Mechanism of paclitaxel resistance in a human prostate cancer cell line, PC3-PR, and its sensitization by cabazitaxel

Propofol attenuates prostate cancer progression by upregulating TRHDE-AS1 expression, and METTL14 could mediate its m6A modification

Propofol has become a microtubule-stabilizing drug for prostate cancer (PC) therapy, but propofol resistance impairs the therapeutic effect. This study aimed to explore the regulatory mechanism of propofol in the pathogenesis of PC through mechanisms involving N6-methyladenosine (m6A) modification. The changes in PC cell malignancy were evaluated by means of transwell, cell counting kit 8 (CCK-8), western blotting and tumour xenograft model assays. Long noncoding RNA TRHDE-AS1 and m6A methyltransferase METTL14 expression levels were determined via reverse transcription quantitative polymerase chain reaction (RT-qPCR). The m6A modification of TRHDE-AS1 which was mediated by METTL14 was confirmed by conducting methylated RNA immunoprecipitation (MeRIP) assay. We observed that propofol (200 μM) inhibited PC cell malignancy in vivo and in vitro, elucidating that it impaired cell proliferation, migration and tumour growth but induced apoptosis. TRHDE-AS1 expression was observed to be lower in PC cells and tissues, and propofol induced TRHDE-AS1 upregulation in PC cells. Propofol was capable of reversing the tumour-promoting effect of TRHDE-AS1 knockdown in PC cells. Additionally, METTL14 was upstream of TRHDE-AS1 to induce m6A modification of TRHDE-AS1 in PC cells. Collectively, our results show that propofol prevents PC progression by upregulating TRHDE-AS1 expression and METTL14 is involved in the m6A modification of TRHDE-AS1. These findings suggest that TRHDE-AS1 may be a potential therapeutic target for the improvement of propofol's therapeutic effect.

Autophagy-dependent alternative splicing of ribosomal protein S24 produces a more stable isoform that aids in hypoxic cell survival

Cells remodel splicing and translation machineries to mount specialized gene expression responses to stress. Here, we show that hypoxic human cells in 2D and 3D culture models increase the relative abundance of a longer mRNA variant of ribosomal protein S24 (RPS24L) compared to a shorter mRNA variant (RPS24S) by favoring the inclusion of a 22 bp cassette exon. Mechanistically, RPS24L and RPS24S are induced and repressed, respectively, by distinct pathways in hypoxia: RPS24L is induced in an autophagy-dependent manner, while RPS24S is reduced by mTORC1 repression in a hypoxia-inducible factor-dependent manner. RPS24L produces a more stable protein isoform that aids in hypoxic cell survival and growth, which could be exploited by cancer cells in the tumor microenvironment.

Long Noncoding RNAs in Taxane Resistance of Breast Cancer

Breast cancer is a common cancer in women and a leading cause of mortality. With the early diagnosis and development of therapeutic drugs, the prognosis of breast cancer has markedly improved. Chemotherapy is one of the predominant strategies for the treatment of breast cancer. Taxanes, including paclitaxel and docetaxel, are widely used in the treatment of breast cancer and remarkably decrease the risk of death and recurrence. However, taxane resistance caused by multiple factors significantly impacts the effect of the drug and leads to poor prognosis. Long noncoding RNAs (lncRNAs) have been shown to play a significant role in critical cellular processes, and a number of studies have illustrated that lncRNAs play vital roles in taxane resistance. In this review, we systematically summarize the mechanisms of taxane resistance in breast cancer and the functions of lncRNAs in taxane resistance in breast cancer. The findings provide insight into the role of lncRNAs in taxane resistance and suggest that lncRNAs may be used to develop therapeutic targets to prevent or reverse taxane resistance in patients with breast cancer.

The potential anti-cancer effects of quercetin on blood, prostate and lung cancers: An update

Cancer is caused by abnormal proliferation of cells and aberrant recognition of the immune system. According to recent studies, natural products are most likely to be effective at preventing cancer without causing any noticeable complications. Among the bioactive flavonoids found in fruits and vegetables, quercetin is known for its anti-inflammatory, antioxidant, and anticancer properties. This review aims to highlight the potential therapeutic effects of quercetin on some different types of cancers including blood, lung and prostate cancers.

Exosomes: special nano-therapeutic carrier for cancers, overview on anticancer drugs

Chemotherapy drugs are the first line of cancer treatment, but problems such as low intratumoral delivery, poor bioavailability, and off-site toxicity must be addressed. Cancer-specific drug delivery techniques could improve the therapeutic outcome in terms of patient survival. The current study investigated the loading of chemotherapy drugs loaded into exosomes for cancer treatment. Exosomes are the smallest extracellular vesicles found in body fluids and can be used to transfer information by moving biomolecules from cell to cell. This makes them useful as carriers. As the membranes of these nanoparticles are similar to cell membranes, they can be easily transported to carry different components. As most chemotherapy drugs are not easily soluble in liquid, loading them into exosomes can be a suitable solution to this problem. This cancer treatment could avert the injection of high doses of drugs and provide a more appropriate release mechanism.

