Altered cell cycle response of drug-resistant lung carcinoma cells to doxorubicin

Comprehensive Identification of Costus pictus Rhizome Extract as a Potent Plant Food: Unveiling Anti-Diabetic, Antimicrobial, Anticancer, and Anti-Inflammatory Properties

Plant-derived foods are esteemed as natural preventives due to the constraints of contemporary pharmaceuticals, intensifying scrutiny of traditional medicinal flora. This study marked the first extensive evaluation of the anti-diabetic, anticancer, and anti-inflammatory effects of Costus pictus rhizomes, expanding beyond its well-known anti-diabetic properties in leaves. Hot air-dried C. pictus rhizomes underwent ultrasound-assisted extraction to produce the rhizome extract. Anti-diabetic effects were determined through enzymatic inhibition studies targeting "α-amylase and α-glucosidase," crucial enzymes in glucose regulation, revealing potent inhibitory effects with IC50 values of 266.591 and 324.938 µg/ml, respectively. The ubiquity of breast cancer and constrained therapeutic alternatives for triple negative breast cancer led to the utilization of the "MDA-MB 231 cell line" for the study. The rhizome extracts demonstrated cytotoxicity at an IC50 concentration of 770 µg/ml, with a pronounced decline in the "reactive oxygen species (ROS)" and "mitochondrial membrane potential (MMP)." They also regulated the cell cycle arrest at the G2/M phase and positively induced apoptosis, thus making it a potent anticancer candidate. Anti-inflammatory effects were assessed using "RAW 264.7 macrophage cell line" and exhibited dose-dependent reduction with IC50 of 495.074 µg/ml, declining nitric oxide (NO) levels. Antimicrobial studies provided insights into its effectiveness against pathogens. This pivotal understanding laid groundwork for advancing C. pictus rhizome extract as a potential ingredient in pharmaceuticals or functional foods, leading to favorable health outcomes.

PPARγ activation by pioglitazone enhances the anti-proliferative effects of doxorubicin on pro-monocytic THP-1 leukemia cells via inducing apoptosis and G2/M cell cycle arrest

PURPOSE

Doxorubicin (DOX) is a common chemotherapeutic agent, with toxic side effects, and chemoresistance. Combination chemotherapy is a successful approach to overcome these limitations. Here, we investigated the effects of pioglitazone (PGZ), a PPARγ agonist, and/or DOX on the viability, cell cycle, apoptosis on THP-1 cells and normal human monocytes (NHMs).

METHODS

MTT assay was used to evaluate the cytotoxicity of DOX and/or PGZ. Cell cycle progression and apoptosis induction were examined by PI or Annexin V-PI double staining, and analyzed by flow cytometry. Quantitative RT-PCR was used to evaluate the changes in the mRNA expression of cell cycle progression or apoptosis-associated genes including P27, P21, CDK2, P53, BCL2 and FasR.

RESULTS

DOX, PGZ and DOX + PGZ exerted their cytotoxic effects in a dose- and time-dependent manner with low toxicity on NHMs. The cell growth inhibitory effects of DOX were in association with G2/M arrest, while PGZ executed S phase arrest. PGZ treatment enhanced G2/M among DOX-treated combinations with moderate elevation in the S phase. DOX, PGZ and combined treatments induced apoptosis (mostly late phase) in a dose-dependent manner. All treatments resulted in the significant overexpression of p21, p27, p53 and FasR genes and downregulation of CDK2. DOX + PGZ combined treatments exhibited the most significant changes in mRNA expression.

CONCLUSION

We demonstrated that the antiproliferative, cell cycle regulation and apoptosis-inducing capacity of DOX was enhanced by PGZ in THP-1 leukemia cells in a dose-dependent manner. Therefore, the combination of DOX + PGZ could be used as a novel combination to target AML.

