CDK inhibitors induce mitochondria-mediated apoptosis through the activation of polyamine catabolic pathway in LNCaP, DU145 and PC3 prostate cancer cells

A new 68Ga-labeled ornithine derivative for PET imaging of ornithine metabolism in tumors

Ornithine metabolism plays a vital role in tumorigenesis. For cancer cells, ornithine is mainly used as a substrate for ornithine decarboxylase (ODC) for the synthesis of polyamines. The ODC as a key enzyme of polyamine metabolism has become an important target for cancer diagnosis and treatment. To non-invasively detect the levels of ODC expression in malignant tumors, we have synthesized a novel ⁶⁸Ga-labeled ornithine derivative ([⁶⁸Ga]Ga-NOTA-Orn). The synthesis time of [⁶⁸Ga]Ga-NOTA-Orn was about 30 min with a radiochemical yield of 45-50% (uncorrected), and the radiochemical purity was > 98%. [⁶⁸Ga]Ga-NOTA-Orn was stable in saline and rat serum. Cellular uptake and competitive inhibition assays using DU145 and AR42J cells demonstrated that the transport pathway of [⁶⁸Ga]Ga-NOTA-Orn was similar to that of L-ornithine, and it could interact with the ODC after transporting into the cell. Biodistribution and micro-positron emission tomography (Micro-PET) imaging studies showed that [⁶⁸Ga]Ga-NOTA-Orn exhibited rapid tumor uptake and was rapidly excreted through the urinary system. All above results suggested that [⁶⁸Ga]Ga-NOTA-Orn is a novel amino acid metabolic imaging agent with great potential of tumor diagnosis.

Polyamine homeostasis-based strategies for cancer: The role of combination regimens

Spermine, spermidine and putrescine polyamines are naturally occurring ubiquitous positively charged amines and are essential metabolites for biological functions in our life. These compounds play a crucial role in many cell processes, including cellular proliferation, growth, and differentiation. Intracellular levels of polyamines depend on their biosynthesis, transport and degradation. Polyamine levels are high in cancer cells, which leads to the promotion of tumor growth, invasion and metastasis. Targeting polyamine metabolism as an anticancer strategy is considerably rational. Due to compensatory mechanisms, a single strategy does not achieve satisfactory clinical effects when using a single agent. Combination regimens are more clinically promising for cancer chemoprevention because they work synergistically with causing little or no adverse effects due to each individual agent being used at lower doses. Moreover, bioactive substances have advantages over single chemical agents because they can affect multiple targets. In this review, we discuss anticancer strategies targeting polyamine metabolism and describe how combination treatments and effective natural active ingredients are promising therapies. The existing research suggests that polyamine metabolic enzymes are important therapeutic targets and that combination therapies can be more effective than monotherapies based on polyamine depletion.

The First Insight Into the Supramolecular System of D,L-α-Difluoromethylornithine: A New Antiviral Perspective

Targeting the polyamine biosynthetic pathway by inhibiting ornithine decarboxylase (ODC) is a powerful approach in the fight against diverse viruses, including SARS-CoV-2. Difluoromethylornithine (DFMO, eflornithine) is the best-known inhibitor of ODC and a broad-spectrum, unique therapeutical agent. Nevertheless, its pharmacokinetic profile is not perfect, especially when large doses are required in antiviral treatment. This article presents a holistic study focusing on the molecular and supramolecular structure of DFMO and the design of its analogues toward the development of safer and more effective formulations. In this context, we provide the first deep insight into the supramolecular system of DFMO supplemented by a comprehensive, qualitative and quantitative survey of non-covalent interactions via Hirshfeld surface, molecular electrostatic potential, enrichment ratio and energy frameworks analysis visualizing 3-D topology of interactions in order to understand the differences in the cooperativity of interactions involved in the formation of either basic or large synthons (Long-range Synthon Aufbau Modules, LSAM) at the subsequent levels of well-organized supramolecular self-assembly, in comparison with the ornithine structure. In the light of the drug discovery, supramolecular studies of amino acids, essential constituents of proteins, are of prime importance. In brief, the same amino-carboxy synthons are observed in the bio-system containing DFMO. DFT calculations revealed that the biological environment changes the molecular structure of DFMO only slightly. The ADMET profile of structural modifications of DFMO and optimization of its analogue as a new promising drug via molecular docking are discussed in detail.