Rational Design of a Novel Tubulin Inhibitor with a Unique Mechanism of Action

In this study, we capitalized on our previously performed crystallographic fragment screen and developed the antitubulin small molecule Todalam with only two rounds of straightforward chemical synthesis. Todalam binds to a novel tubulin site, disrupts microtubule networks in cells, arrests cells in G2/M, induces cell death, and synergizes with vinblastine. The compound destabilizes microtubules by acting as a molecular plug that sterically inhibits the curved-to-straight conformational switch in the α-tubulin subunit, and by sequestering tubulin dimers into assembly incompetent oligomers. Our results describe for the first time the generation of a fully rationally designed small molecule tubulin inhibitor from a fragment, which displays a unique molecular mechanism of action. They thus demonstrate the usefulness of tubulin-binding fragments as valuable starting points for innovative antitubulin drug and chemical probe discovery campaigns.

Acquisition of paclitaxel resistance modulates the biological traits of gastric cancer AGS cells and facilitates epithelial to mesenchymal transition and angiogenesis

PURPOSE

This study aims to develop a paclitaxel (PTX)-resistant gastric cancer AGS cells (AGS-R) and evaluate the mechanisms of drug resistance.

METHODS

AGS cells were successively treated with increasing PTX concentrations. Cross-resistance of established AGS-R, the molecular patterns of cell survival, evasion of apoptosis, epithelial-mesenchymal transition (EMT), and the angiogenic potential were evaluated.

RESULTS

AGS-R was induced within six months of PTX exposure. Extension of the treatment resulted in PTX-resistance beyond clinical levels. The established AGS-R showed resistance to vincristine and doxorubicin but not cisplatin. Upon induction of resistance, the expressions of MDR-1 (P < 0.001) and MRP-1 (P < 0.01) genes and proteins significantly increased. AGS-R cells had elevated levels of BCL-2, pro-CASP3, cleaved-NOTCH1, HES1, HEY1, NF-κB, PI3K, p-AKT, HIF-1α, Cyclin A, and B1 as compared with parental cells (at least P < 0.01). The protein levels of BAX, CASP3, P53, and P21 (at least P < 0.01) as well as intracellular ROS (P < 0.001) were reduced in AGS-R. A relative arrest at the G2/M phase (15.8 ± 0.75 vs. 26.7 ± 1.67) of the cell cycle and enrichment of AGS-R cells for CD44 marker (9 ± 0.6 vs. 1 ± 0.8) (P < 0.001) were detected by flow cytometry. While the E-cadherin expression was reduced (P < 0.001), the protein levels of Vimentin, N-cadherin, SLUG, and SNAIL were increased (at least P < 0.05). The angiogenic activity and release of VEGF and MMP2/9 were increased in AGS-R cells relative to the AGS line (P < 0.001).

CONCLUSION

AGS-R cells could bypass chemotherapy stress by expressing the genes coding for efflux pumps and altering some key signaling in favor of survival, EMT, and angiogenesis.

Generation of Two Paclitaxel-Resistant High-Grade Serous Carcinoma Cell Lines With Increased Expression of P-Glycoprotein

Debulking surgery followed by chemotherapy are the standard of care for high-grade serous carcinoma. After an initial good response to treatment, the majority of patients relapse with a chemoresistant profile, leading to a poor overall survival. Chemotherapy regimens used in high-grade serous carcinomas are based in a combination of classical chemotherapeutic drugs, namely, Carboplatin and Paclitaxel. The mechanisms underlying drug resistance and new drug discovery are crucial to improve patients’ survival. To uncover the molecular mechanisms of chemoresistance and test drugs capable of overcoming this resistant profile, it is fundamental to use good cellular models capable of mimicking the chemoresistant disease. Herein, we established two high-grade serous carcinoma cell lines with intrinsic resistance to Carboplatin and induced Paclitaxel resistance (OVCAR8 PTX R C and OVCAR8 PTX R P) derived from the OVCAR8 cell line. These two chemoresistant cell line variants acquired an enhanced resistance to Paclitaxel-induced cell death by increasing the drug efflux capacity, and this resistance was stable in long-term culture and following freeze/thaw cycles. The mechanism underlying Paclitaxel resistance resides in a significant increase in P-glycoprotein expression and, when this drug efflux pump was blocked with Verapamil, cells re-acquired Paclitaxel sensitivity. We generated two high-grade serous carcinoma cell lines, with a double-chemoresistant (Carboplatin and Paclitaxel) phenotype that mimics the majority of tumor recurrences in ovarian cancer context. This robust tool is suitable for preliminary drug testing towards the development of therapeutic strategies to overcome chemoresistance.

Microalgal Co-Cultivation Prospecting to Modulate Vitamin and Bioactive Compounds Production

Microalgal biotechnology is gaining importance. However, key issues in the pipeline from species selection towards large biomass production still require improvements to maximize the yield and lower the microalgal production costs. This study explores a co-cultivation strategy to improve the bioactive compounds richness of the harvested microalgal biomass. Based on their biotechnological potential, two diatoms (Skeletonema marinoi, Cyclotella cryptica) and one eustigmatophyte (Nannochloropsis oceanica) were grown alone or in combination. Concentrations of ten vitamins (A, B₁, B₂, B₆, B₁₂, C, D₂, D₃, E and H), carotenoids and polyphenols, together with total flavonoids, sterols, lipids, proteins and carbohydrates, were compared. Moreover, antioxidant capacity and chemopreventive potential in terms inhibiting four human tumor-derived and normal cell lines proliferation were evaluated. Co-cultivation can engender biomass with emergent properties regarding bioactivity or bioactive chemical profile, depending on the combined species. The high vitamin content of C. cryptica or N. oceanica further enhanced (until 10% more) when co-cultivated, explaining the two-fold increase of the antioxidant capacity of the combined C. cryptica and N. oceanica biomass. Differently, the chemopreventive activity was valuably enhanced when coupling the two diatoms C. cryptica and S. marinoi. The results obtained in this pilot study promote microalgal co-cultivation as a valuable strategy aiming to boost their application in eco-sustainable biotechnology.

