Drug resistance reversal--are we getting closer?

Bioengineering approaches to study multidrug resistance in tumor cells

The ability of cancer cells to become resistant to chemotherapeutic agents is a major challenge for the treatment of malignant tumors. Several strategies have emerged to attempt to inhibit chemoresistance, but the fact remains that resistance is a problem for every effective anticancer drug. The first part of this review will focus on the mechanisms of chemoresistance. It is important to understand the environmental cues, transport limitations and the cellular signaling pathways associated with chemoresistance before we can hope to effectively combat it. The second part of this review focuses on the work that needs to be done moving forward. Specifically, this section focuses on the necessity of translational research and interdisciplinary directives. It is critical that the expertise of oncologists, biologists, and engineers be brought together to attempt to tackle the problem. This discussion is from an engineering perspective, as the dialogue between engineers and other cancer researchers is the most challenging due to non-overlapping background knowledge. Chemoresistance is a complex and devastating process, meaning that we urgently need sophisticated methods to study the process of how cells become resistant.

Co-expression of CD147/EMMPRIN with monocarboxylate transporters and multiple drug resistance proteins is associated with epithelial ovarian cancer progression

Cancer metastasis and anti-cancer drug resistance are the major reason for the failure of clinical cancer treatment. We evaluated CD147, monocarboxylate transporters (MCT1 and MCT4), and multidrug resistance (MDR) markers (MDR1 and MRP2) in 4 epithelial ovarian cancer (EOC) cell lines and primary tumors (n = 120) along with the matched metastatic lesions (n = 40) with immunofluorescence labeling. We correlated CD147 with MCT1, MCT4, MDR1 and MRP2 markers in primary and metastatic cells in cell lines and tissues using confocal microscopy. We also investigated the relationship of expression of CD147, MCT1 and MCT4 with various progression parameters. Our results indicate that the co-expression of CD147 with MCTs or MDR markers was found in primary and metastatic EOC cells and stromal cells; the over-expression of CD147, MCT1 and MCT4 was found in most primary and the matched metastatic lesions of EOC, and was significantly associated with tumor stage, grade, residual disease status and presence of ascites (P < 0.05) but not with histology type (P > 0.05). These results suggest that over-expression of CD147, MCT1 and MCT4 is correlated with EOC progression, and co-expression of CD147 and MCT1/MCT4 is related to drug resistance during EOC metastasis and could be useful therapeutic targets to prevent the development of incurable, recurrent and drug resistance EOC.

Development and in vitro characterization of galactosylated low molecular weight chitosan nanoparticles bearing doxorubicin

The aim of the present research was to evaluate the potential of galactosylated low molecular weight chitosan (Gal-LMWC) nanoparticles bearing positively charged anticancer, doxorubicin (DOX) for hepatocyte targeting. The chitosan from crab shell was depolymerized, and the lactobionic acid was coupled with LMWC using carbodiimide chemistry. The depolymerized and galactosylated polymers were characterized. Two types of Gal-LMWC(s) with variable degree of substitution were employed to prepare the nanoparticles using ionotropic gelation with pentasodium tripolyphosphate anions. Factors affecting nanoparticles formation were discussed. The nanoparticles were characterized by transmission electron microscopy and photon correlation spectroscopy and found to be spherical in the size range 106-320 nm. Relatively higher percent DOX entrapment was obtained for Gal-LMWC(s) nanoparticles than for LMWC nanoparticles. A further increase in drug entrapment was found with nanoparticles prepared by Gal-LMWC with higher degree of substitution. A hypothesis which correlates the ionic concentration of DOX in nanoparticles preparation medium and percent DOX entrapment in cationic polymer has been proposed to explain the enhanced DOX entrapment. In-vitro drug release study demonstrated an initial burst release followed by a sustained release. The targeting potential of the prepared nanoparticles was assessed by in vitro cytotoxicity study using the human hepatocellular carcinoma cell line (HepG(2)) expressing the ASGP receptors on their surfaces. The enthusiastic results showed the feasibility of Gal-LMWC(s) to entrap the cationic DOX and targeting potential of developed Gal-LMWC(s) nanoparticles to HepG(2) cell line.

Mismatch repair deficient colorectal cancer in the era of personalized treatment

The molecular and genetic subtyping of cancer has allowed the emergence of individualized therapies. This approach could potentially deliver treatments that have both increased efficacy as well as reduced toxicity. A well-defined subtype of colorectal cancer (CRC) is characterized by a deficiency in the mismatch repair (MMR) pathway. MMR deficiency not only contributes to the pathogenesis of a large proportion of CRC, but also determines the response to many of the drugs that are frequently used to treat this disease. In this Review we describe the MMR deficient phenotype and discuss how a deficiency in this DNA repair process may impact on the management of CRC, including surgery, adjuvant chemotherapy and the choice of systemic agents for the palliation of advanced disease. We also discuss how the DNA repair defect in MMR deficient CRC could be exploited in the development of novel therapeutic strategies.

Identification and functional analysis of genes which confer resistance to cisplatin in tumor cells

The efficacy of cisplatin during cancer chemotherapy is often impaired by the emergence of cancer cells which become resistant to chemotherapeutic agents. While various mechanisms have been proposed to explain resistance to cisplatin, the genes involved in this process still remain unclear. By using DNA microarrays, we performed a genome-wide analysis of cisplatin-resistant HeLa cells in order to identify genes involved in resistance. We identified nine genes (NAPA, CITED2, CABIN1, ADM, HIST1H1A, EHD1, MARK2, PTPN21, and MVD), which were consistently upregulated in two cisplatin-resistant HeLa cell lines. The upregulated genes, here referred to as cisplatin resistance genes (CPR), were further analyzed for their ability to modify the response of HEK293 cells to cisplatin. Short-hairpin RNA (shRNA) knockdown of CPR genes, individually or in combination, was shown to sensitize HEK293 cells to cisplatin, but not to vincristine or taxol, suggesting that CPR genes may be involved specifically in cisplatin resistance. Among the treatments performed, shRNA knockdown of NAPA was the most efficient treatment able to sensitize cells to cisplatin. Furthermore, shRNA knockdown of a single CPR gene was sufficient to partially reverse acquired cisplatin resistance in HeLa cells. Sensitization to cisplatin following knockdown of CPR genes was also observed in the tumorigenic cell lines Sk-ov-3, H1155, and CG-1. Based on these results, we propose that the CPR genes identified here may represent potential candidates for novel target therapies aimed at preventing resistance to cisplatin during chemotherapy.

