Exploring long-term protection of normal human fibroblasts and epithelial cells from chemotherapy in cell culture

Harnessing p53 for targeted cancer therapy: new advances and future directions

The transcription factor p53 is the most frequently impaired tumor suppressor in human cancers. In response to various stress stimuli, p53 activates transcription of genes that mediate its tumor-suppressive functions. Distinctive characteristics of p53 outlined here enable a well-defined program of genes involved in cell cycle arrest, apoptosis, senescence, differentiation, metabolism, autophagy, DNA repair, anti-viral response, and anti-metastatic functions, as well as facilitating autoregulation within the p53 network. This versatile, anti-cancer network governed chiefly by a single protein represents an immense opportunity for targeted cancer treatment, since about half of human tumors retain unmutated p53. During the last two decades, numerous compounds have been developed to block the interaction of p53 with the main negative regulator MDM2. However, small molecule inhibitors of MDM2 only induce a therapeutically desirable apoptotic response in a limited number of cancer types. Moreover, clinical trials of the MDM2 inhibitors as monotherapies have not met expectations and have revealed hematological toxicity as a characteristic adverse effect across this drug class. Currently, combination treatments are the leading strategy for enhancing efficacy and reducing adverse effects of MDM2 inhibitors. This review summarizes efforts to identify and test therapeutics that work synergistically with MDM2 inhibitors. Two main types of drugs have emerged among compounds used in the following combination treatments: first, modulators of the p53-regulated transcriptome (including chromatin modifiers), translatome, and proteome, and second, drugs targeting the downstream pathways such as apoptosis, cell cycle arrest, DNA repair, metabolic stress response, immune response, ferroptosis, and growth factor signaling. Here, we review the current literature in this field, while also highlighting overarching principles that could guide target selection in future combination treatments.

Tracking of Endothelial Cell Migration and Stiffness Measurements Reveal the Role of Cytoskeletal Dynamics

Cell migration is a complex, tightly regulated multistep process in which cytoskeletal reorganization and focal adhesion redistribution play a central role. Core to both individual and collective migration is the persistent random walk, which is characterized by random force generation and resistance to directional change. We first discuss a model that describes the stochastic movement of ECs and characterizes EC persistence in wound healing. To that end, we pharmacologically disrupted cytoskeletal dynamics, cytochalasin D for actin and nocodazole for tubulin, to understand its contributions to cell morphology, stiffness, and motility. As such, the use of Atomic Force Microscopy (AFM) enabled us to probe the topography and stiffness of ECs, while time lapse microscopy provided observations in wound healing models. Our results suggest that actin and tubulin dynamics contribute to EC shape, compressive moduli, and directional organization in collective migration. Insights from the model and time lapse experiment suggest that EC speed and persistence are directionally organized in wound healing. Pharmacological disruptions suggest that actin and tubulin dynamics play a role in collective migration. Current insights from both the model and experiment represent an important step in understanding the biomechanics of EC migration as a therapeutic target.

Metformin and sodium dichloroacetate effects on proliferation, apoptosis, and metabolic activity tested alone and in combination in a canine prostate and a bladder cancer cell line

An important approach in tumor therapy is combining substances with different action mechanisms aiming to enhance the antineoplastic effect, decrease the therapeutic dosage, and avoid resistance mechanisms. Moreover, evaluating compounds already approved for the treatment of non-neoplastic diseases is promising for new antineoplastic therapies. Sodium dichloroacetate (DCA) reactivates oxidative phosphorylation in the cancer cell mitochondria, reducing apoptosis resistance in cancer cells. Furthermore, metformin inhibits the proliferation of tumor cells and CD133+ cancer -stem-like cells. In the present study, we evaluated the independent and synergistic effect of metformin and DCA on the metabolic activity, cell proliferation, and apoptosis of a canine prostate adenocarcinoma (Adcarc1258) and a transitional cell carcinoma cell line (TCC1506) in comparison to a primary canine fibroblast culture. Determining metformin uptake in tumor cells was performed by quantitative HPLC. Depending on the dosage, metformin as a single agent inhibited the metabolic activity and cell proliferation of the tumor cells, showing only minor effects on the fibroblasts. Furthermore, 1 mM metformin increased apoptosis over 96 h in the tumor cell lines but not in fibroblasts. Additionally, metformin uptake into the tumor cells in vitro was measurable by quantitative HPLC. Synergistic effects for the combination therapy were observed in both neoplastic cell lines as well as in the fibroblasts. Based on these results, metformin might be a promising therapeutic agent for canine urogenital tumors. Further studies on kinetics, toxicology, bioavailability, and application of metformin in dogs are necessary.

P53 activation suppresses irinotecan metabolite SN-38-induced cell damage in non-malignant but not malignant epithelial colonic cells

Nutlin-3a is a p53 activator and potential cyclotherapy approach that may also mitigate side effects of chemotherapeutic drugs in the treatment of colorectal cancer. We investigated cell proliferation in a panel of colorectal cancer (CRC) cell lines with wild-type or mutant p53, as well as a non-tumorigenic fetal intestinal cell line following Nutlin-3a treatment (10 μM). We then assessed apoptosis at 24 and 48 h following administration of the active irinotecan metabolite, SN-38 (0.001 μM - 1 μM), alone or following pre-treatment with Nutlin-3a (10 μM). Nutlin-3a treatment (10 μM) significantly reduced proliferation in wild-type p53 expressing cell lines (FHS 74 and HCT116^+/+) at 72 and 96 h, but was without effect in cell lines with mutated or deleted p53 (Caco-2, SW480, and HCT 116^-/-). SN-38 treatment induced significant apoptosis in all cell lines after 48 h. Nutlin-3a unexpectedly increased cell death in the p53 wild-type CRC cell line, HCT116^+/+, while Nutlin-3a pre-treatment provided protection from SN-38 in the p53 wild-type normal cell line, FHs 74. These results demonstrate Nutlin-3a's selective growth-arresting efficacy in p53 wild-type non-malignant intestinal cell lines, enabling the selective targeting of malignant cells with chemotherapy drugs. These studies highlight the potential of Nutlin-3a to minimise intestinal mucosal damage following chemotherapy.