Propofol enhanced the cell sensitivity to paclitaxel (PTX) in prostatic cancer (PC) through modulation of HOTAIR

BACKGROUND

PTX is widely used in cancer treatments.

OBJECTIVE

In this paper, we explored the role and potential molecular mechanism of propofol in regulating PTX sensitivity in PC cells.

METHODS

Prostatic cancer cell line PC3 was treated using different concentrations of PTX (10 nM, 50 nM), propofol (150 μM, 300 μM) or transfected with overexpressed HOTAIR plasmid. HOTAIR expression was analyzed by RT-qPCR. Apoptosis of PC3 cells was observed by flow cytometry method while cell viability was evaluated by CCK-8. Moreover, apoptosis-related genes, Bcl-2 and Bax were detected by Western blot methods. E-cadherin, N-cadherin and Vimentin protein concentrations were monitored by ELISA.

RESULTS

PTX significantly increased apoptosis of PC3 cells and reduced cell viability in a dose-dependent manner. Moreover, Protein expression of Bcl-2 was obviously inhibited while Bax protein expression level was provoked. Furthermore, E-cadherin protein concentration increased while N-cadherin and Vimentin decreased due to increasing PTX treatments. HOTAIR expression dropped due to PTX treatment while overexpression of HOTAIR induced cell viability, EMT and deterred apoptosis. Propofol ignited the PTX function while upregulation of HOTAIR partially reversed this.

CONCLUSION

Propofol enhanced paclitaxel sensitivity in prostatic cancer cells through modulation of HOTAIR in vitro.

Therapeutic strategies to overcome taxane resistance in cancer

One of the primary causes of attenuated or loss of efficacy of cancer chemotherapy is the emergence of multidrug resistance (MDR). Numerous studies have been published regarding potential approaches to reverse resistance to taxanes, including paclitaxel (PTX) and docetaxel, which represent one of the most important classes of anticancer drugs. Since 1984, following the FDA approval of paclitaxel for the treatment of advanced ovarian carcinoma, taxanes have been extensively used as drugs that target tumor microtubules. Taxanes, have been shown to affect an array of oncogenic signaling pathways and have potent cytotoxic efficacy. However, the clinical success of these drugs has been restricted by the emergence of cancer cell resistance, primarily caused by the overexpression of MDR efflux transporters or by microtubule alterations. In vitro and in vivo studies indicate that the mechanisms underlying the resistance to PTX and docetaxel are primarily due to alterations in α-tubulin and β-tubulin. Moreover, resistance to PTX and docetaxel results from: 1) alterations in microtubule-protein interactions, including microtubule-associated protein 4, stathmin, centriole, cilia, spindle-associated protein, and kinesins; 2) alterations in the expression and activity of multidrug efflux transporters of the ABC superfamily including P-glycoprotein (P-gp/ABCB1); 3) overexpression of anti-apoptotic proteins or inhibition of apoptotic proteins and tumor-suppressor proteins, as well as 4) modulation of signal transduction pathways associated with the activity of several cytokines, chemokines and transcription factors. In this review, we discuss the abovementioned molecular mechanisms and their role in mediating cancer chemoresistance to PTX and docetaxel. We provide a detailed analysis of both in vitro and in vivo experimental data and describe the application of these findings to therapeutic practice. The current review also discusses the efficacy of different pharmacological modulations to achieve reversal of PTX resistance. The therapeutic roles of several novel compounds, as well as herbal formulations, are also discussed. Among them, many structural derivatives had efficacy against the MDR phenotype by either suppressing MDR or increasing the cytotoxic efficacy compared to the parental drugs, or both. Natural products functioning as MDR chemosensitizers offer novel treatment strategies in patients with chemoresistant cancers by attenuating MDR and increasing chemotherapy efficacy. We broadly discuss the roles of inhibitors of P-gp and other efflux pumps, in the reversal of PTX and docetaxel resistance in cancer cells and the significance of using a nanomedicine delivery system in this context. Thus, a better understanding of the molecular mechanisms mediating the reversal of drug resistance, combined with drug efficacy and the application of target-based inhibition or specific drug delivery, could signal a new era in modern medicine that would limit the pathological consequences of MDR in cancer patients.