Perturbation of microRNA signalling by doxorubicin in spermatogonial, Leydig and Sertoli cell lines in vitro

We have previously shown that in addition to its widely recognised cardiotoxicity, the chemotherapeutic doxorubicin (DOX) is able to induce transcriptional, microRNA (miRNA) and DNA methylation changes in the mouse testis. These changes perturb pathways involved in stress/cell death and survival and testicular function and lead to germ cell loss and reproductive organ damage. Here, we further investigated the differential miRNA expression induced by DOX in mouse spermatogonial (GC1), Leydig (TM3) and Sertoli (TM4) cell lines in vitro. We began by performing cell cycle analysis of the three mouse testicular cell lines to evaluate their sensitivity to DOX and thus select suitable doses for miRNA profiling. In keeping with our in vivo data, the spermatogonial cell line was the most sensitive, and the Sertoli cell line the most resistant to DOX-induced cell cycle arrest. We then further demonstrated that each cell line has a distinct miRNA profile, which is perturbed upon treatment with DOX. Pathway analysis identified changes in the miRNA-mediated regulation of specialised signalling at germ-Sertoli and Sertoli-Sertoli cell junctions following treatment with DOX. Amongst the most significant disease categories associated with DOX-induced miRNA expression were organismal injury and abnormalities, and reproductive system disease. This suggests that miRNAs play significant roles in both normal testicular function and DOX-induced testicular toxicity. Comparison of our in vitro and in vivo data highlights that in vitro cell models can provide valuable mechanistic information, which may also help facilitate the development of biomarkers of testicular toxicity and high-throughput in vitro screening methods to identify potential testicular toxicants.

Acquired tumor cell resistance to sunitinib by increased invasion and epithelial-mesenchymal transition in LL/2 murine lung cancer

OBJECTIVE

This study aims to investigate biological behavior changes in a murine lung cancer cell characterized by acquired resistance to sunitinib, a potent inhibitor of multiple-targeted receptor tyrosine kinase.

METHODS

A lung cancer cell line resistant to sunitinib (LL/2-R) was developed from its parental cell line (LL/2-P). Differences in biological characteristics and associated molecular profiles between these two cells were compared in vitro and in vivo.

RESULTS

LL/2-R cells showed an approximately 5-fold higher IC₅₀ of sunitinib than LL/2-P cells and exhibited a reduced growth inhibition following sunitinib treatment compared with LL/2-P. In LL/2-R cells and tumors, increased migration, invasion and metastasis were observed, along with upregulation of MMP-2 and MMP-9. We also analyzed the molecular profiles involved in EMT, and found that E-cadherin was downregulated in LL/2-R tumors, and vimentin was upregulated in LL/2-R cells and tumors, along with β-catenin translocating to the nuclei in LL/2-R cells. Furthermore, transcriptional factors mediated EMT, snail and twist, and the secretion of TGFβ1 also increased in LL/2-R cells and tumors.

CONCLUSIONS

We established a sunitinib-resistant lung cancer cell line and confirmed its drug-resistance to sunitinib in vivo. Our results implied that increased invasion and EMT may associate with the acquisition of resistant phenotype to sunitinib in cancer cells.

Antioxidant and antiproliferative effects of different solvent fractions from Terminalia belerica Roxb. fruit on various cancer cells

Terminalia belerica Roxb. fruits have been previously reported against diabetes, ulcer, microbial problems and hepatotoxicity. The present study was aimed to investigate antioxidant and anticancer potential of sequentially fractionated hexane (TBHE), chloroform (TBCE), ethyl acetate (TBEE), butanol (TBBE) and water (TBWE) extracts from the 70% methanolic extract of T. belerica fruits. TBCE, TBEE, TBBE and TBWE showed excellent ROS (reactive oxygen species) and RNS (reactive nitrogen species) scavenging activities which was investigated using 11 different assays for various free radicals. Among 5 fractions, TBHE and TBCE remained nontoxic to any of the malignant cell lines including normal cells (WI-38). TBBE and TBWE inhibited the proliferation of breast (MCF-7), cervical (HeLa) and brain (U87) cancer cells by inducing G2/M arrest while TBEE caused apoptosis. However, these fractions did not inhibit the proliferation of lung (A549) and liver (HepG2) cancer cells. BrdU incorporation study also suggested the efficient anticancer potential of TBEE, TBBE and TBWE. Moreover, TBBE and TBWE treated MCF-7, HeLa and U87 cells showed upregulation of p53 and p21 proteins. Phytochemical analysis reflected the presence of adequate quantities of different phytochemicals. Moreover, HPLC analysis show peaks of purpurin, catechin, tannic acid, reserpine, ellagic acid, methyl gallate, aconitine and rutin in TBBE, TBWE and TBEE. Hence these polar extracts of T. belerica can be used to develop drug against different types of cancer.

