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Background/aim: Matrix-producing breast carcinoma (MPBC) is a rare and usually aggressive triple-negative breast cancer (TNBC). In the present report, we determined the drug sensitivity for a triple-negative MPBC using a patient-derived orthotopic xenograft (PDOX) model., Materials and Methods: The PDOX model was established in the left 2 nd mammary by surgical orthotopic implantation (SOI). MPBC PDOX models were randomized into 4 groups (6 mice per group) when the tumor volume became 80 mm 3 : G1, control group; G2, cisplatinum group [intraperitoneal (i.p.) injection, weekly, for 2 weeks]; G3, paclitaxel group (i.p., weekly, for 2 weeks); G4, eribulin group [intravenous (i.v.) injection, weekly, for 2 weeks]. All mice were sacrificed on day 15. Tumor volume and body weight were measured one time per week., Results: The MPBC PDOX model was resistant to cisplatinum (p=0.800). Paclitaxel suppressed tumor growth compared to the control group (p=0.009). However, only eribulin regressed the tumor (p=0.001)., Conclusion: Eribulin has clinical potential for triple-negative MPBC patients., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Dedifferentiated liposarcoma (DDLPS) is associated with a poor survival rate even with multi-modality treatment. In the present study, we evaluated the efficacy of recombinant methioninase (rMETase) combined with tumor-targeting Salmonella typhimurium (S. typhimurium) A1-R against a doxorubicin-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) mouse model., Materials and Methods: A recurrent high-grade DDLPS from the right retroperitoneum of a patient was grown orthotopically in the retroperitoneum of nude mice to establish a PDOX model. The PDOX models were randomly divided into the following groups: Control, no treatment; doxorubicin monotherapy; rMETase monotherapy; S. typhimurium A1-R monotherapy; S. typhimurium A1-R and rMETase combination therapy. Tumor length and width were measured before and after treatment., Results: On day 14 after treatment, all treatments significantly inhibited DDLPS PDOX tumor growth compared to the untreated control except for doxorubicin monotherapy. rMETase combined with S. typhimurium A1-R was significantly more effective and regressed tumor volume compared to either rMETase or S. typhimurium A1-R alone. The relative body weight did not significantly differ between days 0 and 14 for individual groups., Conclusion: The combination of rMETase and S. typhimurium A1-R has important clinical potential for this recalcitrant sarcoma., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Matrix-producing breast carcinoma (MPBC) is a rare and usually aggressive triple-negative breast cancer (TNBC). In this study, we determined drug sensitivity for a triple-negative MPBC, without BRCA mutations, in a patient-derived orthotopic xenograft (PDOX) model., Materials and Methods: The MPBC PDOX model was established in the left 2 nd mammary gland of nude mouse by implantation of the patient tumor using surgical orthotopic implantation (SOI). We randomized MPBC PDOX mice into 5 groups (n=5 mice/per treatment group) when the tumor volume reached 80 mm 3 : G1, control-no treatment; G2, bevacizumab [intra-peritoneal (i.p.), weekly, for 2 weeks]; G3, vinorelbine (i.p., weekly, for 2 weeks); G4, olaparib (oral., daily, for 2 weeks); G5, eribulin [intravenous (i.v.), weekly, for 2 weeks]. The mice in each treatment group were sacrificed on day 15. Tumor volume and body weight were measured once/week., Results: The MPBC PDOX model was resistant to olaparib (p=0.22). The MPBC PDOX model treated with bevacizumab and vinorelbine showed significantly suppressed tumor growth compared to the untreated group (p=0.005 and 0.002, respectively). However, only eribulin regressed the tumor (p=0.0001). Eribulin was more effective than olaparib (p=0.0001), bevacizumab (p=0.0025) and vinorelbine (p=0.0061)., Conclusion: Eribulin has clinical potential as treatment for triple-negative MPBC patients that are resistant to a PARP inhibitor such as olaparib., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: In the present study, the breast cancer patient-derived orthotopic xenograft (PDOX) model was used to identify an effective drug for a highly aggressive triple negative breast cancer (TNBC)., Materials and Methods: The TNBC tumor from a patient was implanted in the right 4th inguinal mammary fat pad of nude mice to establish a PDOX