Gonadotropin-releasing hormone agonists sensitize, and resensitize, prostate cancer cells to docetaxel in a p53-dependent manner

Ligand-conjugated multiwalled carbon nanotubes for cancer targeted drug delivery

Multiwalled carbon nanotubes (MWCNTs) are at the forefront of nanotechnology-based advancements in cancer therapy, particularly in the field of targeted drug delivery. The nanotubes are characterized by their concentric graphene layers, which give them outstanding structural strength. They can deliver substantial doses of therapeutic agents, potentially reducing treatment frequency and improving patient compliance. MWCNTs' diminutive size and modifiable surface enable them to have a high drug loading capacity and penetrate biological barriers. As a result of the extensive research on these nanomaterials, they have been studied extensively as synthetic and chemically functionalized molecules, which can be combined with various ligands (such as folic acid, antibodies, peptides, mannose, galactose, polymers) and linkers, and to deliver anticancer drugs, including but not limited to paclitaxel, docetaxel, cisplatin, doxorubicin, tamoxifen, methotrexate, quercetin and others, to cancer cells. This functionalization facilitates selective targeting of cancer cells, as these ligands bind to specific receptors overexpressed in tumor cells. By sparing non-cancerous cells and delivering the therapeutic payload precisely to cancer cells, this therapeutic payload delivery ability reduces chemotherapy systemic toxicity. There is great potential for MWCNTs to be used as targeted delivery systems for drugs. In this review, we discuss techniques for functionalizing and conjugating MWCNTs to drugs using natural and biomacromolecular linkers, which can bind to the cancer cells' receptors/biomolecules. Using MWCNTs to administer cancer drugs is a transformative approach to cancer treatment that combines nanotechnology and pharmacotherapy. It is an exciting and rich field of research to explore and optimize MWCNTs for drug delivery purposes, which could result in significant benefits for cancer patients.

Qualitative Analysis of Interviews and Focus Groups Exploring Factors Contributing to Adherence to GnRH Agonists in Men with Prostate Cancer

OBJECTIVES

Side effects from the prolonged use of gonadotropin-releasing hormone (GnRH) agonists may lead to nonadherence to the treatment in men with advanced prostate cancer (PCa). We investigated the reasons contributing to nonadherence to GnRH agonists through interviews with men with PCa and focus groups with their health care professionals.

DATA SOURCES

The three stages of the study were validation of themes, interviews with men on GnRH agonists, and focus groups with oncology specialists and clinical nurse specialists. An experienced oncologist validated factors contributing to nonadherence identified from the literature. A total of 10 men with PCa were recruited from a large teaching hospital and were interviewed on a one-to-one basis using a topic guide. In stage three, two separate focus groups were held with oncology specialists and clinical nurse specialists treating men with PCa. The interviews and focus groups were audio recorded and transcribed verbatim. Initial codes identified from stage three were grouped into themes and thematically analyzed.

CONCLUSION

Themes identified from the interviews and focus groups influencing adherence to treatment were side effects of treatment, patient belief system, benefits outweigh harm, quality of life over quantity of life, social support, and patient-clinician relationship. Although side effects such as hot flushes and loss of libido were sometimes overwhelming for many, these men felt that treatment benefits outweighed harm.

IMPLICATIONS FOR NURSING PRACTICE

Reasons leading to nonadherence can be multifactorial and unique to each patient. Employing different strategies by health care professionals may lead to the eventual acceptance of treatment, while also acknowledging their reasons for nonadherence.

Quercetin Synergistically Enhances the Anticancer Efficacy of Docetaxel through Induction of Apoptosis and Modulation of PI3K/AKT, MAPK/ERK, and JAK/STAT3 Signaling Pathways in MDA-MB-231 Breast Cancer Cell Line

Docetaxel is widely used in the treatment of metastatic breast cancer. However, its effectiveness is limited due to chemoresistance and its undesirable side effects. The combination of chemotherapeutic agents and natural compounds is an effective strategy to overcome drug resistance and the ensuing inevitable toxicities. Quercetin is a natural flavonoid with strong antioxidant and anticancer activities. This study aimed to evaluate the cytotoxic and modulatory effects of combined docetaxel and quercetin on the MDA-MB-231 human breast cancer cell line. The cell viability was assessed by MTT assay. The induction of apoptosis was examined using flow cytometry. The role of p53 in the apoptotic process was evaluated via qRT-PCR. The levels of BAX, BCL2, ERK1/2, AKT, and STAT3 proteins were measured by Western blot analysis. The results showed that the single-agent treatment with docetaxel or quercetin leads to a decrease in the viability of the MDA-MB-231 cells at 48 h. Furthermore, the combination of docetaxel (7 nM) and quercetin (95 μM) displayed the greatest synergistic effects with a combination index value of 0.76 accompanied by the up regulation of p53 and a significant increase in BAX level, as well as decrease in the levels of BCL2, pERK1/2, AKT, and STAT3 proteins (P < 0.05). The concomitant use of docetaxel and quercetin leads to the cell growth inhibition associated with the induction of apoptosis and inhibition of cell survival. Therefore, this study provides a promising therapeutic approach to enhance the efficacy of docetaxel in a less-toxic manner.