CDK9: A Comprehensive Review of Its Biology, and Its Role as a Potential Target for Anti-Cancer Agents

Cyclin-dependent kinases (CDKs) are proteins pivotal to a wide range of cellular functions, most importantly cell division and transcription, and their dysregulations have been implicated as prominent drivers of tumorigenesis. Besides the well-established role of cell cycle CDKs in cancer, the involvement of transcriptional CDKs has been confirmed more recently. Most cancers overtly employ CDKs that serve as key regulators of transcription (e.g., CDK9) for a continuous production of short-lived gene products that maintain their survival. As such, dysregulation of the CDK9 pathway has been observed in various hematological and solid malignancies, making it a valuable anticancer target. This therapeutic potential has been utilized for the discovery of CDK9 inhibitors, some of which have entered human clinical trials. This review provides a comprehensive discussion on the structure and biology of CDK9, its role in solid and hematological cancers, and an updated review of the available inhibitors currently being investigated in preclinical and clinical settings.

The Emerging Clinical Role of Spermine in Prostate Cancer

Spermine, a member of polyamines, exists in all organisms and is essential for normal cell growth and function. It is highly expressed in the prostate compared with other organs and is detectable in urine, tissue, expressed prostatic secretions, and erythrocyte. A significant reduction of spermine level was observed in prostate cancer (PCa) tissue compared with benign prostate tissue, and the level of urinary spermine was also significantly lower in men with PCa. Decreased spermine level may be used as an indicator of malignant phenotype transformation from normal to malignant tissue in prostate. Studies targeting polyamines and key rate-limiting enzymes associated with spermine metabolism as a tool for PCa therapy and chemoprevention have been conducted with various polyamine biosynthesis inhibitors and polyamine analogues. The mechanism between spermine and PCa development are possibly related to the regulation of polyamine metabolism, cancer-driving pathways, oxidative stress, anticancer immunosurveillance, and apoptosis regulation. Although the specific mechanism of spermine in PCa development is still unclear, ongoing research in spermine metabolism and its association with PCa pathophysiology opens up new opportunities in the diagnostic and therapeutic roles of spermine in PCa management.

Synthesis of Some Novel Benzimidazole Derivatives as Anticancer Agent, and Evaluation for CDK2 Inhibition Activity

BACKGROUND

Thiobezimidazoles reveal various pharmacological activities due to similarities with many natural and synthetic molecules, they can easily interact with biomolecules of living systems.

OBJECTIVE

A series of substituted 2-thiobezimidazoles has been synthesized .Twelve final compounds were screened for in vitro anti-cancer activities against sixty different cell-lines.

METHODS

The spectral data of the synthesized compounds were characterized. Docking study for active anticancer compounds and CDK2/CyclinA2 Kinase assay against standard reference; Imatinib were performed.

RESULTS

Two compounds (3c&3l) from the examined series revealed effective antitumor activity in vitro against two-cancer cell lines (Colon Cancer (HCT-116) and Renal Cancer (TK-10). The docking study of synthesized molecules discovered a requisite binding pose in CDK-ATP binding pocket. 3c &3l were promoted in the CDK2/CyclinA2 Kinase assay against standard reference Imatinib.

CONCLUSION

Against all tested compounds ; two compounds 3c &3l were found active against two types of cell-lines.

The Role of CDK5 in Tumours and Tumour Microenvironments

Cyclin-dependent kinase 5 (CDK5), which belongs to the protein kinase family, regulates neuronal function but is also associated with cancer development and has been proposed as a target for cancer treatment. Indeed, CDK5 has roles in cell proliferation, apoptosis, angiogenesis, inflammation, and immune response. Aberrant CDK5 activation triggers tumour progression in numerous types of cancer. In this review, we summarise the role of CDK5 in cancer and neurons and CDK5 inhibitors. We expect that our review helps researchers to develop CDK5 inhibitors as treatments for refractory cancer.