model. Three weeks later, 19 mice were randomized into the untreated-control group (n=10) and the eribulin treatment group (n=9, eribulin, 0.3 mg/kg, i.p., day 1)., Results: On day 8, eribulin significantly inhibited tumor volume compared to the control group (p<0.01). Eribulin regressed tumors in 3 mice (33.3%) and apparently eradicated them in 6 mice (66.7%). At day 14, tumor regrowth was observed in 2 mice of the eribulin group, which was undetectable on day 8. However, 44.4% (4 out of 9) of the mice in the eribulin group were tumor-free on day 14., Conclusion: A single low-dose eribulin was efficacious on a highly aggressive TNBC. The breast cancer PDOX model can be used to identify highly effective drugs for TNBC., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: The aim of the present study was to determine the efficacy of trabectedin combined with FOLFIRI (irinotecan, leucovorin and 5-fluorouracil) on a colorectal cancer (CRC) patient-derived orthotopic xenograft (iPDOX) mouse model., Materials and Methods: A CRC tumor from a patient previously established in nude mice was implanted subcutaneously in transgenic green fluorescence protein (GFP)-expressing nude mice in order to label the tumor stromal cells with GFP. Mice were randomized into four groups: Group 1, untreated control; group 2, FOLFIRI; group 3, trabectedin alone; group 4, trabectedin plus FOLFIRI. Tumor width, length, and mouse body weight was measured twice every week., Results: All three treatment groups showed inhibited tumor growth compared to the untreated control group. Only the combination of FOLFIRI and trabectedin arrested tumor growth. No significant changes was observed in body weight in any group., Conclusion: These findings suggest that the combination of trabectedin plus FOLFIRI has clinical potential for patients with CRC., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: In the present study, we aimed to determine the efficacy of trabectedin (TRAB) combined with oxaliplatinum (OXA)+5-fluorouracil (5-FU) on a colorectal cancer (CRC) patient-derived orthotopic xenograft (PDOX) mouse model., Materials and Methods: A patient CRC tumor previously established in nude mice was implanted subcutaneously in transgenic green fluorescence protein (GFP)-expressing nude mice. Harvested tumor fragments were transplanted orthotopically in non-transgenic nude mice. Mice were randomized into three groups: Group 1 (G1), untreated-control; Group 2 (G2), OXA+5-FU; Group 3 (G3), TRAB+OXA+5-FU. Tumor width, length, and mouse body weight were measured twice a week., Results: Both treatment groups inhibited tumor growth compared to the untreated control group. The combination of TRAB, OXA and 5-FU was significantly more efficacious than OXA+5-FU and arrested tumor growth. No significant changes were observed in body-weight in any of the three groups., Conclusion: TRAB, OXA and 5-FU combination has clinical potential for this and other CRC patients., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Gemcitabine is standard first-line treatment for patients with advanced pancreatic cancer, however the efficacy is limited. Although acquired drug resistance and side-effects are known to limit efficacy, opposite effects of a drug, which enhance the malignancy of treated cancer, have been observed but are not well understood. The aim of the present study was to determine whether gemcitabine has such opposite effects on the BxPC-3 human pancreatic cancer cell line expressing green fluorescent protein (BxPC-3-GFP) in an orthotopic mouse model., Materials and Methods: BxPC-3-GFP tumors grown subcutaneously in nude mice were harvested. Tumor fragments were orthotopically implanted in the tail of the pancreas of nude mice using the technique of surgical orthotopic implantation. The BxPC-3-GFP orthotopic models were divided randomly into three groups: Group 1: untreated control; Group 2: low-dose gemcitabine (weekly intraperitoneal injection at 25 mg/kg for 6 weeks); Group 3: high-dose gemcitabine (weekly intraperitoneal injection at 125 mg/kg for 6 weeks). Each group comprised eight mice. Tumor size, fluorescent area of metastases, and body weight were measured., Results: Low- and high-dose gemcitabine inhibited primary tumor growth in a dose-dependent manner, and to the greatest extent by high-dose gemcitabine compared to the untreated control (p=0.0134). In contrast, the extent of metastasis on the peritoneum was significantly increased by low-dose gemcitabine