Oral bioavailability and evaluation of docetaxel–nicotinamide complex loaded chitosan nanoparticles

DTX–NA/NPs, synergism of DTX–NA complex and positively charged chitosan nanoparticles, can considerably enhance oral bioavailability.

Different types of cell cycle- and apoptosis-related gene expressions alter in corticosteroid-, vincristine-, and melphalan-resistant u-266 multiple myeloma cell lines

Objective: Deregulation of the cell cycle and apoptosis mechanisms in normal cells causes many problems, including cancer. In this study, a genome-wide expression analysis of cell cycle- and apoptosis-related genes in corticosteroid-, vincristine-, and melphalan-resistant U-266 multiple myeloma cell lines was conducted.

Materials and Methods: Resistant U-266 sublines were induced by application of each drug by stepwise dose increments. Resistance gained by the cells was confirmed with XTT cytotoxicity assay and microarray analyses were carried out. Among the cell cycle- and apoptosis-related gene expressions, alterations of more than 2-fold were considered significant.

Results: Cyclin E2 was drastically overexpressed in the vincristine-resistant subline and a general upregulation was observed for various cyclin-dependent kinases. Some of the cyclin-dependent kinase inhibitor encoding genes were downregulated in resistant sublines in general. Tumor necrosis factor receptor genes were generally downregulated in corticosteroid- and melphalan-resistant U-266 sublines. Different types of effector caspases were downregulated in all resistant sublines. Ceramide metabolism genes seemed to be changed in favor of survival, especially in the melphalan-resistant subline.

Conclusion: This report shows that different types of chemotherapeutic drugs alter different apoptotic and cell cycle-related gene expressions and, as a result, may cause drug-resistant phenotypes in U-266 multiple myeloma cell lines. Among those gene expressions, the most drastic increase in cyclin E2 could be important for the survival of vincristine-resistant U-266 cell lines, whereas alteration of ceramide metabolism genes could be important in melphalan resistance.

Roles of signaling pathways in drug resistance, cancer initiating cells and cancer progression and metastasis

The EGFR/PI3K/PTEN/Akt/mTORC pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance, cancer initiating cells (CICs) and metastasis. The expression of this pathway is frequently altered in breast and other cancers due to mutations at or aberrant expression of: HER2, EGFR1, PIK3CA, and PTEN as well as other oncogenes and tumor suppressor genes. miRs and epigenetic mechanisms of gene regulation are also important events which regulate this pathway. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway has been associated with CICs and in some cases resistance to therapeutics. We will review the effects of activation of the EGFR/PI3K/PTEN/Akt/mTORC pathway primarily in breast cancer and development of drug resistance. The targeting of this pathway and other interacting pathways will be discussed as well as clinical trials with novel small molecule inhibitors as well as established drugs that are used to treat other diseases. In this manuscript, we will discuss an inducible EGFR model (v-ERB-B:ER) and its effects on cell growth, cell cycle progression, activation of signal transduction pathways, prevention of apoptosis in hematopoietic, breast and prostate cancer models.

Dillenia Suffruticosa extract inhibits proliferation of human breast cancer cell lines (MCF-7 and MDA-MB-231) via induction of G2/M arrest and apoptosis

