The dynamic relationship between inorganic polyphosphate and adenosine triphosphate in human non-small cell lung cancer H1299 cells.

Inorganic polyphosphate (polyP) plays a vital role in cellular energy metabolism and signaling, owing to its structure and high-energy phosphate bonds. Intracellular ATP functions both as a cellular energy source and a key factor in cell death, and ATP dynamics in tumor cells are crucial for advancing cancer therapy. In this study, we explored the interplay between polyP and ATP in cellular energy metabolism. Treatment with polyP did not affect cell proliferation of human non-small cell lung cancer H1299 and human glioblastoma T98G cell lines as compared to their respective control cells until 72 h post-treatment. The mitochondrial membrane potential (MMP) in polyP-treated cells was low, contrasting with the time-dependent increase observed in control cells. While the ATP content increased over time in untreated and Na-phosphate-treated control cells, it remained unchanged in polyP-treated cells. Furthermore, the addition of cyclosporine A, a mitochondrial permeability transition pore (mPTP) inhibitor, failed to restore ATP levels in polyP-treated cells. We performed lactate assays and western blot analysis to evaluate the effect of polyP on glucose metabolism and found no significant differences in lactate secretion or glucose-6-phosphate dehydrogenase (G6PD) activity between polyP-treated and control cells. Additional pyruvate restored MMP but had no effect on the cellular ATP content in polyP-treated cells. We observed no correlation between the Warburg effect and glucose metabolism during ATP depletion in polyP-treated cells. Further investigation is warranted to explore the roles of polyP and ATP in cancer cell energy metabolism, which might offer potential avenues for therapeutic interventions.

Estimation of the Internal Dose Imparted by 18F-Fluorodeoxyglucose to Tissues by Using Fricke Dosimetry in a Phantom and Positron Emission Tomography.

Purpose: Assessment of the radiation dose delivered to a tumor and different organs is a major issue when using radiolabelled compounds for diagnostic imaging or endoradiotherapy. The present article reports on a study to correlate the mean 18F-fluorodeoxyglucose (18F-FDG) activity in different tissues measured in a mouse model by positron emission tomography (PET) imaging, with the dose assessed in vitro by Fricke dosimetry. Methods: The dose-response relationship of the Fricke dosimeter and PET data was determined at different times after adding 18F-FDG (0-80 MBq) to a Fricke solution (1 mM ferrous ammonium sulfate in 0.4 M sulfuric acid). The total dose was assessed at 24 h (~13 half-lives of 18F-FDG). The number of coincident events produced in 3 mL of Fricke solution or 3 mL of deionized water that contained 60 MBq of 18F-FDG was measured using the Triumph/LabPET8TM preclinical PET/CT scanner. The total activity concentration measured by PET was correlated with the calculated dose from the Fricke dosimeter, at any exposure activity of 18F-FDG. Results: The radiation dose measured with the Fricke dosimeter increased rapidly during the first 4 h after adding 18F-FDG and then gradually reached a plateau. Presence of non-radioactive-FDG did not alter the Fricke dosimetry. The characteristic responses of the dosimeter and PET imaging clearly exhibit linearity with injected activity of 18F-FDG. The dose (Gy) to time-integrated activity (MBq.h) relationship was measured, yielding a conversion factor of 0.064 ± 0.06 Gy/MBq.h in the present mouse model. This correlation provides an efficient alternative method to measure, three-dimensionally, the total and regional dose absorbed from 18F-radiotracers. Conclusions: The Fricke dosimeter can be used to calibrate a PET scanner, thus enabling the determination of dose from the measured radioactivity emitted by 18F-FDG in tissues. The method should be applicable to radiotracers with other positron-emitting radionuclides.

Concomitant Chemoradiation Therapy with Gold Nanoparticles and Platinum Drugs Co-Encapsulated in Liposomes.