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.

Resistance of human primary mesenchymal stem cells to cytotoxic effects of nutlin-3 in vitro

BACKGROUND

The small-molecule nutlin-3 was found to be an effective therapeutic compound and p53 activator, and acts as a murine double minute 2 antagonist, although these findings need to be clinically confirmed. The essential components of the bone marrow include mesenchymal stem cells (MSCs), which play a key role in protecting, regenerating, and proliferating hematopoietic stem cells (HSCs). This feature is vital for HSC after exposure to myelotoxic anticancer agents; nevertheless, the effects of nutlin-3 on MSCs remain to be disclosed. The present research study was conducted to examine the antiproliferative and proapoptotic effectiveness of nutlin-3 in bone marrow MSCs (BMSCs).

MATERIALS AND METHODS

Human-derived BMSCs were cultured for different durations, that is, 24, 48, and 72 hours, and treated using various concentrations of nutlin-3, including 5, 10, 25, 50, and 100 μΜ. To investigate the effect of nutlin-3 on the apoptosis, cell vitality and proliferation in BMSCs, the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), thiazolyl blue tetrazolium bromide, propidium iodide (PI) and annexin V assay, as well as real-time polymerase chain reaction, were used.

RESULTS

BMSCs viability significantly decreased (P < .05) in the cells treated at concentrations of 50 and 100 μM for 24 hours and concentrations of 25, 50, and 100 μM for 48 hours and at all concentrations for 72 hours. The apoptosis of BMSCs (TUNEL positive) was significantly more visible at concentrations of 25 and 50 μM compared with that in the controls (P < .05), while this increased through dose-dependent processes. Annexin V/PI staining revealed negligible dose-dependent increases in all the apoptotic cells after 72 hours of incubation, and this apoptosis elevation was significant at 25 and 50 μM (P < .05).

CONCLUSION

Resistance to nutlin-3 was observed in human bone marrow-derived MSCs; nevertheless, further clinical data are required to be obtained with long-duration exposure to confirm the present findings.

Starvation-Induced Differential Virotherapy Using an Oncolytic Measles Vaccine Virus

Starvation sensitizes tumor cells to chemotherapy while protecting normal cells at the same time, a phenomenon defined as differential stress resistance. In this study, we analyzed if starvation would also increase the oncolytic potential of an oncolytic measles vaccine virus (MeV-GFP) while protecting normal cells against off-target lysis. Human colorectal carcinoma (CRC) cell lines as well as human normal colon cell lines were subjected to various starvation regimes and infected with MeV-GFP. The applied fasting regimes were either short-term (24 h pre-infection) or long-term (24 h pre- plus 96 h post-infection). Cell-killing features of (i) virotherapy, (ii) starvation, as well as (iii) the combination of both were analyzed by cell viability assays and virus growth curves. Remarkably, while long-term low-serum, standard glucose starvation potentiated the efficacy of MeV-mediated cell killing in CRC cells, it was found to be decreased in normal colon cells. Interestingly, viral replication of MeV-GFP in CRC cells was decreased in long-term-starved cells and increased after short-term low-glucose, low-serum starvation. In conclusion, starvation-based virotherapy has the potential to differentially enhance MeV-mediated oncolysis in the context of CRC cancer patients while protecting normal colon cells from unwanted off-target effects.

MDM2-Mediated p21 Proteasomal Degradation Promotes Fluoride Toxicity in Ameloblasts

Fluoride overexposure is an environmental health hazard and can cause enamel and skeletal fluorosis. Previously we demonstrated that fluoride increased acetylated-p53 and its downstream target p21 in ameloblast-derived LS8 cells. However, p21 function in fluoride toxicity is not well characterized. This study seeks to gain a better understanding of how p53 down-stream mediators, p21 and MDM2, respond to fluoride toxicity. LS8 cells were treated with NaF with/without MG-132 (proteasome inhibitor) or Nutlin-3a (MDM2 antagonist). NaF treatment for 2-6 h increased phospho-p21, which can inhibit apoptosis. However, phospho-p21 and p21 were decreased by NaF at 24 h, even though p21 mRNA was significantly increased at this time point. MG-132 reversed the fluoride-mediated p21 decrease, indicating that fluoride facilitates p21 proteasomal degradation. MG-132 suppressed fluoride-induced caspase-3 cleavage, suggesting that the proteasome plays a pro-apoptotic role in fluoride toxicity. NaF increased phospho-MDM2 in vitro and in mouse ameloblasts in vivo. Nutlin-3a suppressed NaF-mediated MDM2-p21 binding to reverse p21 degradation which increased phospho-p21. This suppressed apoptosis after 24 h NaF treatment. These results suggest that MDM2-mediated p21 proteasomal degradation with subsequent phospho-p21 attenuation contributes to fluoride-induced apoptosis. Inhibition of MDM2-mediated p21 degradation may be a potential therapeutic target to mitigate fluoride toxicity.

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.

Human Oncoviruses and p53 Tumor Suppressor Pathway Deregulation at the Origin of Human Cancers

Viral oncogenesis is a multistep process largely depending on the complex interplay between viruses and host factors. The oncoviruses are capable of subverting the cell signaling machinery and metabolic pathways and exploit them for infection, replication, and persistence. Several viral oncoproteins are able to functionally inactivate the tumor suppressor p53, causing deregulated expression of many genes orchestrated by p53, such as those involved in apoptosis, DNA stability, and cell proliferation. The Epstein–Barr virus (EBV) BZLF1, the high-risk human papillomavirus (HPV) E6, and the hepatitis C virus (HCV) NS5 proteins have shown to directly bind to and degrade p53. The hepatitis B virus (HBV) HBx and the human T cell lymphotropic virus-1 (HTLV-1) Tax proteins inhibit p53 activity through the modulation of p300/CBP nuclear factors, while the Kaposi’s sarcoma herpesvirus (HHV8) LANA, vIRF-1 and vIRF-3 proteins have been shown to destabilize the oncosuppressor, causing a decrease in its levels in the infected cells. The large T antigen of the Merkel cell polyomavirus (MCPyV) does not bind to p53 but significantly reduces p53-dependent transcription. This review describes the main molecular mechanisms involved in the interaction between viral oncoproteins and p53-related pathways as well as in the development of therapeutic strategies targeting such interactions.

