Sensitivity to thermochemotherapy of AKR lymphoma and B16 melanoma variants of malignancy

N-acetylglycoside of oleanolic acid (aridanin) displays promising cytotoxicity towards human and animal cancer cells, inducing apoptotic, ferroptotic and necroptotic cell death

BACKGROUND

The discovery of novel phytochemicals represents a reasonable approach to fight malignancies, especially those which are resistant to standard chemotherapy.

PURPOSE

We evaluated the cytotoxic potential of a naturally occurring N-acetylglycoside of oleanolic acid, aridanin, on 18 cancer cell lines, including sensitive and drug-resistant phenotypes mediated by P-glycoprotein, BCRP, p53 knockout, deletion-mutated EGFR, or BRAF mutations. Furthermore, metastasizing B16/F10 cells, HepG2 hepatocarcinoma and normal AML12 hepatocytes were investigated. The mechanisms of aridanin-induced cell death was further investigated.

METHODS

The resazurin reduction assay (RRA) was applied to evaluate the cytotoxicity, autophagy, ferroptotic and necroptotic cell death. CCRF-CEM leukemia cells were used for all mechanistic studies. A caspase-Glo assay was applied to evaluate the caspase activities. Flow cytometry was applied for the analyses of cell cycle (PI staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP; JC-1) and reactive oxygen species (ROS; H2DCFH-DA).

RESULTS

Aridanin and doxorubicin (positive control) inhibited the proliferation of all cancer cell lines tested. The IC50 values for aridanin varied from 3.18 µM (CCRF-CEM cells) to 9.56 µM (HepG2 cells). Aridanin had considerably lower IC50 values than that of doxorubicin against multidrug-resistant CEM/ADR5000 cells and melanoma cell lines (MaMel-80a, Mel-2a, MV3, and SKMel-505). Aridanin induced apoptosis in CCRF-CEM cells through increase of ROS levels and MMP breakdown, and to a lesser extent via caspases activation. Aridanin also induced ferroptotic and necroptotic cell death.

CONCLUSION

The present study opens good perpectives for the use of this phytochemical as an anticancer drug to combat multi-facorial resistance to established chemotherapeutics.

Effect of hyperthermia on AKR lymphoma variants differing in degree of malignancy

The effect of hyperthermic treatment on AKR lymphoma cells of varying malignancy was investigated. Tumor cells were pretreated at 37 or 43 degrees C and then injected to mice. The effect on the highly malignant variant, TAU-38, was compared to that on the low-malignancy variant, TAU-39, following both subcutaneous (s.c.) and intravenous (i.v.) inoculation. Hyperthermia showed no effect on the TAU-39 variant following s.c. inoculation on the primary tumors or mice survival, but the TAU-38 variant exhibited a significant delay of tumor appearance following treatment, namely, decreased tumor size and increased life span. Following i.v. inoculation, in both variants, hyperthermia caused a significant decrease in metastatic spread and an increased life span. We conclude that hyperthermia, in addition to exerting a greater effect on the high-malignancy variant, acts at the late phases of metastasis. Hyperthermia might therefore have a place in the management of cancer in its advanced disseminated phase.

Apoptosis and cell proliferation capacity in AKR lymphoma malignancy variants

Dysregulation in apoptotic cell death has recently emerged as a factor in tumorigenesis, but its effect in tumor progression is not yet established. In the present study we evaluated the levels of proliferative and apoptotic cell fractions in a T-cell lymphoma tumor progression model. We compared these features and the expression of apoptosis-related genes in primary tumors of several AKR lymphoma malignancy variants. According to DNA flow cytometry, a considerable proportion of cells (35-40%) was in the proliferative (S + G2/M) phase in all variants, but a slight augmentation with increasing malignancy was noted. Apoptotic cell content was, unexpectedly, the lowest in the less malignant variant. This might be due to the higher content in macrophages observed in this variant, which possibly partly eliminated apoptotic bodies. We found an increase in bcl-2 level with increasing malignancy that was probably counterbalanced by the simultaneous increase observed in the Fas receptor.