The present research was designed to evaluate the anticancer properties of Dillenia suffruticosa extract. Our focus was on the mode of cell death and cell cycle arrest induced in breast cancer cells by the active fractions (designated as D/F4, D/F5 and EA/P2) derived from chromatographic fractionation of D. suffruticosa extracts. The results showed that the active fractions are more cytotoxic towards MCF-7 (estrogen positive breast cancer cells) and MDA-MB-231 (estrogen negative breast cancer cells) as compared to other selected cancer cell lines that included HeLa, A459 and CaOV3. The induction of cell death through apoptosis by the active fractions on the breast cancer cells was confirmed by Annexin V-FITC and PI staining. Cell cycle analysis revealed that D/F4 and EA/P2 induced G2/M phase cell cycle arrest in MCF-7 cells. On the other hand, MDA-MB-231 cells treated with D/F4 and D/F5 accumulated in the sub-G₁ phase without cell cycle arrest, suggesting the induction of cell death through apoptosis. The data suggest that the active fractions of D. suffruticosa extract eliminated breast cancer cells through induction of apoptosis and cell cycle arrest. The reason why MCF-7 was more sensitive towards the treatment than MDA-MB-231 remains unclear. This warrants further work, especially on the role of hormones in response towards cytotoxic agents. In addition, more studies on the mechanisms underlying the induction of apoptosis and cell cycle arrest by the plant extract also need to be carried out.

Folic acid conjugated δ-valerolactone-poly(ethylene glycol) based triblock copolymer as a promising carrier for targeted doxorubicin delivery

The aim of this study is to test the hypothesis that the newly synthesized poly(δ-valerolactone)/poly(ethylene glycol)/poly(δ-valerolactone) (VEV) copolymer grafted with folic acid would impart targetability and further enhance the anti-tumor efficacy of doxorubicin (DOX). Here, folic acid conjugated VEV (VEV-FOL) was synthesized by a modified esterification method and characterized using IR and NMR. DOX loaded VEV-FOL micelles were synthesized using a novel solvent evaporation method and were obtained with a mean diameter of 97 nm with high encapsulation efficiency and sustained in vitro release profile. Comparative studies of polymer micelles with and without folate for cellular uptake and cytotoxicity were done on folate receptor-positive breast cancer cell line, MDAMB231. The intracellular uptake tests showed significant increase in folate micellar uptake when compared to non-folate-mediated micelles. MTT assay followed by apoptosis assays clearly indicated that folate decorated micelles showed significantly better cytotoxicity (IC50 = 0.014 µM) and efficiency to induce apoptosis than other treated groups. Moreover, a significant G2/M arrest was induced by DOX loaded VEV-FOL micelles at a concentration where free drug failed to show any activity. Thus, our results show that the folic acid-labeled VEV copolymer is a promising biomaterial with controlled and sustainable tumor targeting ability for anticancer drugs which can open new frontiers in the area of targeted chemotherapy.

Potentiation of in vitro and in vivo antitumor efficacy of doxorubicin by cyclin-dependent kinase inhibitor P276-00 in human non-small cell lung cancer cells

Background

In the present study, we show that the combination of doxorubicin with the cyclin-dependent kinase inhibitor P276-00 was synergistic at suboptimal doses in the non-small cell lung carcinoma (NSCLC) cell lines and induces extensive apoptosis than either drug alone in H-460 human NSCLC cells.

Methods

Synergistic effects of P276-00 and doxorubicin on growth inhibition was studied using the Propidium Iodide (PI) assay. The doses showing the best synergistic effect was determined and these doses were used for further mechanistic studies such as western blotting, cell cycle analysis and RT-PCR. The in vivo efficacy of the combination was evaluated using the H-460 xenograft model.

Results

The combination of 100 nM doxorubicin followed by 1200 nM P276-00 showed synergistic effect in the p53-positive and p53-mutated cell lines H-460 and H23 respectively as compared to the p53-null cell line H1299. Abrogation of doxorubicin-induced G2/M arrest and induction of apoptosis was observed in the combination treatment. This was associated with induction of tumor suppressor protein p53 and reduction of anti-apoptotic protein Bcl-2. Furthermore, doxorubicin alone greatly induced COX-2, a NF-κB target and Cdk-1, a target of P276-00, which was downregulated by P276-00 in the combination. Doxorubicin when combined with P276-00 in a sequence-specific manner significantly inhibited tumor growth, compared with either doxorubicin or P276-00 alone in H-460 xenograft model.

