Enhancement of cytotoxicity of natural product drugs against multidrug resistant variant cell lines of human head and neck squamous cell carcinoma and breast carcinoma by tesmilifene

Silencing the OCT4-PG1 pseudogene reduces OCT-4 protein levels and changes characteristics of the multidrug resistance phenotype in chronic myeloid leukemia

Cancer stem cells show epigenetic plasticity and intrinsic resistance to anti-cancer therapy, rendering capable of initiating cancer relapse and progression. Transcription factor OCT-4 regulates various pathways in stem cells, but its expression can be regulated by pseudogenes. This work evaluated how OCT4-PG1 pseudogene can affect OCT-4 expression and mechanisms related to the multidrug resistance (MDR) phenotype in FEPS cells. Considering that OCT-4 protein is a transcription factor that regulates expression of ABC transporters, level of gene expression, activity of ABC proteins and cell sensitivity to chemotherapy were evaluated after OCT4-PG1 silencing. Besides we set up a STRING network. Results showed that after OCT4-PG1 silencing, cells expressed OCT-4 gene and protein to a lesser extent than mock cells. The gene and protein expression of ABCB1, as well as its activity were reduced. On the other hand, ALOX5 and ABCC1 genes was increased even as the activity of this transporter. Moreover, the silencing cells become sensitive to two chemotherapics tested. The network structure demonstrated that OCT4-PG1 protein interacts directly with OCT-4, SOX2, and NANOG and indirectly with ABC transporters. We conclude that OCT4-PG1 pseudogene plays a key role in the regulation OCT-4 transcription factor, which alters MDR phenotype in the FEPS cell line.

Novel anti-cancer drug COTI-2 synergizes with therapeutic agents and does not induce resistance or exhibit cross-resistance in human cancer cell lines

Emerging drug-resistance and drug-associated toxicities are two major factors limiting successful cancer therapy. Combinations of chemotherapeutic drugs have been used in the clinic to improve patient outcome. However, cancer cells can acquire resistance to drugs, alone or in combination. Resistant tumors can also exhibit cross-resistance to other chemotherapeutic agents, resulting in sub-optimal treatment and/or treatment failure. Therefore, developing novel oncology drugs that induce no or little acquired resistance and with a favorable safety profile is essential. We show here that combining COTI-2, a novel clinical stage agent, with multiple chemotherapeutic and targeted agents enhances the activity of these drugs in vitro and in vivo. Importantly, no overt toxicity was observed in the combination treatment groups in vivo. Furthermore, unlike the tested chemotherapeutic drugs, cancer cells did not develop resistance to COTI-2. Finally, some chemo-resistant tumor cell lines only showed mild cross-resistance to COTI-2 while most remained sensitive to it.

Synergistic Antiproliferative Activity of the RAD51 Inhibitor IBR2 with Inhibitors of Receptor Tyrosine Kinases and Microtubule Protein

Although cancer cell genetic instability contributes to characteristics that mediate tumorigenicity, it also contributes to the tumor-selective toxicity of some chemotherapy drugs. This synthetic lethality can be enhanced by inhibitors of DNA repair. To exploit this potential Achilles heel, we tested the ability of a RAD51 inhibitor to potentiate the cytotoxicity of chemotherapy drugs. 2-(Benzylsulfonyl)-1-(1H-indol-3-yl)-1,2-dihydroisoquinoline (IBR2) inhibits RAD51-mediated DNA double-strand break repair but also enhances cytotoxicity of the Bcr-Abl inhibitor imatinib. The potential for synergy between IBR2 and more drugs was examined in vitro across a spectrum of cancer cell lines from various tissues. Cells were exposed to IBR2 simultaneously with inhibitors of receptor tyrosine kinases, DNA-damaging agents, or microtubule disruptors. IBR2, at concentrations that inhibited proliferation between 0% and 75%, enhanced toxicity by up to 80% of imatinib and regorafenib (targets RAF and kit); epidermal growth factor receptor inhibitors erlotinib, gefitinib, afatinib, and osimertinib; and vincristine, an inhibitor of microtubule function. However, IBR2 antagonized the action of olaparib, cisplatin, melphalan, and irinotecan. A vincristine-resistant squamous cell line was not cross resistant to imatinib, but IBR2 and another RAD51 inhibitor (B02) enhanced imatinib toxicity in this cell line, its HN-5a parent, and the colon cancer line HT-29 by up to 60% and much better than verapamil, a P-glycoprotein inhibitor (P < 0.05). Given the disparate agents the functions of which are enhanced by IBR2, the mechanisms of enhancement may be multimodal. Whether RAD51 is common to these mechanisms remains to be elucidated, but it provides the potential for selectivity to tumor cells.

