Radiosensitization of Meth-A fibrosarcoma in mice by Lonidamine

Lonidamine Induced Selective Acidification and De-Energization of Prostate Cancer Xenografts: Enhanced Tumor Response to Radiation Therapy

Prostate cancer is a multi-focal disease that can be treated using surgery, radiation, androgen deprivation, and chemotherapy, depending on its presentation. Standard dose-escalated radiation therapy (RT) in the range of 70-80 Gray (GY) is a standard treatment option for prostate cancer. It could be used at different phases of the disease (e.g., as the only primary treatment when the cancer is confined to the prostate gland, combined with other therapies, or as an adjuvant treatment after surgery). Unfortunately, RT for prostate cancer is associated with gastro-intestinal and genitourinary toxicity. We have previously reported that the metabolic modulator lonidamine (LND) produces cancer sensitization through tumor acidification and de-energization in diverse neoplasms. We hypothesized that LND could allow lower RT doses by producing the same effect in prostate cancer, thus reducing the detrimental side effects associated with RT. Using the Seahorse XFe96 and YSI 2300 Stat Plus analyzers, we corroborated the expected LND-induced intracellular acidification and de-energization of isolated human prostate cancer cells using the PC3 cell line. These results were substantiated by non-invasive 31P magnetic resonance spectroscopy (MRS), studying PC3 prostate cancer xenografts treated with LND (100 mg/kg, i.p.). In addition, we found that LND significantly increased tumor lactate levels in the xenografts using 1H MRS non-invasively. Subsequently, LND was combined with radiation therapy in a growth delay experiment, where we found that 150 µM LND followed by 4 GY RT produced a significant growth delay in PC3 prostate cancer xenografts, compared to either control, LND, or RT alone. We conclude that the metabolic modulator LND radio-sensitizes experimental prostate cancer models, allowing the use of lower radiation doses and diminishing the potential side effects of RT. These results suggest the possible clinical translation of LND as a radio-sensitizer in patients with prostate cancer.

pH-dependent structural characteristics of lonidamine: 1H and 13C NMR study

Lonidamine (LND) is an anti-cancer drug with great potential as a metabolic modulator of chemotherapy, radiotherapy, hyperthermia, and photodynamic therapy in cancer treatment. LND affects several important aspects of cancer cell metabolism: it inhibits Complex I and II of the electron transport chain (ETC) and pyruvate carriers (mitochondrial), and monocarboxylate transporters in the plasma membrane of the cell. Cancer cells are affected by changes in pH on the molecular level, and so are the drugs used to treat cancer, thus it is important to understand how pH affects their structures and LND is no exception. LND dissolves at a pH of 8.3 in tris-glycine buffer but has limited solubility at pH 7. To understand how pH affects the structure of LND, and its effect as a metabolic modulator on cancer therapy, we made up samples of LND at pH 2, pH 7, and pH 13, and analyzed these samples using ¹H and ¹³C NMR. We looked for ionization sites to explain the behavior of LND in solution. Our results showed considerable chemical shifts between the extremes of our experimental pH range. LND was ionized at its indazole α-nitrogen, however, we did not directly observe the protonation of the carboxyl group oxygen that is expected at pH 2, which may be the result of a chemical-exchange phenomenon.

Tumoral Oxygenation and Biodistribution of Lonidamine Oxygen Microbubbles Following Localized Ultrasound-Triggered Delivery

Prior work has shown that microbubble-assisted delivery of oxygen improves tumor oxygenation and radiosensitivity, albeit over a limited duration. Lonidamine (LND) has been investigated because of its ability to stimulate glycolysis, lactate production, inhibit mitochondrial respiration, and inhibit oxygen consumption rates in tumors but suffers from poor bioavailability. The goal of this work was to characterize LND-loaded oxygen microbubbles and assess their ability to oxygenate a human head and neck squamous cell carcinoma (HNSCC) tumor model, while also assessing LND biodistribution. In tumors treated with surfactant-shelled microbubbles with oxygen core (SE61O₂) and ultrasound, pO₂ levels increased to a peak 19.5±9.7 mmHg, 50 seconds after injection and returning to baseline after 120 seconds. In comparison, in tumors treated with SE61O₂/LND and ultrasound, pO₂ levels showed a peak increase of 29.0±8.3 mmHg, which was achieved 70 seconds after injection returning to baseline after 300 seconds (p<0.001). The co-delivery of O₂andLNDvia SE61 also showed an improvement of LND biodistribution in both plasma and tumor tissues (p<0.001). In summary, ultrasound-sensitive microbubbles loaded with O₂ and LND provided prolonged oxygenation relative to oxygenated microbubbles alone, as well as provided an ability to locally deliver LND, making them more appropriate for clinical translation.

Effect of Differences in Metabolic Activity of Melanoma Models on Response to Lonidamine plus Doxorubicin

Lonidamine (LND), a metabolic modulator, sensitizes DB-1 human melanoma to doxorubicin (DOX) chemotherapy by acidifying and de-energizing the tumor. This report compares the effects of LND on two human melanoma lines, DB-1 and WM983B, which exhibit different metabolic properties. Using liquid chromatography mass spectrometry and Seahorse analysis, we show that DB-1 was more glycolytic than WM983B in vitro. ³¹P magnetic resonance spectroscopy (MRS) indicates that LND (100 mg/kg, i.p.) induces similar selective acidification and de-energization of WM983B xenografts in immunosuppressed mice. Over three hours, intracellular pH (pHi) of WM983B decreased from 6.91 ± 0.03 to 6.59 ± 0.10 (p = 0.03), whereas extracellular pH (pHe) of this tumor changed from 7.03 ± 0.05 to 6.89 ± 0.06 (p = 0.19). A decline in bioenergetics (β-NTP/Pi) of 55 ± 5.0% (p = 0.03) accompanied the decline in pHi of WM983B. Using ¹H MRS with a selective multiquantum pulse sequence and Hadamard localization, we show that LND induced a significant increase in tumor lactate levels (p < 0.01). LND pre-treatment followed by DOX (10 mg/kg, i.v.) produced a growth delay of 13.7 days in WM983B (p < 0.01 versus control), a growth delay significantly smaller than the 25.4 days that occurred with DB-1 (p = 0.03 versus WM983B). Differences in relative levels of glycolysis may produce differential therapeutic responses of DB-1 and WM983B melanomas.

