High efficacy of tumor-targeting Salmonella typhimurium A1-R on a doxorubicin- and dactolisib-resistant follicular dendritic-cell sarcoma in a patient-derived orthotopic xenograft PDOX nude mouse model

Hacking the Immune Response to Solid Tumors: Harnessing the Anti-Cancer Capacities of Oncolytic Bacteria

Oncolytic bacteria are a classification of bacteria with a natural ability to specifically target solid tumors and, in the process, stimulate a potent immune response. Currently, these include species of Klebsiella, Listeria, Mycobacteria, Streptococcus/Serratia (Coley's Toxin), Proteus, Salmonella, and Clostridium. Advancements in techniques and methodology, including genetic engineering, create opportunities to "hijack" typical host-pathogen interactions and subsequently harness oncolytic capacities. Engineering, sometimes termed "domestication", of oncolytic bacterial species is especially beneficial when solid tumors are inaccessible or metastasize early in development. This review examines reported oncolytic bacteria-host immune interactions and details the known mechanisms of these interactions to the protein level. A synopsis of the presented membrane surface molecules that elicit particularly promising oncolytic capacities is paired with the stimulated localized and systemic immunogenic effects. In addition, oncolytic bacterial progression toward clinical translation through engineering efforts are discussed, with thorough attention given to strains that have accomplished Phase III clinical trial initiation. In addition to therapeutic mitigation after the tumor has formed, some bacterial species, referred to as "prophylactic", may even be able to prevent or "derail" tumor formation through anti-inflammatory capabilities. These promising species and their particularly favorable characteristics are summarized as well. A complete understanding of the bacteria-host interaction will likely be necessary to assess anti-cancer capacities and unlock the full cancer therapeutic potential of oncolytic bacteria.

<italic>Salmonella typhimurium</italic> may support cancer treatment: a review

<p indent="0mm">Antitumour treatments are evolving, including bacteria-mediated cancer therapy which is concurrently an ancient and cutting-edge approach. <italic>Salmonella typhimurium</italic> is a widely studied bacterial species that colonizes tumor tissues, showing oncolytic and immune system-regulating properties. It can be used as a delivery vector for genes and drugs, supporting conventional treatments that lack tumor-targeting abilities. This article summarizes recent evidence on the anticancer mechanisms of <italic>S</italic>. <italic>typhimurium</italic> alone and in combination with other anticancer treatments, suggesting that it may be a suitable approach to disease management. </p>.

Recombinant Attenuated Salmonella enterica as a Delivery System of Heterologous Molecules in Cancer Therapy

Simple Summary

Cancer is among the main causes of death of millions of individuals worldwide. Although survival has improved with conventional treatments, the appearance of resistant cancer cells leads to patient relapses. It is, therefore, necessary to find new antitumor therapies that can completely eradicate transformed cells. Bacteria-based tumor therapy represents a promising alternative treatment, particularly the use of live-attenuated Salmonella enterica, with its potential use as a delivery system of antitumor heterologous molecules such as tumor-associated antigens, cytotoxic molecules, immunomodulatory molecules, pro-apoptotic proteins, nucleic acids, and nanoparticles. In this review, we present the state of the art of current preclinical and clinical research on the use of Salmonella enterica as a potential therapeutic ally in the war against cancer.

Abstract

Over a century ago, bacterial extracts were found to be useful in cancer therapy, but this treatment modality was obviated for decades. Currently, in spite of the development and advances in chemotherapies and radiotherapy, failure of these conventional treatments still represents a major issue in the complete eradication of tumor cells and has led to renewed approaches with bacteria-based tumor therapy as an alternative treatment. In this context, live-attenuated bacteria, particularly Salmonella enterica, have demonstrated tumor selectivity, intrinsic oncolytic activity, and the ability to induce innate or specific antitumor immune responses. Moreover, Salmonella enterica also has strong potential as a delivery system of tumor-associated antigens, cytotoxic molecules, immunomodulatory molecules, pro-apoptotic proteins, and nucleic acids into eukaryotic cells, in a process known as bactofection and antitumor nanoparticles. In this review, we present the state of the art of current preclinical and clinical research on the use of Salmonella enterica as a potential therapeutic ally in the war against cancer.