Expression of ABC-transport proteins in canine mammary cancer: consequences for chemotherapy

Intrinsic or acquired drug resistance is a major barrier for chemotherapy of cancer. Importantly, the presence of ATP-binding cassette, ABC-transport proteins in tumour cells circumvents an intracellular accumulation of chemotherapeutic drugs. In this study, 103 canine mammary tumour probes were investigated for mRNA expression of seven ABC-transporters by RT-PCR. All tumour samples expressed multidrug resistance-associated protein 1 (MRP1) and breast cancer resistance protein (BCRP). MRP7 was detected in 97.1% of tumour probes, MRP3 in 96.1%, Pgp in 92.2%, MRP5 in 85.4% and MRP6 in 64.1%. More of the half of tumour samples (56.1%) expressed all of the examined ABC-transport proteins. Approximately one-third of the tumour samples (32.7%) were lacking in one transporter and only 11.2% possessed from three to five transporters. The canine transporter cBCRP was functionally analysed in stable transfected Madin-Darby canine kidney-II cells using an MTT viability test. cBCRP transfected cells showed a 5.4-fold resistance to 10 microm doxorubicin. Cell survival in the presence of methotrexate was not affected by cBCRP. In conclusion, absence of efficiency of chemotherapy of canine mammary cancer can be caused by expression of seven various ABC-transport proteins. Because cBCRP is expressed in all examined tumour probes and induces resistance to doxorubicin, the application of doxorubicin for treatment of canine mammary is inappropriate.

Human mutations that confer paclitaxel resistance

The involvement of tubulin mutations as a cause of clinical drug resistance has been intensely debated in recent years. In the studies described here, we used transfection to test whether beta1-tubulin mutations and polymorphisms found in cancer patients are able to confer resistance to drugs that target microtubules. Three of four mutations (A185T, A248V, R306C, but not G437S) that we tested caused paclitaxel resistance, as indicated by the following observations: (a) essentially 100% of cells selected in paclitaxel contained transfected mutant tubulin; (b) paclitaxel resistance could be turned off using tetracycline to turn off transgene expression; (c) paclitaxel resistance increased as mutant tubulin production increased. All the paclitaxel resistance mutations disrupted microtubule assembly, conferred increased sensitivity to microtubule-disruptive drugs, and produced defects in mitosis. The results are consistent with a mechanism in which tubulin mutations alter microtubule stability in a way that counteracts drug action. These studies show that human tumor cells can acquire spontaneous mutations in beta1-tubulin that cause resistance to paclitaxel, and suggest that patients with some polymorphisms in beta1-tubulin may require higher drug concentrations for effective therapy.

Effects of pluronic and doxorubicin on drug uptake, cellular metabolism, apoptosis and tumor inhibition in animal models of MDR cancers

Cancer chemotherapy is believed to be impeded by multidrug resistance (MDR). Pluronic (triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), PEO-b-PPO-b-PEO) were previously shown to sensitize MDR tumors to antineoplastic agents. This study uses animal models of Lewis lung carcinoma (3LL-M27) and T-lymphocytic leukemia (P388/ADR and P388) derived solid tumors to delineate mechanisms of sensitization of MDR tumors by Pluronic P85 (P85) in vivo. First, non-invasive single photon emission computed tomography (SPECT) and tumor tissue radioactivity sampling demonstrate that intravenous co-administration of P85 with a Pgp substrate, 99Tc-sestamibi, greatly increases the tumor uptake of this substrate in the MDR tumors. Second, 31P magnetic resonance spectroscopy (31P-MRS) in live animals and tumor tissue sampling for ATP suggest that P85 and doxorubicin (Dox) formulations induce pronounced ATP depletion in MDR tumors. Third, these formulations are shown to increase tumor apoptosis in vivo by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and reverse transcription polymerase chain reaction (RT-PCR) for caspases 8 and 9. Altogether, formulation of Dox with P85 results in increased inhibition of the growth solid tumors in mice and represents novel and promising strategy for therapy of drug resistant cancers.

iNOS activity is necessary for the cytotoxic and immunogenic effects of doxorubicin in human colon cancer cells

BACKGROUND

Doxorubicin is one of the few chemotherapeutic drugs able to exert both cytotoxic and pro-immunogenic effects against cancer cells. Following the drug administration, the intracellular protein calreticulin is translocated with an unknown mechanism onto the plasma membrane, where it triggers the phagocytosis of tumour cells by dendritic cells. Moreover doxorubicin up-regulates the inducible nitric oxide (NO) synthase (iNOS) gene in cancer cells, leading to huge amounts of NO, which in turn acts as a mediator of the drug toxicity and as a chemosensitizer agent in colon cancer. Indeed by nitrating tyrosine on the multidrug resistance related protein 3, NO decreases the doxorubicin efflux from tumour cells and enhances the drug toxicity. It is not clear if NO, beside playing a role in chemosensitivity, may also play a role in doxorubicin pro-immunogenic effects. To clarify this issue, we compared the doxorubicin-sensitive human colon cancer HT29 cells with the drug-resistant HT29-dx cells and the HT29 cells silenced for iNOS (HT29 iNOS-).