Lonidamine in Advanced Colorectal Cancer: A Phase II Study of the Italian Oncology Group for Clinical Research (Goirc)

Twenty-one patients with metastatic colorectal adenocarcinoma, all previously treated with chemotherapy for metastatic disease, were treated with lonidamine (LDN). The major toxicity encountered was muscular (myalgias in 48%) and gastrointestinal (nausea and/or vomiting in 52%). Other toxicities included abdominal pain, somnolence, fever, arthralgia and ototoxicity. In the 14 patients evaluable for response we observed no complete or partial remission, 8 stable disease and 6 progressive disease. LND has no clinically worthwhile activity against colorectal carcinoma refractory to conventional chemotherapy.

Lonidamine in Non-Small-Cell Lung Cancer: A Phase II Study

The activity of lonidamine (a derivative of indazole-carboxylic acid and a new drug with a characteristic antitumor activity) was evaluated In non-small-cell lung cancer (NSCLC). Twenty-five patients with NSCLC with or without prior treatment received lonidamine at the dose of 450 mg/daily p.o. up to progression. Objective responses obtained were: 3 (12%) partial responses and 3 (12%) minor responses with a mean duration of 13.7 weeks for partial responses. Mean duration of treatment was 20 weeks (range 4-97+). During to the drug's characteristics, bone marrow toxicity was not observed; myalgia and mild testicular pain were the most significant side effects.

Mechanism of antineoplastic activity of lonidamine

Lonidamine (LND) was initially introduced as an antispermatogenic agent. It was later found to have anticancer activity sensitizing tumors to chemo-, radio-, and photodynamic-therapy and hyperthermia. Although the mechanism of action remained unclear, LND treatment has been known to target metabolic pathways in cancer cells. It has been reported to alter the bioenergetics of tumor cells by inhibiting glycolysis and mitochondrial respiration, while indirect evidence suggested that it also inhibited l-lactic acid efflux from cells mediated by members of the proton-linked monocarboxylate transporter (MCT) family and also pyruvate uptake into the mitochondria by the mitochondrial pyruvate carrier (MPC). Recent studies have demonstrated that LND potently inhibits MPC activity in isolated rat liver mitochondria (K_i 2.5μM) and cooperatively inhibits l-lactate transport by MCT1, MCT2 and MCT4 expressed in Xenopus laevis oocytes with K_0.5 and Hill coefficient values of 36-40μM and 1.65-1.85, respectively. In rat heart mitochondria LND inhibited the MPC with similar potency and uncoupled oxidation of pyruvate was inhibited more effectively (IC₅₀~7μM) than other substrates including glutamate (IC₅₀~20μM). LND inhibits the succinate-ubiquinone reductase activity of respiratory Complex II without fully blocking succinate dehydrogenase activity. LND also induces cellular reactive oxygen species through Complex II and has been reported to promote cell death by suppression of the pentose phosphate pathway, which resulted in inhibition of NADPH and glutathione generation. We conclude that MPC inhibition is the most sensitive anti-tumour target for LND, with additional inhibitory effects on MCT-mediated l-lactic acid efflux, Complex II and glutamine/glutamate oxidation.

The anti-tumour agent lonidamine is a potent inhibitor of the mitochondrial pyruvate carrier and plasma membrane monocarboxylate transporters

Lonidamine (LND) is an anti-tumour drug particularly effective at selectively sensitizing tumours to chemotherapy, hyperthermia and radiotherapy, although its precise mode of action remains unclear. It has been reported to perturb the bioenergetics of cells by inhibiting glycolysis and mitochondrial respiration, whereas indirect evidence suggests it may also inhibit L-lactic acid efflux from cells mediated by members of the proton-linked monocarboxylate transporter (MCT) family and also pyruvate uptake into the mitochondria by the mitochondrial pyruvate carrier (MPC). In the present study, we test these possibilities directly. We demonstrate that LND potently inhibits MPC activity in isolated rat liver mitochondria (Ki2.5 μM) and co-operatively inhibits L-lactate transport by MCT1, MCT2 and MCT4 expressed in Xenopus laevisoocytes with K0.5 and Hill coefficient values of 36-40 μM and 1.65-1.85 respectively. In rat heart mitochondria LND inhibited the MPC with similar potency and uncoupled oxidation of pyruvate was inhibited more effectively (IC50~ 7 μM) than other substrates including glutamate (IC50~ 20 μM). In isolated DB-1 melanoma cells 1-10 μM LND increased L-lactate output, consistent with MPC inhibition, but higher concentrations (150 μM) decreased L-lactate output whereas increasing intracellular [L-lactate] > 5-fold, consistent with MCT inhibition. We conclude that MPC inhibition is the most sensitive anti-tumour target for LND, with additional inhibitory effects on MCT-mediated L-lactic acid efflux and glutamine/glutamate oxidation. Together these actions can account for published data on the selective tumour effects of LND onL-lactate, intracellular pH (pHi) and ATP levels that can be partially mimicked by the established MPC and MCT inhibitor α-cyano-4-hydroxycinnamate (CHC).