Novel [(N-alkyl-3-indolylmethylene)hydrazono]oxindoles arrest cell cycle and induce cell apoptosis by inhibiting CDK2 and Bcl-2: synthesis, biological evaluation and in silico studies

As a continuation for our previous work, a novel set of N-alkylindole-isatin conjugates (7, 8a-c, 9 and 10a-e) is here designed and synthesised with the prime aim to develop more efficient isatin-based antitumor candidates. Utilising the SAR outputs from the previous study, our design here is based on appending four alkyl groups with different length (ethyl and n-propyl), bulkiness (iso-propyl) and unsaturation (allyl) on N-1 of indole motif, with subsequent conjugation with different N-unsubstituted isatin moieties to furnish the target conjugates. As planned, the adopted strategy achieved a substantial improvement in the growth inhibitory profile for the target conjugates in comparison to the reported lead VI. The best results were obtained with N-propylindole -5-methylisatin hybrid 8a which displayed broad spectrum anti-proliferative action with efficient sub-panel GI50 (MG-MID) range from 1.33 to 4.23 µM, and promising full-panel GI50 (MG-MID) equals 3.10 µM, at the NCI five-dose assay. Also, hybrid 8a was able to provoke cell cycle disturbance and apoptosis in breast T-47D cells as evidenced by the DNA flow cytometry and Annexin V-FITC/PI assays. Furthermore, hybrid 8a exhibited good inhibitory action against cell cycle regulator CDK2 protein kinase and the anti-apoptotic Bcl-2 protein (IC50= 0.85 ± 0.03 and 0.46 ± 0.02 µM, respectively). Interestingly, molecular docking for hybrid 8a in CDK2 and Bcl-2 active sites unveiled that N-propyl group is involved in significant hydrophobic interactions. Taken together, the results suggested conjugate 8a as a promising lead for further development and optimisation as an efficient antitumor drug.

Thymoquinone and Difluoromethylornithine (DFMO) Synergistically Induce Apoptosis of Human Acute T Lymphoblastic Leukemia Jurkat Cells Through the Modulation of Epigenetic Pathways

Thymoquinone (TQ), a natural anticancer agent exerts cytotoxic effects on several tumors by targeting multiple pathways, including apoptosis. Difluoromethylornithine (DFMO), an irreversible inhibitor of the ornithine decarboxylase (ODC) enzyme, has shown promising inhibitory activities in many cancers including leukemia by decreasing the biosynthesis of the intracellular polyamines. The present study aimed to investigate the combinatorial cytotoxic effects of TQ and DFMO on human acute T lymphoblastic leukemia Jurkat cells and to determine the underlying mechanisms. Here, we show that the combination of DFMO and TQ significantly reduced cell viability and resulted in significant synergistic effects on apoptosis when compared to either DFMO or TQ alone. RNA-sequencing showed that many key epigenetic players including Ubiquitin-like containing PHD and Ring finger 1 (UHRF1) and its 2 partners DNA methyltransferase 1 (DNMT1) and histone deacetylase 1 (HDAC1) were down-regulated in DFMO-treated Jurkat cells. The combination of DFMO and TQ dramatically decreased the expression of UHRF1, DNMT1 and HDAC1 genes compared to either DFMO or TQ alone. UHRF1 knockdown led to a decrease in Jurkat cell viability. In conclusion, these results suggest that the combination of DFMO and TQ could be a promising new strategy for the treatment of human acute T lymphoblastic leukemia by targeting the epigenetic code.

Epibrassinolide-induced autophagy occurs in an Atg5-independent manner due to endoplasmic stress induction in MEF cells