RESULTS

In both HT29-dx and HT29 iNOS- cells, doxorubicin did not induce NO synthesis, had a lower intracellular accumulation and a lower toxicity. Moreover the drug failed to promote the translocation of calreticulin and the phagocytosis of HT29-dx and HT29 iNOS-cells, which resulted both chemoresistant and immunoresistant. However, if NO levels were exogenously increased by sodium nitroprusside, the chemosensitivity to doxorubicin was restored in HT29 iNOS-cells. In parallel the NO donor per se was sufficient to induce the exposure of calreticulin and to increase the phagocytosis of HT29 iNOS- cells by DCs and their functional maturation, thus mimicking the pro-immunogenic effects exerted by doxorubicin in the parental drug-sensitive HT29 cells.

CONCLUSION

Our data suggest that chemo- and immuno-resistance to anthracyclines are associated in colon cancer cells and rely on a common mechanism, that is the inability of doxorubicin to induce iNOS. Therefore NO donors might represent a promising strategy to restore both chemosensitivity and immunosensitivity to doxorubicin in resistant cells.

The epothilones: how pharmacology relates to clinical utility

OBJECTIVE

To review the pharmacologic properties of a novel class of chemotherapeutic agents, the epothilones, and to summarize findings from recent clinical trials investigating the various epothilones in cancer therapy.

DATA SOURCES

Literature searches were conducted using MEDLINE, PubMed, and the abstract search engines for the American Society of Clinical Oncology and American Association for Cancer Research annual meetings (all searches through November 2008). Primary search terms included epothilone, BMS-247550, ixabepilone, EPO906, patupilone, sagopilone, and ZK-EPO.

STUDY SELECTION AND DATA EXTRACTION

Publications were given priority for inclusion if they discussed structural or pharmacologic properties of the epothilones as a class or if they included preclinical or clinical data for epothilones currently in clinical development.

DATA SYNTHESIS

The epothilones are a novel class of microtubule-stabilizing agents (MSAs). Epothilones are structurally and pharmacologically distinct from taxanes, but the exact ways in which the pharmacophores of the 2 classes differ has not been firmly established. A number of natural, semisynthetic, and fully synthetic epothilones are in various stages of clinical development. These agents differ from each other and from existing MSAs; these differences influence potency, stability, and solubility. Ixabepilone is currently approved to treat multidrug-resistant metastatic breast cancer and has demonstrated efficacy in earlier stages of breast cancer and in several other tumor types. Patupilone and sagopilone are currently under clinical investigation and have each shown promise in a number of treatment settings and tumor types. All 3 agents appear to be associated with manageable toxicities, but no class-wide toxicity profile exists for the epothilones and dose-limiting toxicities differ among the agents.

CONCLUSIONS

The epothilones have demonstrated significant potential for addressing the growing therapeutic challenge of taxane resistance, and the ever-increasing pool of information regarding structure-activity relationships of these MSAs will help to optimize microtubule-targeted chemotherapy.

Targeting synuclein-gamma to counteract drug resistance in cancer

BACKGROUND

Expression of synuclein-gamma (SNCG) protein is elevated in the advanced stages of many types of cancers, including ovarian, lung, liver, esophagus, colon, prostate and, in particular, breast. In breast carcinoma, SNCG is causatively linked to stimulated proliferation, metastasis and drug resistance.

OBJECTIVE

To establish SNCG as a potential therapeutic target and to discuss clinical use of SNCG inhibiting peptide.

METHODS

This review focuses on the plausible mechanisms of SNCG activity, SNCG mediated drug resistance and its inhibition.

RESULTS/CONCLUSION

Evidence based research shows that the aberrant expression of SNCG has a strong correlation with breast cancer progression and poor clinical outcome. A peptide based inhibitor counters activity of SNCG, which may be developed as an adjuvant therapy.

The role of cellular accumulation in determining sensitivity to platinum-based chemotherapy

The platinum (Pt) drugs cisplatin and carboplatin are heavily employed in chemotherapy regimens; however, similar to other classes of drugs, a number of intrinsic and acquired resistance mechanisms hamper their effectiveness. The method by which Pt drugs enter cells has traditionally been attributed to simple passive diffusion. However, recent evidence suggests a number of active uptake and efflux mechanisms are at play, and altered regulation of these transporters is responsible for the reduced accumulation of drug in resistant cells. This review suggests a model that helps reconcile the disparate literature by describing multiple pathways for Pt-containing drugs into and out of the cell.

The involvement of FOXO1 in cytotoxic stress and drug-resistance induced by paclitaxel in ovarian cancers

The role of transcriptional factor FOXO1 in the mechanism of drug-resistance in ovarian cancer has not been elucidated. In ovarian cancer cell lines, FOXO1 expression and its correlation with paclitaxel treatment was investigated by cytotoxic assay and silencing experiment. Clinical ovarian cancer samples were also examined for FOXO1 expression by immunohistochemistry. FOXO1 expression was distinctively upregulated in paclitaxel-resistant cell line, and enhanced by exposure to paclitaxel. FOXO1 overexpression was frequently observed in tissue samples from chemoresistant patients compared to chemosensitive patients. FOXO1 silencing in paclitaxel-resistant cell line decreased its resistance. Modification of oxidative stress by co-treatment with pharmacologic modulators of reactive oxygen species attenuated cytotoxicity of paclitaxel. Downstream targets of FOXO1 involving oxidative stress were also attenuated in silencing experiment, suggesting its involvement in altered sensitivity to paclitaxel. These results indicate that FOXO1 links to cytotoxic stress induced by paclitaxel and contributes to the drug-resistance in ovarian cancers.