Lonidamine induces intracellular tumor acidification and ATP depletion in breast, prostate and ovarian cancer xenografts and potentiates response to doxorubicin

We demonstrate that the effects of lonidamine (LND, 100 mg/kg, i.p.) are similar for a number of xenograft models of human cancer including DB-1 melanoma and HCC1806 breast, BT-474 breast, LNCaP prostate and A2870 ovarian carcinomas. Following treatment with LND, each of these tumors exhibits a rapid decrease in intracellular pH, a small decrease in extracellular pH, a concomitant monotonic decrease in nucleoside triphosphate and an increase in inorganic phosphate over a 2-3 h period. We have previously demonstrated that selective intracellular tumor acidification potentiates response of this melanoma model to melphalan (7.5 mg/kg, i.v.), producing an estimated 89% cell kill based on tumor growth delay analysis. We now show that, in both DB-1 melanoma and HCC1806 breast carcinoma, LND potentiates response to doxorubicin, producing 95% cell kill in DB-1 melanoma at 7.5 mg/kg, i.v. doxorubicin and 98% cell kill at 10.0 mg/kg doxorubicin, and producing a 95% cell kill in HCC1806 breast carcinoma at 12.0 mg/kg doxorubicin. Potentiation of doxorubicin may result from cation trapping of the weakly basic anthracycline. Recent experience with the clinical treatment of melanoma and other forms of human cancer suggests that these diseases will probably not be cured by a single therapeutic procedure other than surgery. A multimodality therapeutic approach will be required. As a potent modulator of tumor response to N-mustards and anthracyclines as well as tumor thermo- and radiosensitivity, LND promises to play an important clinical role in the management and possible complete local control of a number of prevalent forms of human cancer.

Effect of acyclovir on the radiation-induced micronuclei and cell death

Treatment of HeLa cells with 0.1 microM Acyclovir [9-(2-hydroxyethoxymethyl)guanine] (ACV) before exposure to 0, 0.25, 0.5, 1, 2 and 3 Gy of gamma-radiation resulted in a dose-dependent decline in the growth kinetics and cell proliferation indices at 20, 30 and 40 h post-irradiation when compared with the PBS+irradiation group. These results were reflected in the cell survival, which declined in a dose-dependent manner and the surviving fraction of cells was significantly lower in ACV+irradiation group than that of PBS+irradiation group. The effect of ACV+1 Gy irradiation was almost similar to PBS+3 Gy irradiation suggesting an enhancement of the radiation effect by ACV pretreatment. The frequency of micronuclei increased in a dose-dependent manner at all the post-irradiation time periods in both PBS+irradiation and ACV+irradiation group and it was significantly elevated in the latter when compared with the former group. The dose-response for both groups was linear. The surviving fraction of HeLa cells declined with the increasing MN frequency and a close linear quadratic correlation between cell survival and micronuclei-induction was observed.

Potential complications associated with normothermic lonidamine infusion and with systemic acidosis in dogs receiving lonidamine during whole body hyperthermia (WBH)

The vascular toxicosis of lonidamine (40 mg/h) or vehicle infusion was investigated in six dogs. Vasculitis and thrombosis were observed in veins infused with lonidamine but not in veins infused with vehicle. This finding suggests that it may not be possible to use lonidamine infusion to circumvent therapeutic limitations associated with the oral lonidamine formulation currently used in patients. We also investigated the systemic toxicosis of lonidamine (400 mg/m2; rapid intravenous bolus) or vehicle in six other dogs that developed systemic acidosis (pH < or = 7.0) during whole body hyperthermia (42 degrees C x 90 min). Gross and histologic haemorrhage was observed in all dogs; however, haemorrhagic lesions in acidotic dogs receiving lonidamine + WBH were more severe than changes observed in acidotic dogs receiving vehicle + WBH. These observations confirm the results of in vitro studies which suggest that the combined effect of lonidamine and hyperthermia is enhanced under acidic conditions. Furthermore, these findings indicate that acid-base status of patients receiving lonidamine during WBH must be monitored carefully to avoid serious complications.

Mechanism of action of lonidamine in the 9L brain tumor model involves inhibition of lactate efflux and intracellular acidification

Malignant gliomas have been associated with a high rate of glycolytic activity which is believed necessary to sustain cellular function and integrity. Since lonidamine (LND) is believed to reduce tumor glucose utilization by inhibition of the mitochondrially-bound glycolytic enzyme hexokinase (HK), 31P magnetic resonance spectroscopy (MRS) was used to noninvasively follow the effects of LND on both tumor pH and the high-energy phosphate metabolites: ATP, phosphocreatine (PCr) and inorganic phosphate (Pi) in subcutaneous rat 9L gliosarcomas. 31P tumor spectra acquired in 5 min intervals pre- and post LND administration of 50 and 100 mg/kg, i.p. revealed an acidotic pH shift of -0.25 and -0.45 pH units, respectively within 30 min post administration. The ATP/Pi ratio of 9L tumors decreased to 40% of control and Pi levels increased to 280% of control over a 3 hr period. LND exerted no effect on tumor blood flow and mean arterial blood pressure. Brain and muscle metabolite levels and pH were also unaffected by LND. In vitro measurements of cultured 9L tumor cell intra- and extracellular lactate, pentose phosphate pathway (PPP) and hexokinase (HK) activities suggest that the mode of action of LND involves inhibition of lactate efflux and intracellular acidification. The selective reduction of tumor energy metabolites and pH by LND may be exploitable for sensitizing gliomas to radiation, chemotherapy or hyperthermia.