Color-Coded Imaging of the Tumor Microenvironment (TME) in Human Patient-Derived Orthotopic Xenograft (PDOX) Mouse Models

The tumor microenvironment (TME) contains stromal cells in a complex interaction with cancer cells. This relationship has become better understood with the use of fluorescent proteins for in vivo imaging, originally developed by our laboratories. Spectrally distinct fluorescent proteins can be used for color-coded imaging of the complex interaction of the tumor microenvironment in the living state using cancer cells expressing a fluorescent protein of one color and host mice expressing another color fluorescent protein. Cancer cells engineered in vitro to express a fluorescent protein were orthotopically implanted into transgenic mice expressing a fluorescent protein of a different color. Confocal microscopy was then used for color-coded imaging of the TME. Color-coded imaging of the TME has enabled us to discover that stromal cells are necessary for metastasis. Patient-derived orthotopic xenograft (PDOX) tumors were labeled by first passaging them orthotopically through transgenic nude mice expressing either green, red, or cyan fluorescent protein in order to label the stromal cells of the tumor. The colored stromal cells become stably associated with the PDOX tumors through multiple passages in transgenic colored nude mice or noncolored nude mice. The fluorescent protein-expressing stromal cells included cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs). Using this model, specific cancer cell or stromal cell targeting by potential therapeutics can be visualized. Color-coded imaging enabled the visualization of apparent fusion of cancer and stromal cells. Color-coded imaging is a powerful tool visualizing the interaction of cancer and stromal cells during cancer progression and treatment.

Integration of Salmonella into Combination Cancer Therapy

Simple Summary

Despite significant advances in the development of new treatments, cancer continues to be a major public health concern due to the high mortality associated with the disease. The introduction of immunotherapy as a new modality for cancer treatment has led to unprecedented clinical responses, even in terminal cancer patients. However, for reasons that remain largely unknown, the percentage of patients who respond to this treatment remains rather modest. In the present article, we highlight the potential of using attenuated Salmonella strains in cancer treatment, particularly as a means to enhance therapeutic efficacy of other cancer treatments, including immunotherapy, chemotherapy, and radiotherapy. The challenges associated with the clinical application of Salmonella in cancer therapy are discussed. An increased understanding of the potential of Salmonella bacteria in combination cancer therapy may usher in a major breakthrough in its clinical application, resulting in more favorable and durable outcomes.

Abstract

Current modalities of cancer treatment have limitations related to poor target selectivity, resistance to treatment, and low response rates in patients. Accumulating evidence over the past few decades has demonstrated the capacity of several strains of bacteria to exert anti-tumor activities. Salmonella is the most extensively studied entity in bacterial-mediated cancer therapy, and has a good potential to induce direct tumor cell killing and manipulate the immune components of the tumor microenvironment in favor of tumor inhibition. In addition, Salmonella possesses some advantages over other approaches of cancer therapy, including high tumor specificity, deep tissue penetration, and engineering plasticity. These aspects underscore the potential of utilizing Salmonella in combination with other cancer therapeutics to improve treatment effectiveness. Herein, we describe the advantages that make Salmonella a good candidate for combination cancer therapy and summarize the findings of representative studies that aimed to investigate the therapeutic outcome of combination therapies involving Salmonella. We also highlight issues associated with their application in clinical use.

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.

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.

A Non-invasive Imageable GFP-expressing Mouse Model of Orthotopic Human Bladder Cancer

BACKGROUND/AIM

A more realistic mouse model of bladder cancer is necessary to develop effective drugs for the disease. Tumor models enhanced by bright fluorescent-reporter genes to follow the disease in real-time would enhance the ability to accurately predict the efficacy of various therapeutics on this particularly-malignant human cancer.

MATERIALS AND METHODS

A highly-fluorescent green fluorescent protein (GFP)-expressing bladder cancer model was orthotopically established in nude mice using the UM-UC-3 human bladder-cancer cell line (UM-UC-3-GFP). Fragments from a subcutaneous tumor of UM-UC-3-GFP were surgically implanted into the nude mouse bladder. Non-invasive and intra-vital fluorescence imaging was obtained with a simple imaging box.