Release from apoptosis correlates with tumor progression in the AKR lymphoma

Disturbance of apoptosis is an established factor in tumorigenesis. The role of apoptosis in tumor progression is not yet clear. In the present study we compared the tendency to spontaneous apoptosis (and the proliferative capacity) of tumor cells derived from primary (PT) and metastatic tumor (MT) cells of several AKR lymphoma variants. Apoptosis-related gene expression was also compared. Our results indicate that release from apoptosis has a role in the tumor progression of this T cell lymphoma. At the cellular level, a markedly lower apoptotic tendency was observed in MT than in PT cells. The existence of macrophages only in PT also supports the presence of apoptotic cells in local but not in MTs. By contrast, proliferative capacity does not determine tumor aggressiveness in this system. At the molecular level, we found a higher staining intensity for bcl-2 in MT than in PT cells, suggesting that bcl-2 might be responsible for the reduced apoptosis in MT compared to PT cells. Evidence for p53 overexpression was found in the MT cells of one of the variants but in none of the PT. Comparison of Fas receptor, unexpectedly showed an increased expression in MT versus PT cells, possibly indicating resistance to Fas-induced apoptosis in the MT cells.

Direct measurement of doxorubicin concentration in the intact, living single cancer cell during hyperthermia

BACKGROUND

It is well known that the effect of doxorubicin on cancer cells is enhanced by hyperthermia. The mechanism of this phenomenon is not fully understood.

METHODS

Two esophageal squamous cell carcinoma cell lines, TE-2 and TE-6, were used; these cell lines have different sensitivities for doxorubicin. The cells were exposed to 1 microgram/mL of doxorubicin for 30 minutes. With a confocal laser scanning microscope and a transparent warming plate, doxorubicin concentration was measured continuously in the intact, living single cancer cells, and the two-dimensional distribution of the drug during hyperthermia (43 degrees C) was analyzed.

RESULTS

A doxorubicin sensitivity difference was confirmed between TE-2 and TE-6 cells by colonogenic assay (P < 0.05). Hyperthermia increased the sensitivity of both cell lines to the drug (P < 0.05) and eliminated the sensitivity difference. Doxorubicin accumulated in the nuclei in both cell lines 30 minutes after exposure to the drug in a time-dependent manner (P < 0.05). Without hyperthermia, the doxorubicin concentration in the nuclei of the TE-2 cells (4.8 +/- 0.3 micrograms/mL) was higher than in the nuclei of the TE-6 cells (2.3 +/- 0.5 micrograms/mL) (P < 0.05). With hyperthermia, there was no significant difference in doxorubicin concentration between the nuclei of the TE-2 cells (20.8 +/- 1.3 micrograms/mL) and the nuclei of the TE-6 cells (16.5 +/- 3.9 micrograms/mL).

CONCLUSIONS

Hyperthermia increased the uptake of doxorubicin in the nuclei of cancer cells. Thus, the authors concluded that hyperthermia increases the cells' sensitivity to the drug.

Cell membrane fluidity and adriamycin retention in a tumor progression model of AKR lymphoma

Counteraction of drug resistance is a major challenge in cancer therapy, particularly in advanced stages. The main mechanism of multidrug resistance is related to an increased drug efflux. In the present study we examined the effect of modifying cell membrane lipid fluidity on uptake of adriamycin (ADR) in cells of AKR lymphoma malignancy variants. Modification of cell membrane fluidity, either by lecithin or by lecithin-cholesterol mixtures, induced in a high proportion of cells of all variants a higher capacity to accumulate ADR. The chemosensitizing effect, for lecithin in particular, was proportional to the degree of malignancy of the lymphoma variants. The increased ADR uptake was up to 1.4-fold in the variant of lowest malignancy and up to 5-fold in the one of highest aggressiveness. This tendency correlates with our previous studies and is of particular value since highly-malignant tumors are often drug resistant. The cholesterol-lecithin mixture, induced, however, in part of the variants the appearance of a small subpopulation with very low ADR permeability. Cell membrane rigidification is of value for exposing tumor cell cryptic antigens but may be deleterious when used in conjunction with chemotherapy.