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.

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.

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.

Fluorescence-guided surgery of a highly-metastatic variant of human triple-negative breast cancer targeted with a cancer-specific GFP adenovirus prevents recurrence

We have previously developed a genetically-engineered GFP-expressing telomerase-dependent adenovirus, OBP-401, which can selectively illuminate cancer cells. In the present report, we demonstrate that targeting a triple-negative high-invasive human breast cancer, orthotopically-growing in nude mice, with OBP-401 enables curative fluorescence-guided surgery (FGS). OBP-401 enabled complete resection and prevented local recurrence and greatly inhibited lymph-node metastasis due to the ability of the virus to selectively label and subsequently kill cancer cells. In contrast, residual breast cancer cells become more aggressive after bright (white)-light surgery (BLS). OBP-401-based FGS also improved the overall survival compared with conventional BLS. Thus, metastasis from a highly-aggressive triple-negative breast cancer can be prevented by FGS in a clinically-relevant mouse model.

Tumor-targeting adenovirus OBP-401 inhibits primary and metastatic tumor growth of triple-negative breast cancer in orthotopic nude-mouse models

Our laboratory previously developed a highly-invasive, triple-negative breast cancer (TNBC) variant using serial orthotopic implantation of the human MDA-MB-231 cell line in nude mice. The isolated variant was highly-invasive in the mammary gland and lymphatic channels and metastasized to lymph nodes in 10 of 12 mice compared to 2 of 12 of the parental cell line. In the present study, the tumor-selective telomerase dependent OBP-401 adenovirus was injected intratumorally (i.t.) (1 × 10⁸ PFU) when the high-metastatic MDA-MB-231 primary tumor expressing red fluorescent protein (MDA-MB-231-RFP) reached approximately 500 mm³ (diameter; 10 mm). The mock-infected orthotopic primary tumor grew rapidly. After i.t. OBP-401 injection, the growth of the orthotopic tumors was arrested. Six weeks after implantation, the fluorescent area and fluorescence intensity showed no increase from the beginning of treatment. OBP-401 was then injected into high-metastatic MDA-MB-231-RFP primary orthotopic tumor growing in mice which already had developed metastasis within lymphatic ducts. All 7 of 7 control mice subsequently developed lymph node metastasis. In contrast, none of 7 mice which received OBP-401 had lymph node metastasis. Seven of 7 control mice also had gross lung metastasis. In contrast, none of the 7 mice which received OBP-401 had gross lung metastasis. Confocal laser microscopy imaging demonstrated that all control mice had diffuse lung metastases. In contrast, all 7 mice which received OBP-401 only had a few metastatic cells in the lung. OBP-401 treatment significantly extended survival of the treated mice.

A novel method for RNA extraction from FFPE samples reveals significant differences in biomarker expression between orthotopic and subcutaneous pancreatic cancer patient-derived xenografts

Next-generation sequencing (NGS) can identify and validate new biomarkers of cancer onset, progression and therapy resistance. Substantial archives of formalin-fixed, paraffin-embedded (FFPE) cancer samples from patients represent a rich resource for linking molecular signatures to clinical data. However, performing NGS on FFPE samples is limited by poor RNA purification methods. To address this hurdle, we developed an improved methodology for extracting high-quality RNA from FFPE samples. By briefly integrating a newly-designed micro-homogenizing (mH) tool with commercially available FFPE RNA extraction protocols, RNA recovery is increased by approximately 3-fold while maintaining standard A260/A280 ratios and RNA quality index (RQI) values. Furthermore, we demonstrate that the mH-purified FFPE RNAs are longer and of higher integrity. Previous studies have suggested that pancreatic ductal adenocarcinoma (PDAC) gene expression signatures vary significantly under in vitro versus in vivo and in vivo subcutaneous versus orthotopic conditions. By using our improved mH-based method, we were able to preserve established expression patterns of KRas-dependency genes within these three unique microenvironments. Finally, expression analysis of novel biomarkers in KRas mutant PDAC samples revealed that PEAK1 decreases and MST1R increases by over 100-fold in orthotopic versus subcutaneous microenvironments. Interestingly, however, only PEAK1 levels remain elevated in orthotopically grown KRas wild-type PDAC cells. These results demonstrate the critical nature of the orthotopic tumor microenvironment when evaluating the clinical relevance of new biomarkers in cells or patient-derived samples. Furthermore, this new mH-based FFPE RNA extraction method has the potential to enhance and expand future FFPE-RNA-NGS cancer biomarker studies.

The disintegrin echistatin in combination with doxorubicin targets high-metastatic human osteosarcoma overexpressing ανβ3 integrin in chick embryo and nude mouse models

Echistatin, a cyclic RGD peptide, which is an antagonist of αvβ3 integrin (disintegrin), inhibited human osteosarcoma in the chick chorioallontoic membrane (CAM) model and tumor growth and pulmonary metastases in a nude mouse orthotopic model. A high-metastatic variant of human osteosarcoma, 143B-LM4, overexpressing αvβ3 integrin was used. Tumor angiogenesis by high-metastatic variant 143B-LM4 cells in the CAM was significantly inhibited by echistatin (P<0.05) as was overall growth. A doxorubicin (DOX)-echistatin combination inhibited orthotopic tumor growth compared to untreated control (P<0.01) or DOX alone (P<0.05) in nude mice. Tumor-bearing mice treated with the DOX-echistatin combination survived longer than those treated with DOX alone or control PBS (P<0.01 and P<0.01, respectively). Echistatin also inhibited experimental lung metastasis of 143B-LM4 cells in nude mice. These results suggest that DOX in combination with a disintegrin has potential to treat osteosarcoma and that αvβ3 integrin may be a target for osteosarcoma.

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.