RESULTS

The GFP-expressing orthotopic bladder tumor was imaged in real-time non-invasively as well as intra-vitally, with the two methods correlating at r=0.99.

CONCLUSION

This is the first non-invasive-fluorescence-imaging orthotopic model of bladder cancer and can be used for rapidly screening novel effective agents for this recalcitrant disease.

Patient-derived orthotopic xenograft models of sarcoma

Sarcoma is a rare and recalcitrant malignancy. Although immune and novel targeted therapies have been tested on many cancer types, few sarcoma patients have had durable responses with such therapy. Doxorubicin and cisplatinum are still first-line chemotherapy after four decades. Our laboratory has established the patient-derived orthotopic xenograft (PDOX) model using surgical orthotopic implantation (SOI). Many promising results have been obtained using the sarcoma PDOX model for identifying effective approved drugs and experimental therapeutics, as well as combinations of them for individual patients. In this review, we present our laboratory's experience with PDOX models of sarcoma, and the ability of the PDOX models to identify effective approved agents, as well as experimental therapeutics.

Oral recombinant methioninase combined with oxaliplatinum and 5-fluorouracil regressed a colon cancer growing on the peritoneal surface in a patient-derived orthotopic xenograft mouse model

The aim of this study was to determine the efficacy of oral recombinant methioninase (o-rMETase) on a model of colon cancer growing on the peritoneal surface using a patients-derived orthotopic xenograft (PDOX) nude mouse model. Forty PDOX mouse models with colon cancer growing on the peritoneum were divided into 4 groups of 10 mice each by measuring the tumor size and fluorescence intensity: untreated control; 5-fluorouracil (5-FU) (50 mg/kg, once a week for two weeks, ip) and oxaliplatinum (OXA) (6  mg/kg, once a week for two weeks, ip); o-rMETase (100 units/day, oral 14 consecutive days); combination 5-FU + OXA and o-rMETase. All treatments inhibited tumor growth compared to the untreated control. The combination of 5-FU + OXA plus o-rMETase was significantly more efficacious than the control and each drug alone and was the only treatment that caused tumor regression. The present study is the first demonstrating the efficacy of o-rMETase combination therapy on a PDOX model of peritoneal colon cancer, suggesting potential clinical development of o-rMETase in a recalcitrant cancer.

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.

Efficacy of Tumor-Targeting Salmonella typhimurium A1-R against Malignancies in Patient-Derived Orthotopic Xenograft (PDOX) Murine Models

We developed tumor-targeting Salmonella typhimurium (S. typhimurium) A1-R, a facultative anaerobe that is an auxotroph of leucine and arginine. The tumor-targeting efficacy of S. typhimurium A1-R was demonstrated in vivo and vitro using several malignant cell lines including melanoma, sarcoma, glioma, breast, pancreatic, colon, cervical, prostate, and ovarian cancers. Our laboratory also developed a patient-derived orthotopic xenograft (PDOX) model by implanting patient-derived malignant tumor fragments into orthotopic sites in mice. We reviewed studies of S. typhimurium A1-R against recalcitrant cancers. S. typhimurium A1-R was effective against all PDOX tumor models tested and showed stronger efficacies than chemotherapy or molecular-targeting therapy against some tumors. Furthermore, the synergistic efficacy of S. typhimurium A1-R when combined with chemotherapeutic agents, molecular-targeting agents, or recombinant methioninase was also demonstrated. We suggest potential clinical uses of this S. typhimurium A1-R treatment.

Tumor-targeting Salmonella typhimurium A1-R overcomes nab-paclitaxel resistance in a cervical cancer PDOX mouse model

PURPOSE

Cervical cancer is a recalcitrant disease. To help overcome this problem, we previously established a patient-derived orthotopic xenograft (PDOX) model of cervical cancer. In the previous study, we found the tumor to be resistant to nab-paclitaxal (nab-PTX). We also previously developed the tumor-targeting bacteria Salmonella typhimurium A1-R (S. typhimurium A1-R). The aim of the present study was to investigate the efficacy of S. typhimurium A1-R to overcome nab-PTX resistance in the cervical cancer PDOX model.