Dissecting the Hormonal Signaling Landscape in Castration-Resistant Prostate Cancer

Understanding the molecular mechanisms underlying prostate cancer (PCa) progression towards its most aggressive, castration-resistant (CRPC) stage is urgently needed to improve the therapeutic options for this almost incurable pathology. Interestingly, CRPC is known to be characterized by a peculiar hormonal landscape. It is now well established that the androgen/androgen receptor (AR) axis is still active in CRPC cells. The persistent activity of this axis in PCa progression has been shown to be related to different mechanisms, such as intratumoral androgen synthesis, AR amplification and mutations, AR mRNA alternative splicing, increased expression/activity of AR-related transcription factors and coregulators. The hypothalamic gonadotropin-releasing hormone (GnRH), by binding to its specific receptors (GnRH-Rs) at the pituitary level, plays a pivotal role in the regulation of the reproductive functions. GnRH and GnRH-R are also expressed in different types of tumors, including PCa. Specifically, it has been demonstrated that, in CRPC cells, the activation of GnRH-Rs is associated with a significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic activity. This antitumor activity is mainly mediated by the GnRH-R-associated Gαi/cAMP signaling pathway. In this review, we dissect the molecular mechanisms underlying the role of the androgen/AR and GnRH/GnRH-R axes in CRPC progression and the possible therapeutic implications.

Gonadotropin-Releasing Hormone Receptors in Prostate Cancer: Molecular Aspects and Biological Functions

Pituitary Gonadotropin-Releasing Hormone receptors (GnRH-R) mediate the activity of the hypothalamic decapeptide GnRH, thus playing a key role in the regulation of the reproductive axis. Early-stage prostate cancer (PCa) is dependent on serum androgen levels, and androgen-deprivation therapy (ADT), based on GnRH agonists and antagonists, represents the standard therapeutic approach for PCa patients. Unfortunately, the tumor often progresses towards the more aggressive castration-resistant prostate cancer (CRPC) stage. GnRH receptors are also expressed in CRPC tissues, where their binding to both GnRH agonists and antagonists is associated with significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic effects, mediated by the Gαi/cAMP signaling cascade. GnRH agonists and antagonists are now considered as an effective therapeutic strategy for CRPC patients with many clinical trials demonstrating that the combined use of these drugs with standard therapies (i.e., docetaxel, enzalutamide, abiraterone) significantly improves disease-free survival. In this context, GnRH-based bioconjugates (cytotoxic drugs covalently linked to a GnRH-based decapeptide) have been recently developed. The rationale of this treatment is that the GnRH peptide selectively binds to its receptors, delivering the cytotoxic drug to CRPC cells while sparing nontumor cells. Some of these compounds have already entered clinical trials.

Apoptotic Effects of Drug Targeting Conjugates Containing Different GnRH Analogs on Colon Carcinoma Cells

The wide range of cellular target reactions (e.g., antitumor) of gonadotropin-releasing hormone (GnRH) variants provides the possibility to develop multifunctional GnRH conjugates. The aim of our work was to compare the cytotoxic/apoptotic activity of different GnRH-based, daunorubicin (Dau)-linked conjugates with or without butyrated Lys in position 4 (⁴Lys(Bu)) at a molecular level in a human colorectal carcinoma cell line. Cell viability was measured by impedimetry, cellular uptake and apoptosis were studied by flow cytometry, and the expression of apoptosis-related genes was analyzed by qRT-PCR. The modification with ⁴Lys(Bu) resulted in an increased cytotoxic and apoptotic effects and cellular uptake of the GnRH-I and GnRH-III conjugates. Depending on the GnRH isoform and the presence of ⁴Lys(Bu), the conjugates could regulate the expression of several apoptosis-related genes, especially tumor necrosis factor (TNF), tumor protein p53 (TP53) and the members of growth-factor signaling. The stronger cytotoxicity of GnRH-I and GnRH-III conjugates containing ⁴Lys(Bu) was associated with a stronger inhibitory effect on the expression of growth-factor signaling elements in comparison with their ⁴Ser counterparts, in which the upregulation of TP53 and caspases (e.g., CASP9) seemed to play a more important role. We were able to provide further evidence that targeting the GnRH receptor could serve as a successful therapeutic approach in colon cancer, and GnRH-III-[⁴Lys(Bu),⁸Lys(Dau=Aoa)] proved to be the best candidate for this purpose.

SIRT1 and microRNAs: The role in breast, lung and prostate cancers

Breast cancer and prostate cancer are the most common malignant tumors in female and men, respectively. Furthermore, lung cancer is the leading cause of cancer deaths worldwide. It is an emergency to develop a powerful strategy to treat these threatening cancers more effectively, because of low efficacy and high rates of chemotherapy effects. MicroRNAs (miRNAs), a class of small non-coding RNAs, are key regulators of gene expression via induction of translational repression or mRNA degradation. MiRNA deregulation has been linked to cancer initiation and progression. Silent Inflammation Regulator 2 (SIR2) proteins-sirtuins- are a family of histone deacetylases (HDACs) that catalyze deacetylation of both histone and non- histone lysine residues. SIRT1 can act as an oncogene. It plays a role in tumorigenesis by anti-apoptotic activity and is implicated in diverse cellular process including autophagy, senescence, apoptosis, proliferation, and aging. MicroRNAs and SIRT1 serve as tumor suppressors or tumor promotors depending on the oncogenic pathway specific to particular tumors. MicroRNAs modulate cancer development by targeting SIRT1. In this review, we underlie the specific mechanisms involved in these threatening cancers by microRNAs/SIRT1 pathways.