Tamoxifen prevents apoptosis and follicle loss from cyclophosphamide in cultured rat ovaries

Recent studies documented that the selective estrogen receptor modulator tamoxifen prevents follicle loss and promotes fertility following in vivo exposure of rodents to irradiation or ovotoxic cancer drugs, cyclophosphamide and doxorubicin. In an effort to characterize the ovarian-sparing mechanisms of tamoxifen in preantral follicle classes, cultured neonatal rat ovaries (Day 4, Sprague Dawley) were treated for 1-7 days with active metabolites of cyclophosphamide (i.e., 4-hydroxycyclophosphamide; CTX) (0, 1, and 10 μM) and tamoxifen (i.e., 4-hydroxytamoxifen; TAM) (0 and 10 μM) in vitro, and both apoptosis and follicle numbers were measured. CTX caused marked follicular apoptosis and follicular loss. TAM treatment decreased follicular loss and apoptosis from CTX in vitro. TAM alone had no effect on these parameters. IGF-1 and IGF-1 receptor were assessed in ovarian tissue showing no impact of TAM or CTX on these endpoints. Targeted mRNA analysis during follicular rescue by TAM revealed decreased expression of multiple genes related to inflammation, including mediators of lipoxygenase and prostaglandin production and signaling (Alox5, Pla2g1b, Ptgfr), cytokine binding (Il1r1, Il2rg ), apoptosis (Tnfrsf1a), second messenger signaling (Mapk1, Mapk14, Plcg1), as well as tissue remodeling and vasodilation (Bdkrb2, Klk15). The results suggest that TAM protects the ovary from CTX-mediated toxicity through direct ovarian actions that oppose follicular loss.

Challenges and Potential for Ovarian Preservation with SERMs

Tamoxifen (TAM) is a selective estrogen receptor modulator with tissue-specific effects on estrogen signaling used predominantly for treatment and chemoprevention of breast cancers. Recent studies have shown that TAM prevents infertility and decreases follicular loss from common cancer chemotherapy and radiation therapy in preclinical models. Here we review current and novel uses of selective estrogen receptor modulator s and advantages and challenges for translation of TAM for human fertility preservation.

Effects of tatariside G isolated from Fagopyrum tataricum roots on apoptosis in human cervical cancer HeLa cells

Cervical cancer is the second most common female carcinoma. Current therapies are often unsatisfactory, especially for advanced stage patients. The aim of this study was to explore the effects of tatariside G (TG) on apoptosis in human cervical cancer HeLa cells and the possible mechanism of action involved. An MTT assay was employed to evaluate cell viability. Hoechst 33258 staining and flow cytometry (FCM) assays were used to detect cell apoptosis. The protein expression of phosphorylated JNK, P38, ERK and Akt and cleaved caspase-3 and caspase-9 was evaluated by western blot analysis. Additionally, the mRNA expression of caspase-3 and caspase-9 was measured by fluorescent quantitative reverse transcription-PCR (FQ-RT-PCR). TG notably inhibited cell viability, enhanced the percentage of apoptotic cells, facilitated the phosphorylation of p38 MAPK and JNK proteins and caspase-3 and caspase-9 cracking, downregulated the phosphorylation level of Akt, and increased the loss of MMP and the mRNA expression of caspase-3 and caspase-9. TG-induced apoptosis is associated with activation of the mitochondrial death pathway. TG may be an effective candidate for chemotherapy against cervical cancer.