METHODS

Cervical-cancer tumor fragments were implanted orthotopically into the neck of the uterus of nude mice. The cervical-cancer PDOX models were randomized into the following four groups after the tumor volume reached 60 mm3: G1: untreated group; G2: nab-PTX (i.v., 10 mg/kg, biweekly, 3 weeks); G3: Salmonella typhimurium A1-R (i.v., 5 × 107 CFU/body, weekly, 3 weeks); G4: nab-PTX combined with Salmonella typhimurium A1-R (nab-PTX, 10 mg/kg, i.v., biweekly, 3 weeks; S. typhimurium A1-R, 5 × 107 CFU/body, i.v., weekly, 3 weeks). Each group comprised eight mice. All mice were sacrificed on day 22. Tumor volume was measured on day 0 and day 22. Body weight was measured twice a week.

RESULTS

Nab-PTX and Salmonella typhimurium A1-R did not show significant efficacy as monotherapy compared to the control group (P = 0.564 and P = 0.120, respectively). In contrast, nab-PTX combined with Salmonella typhimurium A1-R significantly suppressed tumor growth compared to the untreated control group and nab-PTX group (P < 0.001 and P = 0.026, respectively).

CONCLUSIONS

Salmonella typhimurium A1-R has potential future clinical application to overcome drug resistance in cervical cancer.

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.

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.

Combining Tumor-Selective Bacterial Therapy with Salmonella typhimurium A1-R and Cancer Metabolism Targeting with Oral Recombinant Methioninase Regressed an Ewing's Sarcoma in a Patient-Derived Orthotopic Xenograft Model

BACKGROUND

Ewing's sarcoma (ES) is a recalcitrant disease in need of transformative therapeutics.

OBJECTIVES

The aim of this study was to investigate the efficacy of tumor-selective Salmonella typhimurium A1-R combined with tumor metabolism targeting with oral administration of recombinant methioninase (o-rMETase), on an ES patient-derived orthotopic xenograft (PDOX) model.

METHODS

The ES PDOX models were previously established in the right chest wall. The ES PDOX models were randomized into 5 groups when the tumor volume reached 80 mm3: G1: untreated control; G2: doxorubicin; G3: S. typhimurium A1-R; G4: o-rMETase; G5: S. typhimurium A1-R combined with o-rMETase. All mice were sacrificed on day 15. Body weight and tumor volume were assessed twice a week.

RESULTS

S. typhimurium A1-R and o-rMETase respectively suppressed tumor growth as monotherapies (p = 0.050 and p = 0.032). S. typhimurium A1-R combined with o-rMETase regressed tumor growth significantly compared to untreated group on day 15 (p < 0.032). S. typhimurium A1-R combined with o-rMETase group was significantly more effective than S. typhimurium A1-R or o-rMETase monotherapy (p = 0.032, p = 0.032).

CONCLUSIONS

The present results suggest that the combination of S. typhimurium A1-R and o-rMETase has promise to be a transformative therapy for ES.

The combination of gemcitabine and nab-paclitaxel as a novel effective treatment strategy for undifferentiated soft-tissue sarcoma in a patient-derived orthotopic xenograft (PDOX) nude-mouse model