Epibrassinolide (EBR), a polyhydroxysteroid belongs to plant growth regulator family, brassinosteroids and has been shown to have a similar chemical structure to mammalian steroid hormones. Our findings indicated that EBR could trigger apoptosis in cancer cells via induction of endoplasmic reticulum (ER) stress, caused by protein folding disturbance in the ER. Normal cells exhibited a remarkable resistance to EBR treatment and avoid from apoptotic cell death. The unfolded protein response clears un/misfolded proteins and restore ER functions. When stress is chronic, cells tend to die due to improper cellular functions. To understand the effect of EBR in non-malign cells, mouse embryonic fibroblast (MEF) cells were investigated in detail for ER stress biomarkers, autophagy, and polyamine metabolism in this study. Evolutionary conserved autophagy mechanism is a crucial cellular process to clean damaged organelles and protein aggregates through lysosome under the control of autophagy-related genes (ATGs). Cells tend to activate autophagy to promote cell survival under stress conditions. Polyamines are polycationic molecules playing a role in the homeostasis of important cellular events such as cell survival, growth, and, proliferation. The administration of PAs has been markedly extended the lifespan of various organisms via inducing autophagy and inhibiting oxidative stress. Our data indicated that ER stress is induced following EBR treatment in MEF cells as well as MEF Atg5^-/- cells. In addition, autophagy is activated following EBR treatment by targeting PI3K/Akt/mTOR in wildtype (wt) cells. However, EBR-induced autophagy targets ULK1 in MEF cells lacking Atg5 expression. Besides, EBR treatment depleted the PA pool in MEF cells through the alterations of metabolic enzymes. The administration of Spd with EBR further increased autophagic vacuole formation. In conclusion, EBR is an anticancer drug candidate with selective cytotoxicity for cancer cells, in addition the induction of autophagy and PA metabolism are critical for responses of normal cells against EBR.

Toxic effects of boscalid on the growth, photosynthesis, antioxidant system and metabolism of Chlorella vulgaris

Boscalid is one of the most frequently detected pesticides in main coastal estuaries in California, with concentrations as high as 36 μg/L. However, ecotoxicology information about boscalid to aquatic organisms is scarce. To investigate toxic effects and mechanisms of boscalid on freshwater algae Chlorella vulgaris (C. vulgaris), C. vulgaris were exposed to a range of boscalid concentrations (0, 0.8, 1.6, 2.4 and 3.2 mg/L) for 96 h to study the changes in photosynthetic pigment contents, responses of the antioxidant enzyme system and alterations in endogenous substances. Results indicated that the growth of algae and the content of chlorophyll and carotenoids were significantly inhibited by 1.6 mg/L boscalid. Reactive oxygen species (ROS) and oxidative damage of C. vulgaris could be induced by boscalid, in accordance with significant changes in ROS levels and a series of antioxidant enzyme activities. Moreover, the alterations in endogenous substances showed that boscalid could affect photosynthesis and energy metabolism of C. vulgaris. These results demonstrated that boscalid could induce impacts on C. vulgaris mainly through disturbing the photosynthesis, oxidative damage and energy metabolism. The present study provided a better understanding of the negative effects and mechanisms of bosaclid in microalgae.

Cyclin-dependent kinase inhibitors, roscovitine and purvalanol, induce apoptosis and autophagy related to unfolded protein response in HeLa cervical cancer cells

Roscovitine (Rosc) and purvalanol (Pur) are competitive inhibitors of cyclin-dependent kinases (CDKs) by targeting their ATP-binding pockets. Both drugs are shown to be effective to decrease cell viability and dysregulate the ratio of pro- and anti-apoptotic Bcl-2 family members, which finally led to apoptotic cell death in different cancer cell lines in vitro. It was well established that Bcl-2 family members have distinct roles in the regulation of other cellular processes such as endoplasmic reticulum (ER) stress. The induction of ER stress has been shown to play critical role in cell death/survival decision via autophagy or apoptosis. In this study, our aim was to investigate the molecular targets of CDK inhibitors on ER stress mechanism related to distinct cell death types in time-dependent manner in HeLa cervical cancer cells. Our results showed that Rosc and Pur decreased the cell viability, cell growth and colony formation, induced ER stress-mediated autophagy or apoptosis in time-dependent manner. Thus, we conclude that exposure of cells to CDK inhibitors induces unfolded protein response and ER stress leading to autophagy and apoptosis processes in HeLa cervical cancer cells.