Comparison of action of the anti-neoplastic drug lonidamine on drug-sensitive and drug-resistant human breast cancer cells: 31P and 13C nuclear magnetic resonance studies

Lonidamine (LND) is a relatively new anti-cancer drug, and several clinical trials have indicated that it may be effective in combinations with other therapeutic modalities. LND is classified within the metabolic inhibitor agents. Multidrug resistance (MDR) phenomenon is often associated with increased energy requirements, and enhanced glycolysis rate. These studies were performed to delineate the mechanism of action of LND on MDR human breast cancer cells, and to investigate whether LND as a single agent, or in combination with another anti-metabolism drug, 2-deoxyglucose (2-DG), may be useful against MDR tumors. The effects of LND on intact perfused drug-sensitive (WT) and 33-fold resistant to Adriamycin (Adr) MCF-7 cells, embedded in alginate micro capsules, were continuously monitored by 31P and 13C nuclear magnetic resonance (NMR) spectroscopy. 31P NMR studies showed that LND induced intracellular acidification and depletion of NTP in both WT and Adr cells. However, pH and NTP levels decreased less in the Adr cells than in the WT cells (p < 0.05 for both parameters). 13C NMR demonstrated that LND inhibited lactate transport, and lactate signals were elevated in both cell lines. However, the intracellular lactate levels increased to a greater extent in the WT than in the Adr cells (p < 0.05). There were major differences in the effects of LND on metabolism between sensitive and resistant cells. While LND enhanced glucose uptake in the WT cells, and its administration was followed by continuous increase of lactate signal, both processes were not affected by LND in the Adr cells. 2-DG is a glucose analogue that inhibits both cellular uptake and utilization of glucose, leading to cell starvation. Combined treatment with LND and 2-DG yielded at best additive, but not synergistic, cellular toxicity, and the metabolic effects of LND were attenuated by 2-DG. These results showed that the principal mechanism of action of LND is inhibition of lactate transport leading to intracellular lactate accumulation and acidification in both WT and Adr cells. The Adr cells were only 2-fold resistant to LND (compared to the WT cells), and since cellular uptake of alkaloid chemotherapy is improved in acidic environment, LND may have a role in the treatment protocols of MDR tumors, especially when given as the initial means for induction of intracellular acidification.

Effects of the inhibitors of energy metabolism, lonidamine and levamisole, on 5-aminolevulinic-acid-induced photochemotherapy

The ability of endogenously synthesized protoporphyrin IX (PpIX) to damage Chinese hamster lung fibroblasts of the line V79 by exposure to light was examined. This treatment induced reduction of cellular ATP, GTP, of the NADH/NAD+ ratio and of oxygen consumption. The present results indicate a close relationship between inhibition of respiration of irradiated cells and their ability to survive, e.g. 1 min of light exposure induced 90% inhibition of oxygen consumption and inactivation of approximately 95% of the cells, while the cellular content of ATP was reduced by only 15%. This indicates that the mitochondria are one of the primary targets of 5-aminolevulinic acid (ALA)-mediated photochemotherapy (PCT). In the present study, ALA-PCT was combined with the modulators of the glycolysis and the respiration chain, levamisole (LEV) and lonidamine (LND). A synergistic effect of combining ALA-PCT with non-toxic concentrations of LND was observed when LND was given prior to light exposure. This synergism was observed despite a substantial LND-induced inhibition of PpIX formation. At increasing doses of LND (>0.15 mM) the combination treatment becomes less efficient. This is due to the inhibition of PpIX synthesis induced by LND. A synergistic effect of ALA-PDT and LEV was found when LEV was given prior to light exposure. This was at least partly due to an LEV-stimulated effect on ALA-induced PpIX formation. However, it is not clear from the present results whether LEV may perturb energy metabolism in V79 cells since LEV alone did not reduce the energy charge or the NADH/NAD+ ratio. When LEV or LND were given after ALA-PCT, these 2 treatment modalities acted in an additive or slightly synergistic manner.

Selective enhancement of radiation response of herpes simplex virus thymidine kinase transduced 9L gliosarcoma cells in vitro and in vivo by antiviral agents

PURPOSE

To demonstrate in a well-characterized tumor model that the radiosensitivity of tumor cells transduced with a herpes simplex virus thymidine kinase gene (HS-tk) would be selectively enhanced by antiviral agents.

METHODS AND MATERIALS

Rat 9L gliosarcoma cells transduced with a retroviral vector containing an HS-tk gene, 9L-tk cells were exposed to various doses of irradiation under either in vitro or in vivo conditions. The radiation sensitizing potential of two antiviral drugs, bromovinyl deoxyuridine (BVdU) and dihydroxymethyl ethyl methyl guanine (acyclovir), was evaluated in vitro. The radiosensitizing ability of BVdU was also evaluated with a 9L-tk tumor growing in the rat brain. Tumors growing in the right hemisphere of rat brains were irradiated stereotactically with single-dose irradiation.

RESULTS

The radiation response of 9L-tk cells was selectively enhanced by antiviral agents relative to nontransduced cells. In the cell culture, when a 24-h drug exposure (20 micrograms/ml) preceded radiation, the sensitizer enhancement ratio (SER) for BVdU and acyclovir was 1.4 +/- 0.1 and 1.3 +/- 0.1, respectively. Exposure of cells to 10 micrograms/ml acyclovir for two 24-h periods both pre- and postirradiation resulted in a SER of 1.6 +/- 0.1. In vivo, a significant increase in median survival time of rats with 9L-tk tumors was found when BVdU was administered prior to single-dose irradiation relative to the survival time of similar rats receiving radiation alone.