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

Follicular dendritic-cell sarcoma (FDCS) is a rare and recalcitrant disease. In the present study, a patient-derived orthotopic xenograft (PDOX) mouse model of FDCS was established in the biceps muscle of nude mice. The FDCS PDOX was resistant to both doxorubicin (DOX) and NVP-BEZ235, dactolisib (BEZ) an experimental agent which is a dual pan-phosphoinositide 3-kinase-mammalian target of rapamycin inhibitor. However, in contrast to DOX and BEZ, the FDCS PDOX was sensitive to the tumor-targeting bacterial strain, Salmonella typhimurium A1-R (S. typhimurium A1-R). The combination of S. typhimurium A1-R and either DOX or BEZ did not increase the antitumor efficacy of S. typhimurium A1-R, indicating that DOX and BEZ were not active in this PDOX model. The efficacy of S. typhimurium A1-R in this recalcitrant FDCS gives strong impetus to move bacterial therapy to clinical trials for this disease. The findings of the present study are of particular importance since it demonstrates that S. typhimurium A1-R is effective in a PDOX model of FDCS established from a patient who failed DOX therapy.

Efficacy of glycogen synthase kinase-3β targeting against osteosarcoma via activation of β-catenin

Development of innovative more effective therapy is required for refractory osteosarcoma patients. We previously established that glycogen synthase kinase-3β (GSK- 3β) is a therapeutic target in various cancer types. In the present study, we explored the therapeutic efficacy of GSK-3β inhibition against osteosarcoma and the underlying molecular mechanisms in an orthotopic mouse model. Expression and phosphorylation of GSK-3β in osteosarcoma and normal osteoblast cell lines was examined, together with efficacy of GSK-3β inhibition on cell survival, proliferation and apoptosis and on the growth of orthotopically-transplanted human osteosarcoma in nude mice. We also investigated changes in expression, phosphorylation and co-transcriptional activity of β-catenin in osteosarcoma cells following GSK-3β inhibition. Expression of the active form of GSK- 3β (tyrosine 216-phosphorylated) was higher in osteosarcoma than osteoblast cells. Inhibition of GSK-3β activity by pharmacological inhibitors or of its expression by RNA interference suppressed proliferation of osteosarcoma cells and induced apoptosis. Treatment with GSK-3β-specific inhibitors attenuated the growth of orthotopic osteosaroma in mice. Inhibition of GSK-3β reduced phosphorylation at GSK- 3β-phospho-acceptor sites in β-catenin and increased β-catenin expression, nuclear localization and co-transcriptional activity. These results suggest the efficacy of GSK-3β inhibitors is associated with activation of β-catenin, a putative tumor suppressor in bone and soft tissue sarcoma and an important component of osteogenesis. Our study thereby demonstrates a critical role for GSK-3β in sustaining survival and proliferation of osteosarcoma cells, and identifies this kinase as a potential therapeutic target against osteosarcoma.

Nutlin-3, A p53-Mdm2 Antagonist for Nasopharyngeal Carcinoma Treatment

Nasopharyngeal carcinoma (NPC) is a form of head and neck cancer of multifactorial etiolo-gies that is highly prevalent among men in the population of Southern China and Southeast Asia. NPC has claimed many thousands of lives worldwide; but the low awareness of NPC remains a hindrance in early diagnosis and prevention of the disease. NPC is highly responsive to radiotherapy and chemothera-py, but radiocurable NPC is still dependent on concurrent treatment of megavoltage radiotherapy with chemotherapy. Despite a significant reduction in loco-regional and distant metastases, radiotherapy alone has failed to provide a significant improvement in the overall survival rate of NPC, compared to chemo-therapy. In addition, chemo-resistance persists as the major challenge in the management of metastatic NPC although the survival rate of advanced metastatic NPC has significantly improved with the admin-istration of chemotherapy adjunctive to radiotherapy. In this regard, targeted molecular therapy could be explored for the discovery of alternative NPC therapies. Nutlin-3, a small molecule inhibitor that specifi-cally targets p53-Mdm2 interaction offers new therapeutic opportunities by enhancing cancer cell growth arrest and apoptosis through the restoration of the p53-mediated tumor suppression pathway while pro-ducing minimal cytotoxicity and side effects. This review discusses the potential use of Nutlin-3 as a p53-activating drug and the future directions of its clinical research for NPC treatment.

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.

Genetic and metabolic comparison of orthotopic and heterotopic patient-derived pancreatic-cancer xenografts to the original patient tumors

Tumors from 25 patients with pancreatic cancer were used to establish two patient-derived xenograft (PDX) models: orthotopic PDX (PDOX) and heterotopic (subcutaneous) PDX (PDHX). We compared gene expression by immunohistochemistry, single-nucleotide polymorphism (SNP), DNA methylation, and metabolite levels. The 4 cases, of the total of 13 in which simultaneous PDHX & PDOX models were established, were randomly selected. The molecular-genetic characteristics of the patient's tumor were well maintained in the two PDX models. SNP analysis demonstrated that both groups were more than 90% identical to the original patient's tumor, and there was little difference between the two models. DNA methylation of most genes was similar among the two models and the original patients tumor, but some gene sets were hypermethylated the in PDOX model and hypomethylated in the PDHX model. Most of the metabolites had a similar pattern to those of the original patient tumor in both PDX tumor models, but some metabolites were more prominent in the PDOX and PDHX models. This is the first simultaneous molecular-genetic and metabolite comparison of patient tumors and their tumors established in PDOX and PDHX models. The results indicate high fidelity of these critical properties of the patient tumors in the two models.

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.

Intra-tumor L-methionine level highly correlates with tumor size in both pancreatic cancer and melanoma patient-derived orthotopic xenograft (PDOX) nude-mouse models

An excessive requirement for methionine (MET) for growth, termed MET dependence, appears to be a general metabolic defect in cancer. We have previously shown that cancer-cell growth can be selectively arrested by MET restriction such as with recombinant methioninase (rMETase). In the present study, we utilized patient-derived orthotopic xenograft (PDOX) nude mouse models with pancreatic cancer or melanoma to determine the relationship between intra-tumor MET level and tumor size. After the tumors grew to 100 mm³, the PDOX nude mice were divided into two groups: untreated control and treated with rMETase (100 units, i.p., 14 consecutive days). On day 14 from initiation of treatment, intra-tumor MET levels were measured and found to highly correlate with tumor volume, both in the pancreatic cancer PDOX (p<0.0001, R²=0.89016) and melanoma PDOX (p<0.0001, R²=0.88114). Tumors with low concentration of MET were smaller. The present results demonstrates that patient tumors are highly dependent on MET for growth and that rMETase effectively lowers tumor MET.