Conclusion

These findings suggest that this combination may increase the therapeutic index over doxorubicin alone and reduce systemic toxicity of doxorubicin most likely via an inhibition of doxorubicin-induced chemoresistance involving NF-κB signaling and inhibition of Cdk-1 which is involved in cell cycle progression.

Aldo-Keto Reductase 1B10 and Its Role in Proliferation Capacity of Drug-Resistant Cancers

The human aldo–keto reductase AKR1B10, originally identified as an aldose reductase-like protein and human small intestine aldose reductase, is a cytosolic NADPH-dependent reductase that metabolizes a variety of endogenous compounds, such as aromatic and aliphatic aldehydes and dicarbonyl compounds, and some drug ketones. The enzyme is highly expressed in solid tumors of several tissues including lung and liver, and as such has received considerable interest as a relevant biomarker for the development of those tumors. In addition, AKR1B10 has been recently reported to be significantly up-regulated in some cancer cell lines (medulloblastoma D341 and colon cancer HT29) acquiring resistance toward chemotherapeutic agents (cyclophosphamide and mitomycin c), suggesting the validity of the enzyme as a chemoresistance marker. Although the detailed information on the AKR1B10-mediated mechanisms leading to the drug resistance process is not well understood so far, the enzyme has been proposed to be involved in functional regulations of cell proliferation and metabolism of drugs and endogenous lipids during the development of chemoresistance. This article reviews the current literature focusing mainly on expression profile and roles of AKR1B10 in the drug resistance of cancer cells. Recent developments of AKR1B10 inhibitors and their usefulness in restoring sensitivity to anticancer drugs are also reviewed.

Evaluation of triblock copolymeric micelles of δ- valerolactone and poly (ethylene glycol) as a competent vector for doxorubicin delivery against cancer

Background

Specific properties of amphiphilic copolymeric micelles like small size, stability, biodegradability and prolonged biodistribution have projected them as promising vectors for drug delivery. To evaluate the potential of δ-valerolactone based micelles as carriers for drug delivery, a novel triblock amphiphilic copolymer poly(δ-valerolactone)/poly(ethylene glycol)/poly(δ-valerolactone) (VEV) was synthesized and characterized using IR, NMR, GPC, DTA and TGA. To evaluate VEV as a carrier for drug delivery, doxorubicin (DOX) entrapped VEV micelles (VEVDMs) were prepared and analyzed for in vitro antitumor activity.

Results

VEV copolymer was successfully synthesized by ring opening polymerization and the stable core shell structure of VEV micelles with a low critical micelle concentration was confirmed by proton NMR and fluorescence based method. Doxorubicin entrapped micelles (VEVDMs) prepared using a modified single emulsion method were obtained with a mean diameter of 90 nm and high encapsulation efficiency showing a pH dependent sustained doxorubicin release. Biological evaluation in breast adenocarcinoma (MCF7) and glioblastoma (U87MG) cells by flow cytometry showed 2-3 folds increase in cellular uptake of VEVDMs than free DOX. Block copolymer micelles without DOX were non cytotoxic in both the cell lines. As evaluated by the IC₅₀ values VEVDMs induced 77.8, 71.2, 81.2% more cytotoxicity in MCF7 cells and 40.8, 72.6, 76% more cytotoxicity in U87MG cells than pristine DOX after 24, 48, 72 h treatment, respectively. Moreover, VEVDMs induced enhanced apoptosis than free DOX as indicated by higher shift in Annexin V-FITC fluorescence and better intensity of cleaved PARP. Even though, further studies are required to prove the efficacy of this formulation in vivo the comparable G2/M phase arrest induced by VEVDMs at half the concentration of free DOX confirmed the better antitumor efficacy of VEVDMs in vitro.

Conclusions

Our studies clearly indicate that VEVDMs possess great therapeutic potential for long-term tumor suppression. Furthermore, our results launch VEV as a promising nanocarrier for an effective controlled drug delivery in cancer chemotherapy.