Epothilones in the treatment of cancer

Epothilones are cytotoxic macrolides with a similar mechanism of action to paclitaxel but with the potential advantage of activity in taxane-resistant settings in preclinical models. The epothilones ixabepilone, patupilone, BMS-310705, KOS-862 and ZK-EPO are in early clinical trials for cancer treatment. Phase I studies have shown that dose-limiting toxicities of epothilones are generally neurotoxicity and neutropoenia although initial studies with patupilone indicated that diarrhoea was dose limiting. Neuropathy induced by ixabepilone may be schedule dependent. Over 20 Phase II studies of epothilones in cancer treatment have been reported, and significant activity in taxane-sensitive tumour types (such as breast, lung and prostate cancers) has been noted. Response rates in taxane-refractory metastatic breast cancer are relatively modest, but ixabepilone and patupilone have shown promising efficacy in hormone-refractory metastatic prostate cancer and in taxane-refractory ovarian cancer.

Chemotherapy and zoledronate sensitize solid tumour cells to Vgamma9Vdelta2 T cell cytotoxicity

Combinations of cellular immune-based therapies with chemotherapy and other antitumour agents may be of significant clinical benefit in the treatment of many forms of cancer. Gamma delta (gammadelta) T cells are of particular interest for use in such combined therapies due to their potent antitumour cytotoxicity and relative ease of generation in vitro. Here, we demonstrate high levels of cytotoxicity against solid tumour-derived cell lines with combination treatment utilizing Vgamma9Vdelta2 T cells, chemotherapeutic agents and the bisphosphonate, zoledronate. Pre-treatment with low concentrations of chemotherapeutic agents or zoledronate sensitized tumour cells to rapid killing by Vgamma9Vdelta2 T cells with levels of cytotoxicity approaching 90%. In addition, zoledronate enhanced the chemotherapy-induced sensitization of tumour cells to Vgamma9Vdelta2 T cell cytotoxicity resulting in almost 100% lysis of tumour targets in some cases. Vgamma9Vdelta2 T cell cytotoxicity was mediated by perforin following TCR-dependent and isoprenoid-mediated recognition of tumour cells. Production of IFN-gamma by Vgamma9Vdelta2 T cells was also induced after exposure to sensitized targets. We conclude that administration of Vgamma9Vdelta2 T cells at suitable intervals after chemotherapy and zoledronate may substantially increase antitumour activities in a range of malignancies.

Control of Mycosphaerella graminicola on wheat seedlings by medical drugs known to modulate the activity of ATP-binding cassette transporters

Medical drugs known to modulate the activity of human ATP-binding cassette (ABC) transporter proteins (modulators) were tested for the ability to potentiate the activity of the azole fungicide cyproconazole against in vitro growth of Mycosphaerella graminicola and to control disease development due to this pathogen on wheat seedlings. In vitro modulation of cyproconazole activity could be demonstrated in paper disk bioassays. Some of the active modulators (amitriptyline, flavanone, and phenothiazines) increased the accumulation of cyproconazole in M. graminicola, suggesting that they reversed cyproconazole efflux. However, synergism between cyproconazole and modulators against M. graminicola on wheat seedlings could not be shown. Despite their low in vitro toxicity to M. graminicola, some modulators (amitriptyline, loperamide, and promazine) did show significant intrinsic disease control activity in preventive and curative foliar spray tests with wheat seedlings. The results suggest that these compounds have indirect disease control activity based on modulation of fungal ABC transporters essential for virulence and constitute a new class of disease control agents.

Design, Synthesis, and Cytotoxic Evaluation of a New Series of 3-Substituted Spiro[(dihydropyrazine-2,5-dione)-6,3‘-(2‘,3‘-dihydrothieno[2,3-b]naphtho-4‘,9‘-dione)] Derivatives

A series of 3-substituted spiro[(dihydropyrazine-2,5-dione)-6,3'-(2',3'-dihydrothieno[2,3-b]naphtho-4',9'-dione)] derivatives were prepared using an easy synthetic route via condensation of the 3-amino-3-(ethoxycarbonyl)-2,3-dihydrothieno[2,3-b]naphtho-4,9-dione system and amino acids followed by intramolecular lactamization. Amino acids containing alkyl and aryl, linear and cyclic, polar and apolar, and basic and acid residues were incorporated. Evaluation of these analogues against the MCF-7 human breast carcinoma and SW 620 human colon carcinoma cell lines revealed, for the 3S,3'R isomers derived from Pro (7a), Cys (11a), and Met (12a) and the 3R,3'S isomer derived from D-Pro (7c), a cytotoxic potency comparable to or greater than that of doxorubicin. Some of these selected analogues were potent cytotoxic agents in several other sensible and resistant human solid tumor cell lines and may be able to circumvent the multiple-drug-resistance mechanism. In particular, only a partial cross-resistance to the compounds 7, 11, and 12 was observed in selected tumor cell sublines known to be resistant to doxorubicin (MCF-7/Dx and A2780/Dx), whereas a very low level of cross-resistance to compounds 7 and 11 was found in a tumor cell subline selected for resistance to cisplatin (A2780/DDP). In addition, the topoisomerase II inhibition activity and DNA-binding properties were investigated.

Polyamide Platinum Anticancer Complexes Designed to Target Specific DNA Sequences

Two new platinum complexes, trans-chlorodiammine[N-(2-aminoethyl)-4-[4-(N-methylimidazole-2-carboxamido)-N-methylpyrrole-2-carboxamido]-N-methylpyrrole-2-carboxamide]platinum(II) chloride (DJ1953-2) and trans-chlorodiammine[N-(6-aminohexyl)-4-[4-(N-methylimidazole-2-carboxamido)-N-methylpyrrole-2-carboxamido]-N-methylpyrrole-2-carboxamide]platinum(II) chloride (DJ1953-6) have been synthesized as proof-of-concept molecules in the design of agents that can specifically target genes in DNA. Coordinate covalent binding to DNA was demonstrated with electrospray ionization mass spectrometry. Using circular dichroism, these complexes were found to show greater DNA binding affinity to the target sequence: d(CATTGTCAGAC)(2), than toward either d(GTCTGTCAATG)(2,) which contains different flanking sequences, or d(CATTGAGAGAC)(2), which contains a double base pair mismatch sequence. DJ1953-2 unwinds the DNA helix by around 13 degrees , but neither metal complex significantly affects the DNA melting temperature. Unlike simple DNA minor groove binders, DJ1953-2 is able to inhibit, in vitro, RNA synthesis. The cytotoxicity of both metal complexes in the L1210 murine leukaemia cell line was also determined, with DJ1953-6 (34 microM) more active than DJ1953-2 (>50 microM). These results demonstrate the potential of polyamide platinum complexes and provide the structural basis for designer agents that are able to recognize biologically relevant sequences and prevent DNA transcription and replication.