CONCLUSION

An antiviral agent can enhance cell killing by radiation with selective action in cells transduced with the herpes simplex virus thymidine kinase gene. The results suggest that the three-pronged therapy of HS-tk gene transduction, systemically administered antiviral drug, and stereotactically targeted radiation therapy will improve the effectiveness of radiation therapy for the treatment of radioresistant tumors.

Whole-body hyperthermia and lonidamine as adjuvant therapy to treatment with cisplatin with or without local radiation in mouse bearing the Lewis lung carcinoma

The Lewis lung carcinoma implanted subcutaneously in the hind leg of a C57BL mouse metastasizes avidly to the lungs of the host. This tumour model system thus allows assessment of both primary and metastatic disease to treatment. Lonidamine (50 mg/kg) administered once or twice daily produced approximately additive tumour growth delay with whole-body hyperthermia (60 min to 42 degrees C and 60 min at 42 degrees C). The addition of lonidamine to treatment with cisplatin (10 mg/kg) and whole-body hyperthermia continued to produce increased tumour growth delay of up to 14.7 days compared with 10.8 days for cisplatin/whole-body hyperthermia. The response of the metastatic disease paralleled that of the primary tumour with a reduction in the number and percent of large metastases (> 3 mm) on day 20 post-tumour implantation. The addition of local fractionated radiation therapy (3 Gy x 5) to the primary tumour produced a very effective treatment regimen resulting in 37.5 days of tumour growth delay along with twice daily lonidamine/cisplatin whole-body hyperthermia. With this treatment regimen there was also a reduction to 50% of control of the number of lung metastases as well as the percent of large metastases on day 20. Further investigation of these treatment combinations is warranted.

Effect of whole-body hyperthermia on the pharmacokinetics and toxicity of lonidamine in dogs

The pharmacokinetics and toxicity of intravenous lonidamine were investigated in dogs receiving four cycles of lonidamine (400 or 800 mg/m2) +/- whole-body hyperthermia (WBH). Clearance and volume of distribution in dogs receiving lonidamine during WBH increased 1.6-2.3 and 1.9-3.5-fold respectively, relative to dogs receiving lonidamine under euthermic conditions (p < 0.02). In dogs receiving lonidamine under euthermic conditions or 400 mg/m2 + WBH, the area under the lonidamine concentration versus time curve (AUC) measured during the fourth treatment was 21-58% lower than the first treatment AUC. However, in dogs receiving 800 mg/m2 + WBH, the fourth treatment AUC was four-fold higher than the first treatment AUC (p < 0.02). This suggests repeated exposure to 800 mg/m2 lonidamine and WBH impairs lonidamine metabolism. Weakness, hypoglycaemia, and elevations in amylase, alanine aminotransferase, alkaline phosphatase and bilirubin were more severe or occurred exclusively in dogs receiving 800 mg/m2 + WBH. Since these changes were attributable to marked AUC increases, which occurred secondary to repeated exposure to 800 mg/m2 lonidamine during WBH, 400 mg/m2 was identified as the maximum tolerable dose to be administered intravenously to dogs during WBH.

Relative cytotoxicities of adriamycin and epirubicin in combination with lonidamine against human bladder cancer cell lines

We have used a panel of bladder cancer cell lines to compare the toxicities of Adriamycin and epirubicin, two drugs used intravesically to treat superficial transitional cell cancer (TCC) of the bladder, alone and in combination with lonidamine, an agent known to be active against anthracycline-resistant disease. Comparing concentrations reducing colony-forming ability by 50%, epirubicin and Adriamycin were similar in their cytotoxicities, although epirubicin was more potent against every line except an Adriamycin-resistant subline. Combinations of the two drugs with a non-cytotoxic concentration (1 microgram/ml) of lonidamine were tested using the Adriamycin-resistant subline MGH-U1R and its sensitive parental line MGH-U1. The addition of lonidamine caused a two-fold increase in the sensitivity of the resistant subline to both drugs, while having no effect on the sensitivity of the parental line. The data indicate that this combination might be of value in anthracycline-resistant disease.

A prospective randomized comparison of radiation therapy plus lonidamine versus radiation therapy plus placebo as initial treatment of clinically localized but nonresectable nonsmall cell lung cancer

PURPOSE

By means of a multicenter, prospective randomized, placebo-controlled study, to assess the impact of adding the radiation-enhancing agent lonidamine to standard "curative-intent" radiation therapy upon overall survival, progression-free survival, and local progression-free survival of patients with clinically localized but nonresectable nonsmall cell lung cancer.

METHODS AND MATERIALS

Lonidamine, or the lonidamine-placebo, was administered at a dose of 265 mg/m2 in three divided daily doses. Drug therapy began 2 days prior to the initiation of radiation therapy and continued until progression of disease mandated a change in therapy. The radiation therapy dose was 55-60 Gy, at a daily dose of 1.8 Gy and five treatments per week. Patients with clinical Stage II or III nonsmall cell lung cancer were stratified within the treatment center, and within two histologic strata: epidermoid vs. other nonsmall cell cancers.