A tamoxifen derivative, N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine, selectively targets P-glycoprotein-positive multidrug resistant Chinese hamster cells

DPPE, a tamoxifen derivative with antihistamine activity, was previously shown to potentiate the toxicity of chemotherapeutic drugs. Recently, a Phase III clinical study using doxorubicin with DPPE demonstrated significant increase in the overall survival of breast cancer patients. In this study we examined the effects of DPPE alone on the growth of drug sensitive and P-gp positive CHO cell line. Our results demonstrate DPPE is selectively toxic to P-gp positive cells and the sensitivity to DPPE alone correlated with the levels of P-gp expression. Moreover, in MDR cells, DPPE-induced apoptosis was significantly reduced with Bcl2 overexpression and in the presence of P-gp ATPase inhibitor, PSC833. Furthermore, knockdown of P-gp expression in MDR cells with P-gp-siRNA reversed DPPE sensitivity and increased their sensitivity to doxorubicin and taxol but not to cisplatin. The addition of DPPE to membrane fractions led to dose-dependent increase in P-gp ATPase that was inhibited with PSC833. Moreover, incubation of P-gp positive cells with DPPE led to a significant increase in superoxide levels and a drop in cellular ATP and GSH pools that were reversible with inhibitors of P-gp ATPase. The combined presence of DPPE and the mitochondria electron transport complex III inhibitor, antimycin A, synergized in their effects on the growth of MDR cells but had no effect on the growth of parental drug sensitive cells. Collectively, the results of this study provide a possible mechanism that may be relevant to the clinical results of DPPE in breast cancer trial and demonstrates DPPE as P-gp collateral sensitivity drug.

Reversal of ATP-binding cassette drug transporter activity to modulate chemoresistance: why has it failed to provide clinical benefit?

Enhanced drug extrusion from cells due to the overexpression of the ATP-binding cassette (ABC) drug transporters inhibits the cytotoxic effects of structurally diverse and mechanistically unrelated anticancer agents and is a major cause of multidrug resistance (MDR) of human malignancies. Multiple compounds can suppress the activity of these efflux transporters and sensitize resistant tumor cells, but despite promising preclinical and early clinical data, they have yet to find a role in oncologic practice. Based on the knowledge of the structure, function, and distribution of MDR-related ABC transporters and the results of their preclinical and clinical evaluation, we discuss probable reasons why these inhibitors have not improved the outcome of therapy for cancer patients. We also outline new MDR-reversing strategies that directly target ABC transporters or circumvent relevant signaling pathways.

Inhibitory effects of tamoxifen and doxorubicin, alone and in combination, on the proliferation of the MG63 human osteosarcoma cell line

The present study aimed to compare the combined effect of tamoxifen (TAM) and doxorubicin (ADM) with the individual effects of TAM and ADM alone on the MG63 human osteosarcoma cell line. Estrogen receptor (ER) expression was detected in the MG63 cells using reverse transcription PCR. The morphological changes during the inhibition of cell growth were observed using an inverted microscope and a 3-(4, 5-dimethy1-2-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) colorimetric assay following the individual or combined addition of TAM and ADM. ERα and ERβ expression was detected in the MG63 cells. The typical apoptotic cell morphology was observed in all groups, with the exception of the control group. The MTT colorimetric analysis demonstrated that the rate of inhibition of cell proliferation in the combination group was significantly increased compared with that in the other groups (P<0.05). ERα and ERβ expression was detected in the MG63 human osteosarcoma cells. TAM and ADM alone were able to inhibit cell proliferation. The combination of TAM and ADM significantly enhanced the inhibitory effect, partly through the enhanced sensitivity of the cells to ADM by TAM, which caused the inhibition of cell proliferation and apoptosis.

Plants and cervical cancer: an overview

INTRODUCTION

Cervical cancer, the second most common gynecological malignant tumor seriously harmful to the health of women, remains a leading cause of cancer-related death for women in developing countries. Although a large amount of scientific research has been reported on plants as a natural source of treatment agents for cervical cancer, it is currently scattered across various publications. A systematic summary and knowledge of future prospects are necessary to facilitate further plant studies for anti-cervical cancer agents.

AREAS COVERED

This review generalizes and analyzes the current knowledge on the anti-cervical cancer properties and mechanisms involved for plants, and discusses the future prospects for the application of these plants.

EXPERT OPINION

This review mainly focuses on the plants which have been scientifically tested in vitro and/or in vivo and proved as potential agents for the treatment of cervical cancer. The failure of conventional chemotherapy to reduce mortality as well as serious side effects involved makes natural products ideal candidates for exerting synergism and attenuation effects on anticancer drugs. Although the chemical components and mechanisms of action of natural plants with anti-cervical cancer potential have been investigated, many others remain unknown. More investigations and clinical trials are necessary to make use of these medical plants reasonably.