Androgen induces G3BP2 and SUMO-mediated p53 nuclear export in prostate cancer

The androgen receptor (AR) has a central role in prostate cancer progression, particularly treatment-resistance disease including castration-resistant prostate cancer. Loss of the p53 tumor suppressor, a nuclear transcription factor, is also known to contribute to prostate malignancy. Here we report that p53 is translocated to the cytoplasm by androgen-mediated induction of G3BP2, a newly described direct target gene of AR. G3BP2 induces both cell cycle progression and blocks apoptosis. Translocation of p53 is regulated by androgen-dependent sumoylation mediated by the G3BP2-interacting SUMO-E3 ligase, RanBP2. G3BP2 knockdown results in reduced tumor growth and increased nuclear p53 accumulation in mouse xenograft models of prostate cancer with or without long-term androgen deprivation. Moreover, strong cytoplasmic p53 localization is correlated clinically with elevated G3BP2 expression and predicts poor prognosis and disease progression to the hormone-refractory state. Our findings reveal a new AR-mediated mechanism of p53 inhibition that promotes treatment-resistant prostate cancer.

miR-34a inhibits cell proliferation in prostate cancer by downregulation of SIRT1 expression

MicroRNA-34a (miR-34a) functions as a tumor suppressor gene and inhibits abnormal cell growth by regulating the expression of other genes. The role of miR-34a in regulating sirtuin 1 (SIRT1) in prostate cancer remains unclear. The objective of the present study was to investigate the biological function and molecular mechanisms of miR-34a regulation of SIRT1 in human prostate cancer samples and the human prostate cancer cell line, PC-3. Fresh prostate tissues were obtained from patients, and the miR-34a expression in prostate cancer tissues was measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). qPCR and western blotting were performed to assess the effects of miR-34a overexpression on SIRT1 regulation in PC-3 cells, and the cell growth was assessed by Cell Counting Kit-8 (CCK-8). Flow cytometry was used to assess the cell cycle status of the cells. The miR-34a expression levels in prostate cancer tissues were significantly reduced compared with adjacent normal prostate tissues (P<0.05). SIRT1 expression levels in PC-3 cells with over-expression of miR-34a were significantly reduced compared with those in the negative control (P<0.05). The over-expression of miR-34a inhibited PC-3 cells growth and resulted in increased cell cycle arrest compared with the negative control (P<0.05). In conclusion, miR-34a inhibits the human prostate cancer cell proliferation, in part, through the downregulation of SIRT1 expression.

Paradoxical and contradictory effects of imatinib in two cell line models of hormone-refractory prostate cancer

BACKGROUND

Imatinib mesylate is a chemotherapeutic drug that inhibits the tyrosine kinase activity of c-KIT and has been successfully used to treat leukemias and some solid tumors. However, its application for treatment of hormone-refractory prostate cancer (HRPC) has shown modest effectiveness and did not follow the outcomes in cultured cells or animal models. Moreover, the molecular pathways by which imatinib induces cytotoxicity in prostate cancer cells are poorly characterized.

METHODS

Two cell line models of HRPC (DU145 and PC3) were exposed to 20 μM of imatinib for 6-72 hr. MTS assay was used to assess cell viability during the course of experiment. Gene expression analysis of c-KIT, cell-cycle and apoptosis regulators, and angiogenic factors was determined by means of real-time PCR, western blot, and/or immunocytochemistry. The enzymatic activity of the apoptosis effector, caspase-3, was determined by a colorimetric assay.

RESULTS

Imatinib significantly decreased the viability of DU145 cells but paradoxically augmented the viability of PC3 cells. DU145 cells displayed diminished expression of anti-apoptotic Bcl-2 protein and augmented levels of caspase-8 and -9, as well as, increased enzymatic activity of caspase-3 in response to imatinib. No differences existed on the expression levels of apoptosis-related proteins in PC3 cells treated with imatinib, though the activity of caspase-3 was decreased. The mRNA levels of angiogenic factor VEGF were decreased in DU145-treated cells, whereas an opposite effect was seen in PC3. In addition, it was shown that DU145 and PC3 cells present a differential expression of c-KIT protein variants.

CONCLUSION

DU145 and PC3 cells displayed a contradictory behavior in response to imatinib, which was underpinned by a distinct expression pattern (or activity) of target regulators of cell-cycle, apoptosis, and angiogenesis. The paradoxical effect of imatinib in PC3 cells may be related with the differential expression of c-KIT protein variants. Moreover, the present findings helped to understand the discrepancies in the efficacy of imatinib as therapeutic option in HRPC.