Anticancer and radiosensitizing effects of the cyclin-dependent kinase inhibitors, AT7519 and SNS‑032, on cervical cancer

Cyclin-dependent kinases (CDK) are considered to be potential targets of anticancer drugs that can interrupt the uncontrolled division of cancer cells. In this study, we selected two selective CDK inhibitors, AT7519 and SNS‑032, from current clinical trials and examined their anticancer and radiosensitizing effects in a cervical cancer model. SNS‑032 was found to be more potent than AT7519, with a lower half maximal inhibitory concentration (IC50) value. Both AT7519 and SNS‑032 induced the apoptosis, premature senescence and cytostasis of cervical cancer cells, which led to the attenuation of tumor growth in vivo. Moreover, using these CDK inhibitors together with radiation synergistically inhibited tumor growth in a human xenograft tumor model. The concomitant activation of the p53 tumor suppressor and the suppression of cell cycle checkpoint responses mediated by Chk1 led to the cytostasis of cervical cancer cells. Finally, AT7519 and SNS‑032 inhibited cancer cell migration, invasion and angiogenesis in vitro, and suppressed lung metastases in a spontaneous metastasis model. On the whole, the findings of this study indicate that the utilization of AT7519 and SNS‑032 as part of an adjuvant treatment may help control cervical cancer progression.

Curcumin inhibits autocrine growth hormone-mediated invasion and metastasis by targeting NF-κB signaling and polyamine metabolism in breast cancer cells

Curcumin is assumed to be a plant-derived therapeutic drug that triggers apoptotic cell death in vitro and in vivo by affecting different molecular targets such as NF-κB. Phase I/II trial of curcumin alone or with chemotherapeutic drugs has been accomplished in pancreatic, colon, prostate and breast cancer cases. Recently, autocrine growth hormone (GH) signaling-induced cell growth, metastasis and drug resistance have been demonstrated in breast cancer. In this study, our aim was to investigate the potential therapeutic effect of curcumin by evaluating the molecular machinery of curcumin-triggered apoptotic cell death via focusing on NF-κB signaling and polyamine (PA) metabolism in autocrine GH-expressing MCF-7, MDA-MB-453 and MDA-MB-231 breast cancer cells. For this purpose, a pcDNA3.1 (+) vector with a GH gene insert was transfected by a liposomal agent in all breast cancer cells and then selection was conducted in neomycin (G418) included media. Autocrine GH-induced curcumin resistance was overcome in a dose-dependent manner and curcumin inhibited cell proliferation, invasion-metastasis and phosphorylation of p65 (Ser536), and thereby partly prevented its DNA binding activity in breast cancer cells. Moreover, curcumin induced caspase-mediated apoptotic cell death by activating the PA catabolic enzyme expressions, which led to generation of toxic by-products such as H₂O₂ in MCF-7, MDA-MB-453 and MDA-MB-231 GH+ breast cancer cells. In addition, transient silencing of SSAT prevented curcumin-induced cell viability loss and apoptotic cell death in each breast cancer cells. In conclusion, curcumin could overcome the GH-mediated resistant phenotype via modulating cell survival, death-related signaling routes and activating PA catabolic pathway.

Inhibition of human prostate cancer (PC-3) cells and targeting of PC-3-derived prostate cancer stem cells with koenimbin, a natural dietary compound from Murraya koenigii (L) Spreng

BACKGROUND

Inhibition of prostate cancer stem cells (PCSCs) is an efficient curative maintenance protocol for the prevention of prostate cancer. The objectives of this study were to assess the efficiency of koenimbin, a major biologically active component of Murraya koenigii (L) Spreng, in the suppression of PC-3 cells and to target PC-3-derived cancer stem cells (CSCs) through apoptotic and CSC signaling pathways in vitro.

MATERIALS AND METHODS

The antiproliferative activity of koenimbin was examined using MTT, and the apoptotic detection was carried out by acridine orange/propidium iodide (AO/PI) double-staining and multiparametric high-content screening (HCS) assays. Caspase bioluminescence assay, reverse transcription polymerase chain reaction (RT-PCR), and immunoblotting were conducted to confirm the expression of apoptotic-associated proteins. Cell cycle analysis was investigated using flow cytometry. Involvement of nuclear factor-kappa B (NF-κB) was analyzed using HCS assay. Aldefluor™ and prostasphere formation examinations were used to evaluate the impact of koenimbin on PC-3 CSCs in vitro.

RESULTS

Koenimbin remarkably inhibited cell proliferation in a dose-dependent manner. Koenimbin induced nuclear condensation, formation of apoptotic bodies, and G0/G1 phase arrest of PC-3 cells. Koenimbin triggered the activation of caspase-3/7 and caspase-9 and the release of cytochrome c, decreased anti-apoptotic Bcl-2 and HSP70 proteins, increased pro-apoptotic Bax proteins, and inhibited NF-κB translocation from the cytoplasm to the nucleus, leading to the activation of the intrinsic apoptotic pathway. Koenimbin significantly (P<0.05) reduced the aldehyde dehydrogenase-positive cell population of PC-3 CSCs and the size and number of PC-3 CSCs in primary, secondary, and tertiary prostaspheres in vitro.