Undifferentiated/unclassified soft-tissue sarcomas (USTS) is recalcitrant neoplasms that is usually treated with doxorubicin (DOX)-containing regimens as first-line therapy. Nanoparticle albumin-bound paclitaxel (nab-PTX) is a nanotechnology-based drug and is widely used in pancreatic cancer in combination with gemcitabine (GEM). The major goal of the present study was to determine the efficacy of nab-PTX in combination with GEM, compared to conventional drugs such as docetaxel (DOC), GEM combined with DOC, or first-line drug DOX on a USTS not-otherwise specified (USTS/NOS) from a striated muscle implanted in the right biceps femoris muscle of nude mice to establish a patient-derived orthotopic xenograft (PDOX) model. USTS PDOX models were randomized into six groups: untreated control; DOX; DOC; nab-PTX; GEM combined with DOC; and GEM combined with nab-PTX. Tumor size and body weight were measured. Tumor growth was inhibited to the greatest extent by GEM combined with nab-PTX. Tumors treated with GEM combined with nab-PTX had the most necrosis. Body weight of the treated mice was not significantly different from the untreated controls. The present study demonstrates the power of the PDOX model to identify a novel effective treatment strategy of the combination of GEM and nab-PTX for recalcitrant soft-tissue sarcomas. These results suggest that combination of GEM and nab-PTX could be a promising therapeutic strategy for USTS.

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.

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.

Cancer Immunotherapy: Priming the Host Immune Response with Live Attenuated Salmonella enterica

In recent years, cancer immunotherapy has undergone great advances because of our understanding of the immune response and the mechanisms through which tumor cells evade it. A century after the first immunotherapy attempt based on bacterial products described by William Coley, the use of live attenuated bacterial vectors has become a promising alternative in the fight against cancer. This review describes the role of live attenuated Salmonella enterica as an oncolytic and immunotherapeutic agent, due to its high affinity for tumor tissue and its ability to activate innate and adaptive antitumor immune response. Furthermore, its potential use as delivery system of tumor antigens and immunomodulatory molecules that induce tumor regression is also reviewed.

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.

Genetically-engineered Salmonella typhimurium expressing TIMP-2 as a therapeutic intervention in an orthotopic glioma mouse model

Glioma is one of the most devastating and refractory cancers. The main factors underlying therapeutic failure include extremely invasive characteristics and lack of effective methods for drug delivery. Attenuated Salmonella strains presented a high concentration of tumor targets in various types of cancer models, suggesting a role as potential vectors for drug delivery. In this study, we genetically engineered an attenuated strain of Salmonella as an anti-invasive vector for the targeted delivery and expression of tissue inhibitor of metalloproteinases 2 (TIMP-2) in an orthotopic nude mouse model of glioma. The bioluminescence signals related to tumor size significantly declined in the TIMP-2-expressing Salmonella (SLpTIMP-2)-treated group compared with the control group. Compared with the control group with a survival rate of an average of 33 days, the SLpTIMP-2 group showed an extended survival rate by nearly 60% and lasted an average period of 53 days with TIMP-2 induction. These results indicated the promising therapeutic potential of S. typhimurium for targeted delivery and secretion of TIMP-2 in glioma.

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.

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.

Therapeutic benefit of Salmonella attributed to LPS and TNF-α is exhaustible and dictated by tumor susceptibility

The potential of bacteria-mediated tumor therapy (BMTT) is highlighted by more than a century of investigation. Attenuated Salmonella has prevailed as promising therapeutic agents. For BMTT - categorized as an immune therapy - the exact contribution of particular immune reactions to the therapeutic effect remains ambiguous. In addition, one could argue for or against the requirement of bacterial viability and tumor targeting. Herein we evaluate the isolated therapeutic efficacy of purified LPS and TNF-α, which together account for a dominant immunogenic pathway of gram negative bacteria like Salmonella. We show that therapeutic efficacy against CT26 tumors does not require bacterial viability. Analogous to viable Salmonella SL7207, tumor regression by a specific CD8⁺ T cell response can be induced by purified LPS or recombinant TNF-α (rTNF-α). Conversely, therapeutic effects against RenCa tumors were abrogated upon bacterial avitalization and limited using isolated adjuvants. This argues for an alternative mechanistic explanation for SL7207 against RenCa that depends on viability and persistence. Unable to boost bacterial therapies by co-injection of rTNF-α suggested therapeutic effects along this axis are exhausted by the intrinsic adjuvanticity of bacteria alone. However, the importance of TNF-α for BMTT was highlighted by its support of tumor invasion and colonization in concert with lower infective doses of Salmonella. In consideration, bacterial therapeutic effectiveness along the axis of LPS and TNF-α appears limited, and does not offer the necessary plasticity for different tumors. This emphasizes a need for recombinant strengthening and vehicular exploitation to accommodate potency, plasticity and distinctiveness in BMTT.