compared to the untreated control (p=0.0112). The extent of metastasis showed no significant difference between the untreated control and mice treated with high-dose gemcitabine. Body weight of the treated mice was not significantly different from that of the untreated mice., Conclusion: The use of very bright GFP expressing of BxPC-3 cells and the orthotopic model demonstrated an unexpected increase in metastasis by low-dose gemcitabine. Future experiments will investigate the mechanism of this phenomenon., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Liver metastasis in colorectal-cancer is a recalcitrant disease. To develop precision individualized therapy of this disease, we developed a patient-derived orthotopic xenograft (PDOX) model of colorectal-cancer liver metastasis. In the present report, we evaluated the efficacy of oral recombinant methioninase (o-rMETase) in combination with 5-fluorouracil (5-FU) and oxaliplatinum (OXA) on the colorectal-cancer liver metastasis PDOX mouse model., Materials and Methods: Colorectal-cancer liver metastasis PDOX models were randomized into three groups of seven mice. Group 1, untreated control with phosphate buffered saline (PBS); Group 2, treated with 5-FU + OXA; and Group 3, treated with 5-FU + OXA + o-rMETase., Results: The colorectal-cancer liver metastasis PDOX model was resistant to 5-FU + OXA (p=0.83 at day 15 of treatment, Group 2). In contrast, the colorectal-cancer liver metastasis PDOX model was arrested by o-rMETase combined with 5-FU + OXA (p<0.01 at day 15, Group 3). No significant body-weight differences were observed among the groups., Conclusion: The combination therapy of 5-FU and OXA with o-rMETase can overcome the resistance of first line drugs for colorectal-cancer liver metastasis., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Osteosarcoma is a rare but recalcitrant type of bone cancer. To discover an effective therapy for osteosarcoma, we used a patient-derived orthotopic xenograft (PDOX) mouse model. A PDOX mouse model has been established for all major cancer types. Strong synergistic efficacy of sorafenib (SFN) and everolimus (EVL) has been demonstrated in several cancers. In the present study, we examined the efficacy of a SFN and EVL combination on a doxorubicin (DOX)-resistant osteosarcoma PDOX., Materials and Methods: The osteosarcoma PDOX models were randomly divided into five treatment groups, each containing six mice: Control; DOX; SFN; EVL; and a combination of SFN and EVL. Mice were treated for 14 days. To observe the efficacy of these treatments, tumor size and body weight were measured, and histological sections were analyzed., Results: Tumor growth regression was observed only in the mice treated with the combination of SFN-EVL. Histological analysis revealed necrosis with degenerative changes in tumors treated with a combination of SFN-EVL., Conclusion: A SFN-EVL combination could be a novel effective treatment option for osteosarcoma., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background: Osteosarcoma is a recalcitrant disease treated with surgery and intensive chemotherapy as standard. The 5-year survival rate of patients with relapsed and lung metastatic osteosarcoma is as low as 20%., Materials and Methods: A 16-year-old patient developed left distal femoral high-grade osteosarcoma and underwent cisplatinum-based neoadjuvant chemotherapy and surgery. From the resected tumor, a patient-derived orthotopic xenograft (PDOX) model was established in the femur of nude mice. PDOX models were randomized into the following groups: untreated control, or treatment with doxorubicin (3 mg/kg, i.p., weekly for 14 days), sunitinib (40 mg/kg, oral gavage, daily for 14 days), pazopanib (100 mg/kg, oral gavage, daily for 14 days), temozolomide(25 mg/kg, oral gavage, daily for 14 days), and eribulin (1.5 mg/kg, i.p., daily for 14 days). Tumor volume and body weight were monitored twice a week., Results: The osteosarcoma PDOX was resistant to doxorubicin, sunitinib, and pazopanib. In contrast, eribulin and temozolomide arrested tumor growth., Conclusion: This study demonstrated the utility of the PDOX model in allowing effective from non-effective drugs to be distinguished in a model in which the tumor was growing on the organ corresponding to that of the patient., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Osteosarcoma is a recalcitrant neoplasm which occurs predominantly in adolescents and young adults. Recently, using a