CONCLUSION

Koenimbin has chemotherapeutic potential that may be employed for future treatment through decreasing the recurrence of cancer, resulting in the improvement of cancer management strategies and patient survival.

Regulatory role of calpain in neuronal death

Calpains are a group of calcium-dependent proteases that are over activated by increased intracellular calcium levels under pathological conditions. A wide range of substrates that regulate necrotic, apoptotic and autophagic pathways are affected by calpain. Calpain plays a very important role in neuronal death and various neurological disorders. This review introduces recent research progress related to the regulatory mechanisms of calpain in neuronal death. Various neuronal programmed death pathways including apoptosis, autophagy and regulated necrosis can be divided into receptor interacting protein-dependent necroptosis, mitochondrial permeability transition-dependent necrosis, pyroptosis and poly (ADP-ribose) polymerase 1-mediated parthanatos. Calpains cleave series of key substrates that may lead to cell death or participate in cell death. Regarding the investigation of calpain-mediated programed cell death, it is necessary to identify specific inhibitors that inhibit calpain mediated neuronal death and nervous system diseases.

mTOR is a fine tuning molecule in CDK inhibitors-induced distinct cell death mechanisms via PI3K/AKT/mTOR signaling axis in prostate cancer cells

Purvalanol and roscovitine are cyclin dependent kinase (CDK) inhibitors that induce cell cycle arrest and apoptosis in various cancer cells. We further hypothesized that co-treatment of CDK inhibitors with rapamycin, an mTOR inhibitor, would be an effective combinatory strategy for the inhibition of prostate cancer regard to androgen receptor (AR) status due to inhibition of proliferative pathway, PI3K/AKT/mTOR, and induction of cell death mechanisms. Androgen responsive (AR+), PTEN(-/-) LNCaP and androgen independent (AR-), PTEN(+/-) DU145 prostate cancer cells were exposed to purvalanol (20 µM) and roscovitine (30 µM) with or without rapamycin for 24 h. Cell viability assay, immunoblotting, flow cytometry and fluorescence microscopy was used to define the effect of CDK inhibitors with or without rapamycin on proliferative pathway and cell death mechanisms in LNCaP and DU145 prostate cancer cells. Co-treatment of rapamycin modulated CDK inhibitors-induced cytotoxicity and apoptosis that CDK inhibitors were more potent to induce cell death in AR (+) LNCaP cells than AR (-) DU145 cells. CDK inhibitors in the presence or absence of rapamycin induced cell death via modulating upstream PI3K/AKT/mTOR signaling pathway in LNCaP cells, exclusively only treatment of purvalanol have strong potential to inhibit both upstream and downstream targets of mTOR in LNCaP and DU145 cells. However, co-treatment of rapamycin with CDK inhibitors protects DU145 cells from apoptosis via induction of autophagy mechanism. We confirmed that purvalanol and roscovitine were strong apoptotic and autophagy inducers that based on regulation of PI3K/AKT/mTOR signaling pathway. Co-treatment of rapamycin with purvalanol and roscovitine exerted different effects on cell survival and death mechanisms in LNCaP and DU145 cell due to their AR receptor status. Our studies show that co-treatment of rapamycin with CDK inhibitors inhibit prostate cancer cell viability more effectively than either agent alone, in part, by targeting the mTOR signaling cascade in AR (+) LNCaP cells. In this point, mTOR is a fine-tuning player in purvalanol and roscovitine-induced apoptosis and autophagy via regulation of PI3K/AKT and the downstream targets, which related with cell proliferation.