A microarray based expression profiling of paclitaxel and vincristine resistant MCF-7 cells

Resistance to the broad spectrum of chemotherapeutic agents in cancer cell lines and tumors has been called multiple drug resistance (MDR). In this study, the molecular mechanisms of resistance to two anticancer agents (paclitaxel and vincristine) in mammary carcinoma cell line MCF-7 were investigated. Drug resistant sublines to paclitaxel (MCF-7/Pac) and vincristine (MCF-7/Vinc) that were developed from sensitive MCF-7 cells (MCF-7/S) were used. cDNA microarray analysis was performed for the RNA samples of sensitive and resistant cells in duplicate experiments. GeneSpring GX 7.3.1 Software was used in data analysis. The results indicated that the upregulation of MDR1 gene is the dominating mechanism of the paclitaxel and vincristine drug resistance. Additionally the upregulation of the genes encoding the detoxifying enzymes (i.e. GSTP1) was observed. Significant downregulation of apoptotic genes (i.e. PDCD2/4/6/8) and upregulation of some cell cycle regulatory genes (CDKN2A, CCNA2 etc.) was seen which may be in close relation to MDR in breast cancer. Drug resistant cancer cells exhibit different gene expression patterns depending on drug treatment, and each drug resistance phenotype is probably genetically different. Further functional studies are needed to demonstrate the complete set of genes contributing to the drug resistance phenotype in breast cancer cells.

Artificial neural networks for classification in metabolomic studies of whole cells using 1H nuclear magnetic resonance

We report the successful classification, by artificial neural networks (ANNs), of (1)H NMR spectroscopic data recorded on whole-cell culture samples of four different lung carcinoma cell lines, which display different drug resistance patterns. The robustness of the approach was demonstrated by its ability to classify the cell line correctly in 100% of cases, despite the demonstrated presence of operator-induced sources of variation, and irrespective of which spectra are used for training and for validation. The study demonstrates the potential of ANN for lung carcinoma classification in realistic situations.

A G-quadruplex stabilizer induces M-phase cell cycle arrest

G-quadruplex stabilizers such as telomestatin and HXDV bind with exquisite specificity to G-quadruplexes, but not to triplex, duplex, or single-stranded DNAs. Studies have suggested that the antiproliferative and possibly anti-tumor activities of these compounds are linked to their inhibitory effect on telomerase and/or telomere function. In the current studies, we show that HXDV, a synthetic analog of telomestatin, exhibits antiproliferative activity against both telomerase-positive and -negative cells and induces robust apoptosis within 16 h of treatment, suggesting a mode of action independent of telomerase. HXDV was also shown to inhibit cell cycle progression causing M-phase cell cycle arrest, as evidenced by accumulation of cells with 4 n DNA content, increased mitotic index, separated centrosomes, elevated histone H3 phosphorylation at Ser-10 (an M-phase marker), and defective chromosome alignment and spindle fiber assembly (revealed by time-lapse microscopy). The M-phase arrest caused by HXDV paralleled with reduction in the expression level of the major M-phase checkpoint regulator Aurora A. All these cellular effects appear to depend on the G-quadruplex binding activity of HXDV as its non-G-quadruplex binding analog, TXTLeu, is completely devoid of all these effects. In the aggregate, our results suggest that HXDV, which exhibits anti-proliferative and apoptotic activities, is also a novel M-phase blocker, with a mode of action dependent on its G-quadruplex binding activity.

Metabolomic studies of human lung carcinoma cell lines using in vitro (1)H NMR of whole cells and cellular extracts

We report principal component analysis (PCA) of (1)H NMR spectra recorded for a group of human lung carcinoma cell lines in culture and (1)H NMR analysis of extracts from the same samples. The samples studied were cells of lung tumour origin with different chemotherapy drug resistance patterns. For whole cells, it was found that the statistically significant causes of spectral variation were an increase in the choline and a decrease in the methylene mobile lipid (1)H resonance intensities, which correlate with our knowledge of the level of resistance displayed by the different cells. Similarly, in the (1)H NMR spectra of the aqueous and lipophilic extracts, significant quantitative differences in the metabolite distributions were apparent, which are consistent with the PCA results.

