of patient-derived xenograft models of cervix carcinoma during serial transplantation

Four patient-derived xenograft (PDX) models (BK-12, ED-15, HL-16, LA-19) of carcinoma of the uterine cervix have been developed in our laboratory, and their stability during serial transplantation in vivo was investigated in this study. Two frozen cell stocks were established, one from xenografted tumors in passage 2 (early generation) and the other from xenografted tumors transplanted serially in mice for approximately two years (late generation), and the biology of late generation tumors was compared with that of early generation tumors. Late generation tumors showed higher incidence of lymph node metastases than early generation tumors in three models (ED-15, HL-16, LA-19), and the increased metastatic propensity was associated with increased tumor growth rate, increased microvascular density, and increased expression of angiogenesis-related and cancer stem cell-related genes. Furthermore, late generation tumors showed decreased fraction of pimonidazole-positive tissue (i.e., decreased fraction of hypoxic tissue) in two models (HL-16, LA-19) and decreased fraction of collagen-I-positive tissue (i.e., less extensive extracellular matrix) in two models (ED-15, HL-16). This study showed that serially transplanted PDXs may not necessarily mirror the donor patients’ diseases, and consequently, proper use of serially transplanted PDX models in translational cancer research requires careful molecular monitoring of the models.

Recombinant methioninase combined with doxorubicin (DOX) regresses a DOX-resistant synovial sarcoma in a patient-derived orthotopic xenograft (PDOX) mouse model

Synovial sarcoma (SS) is a recalcitrant subgroup of soft tissue sarcoma (STS). A tumor from a patient with high grade SS from a lower extremity was grown orthotopically in the right biceps femoris muscle of nude mice to establish a patient-derived orthotopic xenograft (PDOX) mouse model. The PDOX mice were randomized into the following groups when tumor volume reached approximately 100 mm³: G1, control without treatment; G2, doxorubicin (DOX) (3 mg/kg, intraperitoneal [i.p.] injection, weekly, for 2 weeks; G3, rMETase (100 unit/mouse, i.p., daily, for 2 weeks); G4 DOX (3mg/kg), i.p. weekly, for 2 weeks) combined with rMETase (100 unit/mouse, i.p., daily, for 2 weeks). On day 14 after treatment initiation, all therapies significantly inhibited tumor growth compared to untreated control, except DOX: (DOX: p = 0.48; rMETase: p < 0.005; DOX combined with rMETase < 0.0001). DOX combined with rMETase was significantly more effective than both DOX alone (p < 0.001) and rMETase alone (p < 0.05). The relative body weight on day 14 compared with day 0 did not significantly differ between any treatment group or untreated control. The results indicate that r-METase can overcome DOX-resistance in this recalcitrant disease.

Tumor-targeting Salmonella typhimurium A1-R combined with recombinant methioninase and cisplatinum eradicates an osteosarcoma cisplatinum-resistant lung metastasis in a patient-derived orthotopic xenograft (PDOX) mouse model: decoy, trap and kill chemotherapy moves toward the clinic

In the present study, a patient-derived orthotopic xenograft (PDOX) model of recurrent cisplatinum (CDDP)-resistant metastatic osteosarcoma was treated with Salmonella typhimurium A1-R (S. typhimurium A1-R), which decoys chemoresistant quiescent cancer cells to cycle, and recombinant methioninase (rMETase), which selectively traps cancer cells in late S/G₂, and chemotherapy. The PDOX models were randomized into the following groups 14 days after implantation: G1, control without treatment; G2, CDDP (6 mg/kg, intraperitoneal (i.p.) injection, weekly, for 2 weeks); G3, rMETase (100 unit/mouse, i.p., daily, for 2 weeks). G4, S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., weekly, for 2 weeks); G5, S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., weekly, for 2 weeks) combined with rMETase (100 unit/mouse, i.p., daily, for 2 weeks); G6, S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., weekly, for 2 weeks) combined with rMETase (100 unit/mouse, i.p., daily, for 2 weeks) and CDDP (6 mg/kg, i.p. injection, weekly, for 2 weeks). On day 14 after initiation, all treatments except CDDP alone, significantly inhibited tumor growth compared to untreated control: (CDDP: p = 0.586; rMETase: p = 0.002; S. typhimurium A1-R: p = 0.002; S. typhimurium A1-R combined with rMETase: p = 0.0004; rMETase combined with both S. typhimurium A1-R and CDDP: p = 0.0001). The decoy, trap and kill combination of S. typhimurium A1-R, rMETase and CDDP was the most effective of all therapies and was able to eradicate the metastatic osteosarcoma PDOX.