RESULTS

A total of 310 patients were enlisted on study, 152 on the placebo arm and 158 on the lonidamine arm. The median survival durations were 326 days and 392 days for the placebo and lonidamine-treated groups respectively, p = 0.41 for a comparison of the survival curves. Median progression-free survival and median local progression-free survival durations were 197 days and 341 days for placebo + radiation therapy vs. 230 days and 300 days for lonidamine + radiation therapy; p-values for the respective curves were 0.75 and 0.42. Although there were proportionately more lonidamine-treated patients than placebo-treated patients demonstrating continued local control in excess of 12 months, the numbers of patients still at risk after 24 months were too small for meaningful statistical analysis.

CONCLUSION

This multicenter Phase III study failed to demonstrate a significant advantage in the lonidamine-treated population in overally patient survival, in progression-free survival, or in the median duration of local control.

Double-blind randomized study of lonidamine and radiotherapy in head and neck cancer

PURPOSE

Preclinical studies showed lonidamine to potentiate the effects of x-irradiation by inhibiting the repair of potentially lethal damage. This Phase III double blind, placebo-controlled study was performed to evaluate whether lonidamine can increase the tumor control of radiotherapy in the treatment of advanced head and neck cancer without any synergistic toxic effects on the exposed normal tissues.

METHODS AND MATERIALS

Ninety-seven patients with Stages II-IV squamous cell carcinoma of the head and neck were enrolled. Separate analyses were done on the 96 eligible patients and the 90 patients who completed the prescribed treatment regimen. Patients received radiotherapy up to a planned total of 60-66 Gy, in 2 daily fractions of 1.5 Gy each and either lonidamine (450 mg p.o. in three divided daily doses) or placebo, given continuously for 3 months or up to 1 month after the end of radiotherapy.

RESULTS

The rate of tumor clearance was 66% (32/48) in the lonidamine group and 65% (31/48) in the placebo group, while the subsequent failure rate was 50% and 77%, respectively (p < 0.05). The 3 and 5 year locoregional control rates in the adequately treated patients achieving complete tumor clearance were 66% and 63% for lonidamine vs. 41% and 37% for placebo. The disease-free survival in adequately treated patients was significantly better in the lonidamine group (p < 0.03), with 3 and 5 year rates of 44% and 40%, respectively, vs. 23% and 19% in the placebo group. The overall survival rate for all eligible patients at both 3 and 5 years was 44% in the lonidamine group and 44% and 31%, respectively, in the placebo group. Both acute and late radiation reactions were similar in the two groups. Myalgia and testicular pain were the most frequent side effects of lonidamine with an incidence of 8.5% and 4.2%, respectively.

CONCLUSION

The addition of lonidamine to hyperfractionated radiotherapy was correlated with a statistically and clinically significant proportion of long-term disease-free patients. The toxicity of radiotherapy was not aggravated by the drug and the overall tolerance of the combined regimen was acceptable.

Modulation of antitumor alkylating agents by novobiocin, topotecan, and lonidamine

Topoisomerase I and topoisomerase II allow a metabolically active cell to mobilize its supercoiled chromosomal DNA and undergo replication, transcription, recombination, and repair. Several topoisomerase inhibitors have recently been shown to be active in preclinical systems. Topotecan (SK&F 104,864), a water-soluble camptothecin analog, is an inhibitor of topoisomerase I. Novobiocin is an inhibitor of topoisomerase II. Lonidamine depletes cellular adenosine 5'-triphosphate (ATP) and may impede energy-dependent DNA repair, MCF-7 human breast-cancer cells were treated in vitro with topotecan, novobiocin, and lonidamine alone, in paired combinations, and in combination with CDDP and melphalan. The three enzyme inhibitors alone and in combination did not increase tumor cell sensitivity to CDDP. However, the combinations of topotecan/novobiocin and lonidamine/novobiocin did enhance the cytotoxicity of melphalan. Mice bearing the FSaII fibrosarcoma were treated in vivo with topotecan, novobiocin, and lonidamine alone, in paired combinations, and in combination with CDDP, melphalan, BCNU, and cyclophosphamide. The combination of topotecan/novobiocin had the greatest impact on tumor cell sensitivity to each cytotoxic agent tested in both tumor cell-survival and tumor growth-delay assays. This sensitization was greatest at the highest concentrations of the cytotoxic agent tested. Combinations of topoisomerase I and topoisomerase II inhibitors may be useful as modulators of antitumor alkylating agents.

Enhancement of sensitivity to hyperthermia by lonidamine in human cancer cells

Human glioma (87MG) and squamous cell carcinoma of the head and neck UMSCC-1 were shown to be sensitized to hyperthermia by Lonidamine treatment before and during hyperthermia. The degree of thermal sensitization increased with increasing heating times and temperatures. In addition, the thermal sensitization by Lonidamine as well as cellular thermal sensitivity were dependent on pH and increased with the more acidic pH. Even though plateau phase cells were more thermally resistant than exponentially growing cells, Lonidamine treatment caused thermal sensitization under both conditions. These data show that Lonidamine may hold potential to enhance the effectiveness of hyperthermia in cancer treatment and that especially in tumours with low pH an enhanced therapeutic gain may be achieved.

The effect of lonidamine (LND) on radiation and thermal responses of human and rodent cell lines

Rodent and human cells were tested for response to Lonidamine (LND) (1-(2,4 dichlorobenzyl) 1-indazol-3-carboxylic acid) combined with radiation or hyperthermia. Lonidamine exposure before, during, and after irradiation caused varying degrees of inhibition of potentially lethal damage (PLD) repair which was cell line dependent. In human glioma, melanoma, squamous cell carcinoma, and fibroblasts, LND exposure did not inhibit or only partially inhibited repair of potentially lethal damage. LND up to 100 micrograms/ml produced only a low level of toxicity in these cells and only slightly inhibited glucose consumption at the maximum concentration. In human glioma cells, LND treatment alone did not inhibit PLD repair, but when combined with hyperthermia treatment at moderate levels easily achievable in the clinic, there was complete inhibition of potentially lethal damage repair. These data suggest that LND effectiveness is cell type dependent. Combinations of LND, hyperthermia, and radiation may be effective in cancer therapy especially in tumors such as glioma in which repair of potentially lethal damage may be extensive.