A liposomal formulation of gold nanoparticles (GNPs) and carboplatin, named LipoGold, was produced with the staggered herringbone microfluidic method. The radiosensitizing potential of LipoGold and similar concentrations of non-liposomal GNPs, carboplatin and oxaliplatin was evaluated in vitro with the human colorectal cancer cell line HCT116 in a clonogenic assay. Progression of HCT116 tumor implanted subcutaneously in NU/NU mice was monitored after an irradiation of 10 Gy combined with either LipoGold, GNPs or carboplatin injected directly into the tumor by convection-enhanced delivery. Radiosensitization by GNPs alone or carboplatin alone was observed only at high concentrations of these compounds. Furthermore, low doses of carboplatin alone or a combination of carboplatin and GNPs did not engender radiosensitization. However, the same low doses of carboplatin and GNPs administered simultaneously by encapsulation in liposomal nanocarriers (LipoGold) led to radiosensitization and efficient control of cell proliferation. Our study shows that the radiosensitizing effect of a combination of carboplatin and GNPs is remarkably more efficient when both compounds are simultaneously delivered to the tumor cells using a liposomal carrier.

Intratumoral 18F-FLT infusion in metabolic targeted radiotherapy.

BACKGROUND: The goal of targeted radiotherapy (TRT) is to administer radionuclides to tumor cells, while limiting radiation exposure to normal tissues. 3'-Deoxy-3'-[18F]-fluorothymidine (18F-FLT) is able to target tumor cells and emits a positron with energy appropriate for local (~ 1 mm range) radiotherapy. In the present work, we investigated the potential of TRT with a local administration of 18F-FLT alone or in combination with 5-fluorouracil (5FU), which acts as a chemotherapeutic agent and radiosensitizer. Treatment efficiency of 18F-FLT combined or not with 5FU was evaluated by intratumoral (i.t.) infusion into subcutaneous HCT116 colorectal tumors implanted in nu/nu mice. The tumor uptake and kinetics of 18F-FLT were determined and compared to 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) by dynamic positron emission tomography (PET) imaging following i.t. injection. The therapeutic responses of 18F-FLT alone and with 5FU were evaluated and compared with 18F-FDG and external beam radiotherapy (EBRT). The level of prostaglandin E2 (PGE2) biosynthesis was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) in order to determine the level of inflammation to healthy tissues surrounding the tumor, after i.t. injection of 18F-FLT, and compared to EBRT. RESULTS: We found that i.t. administration of 18F-FLT offers (1) the highest tumor-to-muscle uptake ratio not only in the injected tumor, but also in distant tumors, suggesting potential for concurrent metastases treatment and (2) a sixfold gain in radiotherapeutic efficacy in the primary tumor relative to EBRT, which can be further enhanced with concurrent i.t. administration of the radiosensitizer 5FU. While EBRT stimulated PGE2 production in peritumoral tissues, no significant increase of PGE2 was measured in this area following i.t. administration of 18F-FLT. CONCLUSION: Considering the biochemical stability of 18F-FLT and the physical properties of localized 18F, this study shows that TRT via intratumoral infusion of 18F-FLT and 5FU could provide a new effective treatment option for solid tumors. Using this approach in a colorectal tumor model, the tumor and its metastases could be efficiently irradiated locally with much lower doses absorbed by healthy tissues than with i.t. administration of 18F-FDG or conventional EBRT.

New therapeutic possibilities of combined treatment of radiotherapy with oxaliplatin and its liposomal formulation, Lipoxal™, in rectal cancer using xenograft in nude mice.