Cell proliferation and drug resistance in hepatocellular carcinoma are modulated by Rho GTPase signals

Hepatocellular carcinoma is highly resistant to chemotherapeutic agents, thus the need to discover effective therapeutic molecules to suppress cancer cell growth and to overcome drug resistance is urgent. The Rho GTPase is implicated in cancer and metastasis and is directly activated by the Lymphoid blast crisis (Lbc) protooncogene, a Rho guanine-nucleotide exchange factor. The aim of the study was to analyze the expression of Lbc in hepatocarcinoma and to determine the effect of Lbc-induced Rho signaling on expression, growth rate and resistance to genotoxic stress. We found, by immunohistochemical analysis of biopsy samples and Northern and Western blot analyses of cell lines, that Lbc is absent in normal adult liver but is abundantly expressed in hepatocarcinoma, implying an increased Rho pathway signaling. Lbc stably transfected hepatocarcinoma cells exhibit increased proliferation and levels of ERK and cyclin D1 activation, which are blocked by a Rho inhibitor. In contrast, AKT activation was not altered. Moreover, Lbc expression confers increased resistance to genotoxic stress induced by doxorubicin, which is associated with upregulation of Bcl-2 and BAD phosphorylation, and this is reversed by a Rho inhibitor. In conclusion, these data support a role for Rho in liver cancer progression and resistance to therapy and may provide a basis for developing effective treatment for hepatocarcinoma.

Cytogenetic analysis of carboplatin resistance in early-stage epithelial ovarian carcinoma

Ovarian carcinoma is the leading cause of death among women with gynecological malignancies in western Europe. The high mortality rate is largely due to drug resistance. It is thus essential to increase knowledge and understanding of the underlying mechanisms of chemotherapy resistance, which might be caused by changes in the tumor genome. After surgery, carboplatin is the standard treatment for patients with early-stage ovarian cancer. Using comparative genomic hybridization (CGH), we explored cytogenetic alterations in 63 early-stage epithelial ovarian tumors, comparing the aberration patterns in the carboplatin-resistant and carboplatin-sensitive tumors. Several chromosomal regions were more frequently altered in the resistant tumors; some of these differences were statistically significant. We also found differences in tumor histology. Gains of 1q, 5q14 approximately q23, and 13q21 approximately q32, and losses of 8p and 9q were associated with clinical carboplatin resistance. Also, differences were found between the primary resistant and the secondary resistant tumors. Our findings demonstrate biologic observations of clinical drug resistance and specifically reveal chromosomal regions of interest for platinum resistance.

Chemotherapy pretreatment sensitizes solid tumor-derived cell lines to Vα24+ NKT cell-mediated cytotoxicity

There is an increasing awareness of the therapeutic potential for combining immune-based therapies with chemotherapy in the treatment of malignant diseases, but few published studies evaluate possible cytotoxic synergies between chemotherapy and cytotoxic immune cells. Human V alpha 24+/V beta 11+ NKT cells are being evaluated for use in cell-based immunotherapy of malignancy because of their immune regulatory functions and potent cytotoxic potential. In this study, we evaluated the cytotoxicity of combinations of chemotherapy and NKT cells to determine whether there is a potential to combine these treatment modalities for human cancer therapy. The cytotoxicity of NKT cells was tested against solid-tumor derived cell lines NCI-H358, DLD-1, HT-29, DU-145, TSU-Pr1 and MDA-MB231, with or without prior treatment of these target cells, with a range of chemotherapy agents. Low concentrations of chemotherapeutic agents led to sensitization of cell lines to NKT-mediated cytotoxicity, with the greatest effect being observed for prostate cancer cells. Synergistic cytotoxicity occurred in an NKT cell in a dose-dependent manner. Chemotherapy agents induced upregulation of cell surface TRAIL-R2 (DR5) and Fas (CD95) expression, increasing the capacity for NKT cells to recognize and kill via TRAIL- and FasL-mediated pathways. We conclude that administration of cytotoxic immune cells after chemotherapy may increase antitumor activities in comparison with the use of either treatment alone.