Adjunctive therapy (whole body hyperthermia versus lonidamine) to total body irradiation for the treatment of favorable B-cell neoplasms: a report of two pilot clinical trials and laboratory investigations

Based on earlier clinical and preclinical investigations, we designed two different pilot trials for patients with nodular lymphoma or chronic lymphocytic leukemia. These studies evaluated the use of either 41.8 degrees C whole body hyperthermia (WBH), or the nonmyelosuppressive chemotherapeutic drug, lonidamine (LON), as an adjunct to total body irradiation (TBI) (12.5 cGy twice a week, every other week for a planned total dose of 150 cGy). Whole body hyperthermia was initiated approximately 10 min after total body irradiation; lonidamine was administered orally (420 mg/m2) on a daily basis. Although entry to the studies was nonrandomized, the two patient populations were accrued during the same time frame and were comparable in terms of histology, stage of disease, performance status, and prior therapy. Of 8 patients entered on the TBI/WBH study, we observed 3 complete responses (CR), 4 partial responses (PR), and 1 improvement (i.e., a 48% decrease in tumor burden). Of 10 patients entered in the TBI/LON study, there was 1 CR and 4 PR. For the TBI/WBH study, myelosuppression was not treatment-limiting; there were no instances of infection or bleeding and platelet support was never required. The median survival time for the TBI/WBH study is 52.5 months based on Kaplan Meir estimates. Two patients remain in a CR. The median time to treatment failure (MTTF) is 9.4 months (90% confidence interval = 7-15.4 months). In the TBI/LON study, 50% of patients receiving TBI required treatment modification due to platelet-count depression during therapy, but there were no instances of infection or bleeding. Frequently observed LON-related toxicities included myalgias, testicular pain, photophobia and ototoxicity. For the TBI/LON study, median survival is 7.6 months; MTTF was 2.4 months. In analyzing the results of these pilot studies, our subjective clinical impressions lead to the hypothesis that WBH protected against TBI-induced thrombocytopenia during therapy, whereas LON had no effect on TBI-induced myelosuppression. This speculation was tested and confirmed in a series of in vitro and in vivo experiments.

The combined use of radiation therapy and lonidamine in the treatment of brain metastases

Lonidamine is an indazole carboxylic acid that has been shown to be synergistic with radiotherapy (RT) in tissue culture and animal models. Clinical experience has shown that lonidamine is well-tolerated, and appears to potentiate the activity of conventional chemotherapy in the treatment of brain metastases. A prospective randomized trial was undertaken to evaluate the use of lonidamine in combination with RT in the treatment of brain metastases. All patients received 3000 cGy of whole brain radiotherapy (WBRT). Fifty eight patients were enrolled; 31 received lonidamine plus WBRT and 27 received WBRT alone. There was no significant difference in response rate or survival between the treatment groups. Lonidamine blood levels were measured in 30 of the 31 patients who received the drug, and were therapeutic (greater than or equal to 15 micrograms/ml) in 50%. Survival and response rate were unaffected by the presence or absence of a therapeutic lonidamine level. The most common side-effects of lonidamine were myalgia, testicular pain, anorexia, and ototoxicity; however, only 2 patients had to discontinue the drug because of intolerable myalgias. No serious organ toxicity or myelosuppression was observed.

Increased tumor control rates in murine fibrosarcoma by combined therapy with L-alanosine and radiation

L-Alanosine, an analog of L-aspartic acid, was investigated as one of a series of chemical compounds that may have inhibitory effects on the repair of potentially lethal damage caused by radiation using an in vivo murine fibrosarcoma (Meth-A tumor) in BALB/cBy male mice. The combined treatment of single administration of L-alanosine (600 mg/kg) and single dose of X-irradiation (20 Gy) on Meth-A tumors produced 62% tumor control, while the radiation alone resulted in less than 5% tumor control. The potentiating effect by L-alanosine was higher when the drug was administered 8 h prior to X-irradiation. The dose modification factor of the drug is estimated to be 1.4 for Meth-A tumor. The increased tumor control rates with combined alanosine and radiation were highly dependent upon the time and sequence of the combined treatment. The reason for reduced efficacy at treatment times of less than 8 h prior to X-irradiations appears to be related in part to the modulation of the body temperature by L-alanosine when combined with Ketamine, an anesthetic agent.

Potentiation of radiation effects on multicellular tumor spheroids (MTS) of HeLa cells by lonidamine

Lonidamine is a potent inhibitor of spermatogenesis and a hyperthermic sensitizer. The previous study of lonidamine and radiation using two murine tumors demonstrated that tumor cure rates were significantly increased by radiation and concomitant lonidamine. In an effort to determine the radiobiologic factors involved with the potentiating effect of radiation by lonidamine, a series of cell culture studies were carried out using multicellular tumor spheroids (MTS) of HeLa Cells. When the MTS were treated with lonidamine in combination with fractionated irradiation, remarkable enhancement of growth inhibition was observed at the drug concentration of 10 micrograms/ml. On the other hand, there was no demonstrable enhancement of growth inhibition induced by a single dose of irradiation. Although the present findings would be consistent with the inhibitory action of potentially lethal damage repair of radiation by the drug, an alternative possibility is that the cells that have received the combined treatment have undergone a metabolic change, which has altered their sensitivity to the growth inhibitory effects of lonidamine. Based on the studies reported here and in mice, it is suggested that continued drug exposure over a prolonged period may provide an enhanced therapeutic effect, even in tumor varieties where the drug has no apparent antitumor activity on nonirradiated cells.