Taxanes in cancer treatment: Activity, chemoresistance and its overcoming

Since 1984, when paclitaxel was approved by the FDA for the treatment of advanced ovarian carcinoma, taxanes have been widely used as microtubule-targeting antitumor agents. However, their historic classification as antimitotics does not describe all their functions. Indeed, taxanes act in a complex manner, altering multiple cellular oncogenic processes including mitosis, angiogenesis, apoptosis, inflammatory response, and ROS production. On the one hand, identification of the diverse effects of taxanes on oncogenic signaling pathways provides opportunities to apply these cytotoxic drugs in a more rational manner. On the other hand, this may facilitate the development of novel treatment modalities to surmount anticancer drug resistance. In the latter respect, chemoresistance remains a major impediment which limits the efficacy of antitumor chemotherapy. Taxanes have shown impact on key molecular mechanisms including disruption of mitotic spindle, mitosis slippage and inhibition of angiogenesis. Furthermore, there is an emerging contribution of cellular processes including autophagy, oxidative stress, epigenetic alterations and microRNAs deregulation to the acquisition of taxane resistance. Hence, these two lines of findings are currently promoting a more rational and efficacious taxane application as well as development of novel molecular strategies to enhance the efficacy of taxane-based cancer treatment while overcoming drug resistance. This review provides a general and comprehensive picture on the use of taxanes in cancer treatment. In particular, we describe the history of application of taxanes in anticancer therapeutics, the synthesis of the different drugs belonging to this class of cytotoxic compounds, their features and the differences between them. We further dissect the molecular mechanisms of action of taxanes and the molecular basis underlying the onset of taxane resistance. We further delineate the possible modalities to overcome chemoresistance to taxanes, such as increasing drug solubility, delivery and pharmacokinetics, overcoming microtubule alterations or mitotic slippage, inhibiting drug efflux pumps or drug metabolism, targeting redox metabolism, immune response, and other cellular functions.

Cabazitaxel exhibits more favorable molecular changes compared to other taxanes in androgen-independent prostate cancer cells

Taxane-based chemotherapy drugs (cabazitaxel, docetaxel, and paclitaxel) are microtubule inhibitors, which are effectively and frequently used to treat metastatic prostate cancer (PCa). Among these, cabazitaxel is offered as a new therapeutic option for patients with metastatic castration-resistant PC as that are resistant to other taxanes. Here, we investigated the cellular and molecular changes in response to cabazitaxel in comparison with docetaxel and paclitaxel in androgen-independent human PCas. The androgen-independent human PCa cell lines, PC3 and DU145, were treated with 1 to 5nM cabazitaxel, docetaxel, or paclitaxel, and assessed for cell viability (MTT assay), colony forming ability and migration (scratch assay). The induction of apoptosis was determined through measurement of mitochondrial membrane potential (JC-1 assay) and caspase-3 activity assay. The protein expression changes (caspase-3, caspase-8, Bax, Bcl-2, β-tubulin, nuclear factor-κB [NF-κB/p50, NF-κB/p65], vascular endothelial growth factor, WNT1-inducible signaling pathway protein-1 [WISP1], transforming growth factor β [TGF-β]) in response to drug treatment were screened via western blotting. Under our experimental conditions, all taxanes significantly reduced WISP1 and TGF-β expressions, suggesting an anti-metastatic/antiangiogenic effect for these drugs. On the other hand, cabazitaxel induced more cell death and inhibited colony formation compared to docetaxel or paclitaxel. The highest fold change in caspase-3 activity and Bax/Bcl-2 ratio was also detected in response to cabazitaxel. Furthermore, the induction of β-tubulin expression was lower in cabazitaxel-treated cells relative to the other taxanes. In summary, cabazitaxel shows molecular changes in favor of killing PCa cells compared to other taxanes, at least for the parameters analyzed herein. The differences with other taxanes may be important while designing other studies or in clinical settings.

Long non-coding RNA SNHG6 regulates the sensitivity of prostate cancer cells to paclitaxel by sponging miR-186

Background

Chemo-resistance is one of the main obstacles in the treatment of prostate cancer (PCa). Long non-coding RNA small nucleolar RNA host gene 6 (SNHG6) is involved in the chemo-resistance of various tumors. We aim to survey the role and underlying molecular mechanism of SNHG6 in PCa resistance to paclitaxel (PTX).

Methods

The expression of SNHG6 and miR-186 was detected using quantitative real time polymerase chain reaction (qRT-PCR). The proliferation, migration, invasion, and apoptosis of PTX-resistant PCa cells were determined via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), transwell assay, or flow cytometry assay. Protein levels of CyclinD1, matrix metalloproteinase 9 (MMP9), Vimentin, E-cadherin, Cleaved-caspase-3 (Cleaved-casp-3) Cleaved-caspase-9 (Cleaved-casp-9), Multidrug Resistance associated Protein 1 (MRP1), and multidrug resistance-1 (MDR1) were assessed by western blot analysis. The relationship between SNHG6 and miR-186 were confirmed by dual-luciferase reporter assay. The role of SNHG6 in vivo was confirmed by xenograft tumor model.

Results

SNHG6 expression was increased and miR-186 expression was reduced in drug-resistant PCa tissues and cells. SNHG6 knockdown elevated PTX-resistant PCa cells sensitivity to PTX in vitro and in vivo, and repressed proliferation, migration, and invasion of PTX-resistant PCa cells in vitro. Importantly, SNHG6 acted as a sponge of miR-186. Furthermore, miR-186 downregulation reversed SNHG6 silencing-mediated cell sensitivity to PTX, proliferation, migration, and invasion in PTX-resistant PCa cells.

Conclusions

SNHG6 knockdown elevated the sensitivity of PTX-resistant PCa cells to PTX by sponging miR-186, indicating that SNHG6 might be a therapeutic target for PCa.