Therapeutic resistance in lung cancer

Despite considerable progress over the last 25 years in the systemic therapy of lung cancer, intrinsic and acquired resistance to chemotherapeutic agents and radiation remains a vexing problem. The number of mechanisms of therapeutic resistance in lung cancer has expanded considerably over the past three decades, and the crucial role of stress resistance pathways is increasingly recognised as a cause of intrinsic and acquired chemo- and radiotherapy resistance. This paper reviews recent evidence for stress defence proteins, particularly RALBP1/RLIP76, in mediating intrinsic and acquired chemotherapy and radiation resistance in human lung cancer.

Preclinical anti-tumor activity of XR5944 in combination with carboplatin or doxorubicin in non-small-cell lung carcinoma

XR5944 (MLN944) is a novel bis-phenazine currently in phase I clinical trials that has demonstrated potent cytotoxic activity against a variety of tumor models. The combinations of XR5944 with carboplatin or doxorubicin were investigated in COR-L23/P human non-small-cell lung carcinoma (NSCLC) cells in vitro and the corresponding xenografts in vivo. In vitro cytotoxicity was evaluated by the sulforhodamine B assay and the drug interactions following simultaneous or sequential exposure were determined using median-effect analysis to calculate combination indices (CIs). XR5944 demonstrated potent cytotoxicity compared to either carboplatin or doxorubicin in COR-L23/P cells. Simultaneous or sequential exposure of XR5944 followed by carboplatin led to a synergistic response (CI<1), whereas the reverse order of addition showed an additive or antagonistic response (CI< or =1). Sequential administration of doxorubicin followed by XR5944 demonstrated marginally improved cytotoxicity (CI=1.31-0.77) than other schedules (CI=1.50-1.22) relative to individual drugs. Anti-tumor activity against COR-L23/P xenografts in nude mice was enhanced by administration of XR5944 (2 or 5 mg/kg) immediately before carboplatin (50 mg/kg) compared to single-agent treatment at the same doses. Improved efficacy was also observed by sequential administration of 7 mg/kg doxorubicin 48 h before 2.5 or 5 mg/kg XR5944. No additional toxicity was observed with combinations compared to single-agent treatment alone as determined by body weights. These data suggest that combinations of XR5944 with carboplatin or doxorubicin are of significant interest for clinical use, and that the schedule of administration may be important for achieving clinical efficacy over single-agent therapy.

The modulation by xanthines of the DNA-damaging effect of polycyclic aromatic agents. Part II. The stacking complexes of caffeine with doxorubicin and mitoxantrone

Recently accumulated statistical data indicate the protective effect of caffeine consumption against several types of cancer diseases. There are also reports about protective effect of caffeine and other xanthines against tumors induced by polycyclic aromatic hydrocarbons. One of the explanations of this phenomenon is based on biological activation of such carcinogens by cytochromes that are also known for metabolism of caffeine. In the accompanying paper [Kapuscinski et al., this issue] we provide evidence (flow cytometry and the cell cycle analysis) that the cytostatic effects of caffeine (CAF) on two DNA alkylating agents, which do not require the biological activation, depend on their ability to form stacking (pi-pi) complexes. In this study, we use physicochemical techniques (computer aided light absorption and microcalorimetry), and molecular modeling to examine previously published qualitative data. This is published both by our and other group's data, indicates that CAF is able to modify the cytotoxic and/or cytostatic action of the two well known antitumor drugs doxorubicin (DOX) and mitoxantrone (MIT). To obtain the quantitative results from the experimental data we used the statistical-thermodynamical model of mixed aggregation, to find the association constants K(AC) of the CAF-drug interaction (128+/-10 and 356+/-21M(-1) for DOX-CAF and MIT-CAF complex formation, respectively). In addition, the favorable enthalpy change of CAF-MIT (DeltaH=-11.3kcal/mol) was measured by microcalorimetry titration. The molecular modeling (semi-empirical and force field method) allowed us to obtain the geometry of these complexes, which indicated the favorable energy (DeltaE) of complex formation of the protonated drug's molecules in aqueous environment (-7.4 and -8.7kcal/mol for DOX-CAF.5H(2)O and MIT-CAF.8H(2)O complex, respectively). The molecular modeling calculation indicates the existence of CAF-drug complexes in which the MIT molecules are intercalated between two CAF molecules (DeltaE=-29.9kcal/mol). These results indicate that the attenuating effect of caffeine on cytotoxic or mutagenic effects of some polycyclic aromatic mutagens cannot be the result of metabolic activation in the cells, but simply is the physicochemical process of the sequestering of aromatic molecules (e.g. carcinogens or mutagens) by formation of the stacking complexes. The caffeine may then act as the "interceptor" of potential carcinogens (especially in the upper part of digesting track) where its concentration can reach the mM level). There is, however, no indication, both, in the literature or from our experiments, that the xanthines can reverse the damage to nucleic acids at the point when the damage to DNA has already occurred.