Prostate Cancer and Aspirin Use: Synopsis of the Proposed Molecular Mechanisms

Background: Prostate cancer (PCa) is a critical health burden, impacting the morbidity and mortality of millions of men around the world. Most of the patients with PCa have their disease at first sensitive to androgen deprivation treatments, but later they develop resistance to therapy and eventually die of metastatic castration-resistant prostate cancer (CRPC). Although the newly developed anti-androgen therapies are effectively alleviating symptoms and prolonging lives of patients, there are still no curable treatments for CRPC. Recently, statistical studies have shown that the chronic use of aspirin might be significantly associated with better outcomes in PCa patients. Through this review, we aim to identify the different proposed molecular mechanisms relating aspirin to the pathobiology of PCa neoplasms, with a major focus on basic research done in this context.

Methods: Articles were retrieved via online database searching of PubMed and MEDLINE between 1946 and September 2016. Keywords and combinations related to PCa and aspirin were used to perform the search. Abstracts of the articles were studied by two independent reviewers and then data extraction was performed on the relevant articles that met our review objectives.

Results: Aspirin, a non-steroidal anti-inflammatory drug (NSAID), affects the proliferation, apoptosis, resistance and metastasis of PCa cell lines, through both COX-dependent and COX-independent mechanisms. It also lowers levels of the PCa diagnostic marker prostate specific antigen (PSA), suggesting that clinicians need to at least be aware if their patients are using Aspirin chronically.

Conclusion: This review strongly warrants further consideration of the signaling cascades activated by aspirin, which may lead to new knowledge that might be applied to improve diagnosis, prognosis and treatment of PCa.

Difluoromethylornithine in cancer: new advances

Difluoromethylornithine (DFMO; eflornithine) is an irreversible suicide inhibitor of the enzyme ornithine decarboxylase which is involved in polyamine synthesis. Polyamines are important for cell survival, thus DFMO was studied as an anticancer agent and as a chemoprevention agent. DFMO exhibited mainly cytostatic activity and had single agent efficacy as well as activity in combination with other chemotherapeutic drugs for some cancers and leukemias. Herewith, we summarize the current knowledge of the anticancer and chemopreventive properties of DFMO and assess the status of clinical trials.

Anti-cancer effects of torulene, isolated from Sporidiobolus pararoseus, on human prostate cancer LNCaP and PC-3 cells via a mitochondrial signal pathway and the down-regulation of AR expression

Torulene, inhibit LNCaP and PC-3 cells growth through Bcl-2/Bax mediated apoptosis and AR down-regulation.

Targeting CDK9: a promising therapeutic opportunity in prostate cancer

Cyclin-dependent kinase 9 (CDK9) is a key transcriptional regulator and a lucrative target for cancer treatment. Targeting CDK9 can effectively confine the hyperactivity of androgen receptor and the constitutive expression of anti-apoptotic proteins; both being main causes of prostate cancer (PCa) development and progression. In castrate-resistant PCa, traditional therapies that only target androgen receptor (AR) have become obsolete due to reprograming in AR activity to make the cells independent of androgen. CDK9 inhibitors may provide a new and better therapeutic opportunity over traditional treatment options by targeting both androgen receptor activity and anti-apoptotic proteins, improving the chances of positive outcomes, especially in patients with the advanced disease. This review focuses on biological functions of CDK9, its involvement with AR and the potential for therapeutic opportunities in PCa treatment.

The suppression of torulene and torularhodin treatment on the growth of PC-3 xenograft prostate tumors

Torulene and torularhodin are two of the principal carotenoids in Sporidiobolus pararoseus and have a similar structure to that of lycopene. The present study was to elucidate the anti-cancer activity of torulene and torularhodin in vivo with lycopene as a control. Nude mice were orally supplemented every day with a low or high dose [9 or 18 mg/kg body weight (BW)] of lycopene, torularhodin or torulene. Two weeks after the supplementation, mice were injected once with hormone-independent prostatic carcinoma PC-3 cells. When the tumor of the control group load exceeded 200 mm(3), mice were killed and the study was terminated. Compared with the controls, high-carotenoid supplementation lowered the mean number of tumors from 248.13 ± 28.74 to 50.83 ± 7.63, 70.34 ± 6.77, and 60.53 ± 6.78 mm(3) (P < 0.05, n = 8) by, respectively. Histological examination showed tumor degeneration, apoptosis and necrosis presented at the end of the experiment. Quantitative polymerase chain reaction and immunohistochemistry results showed Bcl-2 expression of the control group was higher than that of the carotenoid-treated group while the expression of Bax was lower than the carotenoid-treated group. High-carotenoid supplementation also increased the mRNA expressions of caspase-3, 8 and 9 in tumor tissues. These results show that both torulene and torularhodin supplementation inhibit the growth of prostate cancer in nude mice and suggest that such an action is associated the apoptosis of tumor cells.