Downregulated Mucin 1 alleviates paclitaxel resistance in non‑small cell lung cancer cells

Multidrug resistance of non‑small cell lung cancer (NSCLC) is a common clinical problem, which is one of the main reasons leading to the failure of chemotherapy. Therefore, how to overcome or prevent drug resistance has become a hot and difficult issue in clinical research. The present study was designed to investigate the expression patterns, functions and underlying mechanisms of MUC1 in regulating paclitaxel‑resistant cell line A549/PR in NSCLC. RT‑qPCR and western blot was performed to determine the mRNA and protein level, respectively. CCK‑8 was conducted to determine the cell viability of A549/PR cells. Moreover, flow cytometry assay was applied to examine the apoptosis rate of A549/PR. Herein, the MUC1 was over‑expressed in clinic NSCLC tissues and A549/PR cells. Silence of MUC1 could obviously suppress the proliferation and promote apoptosis of A549/PR cells in treatment of paclitaxel through up‑regulating the expression of Bax and Caspase‑3, and down‑regulating the expression of Bcl‑2, suggesting that chemotherapy combined with the modulation of MUC1 might be characterized as a promising therapeutic approach to overcome paclitaxel‑resistance in NSCLC in the future.

Vaticanol C, a phytoalexin, induces apoptosis of leukemia and cancer cells by modulating expression of multiple sphingolipid metabolic enzymes

Resveratrol (RSV) has recently attracted keen interest because of its pleiotropic effects. It exerts a wide range of health-promoting effects. In addition to health-promoting effects, RSV possesses anti-carcinogenic activity. However, a non-physiological concentration is needed to achieve an anti-cancer effect, and its in vivo bioavailability is low. Therefore, the clinical application of phytochemicals requires alternative candidates that induce the desired effects at a lower concentration and with increased bioavailability. We previously reported a low IC₅₀ of vaticanol C (VTC), an RSV tetramer, among 12 RSV derivatives (Ito T. et al, 2003). However, the precise mechanism involved remains to be determined. Here, we screened an in-house chemical library bearing RSV building blocks ranging from dimers to octamers for cytotoxic effects in several leukemia and cancer cell lines and their anti-cancer drug-resistant sublines. Among the compounds, VTC exhibited the highest cytotoxicity, which was partially inhibited by a caspase 3 inhibitor, Z-VAD-FMK. VTC decreased the expression of sphingosine kinase 1, sphingosine kinase 2 and glucosylceramide synthase by transcriptional or post-transcriptional mechanisms, and increased cellular ceramides/dihydroceramides and decreased sphingosine 1-phosphate (S1P). VTC-induced sphingolipid rheostat modulation (the ratio of ceramide/S1P) is thought to be involved in cellular apoptosis. Indeed, exogenous S1P addition modulated VTC cytotoxicity significantly. A combination of SPHK1, SPHK2, and GCS chemical inhibitors induced sphingolipid rheostat modulation, cell growth suppression, and cytotoxicity similar to that of VTC. These results suggest the involvement of sphingolipid metabolism in VTC-induced cytotoxicity, and indicate VTC is a promising prototype for translational research.

Quercetin Enhanced Paclitaxel Therapeutic Effects Towards PC-3 Prostate Cancer Through ER Stress Induction and ROS Production

Introduction

Prostate cancer is one of the most common cancers threatening public health worldwide. Although chemotherapy plays an important role in treating prostate cancer, it leads to many adverse effects and is prone to drug resistance. Quercetin, a natural product, is used in traditional Chinese medicine because of its strong antitumor activity and few side effects.

Methods

In this study, we combined quercetin and paclitaxel to kill prostate cancer cells in vivo and in vitro, and we investigated the relevant mechanism of this combination treatment. After the cancer cells were treated with quercetin or/and paclitaxel, cell growth inhibition, apoptosis, the cell cycle, reactive oxygen species (ROS) generation, and several endoplasmic reticulum (ER) stress signaling pathway related gene expressions were evaluated.

Results

The combined treatment with quercetin and paclitaxel significantly inhibited cell proliferation, increased apoptosis, arrested the cell cycle at the G2/M phase, inhibited cell migration, dramatically induced ER stress to occur, and increased ROS generation. In a PC-3 cancer-bearing murine model, this combination treatment exerted the most beneficial therapeutic effects, and quercetin increased the cancer cell-killing effects of paclitaxel, with nearly no side effects compared with the single paclitaxel treatment group.

Conclusion

Combination treatment possessed enhanced anti-cancer effects, and these results will provide a basis for treating prostate cancer using a combination of quercetin and paclitaxel.

HE4 overexpression decreases pancreatic cancer Capan-1 cell sensitivity to paclitaxel via cell cycle regulation

BACKGROUND

Paclitaxel is a first-line chemotherapy drug for pancreatic, ovarian, endometrial cancers and other malignancies. However, its efficacy is often compromised by decreased cell sensitivity or the development of resistance. Human epididymis protein 4 (HE4) is highly expressed in gynecologic and pancreatic cancer tissues, and its serum levels are used for patient triage and assistant diagnosis of gynecologic cancers. Previous studies have shown that HE4 overexpression could promote cancer cell proliferation and the growth of tumor xenografts, which suggests its potential involvement in cancer chemosensitivity.

METHODS

Two pancreatic cancer cell lines, Capan-1 and Suit-2, were transiently transfected with an HE4 overexpression plasmid, and transfected cells were treated with paclitaxel. S-phase cells were labeled using BrdU, and cell positivity rates were determined by counting BrdU-positive cells. Following HE4 overexpression and/or drug treatment, a western blotting analysis was performed to determine the protein alterations of PCNA and p21, two important cell cycle regulators.

RESULTS

HE4 overexpression not only promoted the proliferation of the Capan-1 pancreatic cells, but also significantly decreased cell sensitivity to paclitaxel. Results from western blotting showed that paclitaxel inhibited cell proliferation by decreasing the expression of PCNA and increasing the expression of p21. Data analysis indicated interactive actions between HE4 function and paclitaxel effects, both converging to cell cycle regulation.