Thymoquinone from Nigella sativa was more potent than cisplatin in eliminating of SiHa cells via apoptosis with down-regulation of Bcl-2 protein

Thymoquinone (TQ), the active constituent of Nigella sativa or black cumin exhibited cytotoxic effects in several cancer cell lines. In this study, the cytotoxicity of TQ in human cervical squamous carcinoma cells (SiHa) was investigated. TQ was cytotoxic towards SiHa cells with IC50 values of 10.67 ± 0.12 and 9.33 ± 0.19 μg/mL as determined by MTT assay and trypan blue dye exclusion test, respectively, after 72 h of incubation. TQ was more cytotoxic towards SiHa cells compared to cisplatin. Interestingly, TQ was less cytotoxic towards the normal cells (3T3-L1 and Vero). Cell cycle analysis performed by flowcytometer showed a significant increase in the accumulation of TQ-treated cells at sub-G1 phase, indicating induction of apoptosis by the compound. Apoptosis induction by TQ was further confirmed by Annexin V/PI and AO/PI staining. Significant elevation of p53 and down-regulation of the anti-apoptotic Bcl-2 protein was found in the treated cells, without any changes in the expression of the pro-apoptotic Bax protein. In conclusion, thymoquinone from N. sativa was more potent than cisplatin in elimination of SiHa cells via apoptosis with down-regulation of Bcl-2 protein.

Tamoxifen reverses the multi-drug-resistance of an established human cholangiocarcinoma cell line in combined chemotherapeutics

Our previous study established the human multi-drug-resistant cholangiocarcinoma cell line QBC939/ADM. In this study, we investigate further the ability of tamoxifen (TAM) to reverse drug-resistance to chemotherapeutics using QBC939/ADM cells. Cell growth inhibition was determined by the MTT assay, while cell cycle progression, apoptosis and the intra-cellular concentration of adriamycin (ADM) were all determined by flow cytometry. P-glycoprotein (P-gp) protein and mRNA expression was determined by Western blotting and real-time PCR. Growth inhibition and apoptosis induced by ADM, mitomycin (MMC), or vindesine (VDS) were enhanced after pre-treatment with 5 or 10 μM TAM, while only VDS increased cell numbers in the G(2)/M phase. The intra-cellular concentration of ADM rose after pre-treatment with 10 μM TAM, but not 5 μM TAM. Furthermore, real-time PCR and western blot analysis revealed down-regulation of P-gp expression in QBC939/ADM cells after TAM pre-treatment. The enhanced effects of TAM on growth inhibition, apoptosis, and intra-cellular concentration and the down-regulation of P-gp expression were blocked by an anti-P-gp antibody. TAM (10 μM) may reverse the multi-drug-resistance (MDR) of QBC939/ADM and enhance the chemotherapeutic effects on cholangiocarcinoma, by competitively inhibiting over-expressed P-gp.

The growth-inhibition effect of tamoxifen in the combination chemotherapeutics on the human cholangiocarcinoma cell line QBC939

In the individual application of adriamycin, mitomycin, vindesine and their combined application with tamoxifen for the pre-treatment of the human cholangiocarcinoma cell line QBC939, QBC939 was determined by MTT assay to investigate the inhibitive effect and its initial mechanism of TAM on cell growth. Growth cycle and apoptosis of each group were determined by flow cytometry. Concentration of ADM in QBC939 was detected by flow cytometry. The levels of their P-glycoprotein were detected by immunohistochemistry. The mRNA and protein levels of apoptotic-associated genes Bcl-2 and Bax were determined by western blot and real-time PCR. The inhibitive rates of adriamycin, mitomycin, vindesine to QBC939 and the apoptosis rates of QBC939 were enhanced after the pre-treatment of tamoxifen. Influence of tamoxifen in their growth cycle was not so obvious except vindesine group because of the increasing cell numbers of G (2)/M phase in which cells may be blocked. The contents of adriamycin in cells rose after the pre-treatment of tamoxifen. Expression level of the multi-drug resistant protein on cell surface was shown as (+). Furthermore, real-time PCR and Western blot analysis revealed an upregulation of Bcl-2 and a downregulation of Bax in QBC939 after the pre-treatment of tamoxifen. Therefore, tamoxifen may have the ability to enhance the relative sensitivity of QBC939 to chemotherapeutics.