AIM: To determine the benefits of irradiation at the time of maximum linking of oxaliplatin to the DNA of tumor cells, and evaluate the potential of its liposomal formulation, Lipoxal™, for chemoradiation therapy. MATERIALS AND METHODS: Nude mice implanted with human colorectal carcinoma HCT116 cells were injected with oxaliplatin or Lipoxal™. The amount of platinum in tumor, tumoral DNA, normal tissues and blood was measured 4, 24, 48, 72 and 96 h later by inductively coupled plasma mass spectrometry. The effect of concomitant radiotherapy was assessed as tumor growth delay resulting from irradiation 4, 24 and 48 h after drug administration. RESULTS: While the amount of platinum in the tumor reached a peak at 4 h after injection and declined over time, the concentration of oxaliplatin-DNA adducts reached two maxima observed at 4 h and 48 h after drug administration, a behavior not observed with Lipoxal™. The greatest combined effect was obtained when radiation was given at 48 h after drug injection, resulting in an increase of tumor growth delay by factors of 3.71 and 3.33 for treatments with oxaliplatin and Lipoxal™, respectively. CONCLUSION: Our results confirm the importance of irradiating a tumor when the concentration of oxaliplatin bound to tumor DNA is maximal. This finding should have a significant impact on the design of more efficient chemoradiation treatment protocols and should be further explored in clinical studies.

Efficacy of cisplatin and Lipoplatin™ in combined treatment with radiation of a colorectal tumor in nude mouse.

BACKGROUND: Optimal conditions for efficient concomitant chemoradiation treatment of colorectal cancer with cisplatin still need to be better defined. In addition, intolerance of healthy tissue to cisplatin prevents the full exploitation of its radiosensitizing potential. A liposomal formulation of cisplatin, Lipoplatin™, was proposed to overcome its toxicity. Using an animal model of colorectal cancer, we determined the platinum window, defined by studying the pharmacokinetics and time-dependent intracellular distribution of cisplatin and Lipoplatin™. MATERIALS AND METHODS: In nude mice bearing HCT116 human colorectal carcinoma treated with cisplatin or Lipoplatin™, the platinum accumulation in blood, serum, different normal tissues, tumor and different tumor cell compartments was measured by inductively coupled plasma mass spectrometry. Radiation treatment (15 Gy) was given 4, 24, and 48 h after drug administration and was correlated to the amount of platinum-DNA adducts in the cancer cells. The resulting tumor growth delay is reported and correlated to apoptosis analysis. RESULTS: The greatest effects and highest apoptosis were observed when radiation was given at 4 h or 48 h after drug injection. These times correspond to the times of maximal platinum binding to tumor DNA. An enhancement factor (ratio of group treated by combined treatment compared to chemotherapy alone) of 13.00 was obtained with Lipoplatin™, and 4.09 for cisplatin when tumor irradiation was performed 48 h after drug administration. CONCLUSION: The most efficient combination treatment of radiation with cisplatin or Lipoplatin™ was observed when binding of platinum to DNA was highest. These results improve our understanding over the mechanisms of platinum-induced radiosensitization and should have significant impact on the design of more efficient treatment protocols.

Synergism in concomitant chemoradiotherapy of cisplatin and oxaliplatin and their liposomal formulation in the human colorectal cancer HCT116 model.

BACKGROUND: We choose to test the effect of associating chemo-radiotherapy at 8 h (the highest level of DNA-platinum) and 48 h (the lower level of DNA-platinum) to clarify if irradiation at the maximum DNA-platinum concentration could improve the synergism. MATERIALS AND METHODS: Growth inhibition of the human colorectal cancer cell line HCT116 treated with cisplatin, oxaliplatin, Lipoplatin™ and Lipoxal™ plus gamma-radiation was determined by a colony formation assay. The synergism was evaluated using the combination index method. RESULTS: For 8 h and 48 h exposure to cisplatin or Lipoplatin™, followed by irradiation, drug concentrations higher than IC(50) were found to be synergistic, while a lower than IC(50) concentration was antagonistic. For oxaliplatin, exposure to a concentration above IC(50) for 8 h was synergistic, while the exposure to oxaliplatin (at any concentrations) for 48 h was antagonistic. Lipoxal™ significantly improved synergism compared to its parent drugs. All tested platinum drugs sensitize radiation-treated HCT116 cells by inducing G(2) phase. CONCLUSION: The difference of drug concentrations and the time interval between drug administration and radiotherapy could give different results in chemoradiation therapy.