CONCLUSION

These findings suggest that HE4 could be a potential therapeutic target for the sensitization of pancreatic cancer cells to paclitaxel treatment. HE4 expression levels may be used to predict the sensitivity of pancreatic cancer patients to paclitaxel.

Topological properties and in vitro identification of essential nodes of the Paclitaxel and Vincristine interactomes in PC-3 cells

Background

Microtubule-targeting agents (MTAs) disrupt microtubule dynamics, thereby inducing apoptosis via mitochondrial pathway activation through the modulation in the expression of the Bcl-2 family.

Methods

To describe topological features of the MTAs networks associated to intrinsic apoptosis induction in p53-null prostate cancer cells, we predicted and compared the interactomes and topological properties of Paclitaxel and Vincristine, and thus, the essential nodes corresponding with the pro- and anti-apoptotic proteins and their kinetics were subjected to experimental analysis in PC-3 cell line.

Results

The essential nodes of the apoptotic pathways, TP53, and CASP3, were identified in both, Paclitaxel and Vincristine networks, but the intrinsic pathway markers BCL2, BAX, and BCL2L1 were identified as hub nodes only in the Paclitaxel network. An in vitro analysis demonstrated an increase in BimEL and the cleaved-caspase-3 proteins in PC-3 cells exposed to both treatments. Immunoprecipitation analysis showed that treatments induced the releasing of Bax from the anti-apoptotic complex with Bcl-2 protein and the role of BimEL as a de-repressor from sequestering complexes, in addition, new protein complexes were identified between BimEL or Bcl-2 and cleaved-caspase-3, contributing data to the Vincristine network for p53-null cells in response to MTAs.

Conclusion

The differences in sensitivities, protein profiles, and protein complex kinetics observed between the drugs confirmed that the selectivity and stimulation of the apoptotic system vary depending on the cell's genotype, the drug used and its exposure period.

Differentially Expressed Mitochondrial Proteins in Human MCF7 Breast Cancer Cells Resistant to Paclitaxel

Identification of novel proteins with changed expression in resistant cancer cells could be helpful in elucidation mechanisms involved in the development of acquired resistance to paclitaxel. In this study, we carried out a 2D-PAGE using the mitochondrial-enriched fraction from paclitaxel-resistant MCF7/PacR cells compared to original paclitaxel-sensitive MCF7 breast cancer cells. Differentially expressed proteins were identified employing mass spectrometry. We found that lysosomal cathepsin D and mitochondrial abhydrolase-domain containing protein 11 (ABHD11) had decreased expression in MCF7/PacR cells. On the other hand, mitochondrial carbamoyl-phosphate synthetase 1 (CPS1) and ATPase family AAA-domain containing protein 3A and 3B (ATAD3A, ATAD3B) were overexpressed in MCF7/PacR cells. Further, we showed that there was no difference in localization of CPS1 in MCF7 and MCF7/PacR cells. We demonstrated a significant increase in the number of CPS1 positive MCF7/PacR cells, using FACS analysis, compared to the number of CPS1 positive MCF7 cells. Silencing of CPS1 expression by specific siRNA had no significant effect on the resistance of MCF7/PacR cells to paclitaxel. To summarize, we identified several novel proteins of a mitochondrial fraction whose role in acquired resistance to paclitaxel in breast cancer cells should be further assessed.

Combination of metformin and paclitaxel suppresses proliferation and induces apoptosis of human prostate cancer cells via oxidative stress and targeting the mitochondria-dependent pathway

Previous studies have reported that metformin (MET) has anticancer activity. In combination with chemotherapeutic drugs, MET reduces the dosage of chemotherapeutic drugs required and enhances anticancer efficacy. In the present study, the combination of MET and paclitaxel (PTX) in three human prostate cancer (PCa) cell lines (22RV1, PC-3 and LNCaP) was evaluated to investigate the effects on proliferation and apoptosis of PCa cells. The present study explored whether their effects were associated with reactive oxygen species (ROS). An MTT assay and microscopy were used to study the effect of MET + PTX on cell growth. Half maximal inhibitory concentration (IC₅₀) values were obtained for MET (12.281±1.089 mM for 22RV1, 2.248±0.352 mM for PC-3 cells and 3.610±0.577 mM for LNCaP cells) and PTX (13.170±1.12 nM for PC-3 cells) at 48 h. Since the survival rate of 22RV1 and LNCaP cells did not decrease linearly with increasing PTX concentration, it is difficult to estimate accurate IC₅₀; therefore, only IC₅₀ values for PTX in PC-3 cells were given. When treating the cells with 5 mM MET, the IC₅₀ of PTX decreased to 5.423±0.734 nM for PC-3 cells. Annexin V and propidium iodide staining was used to investigate apoptosis by flow cytometry. The apoptotic mechanisms of MET + PTX in PCa were investigated by detecting the expression of apoptosis-related proteins, activities of caspase-3/7, intracellular ROS accumulation, mitochondrial membrane potential, and intracellular levels of adenosine 5′-triphosphate (ATP). MET + PTX induced PCa apoptosis and ROS accumulation, and decreased mitochondrial membrane potential and intracellular levels of ATP. Taken together, these results indicated that MET + PTX suppressed PCa cell proliferation in a dose- and time-dependent manner. In addition, MET + PTX induced apoptosis by increasing ROS levels, reducing mitochondrial membrane potential, and activating mitochondrial-dependent apoptotic pathways.