Influence of irradiation and pentoxifylline on histone H3 phosphorylation in human tumour cell lines

Phosphorylation of histone H3 at Ser-10 correlates with chromatin condensation and this amino terminal modification is now recognized as a specific marker of mitosis. We have monitored the appearance of cells showing histone H3 phosphorylation in four human tumour cell lines to identify cell cycle progression after irradiation. In the human melanoma cell lines Be11 and MeWo and in the squamous cell carcinoma lines 4197 and 4451 a dose of 7 Gy of Co-gamma irradiation increases the number of cells binding anti-histone H3-P antibody 1-8-fold in a p53-independent manner. In the p53 mutant cell lines MeWo and 4451 H3-P phosphorylated cells can be detected as early as 30 min and show a maximum 1 h post-irradiation. In the cell lines Be11, 4197 and 4451 the early wave of H3 phosphorylated cells is followed by a second wave, which reaches a maximum 4.5-7 h post-irradiation and then declines. These events are attributed to damage-induced cell cycle blocks in the G1 and G2 phase of the cell cycle. Addition of the dose modifying drug pentoxifylline before irradiation increases the appearance of cells showing early and the late H3 phosphorylation. When pentoxifylline is added 12-24 h post-irradiation when the cell cycle blocks have reached their maximum the appearance of cells with phosphorylated H3 increases 3-5-fold in the p53 mutant cell lines MeWo and 4451. These observations are consistent with the function of the drug as a G2 block abrogator. The large H3 phosphorylation signal in p53 mutant cells is consistent with early entry of a cohort of G2 cells into mitosis. The smaller H3-P signal in p53 wild type cells correlates with the lower proportion of stable G2 populations in G1 blocked cells. These results indicate that pentoxifylline influences the appearance of histone H3 phosphorylated cells in a manner strongly dependent on the number of cells in G2 phase. This suggests that addition of pentoxifylline indeed abrogates the G2 block and thereby facilitates early entry into mitosis.

In vitro establishment of cis-diammine-dichloroplatinum(II) resistant lung cancer cell line and modulation of apoptotic gene expression as a mechanism of resistant phenotype

After exposure of H460 cells to an increasing concentrations of cis-diammine-dichloroplatinum(II) (cisplatin, CDDP) for 6 months, cisplatin resistant cells were isolated (H460/CIS). The biologic behaviors of H460 and H460/CIS cells were tested using animal experiments. Only the resistant cells developed lung metastases despite cisplatin treatment. The characteristics of H460/CIS cells are as follows, MTT analyses revealed that H460/CIS cells were markedly resistant to cisplatin compared with their parental cells. Also, H460/CIS cells exhibited cross-resistance to DNA damaging agents such as doxorubicin (DXR) and etoposide. Cisplatin treatment dramatically increased p53 expression in parental cells but not in H460/CIS cells which expressed basal levels of p53. Without cisplatin treatment, Bcl-2 and Bax were expressed in H460/CIS cells, but not in parental cell. Our data suggested that p53, Bax and Bcl-2 were up-regulated in H460/CIS cells. These changes could explain some of the mechanisms of cisplatin resistance. Thus, H460/CIS could be useful to investigate the mechanisms of drug resistance to cisplatin including apoptotic gene expressions conferring drug resistance, thereby making progress in the treatment of cisplatin-resistant tumor cells.