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.

Tumor-targeting Salmonella typhimurium A1-R regresses an osteosarcoma in a patient-derived xenograft model resistant to a molecular-targeting drug

Osteosarcoma occurs mostly in children and young adults, who are treated with multiple agents in combination with limb-salvage surgery. However, the overall 5-year survival rate for patients with recurrent or metastatic osteosarcoma is 20-30% which has not improved significantly over 30 years. Refractory patients would benefit from precise individualized therapy. We report here that a patient-derived osteosarcoma growing in a subcutaneous nude-mouse model was regressed by tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R, p<0.001 compared to untreated control). The osteosarcoma was only partially sensitive to the molecular-targeting drug sorafenib, which did not arrest its growth. S. typhimurium A1-R was significantly more effective than sorafenib (P <0.001). S. typhimurium grew in the treated tumors and caused extensive necrosis of the tumor tissue. These data show that S. typhimurium A1-R is powerful therapy for an osteosarcoma patient-derived xenograft model.

Tumor-targeting Salmonella typhimurium A1-R is a highly effective general therapeutic for undifferentiated soft tissue sarcoma patient-derived orthotopic xenograft nude-mouse models

Undifferentiated soft tissue sarcoma (USTS) is a recalcitrant and heterogeneous subgroup of soft tissue sarcoma with high risk of metastasis and recurrence. Due to heterogeneity of USTS, there is no reliably effective first-line therapy. We have generated tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R), which previously showed strong efficacy on single patient-derived orthotopic xenograft (PDOX) models of Ewing's sarcoma and follicular dendritic cell sarcoma. In the present study, tumor resected from 4 patients with a biopsy-proven USTS (2 undifferentiated pleomorphic sarcoma [UPS], 1 undifferentiated sarcoma not otherwise specified [NOS] and 1 undifferentiated spindle cell sarcoma [USS]) were grown orthotopically in the biceps femoris muscle of mice to establish PDOX models. One USS model and one UPS model were doxorubicin (DOX) resistant. One UPS and the NOS model were partially sensitive to DOX. DOX is first-line therapy for these diseases. S. typhimurium A1-R arrested tumor growth all 4 models. In addition to arresting tumor growth in each case, S. typhimurium A1-R was significantly more efficacious than DOX in each case, thereby surpassing first-line therapy. These results suggest that S. typhimurium A1-R can be a general therapeutic for USTS and possibly sarcoma in general.

Tumor-targeting Salmonella typhimurium A1-R combined with temozolomide regresses malignant melanoma with a BRAF-V600E mutation in a patient-derived orthotopic xenograft (PDOX) model

Melanoma is a recalcitrant disease in need of transformative therapuetics. The present study used a patient-derived orthotopic xenograft (PDOX) nude-mouse model of melanoma with a BRAF-V600E mutation to determine the efficacy of temozolomide (TEM) combined with tumor-targeting Salmonella typhimurium A1-R. A melanoma obtained from the right chest wall of a patient was grown orthotopically in the right chest wall of nude mice to establish a PDOX model. Two weeks after implantation, 40 PDOX nude mice were divided into 4 groups: G1, control without treatment (n = 10); G2, TEM (25 mg/kg, administrated orally daily for 14 consecutive days, n = 10); G3, S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks, n = 10); G4, TEM combined with S. typhimurium A1-R (25 mg/kg, administrated orally daily for 14 consecutive days and 5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks, respectively, n = 10). Tumor sizes were measured with calipers twice a week. On day 14 from initiation of treatment, all treatments significantly inhibited tumor growth compared to untreated control (TEM: p < 0.0001; S. typhimurium A1-R: p < 0.0001; TEM combined with S. typhimurium A1-R: p < 0.0001). TEM combined with S. typhimurium A1-R was significantly more effective than either S. typhimurium A1-R (p = 0.0004) alone or TEM alone (p = 0.0017). TEM combined with S. typhimurium A1-R could regress the melanoma in the PDOX model and has important future clinical potential for melanoma patients.