Cucurbit[n]uril binding of platinum anticancer complexes

The encapsulation of cisplatin by cucurbit[7]uril (Q[7]) and multinuclear platinum complexes linked via a 4,4'-dipyrazolylmethane (dpzm) ligand by Q[7] and cucurbit[8]uril (Q[8]) has been studied by NMR spectroscopy and molecular modelling. The NMR studies suggest that some cisplatin binds in the cucurbituril cavity, while cis-[PtCl(NH3)2(H2O)]+ only binds at the portals. Alternatively, the dpzm-linked multinuclear platinum complexes are quantitatively encapsulated within the cavities of both Q[7] and Q[8]. Upon encapsulation, the non-exchangeable proton resonances of the multinuclear platinum complexes show significant upfield shifts in 1H NMR spectra. The H3/H3* resonances shift upfield by 0.08 to 0.55 ppm, the H5/H5* shift by 0.9 to 1.6 ppm, while the methylene resonances shift by 0.74 to 0.88 ppm. The size of the resonance shift is dependent on the cavity size of the encapsulating cucurbituril, with Q[7] encapsulation producing larger shifts than Q[8]. The upfield shifts of the dpzm resonances observed upon cucurbituril encapsulation indicate that the Q[7] or Q[8] is positioned directly over the dpzm linking ligand. The terminal platinum groups of trans-[{PtCl(NH3)2}2 mu-dpzm]2+ (di-Pt) and trans-[trans-{PtCl(NH3)2}2-trans-{Pt(dpzm)2(NH3)2}]4+ (tri-Pt) provide a barrier to the on and off movement of cucurbituril, resulting in binding kinetics that are slow on the NMR timescale for the metal complex. Although the dpzm ligand has relatively few rotamers, encapsulation by the larger Q[8] resulted in a more compact di-Pt conformation with each platinum centre retracted further into each Q[8] portal. Encapsulation of the hydrolysed forms of di-Pt and tri-Pt is considerably slower than for the corresponding Cl forms, presumably due to the high-energy cost of passing the +2 platinum centres through the cucurbituril portals. The results of this study suggest that cucurbiturils could be suitable hosts for the pharmacological delivery of multinuclear platinum complexes.

Insulin-like growth factor receptor I targeting in epithelial ovarian cancer

OBJECTIVES

Preclinical evaluation of the anti-neoplastic activity of an insulin-like growth factor I receptor (IGF-IR) kinase inhibitor in ovarian cancer.

METHODS

The OVCAR-3 and OVCAR-4 cell lines were investigated under serum-free tissue culture conditions. IGF-I and IGF-II production were evaluated by standard ELISA and immunohistochemistry. IGF-IR expression and protein levels were evaluated by Western blotting. Cytotoxicity assays were performed in triplicates using the Alamar colorimetric assay. Apoptosis was evaluated by flow cytometry and by Western blotting for PARP.

RESULTS

The OVCAR-3 and OVCAR-4 cell lines produce IGF-I and IGF-II, and express IGF-IR, detectable by Western blotting, supporting the existence of an autocrine loop. The existence of this loop justified studies of NVP-AEW541, a small molecular weight inhibitor of the IGF-IR kinase. We observed growth inhibition of the ovarian cancer cell lines, with IC50 between 5 and 15 microM. We also observed that NVP-AEW541 sensitized cells to cisplatin in vitro. Western blotting demonstrated that NVP-AEW541 induced apoptosis at the concentrations that were used in the cytotoxicity assays, and decreased the concentration of the phosphorylated AKT signaling protein downstream of the IGF-IR.

CONCLUSIONS

IGF-IR is a potential new molecular target in ovarian cancer. The anti-neoplastic activity of NVP-AEW541 in ovarian cancer was observed at concentrations higher than those previously reported for multiple myeloma, suggesting the possibility that a portion of the observed anti-neoplastic activity could involve targets other than the IGF-IR. Experiments are being conducted to investigate the cytotoxicity profile in vivo and the clinical relevance of NVP-AEW541 in ovarian cancer treatment.

Inhibition of DNA methyltransferase reverses cisplatin induced drug resistance in murine neuroblastoma cells

BACKGROUND

Acquired drug resistance is a major obstacle to the successful treatment of neuroblastoma by chemotherapy. Recent studies from our laboratory have demonstrated that drug-induced alterations in DNA methylation play an important role in this process.

METHODS

The reversal of resistance to cisplatin in murine neuroblastoma (MNB) was induced by inhibition of DNA methyltransferase activity. MNB cells overexpressing DNA methyltransferase activity (Dnmt3a or Dnmt3b) were established by stable co-transfection of wild type MNB cells with plasmids containing Dnmt3a or Dnmt3b cDNA. Cytotoxic response (IC50), total DNA methyltransferase activity and expression of Dnmt3a or Dnmt3b methyltransferase were determined in Dnmt3a or Dnmt3b transfected MNB cells, respectively.

RESULTS

These data demonstrated that total DNA methyltransferase activity was increased to 3-fold above controls (P<0.001) in cisplatin resistant MNB cells, 3-fold in Dnmt3a and 4-fold in Dnmt3b transfected MNB cells. Western blot and RT-PCR data confirmed a corresponding increase in Dnmt3a and 3b expression in cisplatin resistant and transfected cells when compared with control MNB cells (P<0.001). MNB clones overexpressing Dnmt3a or Dnmt3b proteins were resistant to cisplatin treatment (10(-6) M). Incubation of cisplatin resistant, Dnmt3a or Dnmt3b overexpressing MNB cells with 5'-azacytidine (5'-azaC), a methylation inhibitor (2.5 microM) significantly decreased DNA methyltransferase activity, expression of Dnmt3a and Dnmt3b proteins and mRNA levels of cisplatin resistant, Dnmt3a and Dnmt3b transfected MNB cells. Cytotoxicity studies using the MTT assay demonstrated that the sensitivity of cisplatin resistant, Dnmt3a and Dnmt3b overexpressing MNB cells to cisplatin was increased 10-fold (P<0.001) following 5'-azaC treatment.

CONCLUSIONS

These findings suggest that the overexpression of DNA methyltransferase is associated with a cisplatin resistant phenotype in MNB cells that may or may not be true in animal studies or in the clinical setup. Thus, DNA methylation plays a central role in onset of drug resistance in cisplatin resistant neuroblastoma cells in vitro.