patient-derived orthotopic xenograft (PDOX) model of malignant soft-tissue sarcoma (STS), we showed that oral recombinant methioninase (o-rMETase), in combination with caffeine, was more efficacious than o-rMETase alone in inhibiting STS tumor growth. In the present report, we determined the efficacy of o-rMETase combined with oral caffeine on a cisplatinum (CDDP)-resistant osteosarcoma PDOX model., Materials and Methods: Osteosarcoma PDOX models were randomly divided into seven treatment groups (6 mice in each group): untreated control; CDDP alone; o-rMETase alone; o-rMETase with caffeine; CDDP plus o-rMETase; CDDP plus caffeine; and CDDP plus o-rMETase with caffeine. Tumor size and body weight were measured throughout the treatment., Results: Tumors regressed after treatment with CDDP plus o-rMETase with caffeine. Tumors treated with CDDP plus o-rMETase with caffeine also had the most necrosis., Conclusion: The combination of o-rMETase and caffeine together with first-line chemotherapy was efficacious for drug-resistant osteosarcoma and has clinical potential in the treatment of this highly-resistant neoplasm., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Recurrent osteosarcoma is a recalcitrant disease; therefore, an improved strategy is urgently needed to provide therapy. In order to develop a novel strategy for this disease, our lab has developed a patient-derived orthotopic xenograft (PDOX) mouse model for osteosarcoma. The combination of sorafenib (SFN) and palbociclib (PAL) was shown to be effective of hepatocellular carcinoma. However, whether this combination is efficacious on osteosarcoma has not been reported. The aim of this study was to determine the efficacy of the SFN and PAL combination on a cisplatinum (CDDP)-resistant osteosarcoma PDOX model., Materials and Methods: Osteosarcoma PDOX models were randomly divided into five treatment groups: untreated-control, CDDP, SFN, PAL and the combination of SFN and PAL., Results: Of these agents, the SFN-PAL combination significantly regressed tumor growth, and enhanced tumor necrosis with degenerative changes in the osteosarcoma PDOX., Conclusion: The SFN-PAL combination is an effective treatment strategy for osteosarcoma and therefore holds promise for clinical efficacy., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background: Surgical orthotopic implantation of human colon cancer tissue to the ceca of mice has been used to mimic behavior of cancer in human patients for the development of precision cancer medicine. However, with the current method of serosal surface implantation (SSI) of pieces of human colon cancer tissue, cancer cells are exposed to the peritoneum, which can artificially increase the rate of peritoneal carcinomatosis (PC) during the disease course. The objective of the present study was to introduce a tumor-sealing method (TSM) and compare it with SSI for the ability to produce clinically-relevant metastases without artificial PC., Materials and Methods: HCT116 colon cancer cells transfected with green fluorescence protein (GFP) were cultured and then injected into the subcutaneous layer of athymic nude mice. Subcutaneous tumors were allowed to grow sufficiently to supply adequate tumor for orthotopic implantation. For SSI, a 1 mm 3 -sized tumor fragment was sutured to partially torn serosa of the cecum. For TSM, the blind end of the cecum was folded over the tumor fragment and sealed with sutures. At 20 days after implantation, all mice were opened to visualize PC by intravital fluorescence imaging. At necropsy, distant metastasis was investigated using frozen section of whole blocks of organs., Results: At 20 days after implantation, PC rates in the SSI group and the TSM group were 80% (12/15) and 20% (3/15), respectively (p<0.001). The liver metastasis rate was 41.7% (5/12) in the SSI group and 50% (5/10) in the TSM group (p=0.696). The lung metastasis rate was 0% (0/12) in the SSI group and 10% (1/10) in the TSM group (p=0.201). The mean survival of mice without PC on the 20th day was significantly longer than that of mice with PC on the 20th day (69.1±14.7 vs. 44.5±12.4 days, p=0.001)., Conclusion: These results suggest that TSM might be a more patient-like and useful method as a model of metastatic colon cancer than SSI., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Patient-derived orthotopic xenograft (PDOX) models have patient-like clinical features and may be imaged, in case of some cancers, by passaging of the tumors