Recombinant methioninase (rMETase) is an effective therapeutic for BRAF-V600E-negative as well as -positive melanoma in patient-derived orthotopic xenograft (PDOX) mouse models

Melanoma is a recalcitrant disease. Melanoma patients with the BRAF-V600E mutation have been treated with the drug vemurafenib (VEM) which targets this mutation. However, we previously showed that VEM is not very effective against a BRAF-V600E melanoma mutant in a patient-derived orthotopic xenograft (PDOX) model. In contrast, we demonstrated that recombinant methioninase (rMETase) which targets the general metabolic defect in cancer of methionine dependence, was effective against the BRAF-V600E mutant melanoma PDOX model. In the present study, we demonstrate that rMETase is effective against a BRAF-V600E-negative melanoma PDOX which we established. Forty BRAF-V600E-negative melanoma PDOX mouse models were randomized into four groups of 10 mice each: untreated control (n = 10); temozolomide (TEM) (25 mg/kg, p.o., 14 consecutive days, n = 10); rMETase (100 units, i.p., 14 consecutive days, n = 10); TEM + rMETase (TEM: 25 mg/kg, p.o., rMETase: 100 units, i.p., 14 consecutive days, n = 10). All treatments inhibited tumor growth compared to untreated control (TEM: p = 0.0003, rMETase: p = 0.0006, TEM/rMETase: p = 0.0002) on day 14 after initiation. Combination therapy of TEM and rMETase was significantly more effective than either mono-therapy (TEM: p = 0.0113, rMETase: p = 0.0173). The present study shows that TEM combined with rMETase is effective for BRAF-V600E-negative melanoma PDOX similar to the BRAF-V600E-positive mutation melanoma. These results suggest rMETase in combination with first-line chemotherapy can be highly effective in both BRAF-V600E-negative as well as BRAF-V600E-positive melanoma and has clinical potential for this recalcitrant disease.

Cooperation of Nutlin-3a and a Wip1 inhibitor to induce p53 activity

Targeting the Mdm2 oncoprotein by drugs has the potential of re-establishing p53 function and tumor suppression. However, Mdm2-antagonizing drug candidates, e. g. Nutlin-3a, often fail to abolish cancer cell growth sustainably. To overcome these limitations, we inhibited Mdm2 and simultaneously a second negative regulator of p53, the phosphatase Wip1/PPM1D. When combining Nutlin-3a with the Wip1 inhibitor GSK2830371 in the treatment of p53-proficient but not p53-deficient cells, we observed enhanced phosphorylation (Ser 15) and acetylation (Lys 382) of p53, increased expression of p53 target gene products, and synergistic inhibition of cell proliferation. Surprisingly, when testing the two compounds individually, largely distinct sets of genes were induced, as revealed by deep sequencing analysis of RNA. In contrast, the combination of both drugs led to an expression signature that largely comprised that of Nutlin-3a alone. Moreover, the combination of drugs, or the combination of Nutlin-3a with Wip1-depletion by siRNA, activated p53-responsive genes to a greater extent than either of the compounds alone. Simultaneous inhibition of Mdm2 and Wip1 enhanced cell senescence and G2/M accumulation. Taken together, the inhibition of Wip1 might fortify p53-mediated tumor suppression by Mdm2 antagonists.

Targeting of Chk2 as a countermeasure to dose-limiting toxicity triggered by topoisomerase-II (TOP2) poisons

The DNA damage response (DDR) gene cell cycle checkpoint kinase 2 (Chk2) triggers programmed cell death and lethal radiation-induced toxicity in mice in vivo. However, it is not well established to what extent targeting of Chk2 may protect from dose-limiting toxicities (DLT) inflicted by mainstay cancer chemotherapy. We screened different classes of chemotherapy in wild type and Chk2-deficient cells. Here we show that loss of Chk2 protect from cell death in vitro and lethal toxicity in vivo following treatment with topoisomerase II (TOP2)–inhibitors whereas no such protection was observed following treatment with topoisomerase I (TOP1) inhibitors. Furthermore, through combined in silico and functional screens of the Diversity Set II (NCI/NTP) chemical library we identified the carbanilide-derivative NSC105171, also known as ptu-23, as a novel Chk2 inhibitor (Chk2i). Indeed, NSC105171 can be administered safely to mice to countermeasure etoposide-induced toxicity. Incorporation of Chk2i into chemotherapy protocols employing TOP2-inhibitors may be an effective strategy to prevent DLT's without interfering with treatment.

TFEB ameliorates the impairment of the autophagy-lysosome pathway in neurons induced by doxorubicin

Doxorubicin, a commonly used chemotherapy agent, induces severe cardio- and neurotoxicity. Molecular mechanisms of cardiotoxicity have been extensively studied, but mechanisms by which doxorubicin exhibits its neurotoxic properties remain unclear. Here, we show that doxorubicin impairs neuronal autophagy, leading to the accumulation of an autophagy substrate p62. Neurons treated with doxorubicin contained autophagosomes, damaged mitochondria, and lipid droplets. The brains from mice treated with pegylated liposomal doxorubicin exhibited autophagosomes, often with mitochondria, lipofuscin, and lipid droplets. Interestingly, lysosomes were less acidic in doxorubicin-treated neurons. Overexpression of the transcription factor EB (TFEB), which controls the autophagy-lysosome axis, increased survival of doxorubicin-treated neurons. 2-Hydroxypropyl-β-cyclodextrin (HPβCD), an activator of TFEB, also promoted neuronal survival, decreased the levels of p62, and lowered the pH in lysosomes. Taken together, substantial changes induced by doxorubicin contribute to neurotoxicity, cognitive disturbances in cancer patients and survivors, and accelerated brain aging. The TFEB pathway might be a new approach for mitigating damage of neuronal autophagy caused by doxorubicin.