Development of Nonsymmetrical 1,4-Disubstituted Anthraquinones That Are Potently Active against Cisplatin-Resistant Ovarian Cancer Cells

A novel series of 1,4-disubstituted aminoanthraquinones were prepared by ipso-displacement of 1,4-difluoro-5,8-dihydroxyanthraquinones by hydroxylated piperidinyl- or pyrrolidinylalkylamino side chains. One aminoanthraquinone (13) was further derivatized to a chloropropylamino analogue by treatment with triphenylphosphine-carbon tetrachloride. The compounds were evaluated in the A2780 ovarian cancer cell line and its cisplatin-resistant variants (A2780/cp70 and A2780/MCP1). The novel anthraquinones were shown to possess up to 5-fold increased potency against the cisplatin-resistant cells compared to the wild-type cells. Growth curve analysis of the hydroxyethylaminoanthraquinone 8 in the osteosarcoma cell line U-2 OS showed that the cell cycle is not frozen, rather there is a late cell cycle arrest consistent with the action of a DNA-damaging topoisomerase II inhibitor. Accumulative apoptotic events, using time lapse photography, indicate that 8 is capable of fully engaging cell cycle arrest pathways in G2 in the absence of early apoptotic commitment. 8 and its chloropropyl analogue 13 retained significant activity against human A2780/cp70 xenografted tumors in mice.

Intrinsic chemotherapy resistance to the tubulin-binding antimitotic agents in renal cell carcinoma

Renal cancer is one of the most chemoresistant tumor types. Using a panel of 10 established renal cancer cell lines that have not been subjected to prior drug selection, the range of functional resistance phenotypes to the tubulin-binding agents paclitaxel, vinblastine, vincristine and patupilone (epothilone B, EPO906) was determined, together with expression of P-glycoprotein (PgP), multidrug resistance associated protein-2 (MRP2) and major vault protein (MVP) proteins. The IC(50) values for vincristine correlated positively with PgP expression (r = 0.73; p = 0.031), with values for paclitaxel and vinblastine just failing to reach significance. A significant positive correlation was observed for sensitivity to paclitaxel and MRP2 expression only (r = 0.8; p = 0.013). MVP expression did not correlate with sensitivity to any of the drugs examined. All cell lines exhibited much greater sensitivity to patupilone, demonstrating for the first time the potential use of patupilone in this cancer. In tissue samples from chemotherapy-naive renal cell carcinoma (RCC) patients, marked downregulation or absence of PgP in many tumor cells with expression levels more similar to sensitive cell lines rather than the resistant lines was seen. Similarly, MRP2 was absent or only weakly present in tumor cells, whereas MVP was very strongly upregulated in most tumor samples. This study illustrating discrepancies between results exclusively based on studies in cell lines and findings in vivo suggests that the role of PgP and MRP2 in intrinsic resistance in RCC in vivo may be less than expected from the in vitro findings and supports a potential role for MVP on the basis of in vivo expression studies.

Rad51 siRNA delivered by HVJ envelope vector enhances the anti-cancer effect of cisplatin

BACKGROUND

Every cancer therapy appears to be transiently effective for cancer regression, but cancers gradually transform to be resistant to the therapy. Cancers also develop machineries to resist chemotherapy. Short interfering RNA (siRNA) has been evaluated as an attractive and effective tool for suppressing a target protein by specifically digesting its mRNA. Suppression of the machineries using siRNA may enhance the sensitivity to chemotherapy in cancers when combined with an effective delivery system.

METHODS

To enhance the anti-cancer effect of chemotherapy, we transferred siRNA against Rad51 into various human cancer cells using the HVJ (hemagglutinating virus of Japan, Sendai virus) envelope vector in the presence or absence of cis-diamminedichloroplatinum(II) (CDDP, cisplatin). The inhibition of cell growth was assessed by a modified MTT assay, counting cell number, or fluorescence-activated cell sorting (FACS) analysis after Annexin V labeling. The synthetic Rad51 siRNA was also introduced into subcutaneous tumor masses of HeLa cells in SCID mice with or without intraperitoneal injection of CDDP, and tumor growth was monitored.

RESULTS

When synthetic Rad51 siRNA was delivered into HeLa cells using the HVJ envelope vector, no Rad51 transcripts were detected on day 2, and Rad51 protein completely disappeared for 4 days after siRNA transfer. When HeLa cells were incubated with 0.02 microg/ml CDDP for 3 h after siRNA transfer, the number of colonies decreased to approximately 10% of that with scrambled siRNA. The sensitivity to CDDP was enhanced in various human cancer cells, but not in normal human fibroblasts. When Rad51 siRNA was delivered into tumors using the HVJ envelope vector, the Rad51 transcript level was reduced to approximately 25%. Rad51 siRNA combined with CDDP significantly inhibited tumor growth when compared to siRNA or CDDP alone.

CONCLUSIONS

Rad51 siRNA could enhance the sensitivity to CDDP in cancer cells both in vitro and in vivo. Our results suggest that the combination of CDDP and Rad51 siRNA will be an effective anti-cancer protocol.

Class III β-Tubulin Overexpression Is a Prominent Mechanism of Paclitaxel Resistance in Ovarian Cancer Patients

The vast majority of women with advanced ovarian cancer will ultimately relapse and develop a drug-resistant disease with an overall 5-year survival of &lt;50%. Unfortunately, the mechanisms of drug resistance actually operating in patients are still unknown. To address this issue, in 41 patients affected by advanced ovarian cancer the three main mechanisms of paclitaxel resistance were investigated: overexpression of MDR-1 gene, point mutations at prominently expressed α-tubulin and β-tubulin genes and selective alterations in the expression of β-tubulin isotypes. MDR-1 and the β-tubulin isotypes expression were evaluated by semiquantitative and real-time PCR. On the same specimens, quantitative immunohistochemistry was also done in the tumor area. No statistically significant changes of MDR-1 expression were noticed between the sensitive and resistant patients either at the mRNA or protein level. The tubulin mutations for the ubiquitous α-tubulin and β-tubulin genes were evaluated by automated DNA sequencing, and in all patients, no mutations were detected in both resistant and sensitive cases. With regard to the expression of tubulin isoforms, a statistically significant up-regulation of class III β-tubulin was found in the resistant subset. It is worth noting that this statistically significant increase of the expression of class III β-tubulin was detectable at the mRNA and protein level. By a direct comparison of the three main known mechanisms of paclitaxel resistance, this study indicates that overexpression of class III β-tubulin is the most prominent mechanism of paclitaxel resistance in ovarian cancer.