through transgenic nude mice expressing red-fluorescent protein (RFP) where they stably acquire RFP expressing stroma. The aim of the present study was to quantify red fluorescent area and intensity in colon-cancer peritoneal metastases in PDOX models in non-transgenic nude mice after passage in RFP transgenic nude mice by non-invasive external fluorescence imaging., Materials and Methods: Tumor fragments originating from a colon cancer patient with peritoneal metastases were implanted in transgenic RFP nude mice. Resultant tumors were harvested, and fragments were implanted in the same strain a second time. Passaged tumors stably acquired RFP-expressing stroma from their transgenic hosts. The tumor with RFP-expressing stromal cells were harvested and implanted orthotopically in non-transgenic nude mice. At eight weeks post-implantation, non-invasive external RFP images were obtained. RFP area and intensity were measured and correlated with tumor weight and volume., Results: Metastatic patient colon cancer can be stably and brightly labeled by passage in transgenic RFP-expressing nude mice such that tumor growth could be non-invasively imaged. Tumor growing could be non-invasively imaged when passaged to non-transgenic nude mice. A strong correlation between fluorescence intensity and area values with tumor weight and volume were established by external fluorescence imaging., Conclusion: This new tumor model of metastatic colon cancer can be used to evaluate novel therapeutics in real time for this recalcitrant disease., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Undifferentiated pleomorphic sarcoma (UPS) is a common soft tissue sarcoma and highly recalcitrant. We have previously developed patient-derived orthotopic xenograft (PDOX) mouse models of UPS and other major sarcoma types. Unlike PDOX models of other cancer types, it has been difficult to demonstrate metastasis in the sarcoma PDOX models., Materials and Methods: To visualize metastasis at high resolution in the UPS PDOX model, established tumor fragments were implanted in transgenic nude mice expressing red fluorescent protein (RFP) for one passage. The tumors acquired RFP-expressing stroma from transgenic host. UPS tumor with RFP stromal cells were harvested and implanted orthotopically in non-transgenic nude mice. After six weeks of UPS tumor growth in the PDOX model, the primary tumor was imaged non-invasively and lung, liver, and spleen were resected and imaged ex-vivo in order to visualize the presence of RFP, with a FluorVivo® imaging system and FV1000® confocal laser microscope, respectively., Results: The primary tumor was imaged non-invasively. Confocal microscopy visualized the presence of RFP in the lung and liver indicating metastases in these organs. This is the first report of metastasis in a sarcoma PDOX model., Conclusion: This study should prove very useful to screen for anti-metastatic drugs for the PDOX donor patients and to understand the metastatic process in sarcoma., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Synovial sarcoma (SS) is a recalcitrant neoplasm with low chemosensitivity. We recently reported that recombinant methioninase (rMETase) inhibited SS growth in a patient-derived orthotopic xenograft (PDOX) mouse model and was more effective when administered in combination with the first-line drug doxorubicin (DOX). Caffeine enhances the efficacy of anticancer drugs by overcoming drug-induced cell-cycle arrest and increasing subsequent apoptosis. Here, we determined the efficacy of oral recombinant methioninase (o-rMETase) in combined with caffeine on an SS-PDOX model., Materials and Methods: Mice bearing SS-PDOX tumors were randomized into four treatment groups of six: Untreated control; o-rMETase alone; o-rMETase with caffeine; DOX plus o-rMETase with caffeine. Tumor size and body weight were measured during the treatment and plasma L-methionine (MET) levels were measured at the end of treatment., Results: All treatments significantly inhibited SS-PDOX tumor growth. Combining caffeine with o-rMETase was more effective than o-rMETase alone. DOX combined with o-rMETase and caffeine led to regression of SS-PDOX. Plasma MET levels were reduced with o-rMETase treatment., Conclusion: These results suggest that combining o-rMETase and caffeine along with first-line chemotherapy can be highly effective for SS and has clinical potential for this recalcitrant disease., (Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)