JS-K enhances chemosensitivity of prostate cancer cells to Taxol via reactive oxygen species activation

The aim of the present study was to investigate the influence of the nitric oxide donor prodrug JS-K (C₁₃H₁₆N₆O₈) on Taxol-induced apoptosis in prostate cancer cells, and to investigate a potential reactive oxygen species (ROS)-associated mechanism. The effect of JS-K on the anticancer activity of Taxol was assessed in prostate cancer cells; cell viability, colony formation, apoptosis, ROS generation and expression levels of apoptosis-associated proteins were investigated. The function of ROS accumulation in the combined effects of JS-K and Taxol was determined using the antioxidant N-acetylcysteine (NAC) and the pro-oxidant oxidized glutathione (GSSG). The results of the present study demonstrated that JS-K was able to increase Taxol-induced suppression of prostate cancer cell proliferation, apoptosis, ROS accumulation and upregulation of apoptosis-associated proteins. Furthermore, NAC reversed the effect of JS-K on Taxol-induced apoptosis and conversely, the pro-oxidant GSSG exacerbated the effect of JS-K on Taxol-induced apoptosis in prostate cancer cells. In conclusion, JS-K enhances the chemosensitivity of prostate cancer cells to Taxol, via the upregulation of intracellular ROS.

A novel selenonucleoside suppresses tumor growth by targeting Skp2 degradation in paclitaxel-resistant prostate cancer

Prostate cancer (PC) is the most common disease in men over age 50, and its prevalence rate has been gradually increasing since 1980. Taxane-derived anticancer agents are the primary agents used to treat metastatic prostate cancer patients; however, the side effects and acquired drug resistance limit the success of these therapies. Because there is no specific treatment for paclitaxel-resistant prostate cancer, it is necessary to develop new targets and therapeutic strategies to overcome the acquired resistance. In this study, the antitumor activity of a novel selenonucleoside (4'-selenofuranosyl-2,6-dichloropurine, LJ-2618), a third-generation nucleoside, and its plausible mechanisms of action in paclitaxel-resistant prostate cancer (PC-3-Pa) cells were investigated. The established PC-3-Pa cells exhibited over 100-fold resistance against paclitaxel compared to the paclitaxel-sensitive PC-3 cells. LJ-2618, however, effectively inhibited the proliferation of both cell lines with similar IC₅₀ values in vitro. In PC-3-Pa cells, the activated PI3K/Akt signaling pathway was suppressed by LJ-2618 treatment. In addition, Skp2 was found to be over-expressed in paclitaxel-resistant cells, and the transfection of Skp2 siRNA recovered the sensitivity of paclitaxel in PC-3-Pa cells. Furthermore, LJ-2618 significantly down-regulated Skp2 expression in PC-3-Pa cells by promoting degradation and inducing destabilization of Skp2, which triggers G₂/M cell cycle arrest. In a xenograft mouse model implanted with PC-3-Pa cells, LJ-2618 (3 or 10 mg/kg) effectively inhibited tumor growth with the enhancement of Skp2 degradation and induction of p27 expression in tumor tissues. These findings suggest that LJ-2618 may have potential for overcoming paclitaxel resistance via promoting Skp2 degradation and stabilizing p27 expression in PC-3-Pa cells. Therefore, the novel selenonucleoside LJ-2618 may lead to the development of a new treatment strategy for patients with paclitaxel-resistant, castration-resistant prostate cancer.

The role of AKT and FOXO3 in preventing ovarian toxicity induced by cyclophosphamide

Cyclophosphamide (CTX) has immunosuppressive effects and has been wildly used as one anti-cancer drug in clinical. Significant toxicity has been noticed particularly in the reproductive system. CTX promotes the maturation of ovarian follicles, decreases follicular reserve, and ultimately lead to ovarian failure or even premature ovarian failure (POF). The placental extract (HPE) has been shown to have some beneficial impact on reproductive system; however, little is known regarding to the effect of HPE on protecting CTX-induced ovarian injury and the mechanism involved. Whether human placental extracts (HPE) has a protective effect on CTX-induced toxicity on ovarian was studied by using a CTX-induced ovarian injury animal model. The effects of HEP on histopathology, the number of atretic follicles, the weight of the ovary, serum hormone levels, and apoptosis in granulosa cells were studied in mice with CTX or control vehicle. Our results have demonstrated that HPE inhibited p-Rictor, reduced the expression of Bad, Bax and PPAR, and activated Akt and Foxo3a (increased their phosphorylation). Mice treated with HPE showed higher ovarian weight, lower number of atretic follicles, higher serum levels of the hormones E2 and progesterone, and lower apoptosis and serum levels of LH and FSH in granulosa cells, than that in the control animal group. Our data show that ovarian injury can be attenuated by HPE. HPE likely protects follicular granulosa cells from undergoing significant apoptosis and reduce atresia follicle formation, therefore, alleviates CTX-induced ovarian injury.