Vemurafenib-resistant BRAF-V600E-mutated melanoma is regressed by MEK-targeting drug trametinib, but not cobimetinib in a patient-derived orthotopic xenograft (PDOX) mouse model

Melanoma is a recalcitrant disease. The present study used a patient-derived orthotopic xenograft (PDOX) model of melanoma to test sensitivity to three molecularly-targeted drugs and one standard chemotherapeutic. A BRAF-V600E-mutant melanoma obtained from the right chest wall of a patient was grown orthotopically in the right chest wall of nude mice to establish a PDOX model. Two weeks after implantation, 50 PDOX nude mice were divided into 5 groups: G1, control without treatment; G2, vemurafenib (VEM) (30 mg/kg); G3; temozolomide (TEM) (25 mg/kg); G4, trametinib (TRA) (0.3 mg/kg); and G5, cobimetinib (COB) (5 mg/kg). Each drug was administered orally, daily for 14 consecutive days. Tumor sizes were measured with calipers twice a week. On day 14 from initiation of treatment, TRA, an MEK inhibitor, was the only agent of the 4 tested that caused tumor regression (P < 0.001 at day 14). In contrast, another MEK inhibitor, COB, could slow but not arrest growth or cause regression of the melanoma. First-line therapy TEM could slow but not arrest tumor growth or cause regression. The patient in this study had a BRAF-V600E-mutant melanoma and would be considered to be a strong candidate for VEM as first-line therapy, since VEM targets this mutation. However, VEM was not effective. The PDOX model thus helped identify the very-high efficacy of TRA against the melanoma PDOX and is a promising drug for this patient. These results demonstrate the powerful precision of the PDOX model for cancer therapy, not achievable by genomic analysis alone.

Patient-derived mouse models of cancer need to be orthotopic in order to evaluate targeted anti-metastatic therapy

Patient-derived xenograft (PDX) mouse models of cancer are emerging as an important component of personalized precision cancer therapy. However, most models currently offered to patients have their tumors subcutaneously-transplanted in immunodeficient mice, which rarely metastasize. In contrast, orthotopic-transplant patient-derived models, termed patient-derived orthotopic xenografts (PDOX), usually metastasize as in the patient. We demonstrate in the present report why orthotopic models are so important for the patient, since primary and metastatic tumors developed in an orthotopic model can have differential chemosensitivity, not detectable in standard subcutaneous tumor models. A subcutaneous nude mouse model of HER-2 expressing cervical carcinoma was not sensitive to entinostat (a benzamide histone deactylase inhibitor), which also did not inhibit primary tumor growth in a PDOX model of the same tumor. However, in the PDOX model, entinostat alone significantly reduced the metastatic tumor burden, compared to the control. Thus, only the PDOX model could be used to discover the anti-metastatic activity of entinostat for this patient. The results of the present report indicate the importance of using mouse models that can recapitulate metastatic cancer for precisely individualizing cancer therapy.

Characterizing the immune microenvironment of malignant peripheral nerve sheath tumor by PD-L1 expression and presence of CD8+ tumor infiltrating lymphocytes

Background

Malignant peripheral nerve sheath tumor (MPNST) is an aggressive sarcoma with few treatment options. Tumor immune state has not been characterized in MPNST, and is important in determining response to immune checkpoint blockade. Our aim was to evaluate the expression of programmed death-ligand 1 (PD-L1), programmed cell death protein 1 (PD-1), and presence of CD8+ tumor infiltrating lymphocytes (TILs) in MPNST, and correlate these findings with clinical behavior and outcome.

Results

PD-L1 staining of at least 1% was seen in 0/20 nerves, 2/68 benign lesions and 9/53 MPNST. Two of 68 benign lesions and 7/53 (13%) MPNST had at least 5% PD-L1 staining. CD8 staining of at least 5% was seen in 1/20 (5%) nerves, 45/68 (66%) benign lesions and 30/53 (57%) MPNST. PD-L1 was statistically more prevalent in MPNST than both nerves and benign lesions (p=0.049 and p=0.008, respectively). Expression of PD-1 was absent in all tissue specimens. There was no correlation of PD-L1 or CD8 expression with disease state (primary versus metastatic) or patient survival.