siRNA knockdown of mitochondrial thymidine kinase 2 (TK2) sensitizes human tumor cells to gemcitabine

Nucleoside metabolism enzymes are determinants of chemotherapeutic drug activity. The nucleoside salvage enzyme deoxycytidine kinase (dCK) activates gemcitabine (2', 2'-difluoro-2'-deoxycytidine) and is negatively regulated by deoxycytidine triphosphate (dCTP). Reduction of dCTP in tumor cells could, therefore, enhance gemcitabine activity. Mitochondrial thymidine kinase 2 (TK2) phosphorylates deoxycytidine to generate dCTP. We hypothesized that: (1) TK2 modulates human tumor cell sensitivity to gemcitabine, and (2) antisense knockdown of TK2 would decrease dCTP and increase dCK activity and gemcitabine activation. siRNA downregulation of TK2 sensitized MCF7 and HeLa cells (high and moderate TK2) but not A549 cells (low TK2) to gemcitabine. Combined treatment with TK2 siRNA and gemcitabine increased dCK. We also hypothesized that TK2 siRNA-induced drug sensitization results in mitochondrial damage that enhances gemcitabine effectiveness. TK2 siRNA and gemcitabine decreased mitochondrial redox status, DNA content, and activity. This is the first demonstration of a direct role for TK2 in gemcitabine resistance, or any independent role in cancer drug resistance, and further distinguishes TK2 function from that of other dTMP-producing enzymes [cytosolic TK1 and thymidylate synthase (TS)]. siRNA knockdown of TK1 and/or TS did not sensitize cancer cells to gemcitabine indicating that, among the 3 enzymes, only TK2 is a candidate therapeutic target for combination with gemcitabine.

Purvalanol induces endoplasmic reticulum stress-mediated apoptosis and autophagy in a time-dependent manner in HCT116 colon cancer cells

Purvalanol, a novel cyclin-dependent kinase inhibitor, is referred to as a strong apoptotic inducer which causes cell cycle arrest in various cancer cells such as prostate, breast and colon cancer cell lines. Various physiological and pathological conditions such as glucose starvation, inhibition of protein glycosylation and oxidative stress may cause an accumulation of unfolded proteins in the endoplasmic reticulum (ER), leading to the unfolded protein response (UPR) and autophagy. Lacking proteosomal function on aggregates of unfolded proteins, ER stress may induce autophagic machinery. Autophagy, an evolutionarily conserved process, is characterized by massive degradation of cytosolic contents. In the present study, our aim was to determine the time-dependent, ER-mediated apoptotic and autophagy induction of purvalanol in HCT 116 colon cancer cells. Fifteen micromoles of purvalanol induced a reduction in cell viability by 20 and 35% within 24 and 48 h, respectively. HCT 116 colon cancer cells were exposed to purvalanol, which activated ER stress via upregulation of PERK, IRE1α gene expression, eIF-2α phosphorylation and ATF-6 cleavage at early time-points in the HCT 116 colon cancer cells. Moreover, we determined that during purvalanol-mediated ER stress, autophagic machinery was also activated prior to apoptotic cell death finalization. Beclin-1 and Atg-5 expression levels were upregulated and LC3 was cleaved after a 6 h purvalanol treatment. Purvalanol induced mitochondrial membrane potential loss, caspase-7 and caspase-3 activation and PARP cleavage following a 48 h treatment. Thus, we conclude that the anticancer effect of purvalanol in HCT 116 cells was due to ER stress-mediated apoptosis; however, purvalanol triggered autophagy, which functions as a cell survival mechanism at early time-points.

Torularhodin, isolated from Sporidiobolus pararoseus, inhibits human prostate cancer LNCaP and PC-3 cell growth through Bcl-2/Bax mediated apoptosis and AR down-regulation

Torularhodin is one of the principal carotenoids inSporidiobolus pararoseusand has a similar structure to that of lycopene.