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

Six cycles of the maximum tolerable intravenous doses of lonidamine (400 mg/m2) and doxorubicin (30 mg/m2) were administered to three normothermic dogs and three dogs undergoing whole-body hyperthermia (WBH) (42 degrees C X 90 min), at 3-week intervals. Lonidamine pharmacokinetics was unaltered by WBH. WBH increased doxorubicin clearance 1.6-fold, however this trend was not statistically significant. WBH resulted in a 2.4-fold increase in the volume of distribution (Vdss) of doxorubicin relative to dogs treated under euthermic conditions (p < 0.001). This finding suggests tissue extraction of doxorubicin was increased by WBH. The specific tissues in which this occurred is unknown, but myelosuppression and cardiotoxicity were only minimally increased. Therefore, doxorubicin uptake in critical normal tissues was probably unaffected. The biochemical and haematologic toxicities observed 6 h and 1 week after each treatment did not appear to differ in character or severity from that reported in dogs receiving lonidamine +/- WBH or doxorubicin +/- WBH. These results suggest WBH did not decrease the maximum tolerable dose of doxorubicin when given with lonidamine, and that the antitumour activity of this combination should be assessed.

Malignant phenotype correlating with drug resistance in two human neuroblastoma cell lines

The main cause for the failure of chemotherapeutic treatment of advanced cancer probably lies in the emergence of drug resistance clones. In the present study we compared the sensitivity to adriamycin (ADR) and the capacity of ADR uptake in two human neuroblastoma cell lines differing in properties relevant to metastatic potential, the GP2 and MB, of low- and high-malignancy phenotype, respectively. Examination of the ADR effect on in vitro proliferative capacity of the two cell lines revealed a higher sensitivity of GP2 as compared to the MB variant. Intracellular ADR accumulation was determined by fluorocytometry, spectrofluorometry and fluorescence microscopy. According to the three methods, the GP2 line cells, representing a low-malignancy phenotype, had a higher uptake ability than the MB cells, possessing a phenotype of higher aggressiveness. The quantitative determination revealed that over a broad range of ADR concentrations, the GP2 cells accumulated 2-3.5 folds the amount of cytotoxic agent penetrating the MB cells. The FACS analysis showed that the cell population of each of the variants consisted of two subpopulations varying in their ability to accumulate ADR. In the GP2 line the high permeability subpopulation represented nearly half of the total cell population, whereas in the MB line this subpopulation represented a minority. The correlation observed between ADR uptake capacity and sensitivity to the cytotoxic agent, as evidenced by its effect on proliferative capacity, suggests that the resistance of the MB cells is due to a P-G-P modification-related mechanism.

Effect of whole-body hyperthermia on pharmacokinetics and tissue distribution of doxorubicin

The effect of whole-body hyperthermia (41.5 degrees C, 2 h) on doxorubicin (DOX) tissue distribution and plasma pharmacokinetics was examined in rats bearing a subcutaneous fibrosarcoma. Tumour response to the hyperthermia regimen alone was minimal, but the combination of heat with DOX (5.0 mg/kg, i.v.) enhanced tumour growth delay. The combined therapy, however, showed increased toxicity to normal tissue (especially renal and cardiac). Although DOX levels in spleen tissue were higher in rats exposed to hyperthermia than in control normothermic rats, both groups had comparable levels of drug in tumour, heart, kidney, and small intestine tissue at all time-points examined. Compared with normothermic animals, hyperthermia-treated rats showed decreased DOX in the mean area under the concentration-time curve (AUC) and decreased plasma DOX t1/2 but increased plasma drug clearance. These heat-mediated alterations in DOX pharmacokinetic parameters, however, do not account for the significant increases in thermochemotherapy-mediated cytotoxicities observed in tumour, and in normal renal and cardiac tissues.