Methods

A comprehensive PNST tissue microarray was created from 141 surgical specimens including primary, recurrent, and metastatic MPNST (n=53), neurofibromas (n=57), schwannoma (n=11), and normal nerve (n=20). Cores were stained in triplicate for PD-L1, PD-1, and CD8, and expression compared between tumor types. These data were then examined for survival correlates in 35 patients with primary MPNST.

Conclusions

MPNST is characterized by low PD-L1 and absent PD-1 expression with significant CD8+ TIL presence. MPNST immune microenvironment does not correlate with patient outcome.

Effective molecular targeting of CDK4/6 and IGF-1R in a rare FUS-ERG fusion CDKN2A-deletion doxorubicin-resistant Ewing's sarcoma patient-derived orthotopic xenograft (PDOX) nude-mouse model

Ewing's sarcoma is a rare and aggressive malignancy. In the present study, tumor from a patient with a Ewing's sarcoma with cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) loss and FUS-ERG fusion was implanted in the right chest wall of nude mice to establish a patient-derived orthotopic xenograft (PDOX) model. The aim of the present study was to determine efficacy of cyclin-dependent kinase 4/6 (CDK4/6) and insulin-like growth factor-1 receptor (IGF-1R) inhibitors on the Ewing's sarcoma PDOX. The PDOX models were randomized into the following groups when tumor volume reached 50 mm³: G1, untreated control; G2, doxorubicin (DOX) (intraperitoneal (i.p.) injection, weekly, for 2 weeks); G3, CDK4/6 inhibitor (palbociclib, PD0332991, per oral (p.o.), daily, for 14 days); G4, IGF-1R inhibitor (linsitinib, OSI-906, p.o., daily, for 14 days). Tumor growth was significantly suppressed both in G3 (palbociclib) and in G4 (linsitinib) compared to G1 (untreated control) at all measured time points. In contrast, DOX did not inhibit tumor growth at any time point, which is consistent with the failure of DOX to control tumor growth in the patient. The results of the present study demonstrate the power of the PDOX model to identify effective targeted molecular therapy of a recalcitrant DOX-resistant Ewing's sarcoma with specific genetic alterations. The results of this study suggest the potential of PDOX models for individually-tailored, effective targeted therapy for recalcitrant cancer.

Temozolomide combined with irinotecan regresses a cisplatinum-resistant relapsed osteosarcoma in a patient-derived orthotopic xenograft (PDOX) precision-oncology mouse model

Relapsed osteosarcoma is a recalcitrant tumor. A patient's cisplatinum (CDDP)-resistant relapsed osteosarcoma lung metastasis was previously established orthotopically in the distal femur of mice to establish a patient-derived orthotopic xenograft (PDOX) model. In the present study, the PDOX models were randomized into the following groups when tumor volume reached 100 mm3: G1, control without treatment; G2, CDDP (6 mg/kg, intraperitoneal (i.p.) injection, weekly, for 2 weeks); gemcitabine (GEM) (100 mg/kg, i.p., weekly, for 2 weeks) combined with docetaxel (DOC) (20 mg/kg, i.p., once); temozolomide (TEM) (25 mg/kg, p.o., daily, for 2 weeks) combined with irinotecan (IRN) (4 mg/kg i.p., daily for 2 weeks). Tumor size and body weight were measured with calipers and a digital balance twice a week. After 2 weeks, all treatments significantly inhibited tumor growth except CDDP compared to the untreated control: CDDP: p = 0.093; GEM+DOC: p = 0.0002, TEM+IRN: p < 0.0001. TEM combined with IRN was significantly more effective than either CDDP (p = 0.0001) or GEM combined with DOC (p = 0.0003) and significantly regressed the tumor volume compared to day 0 (p = 0.003). Thus the PDOX model precisely identified the combination of TEM-IRN that could regress the CDDP-resistant relapsed metastatic osteosarcoma PDOX.