Individualized doxorubicin sensitivity testing of undifferentiated soft tissue sarcoma (USTS) in a patient-derived orthotopic xenograft (PDOX) model demonstrates large differences between patients

Doxorubicin (DOX) is often first-line treatment of undifferentiated/unclassified soft tissue sarcoma (USTS). However, the DOX response rate for USTS patients is low. Individualized precision-medicine technology that could identify DOX responders as well as non-responders would be of high value to cancer patients. In the present study, we established 5 patient-derived orthotopic xenograft (PDOX) nude mouse models from 5 USTS patients and evaluated the efficacy of DOX in each PDOX model. USTS's were grown orthotopically in the right thigh of nude mice to establish the PDOX models. Two weeks after implantation, the mouse models were randomized into two groups of 8 mice each: untreated control; and DOX (3 mg/kg, i.p., once a week for 2 weeks). DOX showed significant growth inhibition in only 2 USTS PDOX models out of 5 (p = 0.0054, p = 0.0055, respectively) on day 14 after initiation. DOX was ineffective in the other 3 PDOX models. However, even in the DOX-sensitive cases, DOX could not regress the PDOX tumors responding to treatment. The present study has important implications since this is the first in vivo study to compare the DOX sensitivity for USTS on multiple patient tumors. We showed that only two of five USTS were responsive to DOX, despite DOX being first line chemotherapy for USTS. The 3 resistant cases should not be treated with DOX clinically, in order to spare the patients' unnecessary toxicity. This PDOX model is useful for precise individualized drug sensitivity testing, especially for rare heterogeneous recalcitrant sarcomas such as USTS.

Recombinant methioninase effectively targets a Ewing's sarcoma in a patient-derived orthotopic xenograft (PDOX) nude-mouse model

Methionine dependence is due to the overuse of methionine for aberrant transmethylation reactions in cancer. Methionine dependence may be the only general metabolic defect in cancer. In order to exploit methionine dependence for therapy, our laboratory previously cloned L-methionine α-deamino-γ-mercaptomethane lyase [EC 4.4.1.11]). The cloned methioninase, termed recombinant methioninase, or rMETase, has been tested in mouse models of human cancer cell lines. Ewing's sarcoma is recalcitrant disease even though development of multimodal therapy has improved patients'outcome. Here we report efficacy of rMETase against Ewing's sarcoma in a patient-derived orthotopic xenograft (PDOX) model. The Ewing's sarcoma was implanted in the right chest wall of nude mice to establish a PDOX model. Eight Ewing's sarcoma PDOX mice were randomized into untreated control group (n = 4) and rMETase treatment group (n = 4). rMETase (100 units) was injected intraperitoneally (i.p.) every 24 hours for 14 consecutive days. All mice were sacrificed on day-15, 24 hours after the last rMETase administration. rMETase effectively reduced tumor growth compared to untreated control. The methionine level both of plasma and supernatants derived from sonicated tumors was lower in the rMETase group. Body weight did not significantly differ at any time points between the 2 groups. The present study is the first demonstrating rMETase efficacy in a PDOX model, suggesting potential clinical development, especially in recalcitrant cancers such as Ewing's sarcoma.

Targeting methionine with oral recombinant methioninase (o-rMETase) arrests a patient-derived orthotopic xenograft (PDOX) model of BRAF-V600E mutant melanoma: implications for chronic clinical cancer therapy and prevention

The elevated methionine (MET) use by cancer cells is termed MET dependence and may be the only known general metabolic defect in cancer. Targeting MET by recombinant methioninase (rMETase) can arrest the growth of cancer cells in vitro and in vivo. We previously reported that rMETase, administrated by intra-peritoneal injection (ip-rMETase), could inhibit tumor growth in a patient-derived orthotopic xenograft (PDOX) model of a BRAF-V600E mutant melanoma. In the present study, we compared ip-rMETase and oral rMETase (o-rMETase) for efficacy on the melanoma PDOX. Melanoma PDOX nude mice were randomized into four groups of 5 mice each: untreated control; ip-rMETase (100 units, i.p., 14 consecutive days); o-rMETase (100 units, p.o., 14 consecutive days); o-rMETase+ip-rMETase (100 units, p.o.+100 units, i.p., 14 consecutive days). All treatments inhibited tumor growth on day 14 after treatment initiation, compared to untreated control (ip-rMETase, p<0.0001; o-rMETase, p<0.0001; o-rMETase+ip-rMETase, p<0.0001). o-rMETase was significantly more effective than ip-rMETase (p = 0.0086). o-rMETase+ip-rMETase was significantly more effective than either mono-therapy: ip-rMETase, p = 0.0005; or o-rMETase, p = 0.0367. The present study is the first demonstrating that o-rMETase is effective as an anticancer agent. The results of the present study indicate the potential of clinical development of o-rMETase as an agent for chronic cancer therapy and for cancer prevention and possibly for life extension since dietary MET reduction extends life span in many animal models.