Towards natural mimetics of metformin and rapamycin

Aging is now at the forefront of major challenges faced globally, creating an immediate need for safe, widescale interventions to reduce the burden of chronic disease and extend human healthspan. Metformin and rapamycin are two FDA-approved mTOR inhibitors proposed for this purpose, exhibiting significant anti-cancer and anti-aging properties beyond their current clinical applications. However, each faces issues with approval for off-label, prophylactic use due to adverse effects. Here, we initiate an effort to identify nutraceuticals-safer, naturally-occurring compounds-that mimic the anti-aging effects of metformin and rapamycin without adverse effects. We applied several bioinformatic approaches and deep learning methods to the Library of Integrated Network-based Cellular Signatures (LINCS) dataset to map the gene- and pathway-level signatures of metformin and rapamycin and screen for matches among over 800 natural compounds. We then predicted the safety of each compound with an ensemble of deep neural network classifiers. The analysis revealed many novel candidate metformin and rapamycin mimetics, including allantoin and ginsenoside (metformin), epigallocatechin gallate and isoliquiritigenin (rapamycin), and withaferin A (both). Four relatively unexplored compounds also scored well with rapamycin. This work revealed promising candidates for future experimental validation while demonstrating the applications of powerful screening methods for this and similar endeavors.

The influence of ketogenic therapy on the 5 R's of radiobiology

PURPOSE

Radiotherapy (RT) is a mainstay in the treatment of solid tumors and works by inducing free radical stress in tumor cells, leading to loss of reproductive integrity. The optimal treatment strategy has to consider damage to both tumor and normal cells and is determined by five factors known as the 5 R's of radiobiology: Reoxygenation, DNA repair, radiosensitivity, redistribution in the cell cycle and repopulation. The aim of this review is (i) to present evidence that these 5 R's are strongly influenced by cellular and whole-body metabolism that in turn can be modified through ketogenic therapy in form of ketogenic diets and short-term fasting and (ii) to stimulate new research into this field including some research questions deserving further study.

CONCLUSIONS

Preclinical and some preliminary clinical data support the hypothesis that ketogenic therapy could be utilized as a complementary treatment in order to improve the outcome after RT, both in terms of higher tumor control and in terms of lower normal tissue complication probability. The first effect relates to the metabolic shift from glycolysis toward mitochondrial metabolism that selectively increases ROS production and impairs ATP production in tumor cells. The second effect is based on the differential stress resistance phenomenon, which is achieved when glucose and growth factors are reduced and ketone bodies are elevated, reprogramming normal but not tumor cells from proliferation toward maintenance and stress resistance. Underlying both effects are metabolic differences between normal and tumor cells that ketogenic therapy seeks to exploit. Specifically, the recently discovered role of the ketone body β-hydroxybutyrate as an endogenous class-I histone deacetylase inhibitor suggests a dual role as a radioprotector of normal cells and a radiosensitzer of tumor cells that opens up exciting possibilities to employ ketogenic therapy as a cost-effective adjunct to radiotherapy against cancer.

High-efficacy targeting of colon-cancer liver metastasis with Salmonella typhimurium A1-R via intra-portal-vein injection in orthotopic nude-mouse models

Liver metastasis is the main cause of colon cancer-related death and is a recalcitrant disease. We report here the efficacy and safety of intra-portal-vein (iPV) targeting of Salmonella typhimurium A1-R on colon cancer liver metastasis in a nude-mouse orthotopic model. Nude mice with HT29 human colon cancer cells, expressing red fluorescent protein (RFP) (HT29-RFP), growing in the liver were administered S. typhimurium A1-R by either iPV (1×10⁴ colony forming units (CFU)/100 μl) or, for comparison, intra-venous injection (iv; 5×10⁷ CFU/100 μl). Similar amounts of bacteria were delivered to the liver with the two doses, indicating that iPV delivery is 5×10³ times more efficient than iv delivery. Treatment efficacy was evaluated by tumor fluorescent area (mm²) and total fluorescence intensity. Tumor fluorescent area and fluorescence intensity highly correlated (p<0.0001). iPV treatment was more effective compared to both untreated control and iv treatment (p<0.01 and p<0.05, respectively with iPV treatment with S. typhimurium arresting metastatic growth). There were no significant differences in body weight between all groups. The results of this study suggest that S. typhimurium A1-R administered iPV has potential for peri-operative adjuvant treatment of colon cancer liver metastasis.

The combination of temozolomide-irinotecan regresses a doxorubicin-resistant patient-derived orthotopic xenograft (PDOX) nude-mouse model of recurrent Ewing's sarcoma with a FUS-ERG fusion and CDKN2A deletion: Direction for third-line patient therapy

The aim of the present study was to determine the usefulness of a patient-derived orthotopic xenograft (PDOX) nude-mouse model of a doxorubicin-resistant metastatic Ewing’s sarcoma, with a unique combination of a FUS-ERG fusion and CDKN2A deletion, to identify effective drugs for third-line chemotherapy of the patient. Our previous study showed that cyclin-dependent kinase 4/6 (CDK4/6) and insulin-like growth factor-1 receptor (IGF-1R) inhibitors were effective on the Ewing’s sarcoma PDOX, but not doxorubicin, similar to the patient’s resistance to doxorubicin. The results of the previous PDOX study were successfully used for second-line therapy of the patiend. In the present study, the PDOX mice established with the Ewing’s sarcoma in the right chest wall were randomized into 5 groups when the tumor volume reached 60 mm³: untreated control; gemcitabine combined with docetaxel (intraperitoneal [i.p.] injection, weekly, for 2 weeks); irinotecan combined with temozolomide (irinotecan: i.p. injection; temozolomide: oral administration, daily, for 2 weeks); pazopanib (oral administration, daily, for 2 weeks); yondelis (intravenous injection, weekly, for 2 weeks). All mice were sacrificed on day 15. Body weight and tumor volume were assessed 2 times per week. Tumor weight was measured after sacrifice. Irinotecan combined with temozolomide was the most effective regimen compared to the untreated control group (p=0.022). Gemcitabine combined with docetaxel was also effective (p=0.026). Pazopanib and yondelis did not have significant efficacy compared to the untreated control (p=0.130, p=0.818). These results could be obtained within two months after the physician’s request and were used for third-line therapy of the patient.