Multidrug-resistant hela cells overexpressing MRP1 exhibit sensitivity to cell killing by hyperthermia: Interactions with etoposide

PURPOSE

Multidrug resistance (MDR) remains one of the primary obstacles in cancer chemotherapy and often involves overexpression of drug efflux transporters such as P-glycoprotein and multidrug resistance protein 1 (MRP1). Regional hyperthermia is undergoing clinical investigation in combination with chemotherapy or radiotherapy. This study evaluates whether hyperthermia can reverse MDR mediated by MRP1 in human cervical adenocarcinoma (HeLa) cells.

METHODS AND MATERIALS

Cytotoxicity of hyperthermia and/or etoposide was evaluated using sulforhodamine-B in HeLa cells overexpressing MRP1 and their drug-sensitive counterparts. Glutathione, glutathione peroxidase (GPx), and glutathione S-transferase (GST) were quantified by spectrophotometry. GST isoenzymes were quantified by immunodetection. Caspase activation was evaluated by fluorometry and chromatin condensation by fluorescence microscopy using Hoechst 33258. Necrosis was determined using propidium iodide.

RESULTS

The major finding is that HeLa and HeLaMRP cells are both sensitive to cytotoxicity of hyperthermia (41-45 degrees C). Hyperthermia induced activation of caspase 3 and chromatin condensation. Although total levels of cell killing were similar, there was a switch from apoptotic to necrotic cell death in MDR cells. This could be explained by decreased glutathione and GPx in MDR cells. MDR cells also contained very low levels of GST and were resistant to etoposide-induced apoptosis. Hyperthermia caused a modest increase in etoposide-induced apoptosis in HeLa and HeLaMRP cells, which required appropriate heat-drug scheduling.

CONCLUSIONS

Hyperthermia could be useful in eliminating MDR cells that overexpress MRP1.

Description of paclitaxel resistance-associated genes in ovarian and breast cancer cell lines

PURPOSE

To identify genes involved in the paclitaxel resistance phenotype.

METHODS

High-density Affymetrix HG-U95Av2 microarrays were used to quantify gene expression in the resulting cell lines, SKOV-3TR, OVCAR8TR and MCF-7TR, and their drug-sensitive parental lines, SKOV-3, OVCAR8 and MCF-7.

RESULTS

Three paclitaxel-resistant human ovarian and breast cancer cell lines were established. We identified 790 (SKOV-3TR), 689 (OVCAR8TR) and 964 (MCF-7TR) transcripts that were more than twofold overexpressed relative to their expression in the corresponding parental cell line. A comparison of these transcripts identified eight genes that were significantly overexpressed in all three drug-resistant daughter cell lines. These genes included MDR1, a gene often implicated in both in vitro and in vivo resistance to multiple chemotherapeutics, including paclitaxel. The remaining seven genes have not been previously associated with resistance to paclitaxel in human cancer. Furthermore, we identified 815 (SKOV-3TR), 430 (OVCAR8TR) and 332 (MCF-7TR) transcripts that were more than twofold decreased relative to their expression in the corresponding parental cell line. Comparison of these transcripts identified three genes that were significantly underexpressed in all three drug-resistant cell lines, none of which have been previously associated with paclitaxel resistance.

CONCLUSIONS

Our results confirm that the paclitaxel resistance phenotype is associated with a large number of transcriptional changes. In addition, acquired paclitaxel resistance was associated with distinct transcriptional changes in each of the cell lines studied, suggesting that paclitaxel resistance is a complex phenotype that can arise through multiple mechanisms.

Comparison of gene expression in HCT116 treatment derivatives generated by two different 5-fluorouracil exposure protocols

Background

Established colorectal cancer cell lines subjected to different 5-fluorouracil (5-FU) treatment protocols are often used as in vitro model systems for investigations of downstream cellular responses to 5-FU and to generate 5-FU-resistant derivatives for the investigation of biological mechanisms involved in drug resistance. We subjected HCT116 colon cancer cells to two different 5-FU treatment protocols in an attempt to generate resistant derivatives: one that simulated the clinical bolus regimens using clinically-achievable 5-FU levels, the other that utilized serial passage in the presence of increasing 5-FU concentrations (continuous exposure). HCT116 Bolus3, ContinB, and ContinD, corresponding to independently-derived cell lines generated either by bolus exposure or continuous exposure, respectively, were characterized for growth- and apoptosis-associated phenotypes, and gene expression using 8.5 K oligonucleotide microarrays. Comparative gene expression analyses were done in order to determine if transcriptional profiles for the respective treatment derivatives were similar or substantially different, and to identify the signaling and regulatory pathways involved in mediating the downstream response to 5-FU exposure and possibly involved in development of resistance.

Results

HCT116 ContinB and ContinD cells were respectively 27-fold and >100-fold more resistant to 5-FU and had reduced apoptotic fractions in response to transient 5-FU challenge compared to the parental cell line, whereas HCT116 Bolus3 cells were not resistant to 5-FU after 3 cycles of bolus 5-FU treatment and had the same apoptotic response to transient 5-FU challenge as the parental cell line. However, gene expression levels and expression level changes for all detected genes in Bolus3 cells were similar to those seen in both the ContinB (strongest correlation) and ContinD derivatives, as demonstrated by correlation and cluster analyses. Regulatory pathways having to do with 5-FU metabolism, apoptosis, and DNA repair were among those that were affected by 5-FU treatment.

Conclusion

All HCT116 derivative cell lines demonstrated similar transcriptional profiles, despite the facts that they were generated by two different 5-FU exposure protocols and that the bolus exposure derivative had not become resistant to 5-FU. Selection pressures on HCT116 cells as a result of 5-FU challenge are thus similar for both treatment protocols.