Taxane resistance in castration-resistant prostate cancer: mechanisms and therapeutic strategies

Despite its good initial response and significant survival benefit in patients with castration-resistant prostate cancer (CRPC), taxane therapy inevitably encounters drug resistance in all patients. Deep understandings of taxane resistant mechanisms can significantly facilitate the development of new therapeutic strategies to overcome taxane resistance and improve CRPC patient survival. Multiple pathways of resistance have been identified as potentially crucial areas of intervention. First, taxane resistant tumor cells typically have mutated microtubule binding sites, varying tubulin isotype expression, and upregulation of efflux transporters. These mechanisms contribute to reducing binding affinity and availability of taxanes. Second, taxane resistant tumors have increased stem cell like characteristics, indicating higher potential for further mutation in response to therapy. Third, the androgen receptor pathway is instrumental in the proliferation of CRPC and multiple hypotheses leading to this pathway reactivation have been reported. The connection of this pathway to the AKT pathway has received significant attention due to the upregulation of phosphorylated AKT in CRPC. This review highlights recent advances in elucidating taxane resistant mechanisms and summarizes potential therapeutic strategies for improved treatment of CRPC.

Morin promotes prostate cancer cells chemosensitivity to paclitaxel through miR-155/GATA3 axis

Paclitaxel is a first-line microtubule-stabilizing drug in treating prostate cancer. However, most patients develop resistance and experience relapse. Morin (3,5,7,20,40-pentahydroxyflavone) is an anti-tumor flavonoid in a numerous types of cancer cells including breast, ovarian and lung cancers. We therefore researched the effects of morin as an adjuvant to paclitaxel in in treating DU145 and PC-3 cells in vitro and DU145 derived prostate cancers in nude mice models. The chemosensitivities of these cells to the treatments of morin and paclitaxel were tested through viability assays utilizing cell counting kit 8 (CCK-8) and apoptosis assays through flow cytometry analyses. MicroRNA (miRNA) microarray was employed to determine the changes in miRNA profile of morin treated DU145 cells. The results from microarrays were further certified by quantitative real-time reverse transcription-PCR (qRT-PCR). The underlying targets of miR-155 were verified using luciferase assays followed by Western blot assays. In the results, morin was capable of repressing the cell viabilities in the paclitaxel-treated cells. MiR-155might be an effective target that can be down-regulated in morin-treated cells. We also discovered that GATA binding protein 3 (GATA3) was directly repressed by miR-155, and the treatment of morin reversed the expression of GATA3. In conclusion, morin might be a potential adjuvant of paclitaxel in treating prostate cancer through regulating miR-155/GATA3 axis.

Dual PI3K/mTOR inhibitor BEZ235 as a promising therapeutic strategy against paclitaxel-resistant gastric cancer via targeting PI3K/Akt/mTOR pathway

Paclitaxel (PTX) is widely used in the front-line chemotherapy for gastric cancer (GC), but resistance limits its use. Due to the lack of proper models, mechanisms underlying PTX resistance in GC were not well studied. Using established PTX-resistant GC cell sublines HGC-27R, we for the first time integrated biological traits and molecular mechanisms of PTX resistance in GC. Data revealed that PTX-resistant GC cells were characterized by microtubular disorders, an EMT phenotype, reduced responses to antimitotic drugs, and resistance to apoptosis (marked by upregulated β-tubulin III, vimentin, attenuated changes in G₂/M molecules or pro-apoptotic factors in response to antimitotic drugs or apoptotic inducers, respectively). Activation of the phosphoinositide 3-kinase, the serine/threonine kinase Akt and mammalian target of rapamycin (PI3K/Akt/mTOR) and mitogen-activated protein kinase (MAPK) pathways were also observed, which might be the reason for above phenotypic alternations. In vitro data suggested that targeting these pathways were sufficient to elicit antitumor responses in PTX-resistant GC, in which the dual PI3K/mTOR inhibitor BEZ235 displayed higher therapeutic efficiency than the mTOR inhibitor everolimus or the MEK inhibitor AZD6244. Antitumor effects of BEZ235 were also confirmed in mice bearing HGC-27R tumors. Thus, these data suggest that PI3K/Akt/mTOR and MAPK pathway inhibition, especially PI3K/mTOR dual blockade, might be a promising therapeutic strategy against PTX-resistant GC.

Modulation of the sphingolipid rheostat is involved in paclitaxel resistance of the human prostate cancer cell line PC3-PR

Taxoids are anti-cancer drugs frequently used to treat solid tumors, but they are sometimes ineffective and tumors may become resistant to their action. Here, we examined the involvement of sphingolipid metabolic enzymes in paclitaxel (PTX) resistance using a human prostate cancer cell line, PC3, and its PTX-resistant subline, PC3-PR. PTX (20 nM) suppressed cell proliferation and increased various ceramide species in PC3, but not PC3-PR, cells. PC3-PR contained higher S1P levels than did PC3, regardless of PTX treatment. Western blotting revealed that PC3-PR cells expressed higher levels of sphingosine kinase 1 (SPHK1) and glucosylceramide synthase (GCS) but lower levels of acid sphingomyelinase (ASMase) and neutral sphingomyelinase 2 than did PC3 cells. Inhibition of SPHK1 using siRNA or a pharmacological inhibitor decreased S1P levels in PC3-PR cells and inhibited proliferation in the presence or absence of PTX, suggesting that SPHK1 is at least partially responsible for PTX resistance. Similarly, GCS inhibitors (PDMP and PPMP) increased cellular ceramides and suppressed the proliferation of PC3-PR. However, inhibition of proteasome function or histone deacetylase activity increased SMase and ceramide levels and suppressed PC3-PR proliferation. These results suggest that modulation of metabolic enzyme expression and alteration of the sphingolipid rheostat protects cancer cells against PTX.