Combination treatment with recombinant methioninase enables temozolomide to arrest a BRAF V600E melanoma in a patient-derived orthotopic xenograft (PDOX) mouse model

An excessive requirement for methionine termed methionine dependence, appears to be a general metabolic defect in cancer. We have previously shown that cancer-cell growth can be selectively arrested by methionine deprivation such as with recombinant methioninase (rMETase). The present study used a previously-established patient-derived orthotopic xenograft (PDOX) nude mouse model of BRAF V600E-mutant melanoma to determine the efficacy of rMETase in combination with a first-line melanoma drug, temozolomide (TEM). In the present study 40 melanoma PDOX mouse models were randomized into four groups of 10 mice each: untreated control (n=10); TEM (25 mg/kg, oral 14 consecutive days, n=10); rMETase (100 units, intraperitoneal 14 consecutive days, n=10); combination TEM + rMETase (TEM: 25 mg/kg, oral rMETase: 100 units, intraperitoneal 14 consecutive days, n=10). All treatments inhibited tumor growth compared to untreated control (TEM: p=0.0081, rMETase: p=0.0037, TEM-rMETase: p=0.0024) on day 14 after initiation. However, the combination therapy of TEM and rMETase was significantly more efficacious than either mono-therapy (TEM: p=0.0051, rMETase: p=0.0051). The present study is the first demonstrating the efficacy of rMETase combination therapy in a PDOX model, suggesting potential clinical development, especially in recalcitrant cancers such as melanoma, where rMETase may enhance first-line therapy.

A patient-derived orthotopic xenograft (PDOX) mouse model of a cisplatinum-resistant osteosarcoma lung metastasis that was sensitive to temozolomide and trabectedin: implications for precision oncology

In the present study, we evaluated the efficacy of trabectedin (TRAB) and temozolomide (TEM) compared to cisplatinum (CDDP) on a patient-derived orthotopic xenogrraft (PDOX) of a lung-metastasis from an osteosarcoma of a patient who failed CDDP therapy. Osteosarcoma resected from the patient was implanted orthotopically in the distal femur of mice to establish PDOX models which were randomized into the following groups when tumor volume reached approximately 100 mm³: G1, control without treatment; G2, CDDP (6 mg/kg, intraperitoneal injection, weekly, for 2 weeks); G3, TRAB (0.15 mg/kg, intravenous injection, weekly, for 2 weeks); G4, TEM (25 mg/kg, oral, daily, for 14 days). Tumor size and body weight were measured with calipers and a digital balance, respectively, twice a week. On day 14 after initiation of treatment, TEM and TRAB, but not CDDP, significantly inhibited tumor volume compared to untreated control: control (G1): 814.5±258.8 mm³; CDDP (G2): 608.6±126.9 mm³; TRAB (G3): 286.6±133.0 mm³; TEM (G4): 182.9±69.1 mm³. CDDP vs. control, p=0.07; TRAB vs. control, p=0.0004; TEM vs. control p =0.0002; TRAB vs. CDDP, p =0.0002; TEM vs. CDDP, p =0.00003. The results of the present study show that a PDOX model of an osteosarcoma lung-metastasis that recurred after adjuvant CDDP-treatment has identified potentially, highly-effective drugs for this recalcitrant disease, while accurately maintaining the CDDP resistance of the tumor in the patient, thereby demonstrating the potential of the osteosarcoma PDOX model for precision oncology.

A novel anionic-phosphate-platinum complex effectively targets an undifferentiated pleomorphic sarcoma better than cisplatinum and doxorubicin in a patient-derived orthotopic xenograft (PDOX)

A patient high-grade undifferentiated pleomorphic soft-tissue sarcoma (UPS) from a striated muscle was previously orthotopically implanted in the right biceps femoris muscle of nude mice to establish a patient-derived orthotopic xenograft (PDOX) nude-mouse model. In the present study, two weeks after orthotopic transplantation of the UPS, mice were treated intraperitoneally with cisplatinum (CDDP), doxorubicin (DOX) or a novel anionic-phosphate-platinum compound 3Pt. Treatments were repeated weekly for a total of 3 times. Six weeks after transplantation, all mice were sacrificed and evaluated. After two weeks treatment, tumor sizes were as follows: control (G1): 2208.3 mm³; CDDP (G2): 841.8±3 mm³, p=0.0001; DOX (G3): 693.1±3 mm³, p=6.56E-7; 3Pt (G4): 333.7±1 mm³, p=4.8E-8. 3Pt showed significantly more efficacy compared to other therapy drugs tested: CDDP (p=0.0002), DOX (p=0.001). There were no animal deaths in any of the four groups. The present results suggest 3Pt is a promising new candidate for UPS since it was demonstrated to be effective in a PDOX model.

Locally-applied 5-fluorouracil-loaded slow-release patch prevents pancreatic cancer growth in an orthotopic mouse model

To obtain improved efficacy against pancreatic cancer, we investigated the efficacy and safety of a locally-applied 5-fluorouracil (5-FU)-loaded polymeric patch on pancreatic tumors in an orthotopic nude-mouse model. The 5-FU-releasing polymeric patch was produced by 3D printing. After application of the patch, it released the drug slowly for 4 weeks, and suppressed BxPC-3 pancreas cancer growth. Luciferase imaging of BxPC3-Luc cells implanted in the pancreas was performed longitudinally. The drug patch delivered a 30.2 times higher level of 5-FU than an intra-peritoneal (i.p.) bolus injection on day-1. High 5-FU levels were accumulated within one week by the patch. Four groups were compared for efficacy of 5-FU. Drug-free patch as a negative control (Group I); 30% 5-FU-loaded patch (4.8 mg) (Group II); 5-FU i.p. once (4.8 mg) (Group III); 5-FU i.p. once a week (1.2 mg), three times (Group IV). The tumor growth rate was significantly faster in Group I than Group II, III, IV (p=0.047 at day-8, p=0.022 at day-12, p=0.002 at day-18 and p=0.034 at day-21). All mice in Group III died of drug toxicity within two weeks after injection. Group II showed more effective suppression of tumor growth than Group IV (p=0.018 at day-12 and p=0.017 at day-21). Histological analysis showed extensive apoptosis in the TUNEL assay and by Ki -67 staining. Western blotting confirmed strong expression of cleaved caspase-3 in Group II. No significant changes were found hematologically and histologically in the liver, kidney and spleen in Groups I, II, IV but were found in Group III.