Temperature dependence of the Fricke dosimeter and spur expansion time in the low-LET high-temperature radiolysis of water up to 350 °C: a Monte-Carlo simulation study.

Monte-Carlo simulations of the radiolysis of the ferrous sulfate (Fricke) dosimeter with low-linear energy transfer (LET) radiation (such as (60)Co γ-rays or fast electrons) have been performed as a function of temperature from 25 to 350 °C. The predicted yields of Fe(2+) oxidation are found to increase with increasing temperature up to ∼100-150 °C, and then tend to remain essentially constant at higher temperatures, in very good agreement with experiment. By using a simple method based on the direct application of the stoichiometric relationship that exists between the ferric ion yields so obtained G(Fe(3+)) and the sum {3 [g(e(-)(aq) + H˙) + g(HO(2)˙)] + g(˙OH) + 2 g(H(2)O(2))}, where g(e(-)(aq) + H˙), g(HO(2)˙), g(˙OH), and g(H(2)O(2)) are the primary radical and molecular yields of the radiolysis of deaerated 0.4 M H(2)SO(4) aqueous solutions, the lifetime (τ(s)) of the spur and its temperature dependence have been determined. In the spirit of the spur model, τ(s) is an important indicator for overlapping spurs, giving the time required for the changeover from nonhomogeneous spur kinetics to homogeneous kinetics in the bulk solution. The calculations show that τ(s) decreases by about an order of magnitude over the 25-350 °C temperature range, going from ∼4.2 × 10(-7) s at 25 °C to ∼5.7 × 10(-8) s at 350 °C. This decrease in τ(s) with increasing temperature mainly originates from the quicker diffusion of the individual species involved. Moreover, the observed dependence of G(Fe(3+)) on temperature largely reflects the influence of temperature upon the primary free-radical product yields of the radiolysis, especially the yield of H˙ atoms. Above ∼200-250 °C, the more and more pronounced intervention of the reaction of H˙ atoms with water also contributes to the variation of G(Fe(3+)), which may decrease or increase slightly, depending on the choice made for the rate constant of this reaction. All calculations reported herein use the radiolysis database of Elliot (Atomic Energy of Canada Limited) and Bartels (University of Notre Dame) that contains all the best currently available information on the rate constants, reaction mechanisms, and g-values in the range 20 to 350 °C.

Cellular uptake and cytoplasm / DNA distribution of cisplatin and oxaliplatin and their liposomal formulation in human colorectal cancer cell HCT116.

Liposomal formulations of cisplatin and oxaliplatin (Lipoplatin™ and Lipoxal™, respectively) were recently proposed to reduce systemic toxicity, while optimizing the anti-cancer effectiveness of these compounds. As the anti-neoplastic or radio-sensitizing activity of these drugs is attributed to their binding to DNA, we assessed the impact of the liposomal formulations on the time course of accumulation of these platinum compounds in the human colorectal cancer HCT116 cell lines and their distribution between cytoplasm and DNA. Their cytotoxicity was determined by colony formation assay. Intracellular platinum and platinum bound to DNA was measured by inductively coupled plasma mass spectrometry. Although, as a chemotherapeutic agent, cisplatin was as efficient as oxaliplatin after exposure for a short time, oxaliplatin and Lipoxal™ became more active than cisplatin against HCT116 cells after 24 h incubation. Lipoxal™ displayed a higher accumulation in the cytoplasm of HCT116 cells compared to free oxaliplatin, consistent with its proposed mechanism of fusion with the cell membrane. The distribution cytoplasm/DNA of free cisplatin and Lipoplatin™ were similar. Conversely, Lipoxal™ had a significantly different cytoplasm/DNA distribution from oxaliplatin: more than 95% of oxaliplatin transported by the liposome was trapped in the cytoplasm, even after 48 h incubation. Our study indicates that Lipoxal™ can largely improve the cellular uptake of oxaliplatin, but this was not followed by a similar increase in the DNA bound fraction.