Effect of lonidamine on the cytotoxicity of four alkylating agents in vitro

We examined the ability of lonidamine, which has been described as an inhibitor of cellular respiration and glycolysis, to enhance the cytotoxicity of alkylating agents to MCF-7 human breast-carcinoma cells. Lonidamine was increasingly cytotoxic to MCF-7 cells with increasing time of exposure. With a 12-h exposure, the IC50 for lonidamine was about 365 microM, and with a 24-h exposure it was about 170 microM. A drug concentration of 250 microM was chosen for use in the drug combination studies. Lonidamine appeared to have a dose-modifying effect on cisplatin (CDDP), producing increasingly supra-additive cell kill with increasing CDDP concentration. When simultaneously incubated with lonidamine for 1 h, 500 microM CDDP yielded a cell kill that was 2 log greater than additive cytotoxicity. Extending the exposure to lonidamine for 12 h after CDDP treatment led to a small, additional aliquot of cell kill of about 2.5-fold over the CDDP concentration range. Lonidamine also appeared to have a dose-modifying effect on melphalan cytotoxicity in the melphalan concentration range of 100-500 microM. Between concentrations of 10 and 100 microM melphalan, the drug combination survival after 1 h exposure fell within the envelope of additivity for the two agents. However, maintaining the presence of lonidamine for an additional 12 h increased the effect such that the combination was supra-additive over the entire concentration range of melphalan. Simultaneous exposure to 4-hydroperoxycyclophosphamide (4-HC) and lonidamine for 1 h resulted in greater than additive cell kill, and extending the lonidamine exposure period such that lonidamine was present during and 12 h after 4-HC treatment further increased this effect. Lonidamine had a moderate effect on the cytotoxicity of carmustine (BCNU) with a 1 h simultaneous exposure; however, this treatment combination reached greater than additive cytotoxicity only at the highest concentration of BCNU tested. Extending the lonidamine exposure time for an additional 12 h resulted in supra-additive cell kill over the BCNU concentration range. Therefore, when lonidamine was present during exposure to the alkylating agent and its presence was then extended for an additional 12 h, a synergistic cell kill was produced with all four alkylating agents tested.

Phase II double-blind randomized study of lonidamine and radiotherapy in epidermoid carcinoma of the lung

Patients with non metastatic squamous cell lung cancer were treated with radiotherapy (RT) plus lonidamine (LND) or placebo (PLAC), according to a randomized double-blind study design. Treatment with lonidamine 150 mg t.i.d. (27 patients) or placebo (23 patients) started 3 days before RT, lasted up to 7 months. Partial responses were observed in 14 and 6 patients respectively in the LND + RT and PLAC + RT groups. Statistical analysis of the survival curves showed no significant difference between the LND + RT (median 311 days) and PLAC + RT (median 193 days) groups. Stage III patients survived significantly longer (p less than 0.05) when treated with LND + RT (median 318 days) than with PLAC + RT (median 163 days). No synergistic toxic effects between radiation and LND were noted. To confirm these data a new and larger multicentric study is now in progress.

Kinetic and survival response of the M14 cell line to lonidamine associated with adriamycin or hyperthermia

Lonidamine (LND), an indazole-carboxylic acid derivative, was delivered alone and together with adriamycin (ADM) or hyperthermia to the human melanoma cell line M14, and cell survival was assessed. Cell cycle-specific effects were investigated by analyzing sequences of DNA content histograms by means of a suitable mathematical procedure. LND delivered for 1 h at a dose of 50 micrograms/ml did not affect proliferation and survival of the cells. Exposure of the cells for 1 h to ADM (1.0 microgram/ml) followed by LND for 1 h (50 micrograms/ml) produced the highest effect on the survival. Kinetic parameters were affected by the combined treatment slightly more than by ADM exposure alone. Simultaneous delivery of LND (50 micrograms/ml) with hyperthermia (42 degrees C, 1 h) reduced the survival and enhanced the block of cells in the G2M phase, as compared with the heat treatment alone. The effect of the treatments on cell survival appeared to be related to the perturbation of the G2M phase of the cycle.

The potentiation of radiation response on murine tumor by fludarabine phosphate

Fludarabine phosphate is a synthetic analog of beta-arabinofuranosyl adenine (beta-ara-A), an anti-viral agent. Since beta-ara-A has been shown to be an effective inhibitor of potentially lethal damage (PLD) repair in cell culture system but ineffective in in vivo tumors, we carried out experiments to determine whether fludarabine phosphate which is not inactivated by adenosine deaminase potentiates the radiation effects on in vivo murine tumor. The combined effects of single acute fludarabine phosphate (600 mg/kg) and single dose of X-irradiation (20 Gy) on Meth-A fibrosarcomas in BALB/c mice produced more than 90% tumor control, while the radiation alone resulted in less than 10% tumor control. The radiosensitizing effect by fludarabine phosphate was higher when the drug was administered immediately prior to X-irradiation. The dose modifying factor of fludarabine phosphate is estimated to be 1.6 at 400 mg/kg. Experiments with fractionated irradiation and fludarabine phosphate similarly showed a high rate of tumor control. The present study suggests that inhibitors of PLD repair including several antiviral agents may have potential utility in the treatment of some radioresistant human tumors by radiotherapy.