Salmonella typhimurium A1-R targeting of a chemotherapy-resistant BRAF-V600E melanoma in a patient-derived orthotopic xenograft (PDOX) model is enhanced in combination with either vemurafenib or temozolomide

A metastatic melanoma obtained from the right chest wall of a patient was previously established orthotopically in the right chest wall of nude mice as a patient-derived orthotopic xenograft (PDOX) model. We previously showed that the combination of tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) and chemotherapy was highly effective against the melanoma PDOX. In the present study, we investigated the mechanism of the high efficacy of this combination. Two weeks after implantation, 40 PDOX mouse models were randomized into 4 groups of 10 mice each: untreated control (n = 10); treated with S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks, n = 10); treated with temozolomide (TEM) (25 mg/kg, p.o. for 14 consecutive days) combined with S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks, n = 10); treated with vemurafenib (VEM) (30 mg/kg, p.o., for 14 consecutive days) combined with S. typhimurium A1-R (5 × 10⁷ CFU/100 μl, i.v., once a week for 2 weeks) (n = 10). On day 14 from initiation, all treatments significantly inhibited tumor growth compared with untreated control (S. typhimurium A1-R: p < 0.01; TEM combined with S. typhimurium A1-R: p < 0.01; VEM combined with S. typhimurium A1-R: p < 0.01). Combination therapy with S. typhimurium A1-R was significantly more effective on tumor growth than S. typhimurium A1-R alone (with TEM: p < 0.01; with VEM: p < 0.01). Combination therapy significantly increased S. typhimurium A1-R tumor targeting alone (S. typhimurium A1-R + TEM: p < 0.01, S. typhimurium A1-R + VEM: p < 0.01), relative to S. typhimurium A1-R alone, respectively. In conclusion, chemotherapy drugs promoted targeting of S. typhimurium A1-R of melanoma, thereby enhancing efficacy against the melanoma PDOX.

Combination of gemcitabine and docetaxel regresses both gastric leiomyosarcoma proliferation and invasion in an imageable patient-derived orthotopic xenograft (iPDOX) model

Gastric leiomyosarcoma is a recalcitrant cancer and the chemotherapy strategy is controversial. The present study used a patient-derived orthotopic xenograft (PDOX) nude mouse model of gastric leiomyosarcoma to identify an effective therapeutic regimen to develop individualized precision medicine for this disease. The gastric leiomyosarcoma obtained from a patient was first grown in transgenic nude mice ubiquitously expressing red fluorescent protein (RFP) to stably label the tumor stroma. The RFP-expressing tumor was then passaged orthotopically in the gastric wall of non-transgenic nude mice to establish an imageable PDOX (iPDOX) model. The bright fluorescent tumor was readily imaged over time to determine drug efficacy. Four weeks after implantation, 70 PDOX nude mice were divided into 7 groups: control without treatment (n = 10); doxorubicin (DOX) (2.4 mg/kg, intraperitoneally (i.p.), once a week for 2 weeks, n = 10); gemcitabine (GEM)/ docetaxel (DOC) (GEM: 100 mg/kg, DOC: 20 mg/kg, i.p., once a week for 2 weeks, n = 10); cyclophosphamide (CPA) (140 mg/kg, i.p., once a week for 2 weeks, n = 10); temozolomide (TEM) (25 mg/kg, orally, daily for 14 consecutive days, n = 10); yondelis (YON) (0.15 mg/kg, i.v., once a week for 2 weeks, n = 10); pazopanib (PAZ) (100 mg/kg, orally, daily for 14 consecutive days, n = 10). On day 14 from initiation of treatment, all treatments except PAZ significantly inhibited tumor growth compared with untreated control (DOX: p < 0.01, GEM/DOC: p < 0.01, CPA: p < 0.01, TEM: p < 0.01, YON: p < 0.01) on day 14 after initiation. In addition, only GEM/DOC was more significantly effective than DOX (p < 0.05). GEM/DOC could regress the leimyosarcoma in the PDOX model and has important clinical potential for precision individual treatment of leiomyosarcoma patients.

Color-coded intravital imaging demonstrates a transforming growth factor-β (TGF-β) antagonist selectively targets stromal cells in a human pancreatic-cancer orthotopic mouse model

Pancreatic cancer is a recalcitrant malignancy, partly due to desmoplastic stroma which stimulates tumor growth, invasion, and metastasis, and inhibits chemotherapeutic drug delivery. Transforming growth factor-β (TGF-β) has an important role in the formation of stromal desmoplasia. The present study describes the ability of color-coded intravital imaging to demonstrate the efficacy of a TGF-β inhibitor to target stroma in an orthotopic mouse model of pancreatic cancer. The BxPC-3 human pancreatic adenocarcinoma cell line expressing green fluorescent protein (GFP), which also has a high TGF-β expression level, was used in an orthotopic model in transgenic nude mice ubiquitously expressing red fluorescent protein (RFP). Fourteen mice were randomized into a control group (n = 7, vehicle, i.p., weekly, for 3 weeks) and a treated group (n = 7, SB431542 [TGF-β receptor type I inhibitor] 0.3 mg, i.p., weekly, for 3 weeks). Stromal cells expressing RFP and cancer cells expressing GFP were observed weekly for 3 weeks by real-time color-coded intravital imaging. The RFP fluorescence area from the stromal cells, relative to the GFP fluorescence area of the cancer cells, was significantly decreased in the TGF-β-inhibitor-treatment group compared to the control group. The present study demonstrated color-coded imaging in an orthotopic pancreatic-cancer cell-line mouse model can readily detect the selective anti-stromal-cell targeting of a TGF-β inhibitor.