Induction of anoikis by doxazosin in prostate cancer cells is associated with activation of caspase-3 and a reduction of focal adhesion kinase

A Novel Signature Based on Anoikis Associated with BCR-Free Survival for Prostate Cancer

This study aimed to elucidate the role of anoikis in the progression of prostate cancer (PCa) and to develop a prognostic signature based on anoikis-related genes (ARGs). To achieve this, PCa cases were subjected to nonnegative matrix factorization (NMF) analysis, which allowed for the identification of distinct patterns of anoikis modification. Additionally, immune infiltration was evaluated using single-sample gene-set enrichment analysis (ssGSEA). Survival analysis was performed using the Kaplan-Meier method, and a risk score was generated based on the expression levels of ARGs to quantitatively assess the modification of anoikis in PCa. Using the Least Absolute Shrinkage and Selection Operator (LASSO) method, four hub-genes were identified, and patients were classified into different risk groups based on their individual scores. Importantly, the low-risk subtype was characterized by a significantly improved biochemical recurrence-free survival, underscoring the clinical relevance of the ARG-based prognostic signature. To further improve the prognostic accuracy of the signature, patient age, pathological T stage, Gleason score, and prostate-specific antigen level were incorporated into the analysis, yielding a comprehensive prognostic signature. The clinical relevance of this signature was illustrated through a nomogram, providing a visual representation of the prognostic implications of the ARG-based signature. Taken together, these findings highlight the potential of ARGs in predicting the clinical outcomes of PCa patients and provide a novel and clinically relevant prognostic signature based on the modification of anoikis in PCa.

Anoikis in phenotypic reprogramming of the prostate tumor microenvironment

Prostate cancer is one of the most common malignancies in males wherein 1 in 8 men are diagnosed with this disease in their lifetime. The urgency to find novel therapeutic interventions is associated with high treatment resistance and mortality rates associated with castration-resistant prostate cancer. Anoikis is an apoptotic phenomenon for normal epithelial or endothelial cells that have lost their attachment to the extracellular matrix (ECM). Tumor cells that lose their connection to the ECM can die via apoptosis or survive via anoikis resistance and thus escaping to distant organs for metastatic progression. This review discusses the recent advances made in our understanding of the signaling effectors of anoikis in prostate cancer and the approaches to translate these mechanistic insights into therapeutic benefits for reducing lethal disease outcomes (by overcoming anoikis resistance). The prostate tumor microenvironment is a highly dynamic landscape wherein the balance between androgen signaling, cell lineage changes, epithelial-mesenchymal transition (EMT), extracellular matrix interactions, actin cytoskeleton remodeling as well as metabolic changes, confer anoikis resistance and metastatic spread. Thus, these mechanisms also offer unique molecular treatment signatures, exploitation of which can prime prostate tumors to anoikis induction with a high translational significance.

Quinazoline alpha-adrenoreceptor blockers as an adjunct cancer treatment: From bench to bedside

Drug repurposing has been increasingly used by both researchers and clinicians to identify new cancer treatments. The alpha-1 adrenoreceptor blockers are a class of drugs that have been used for many years in the treatment of hypertension and benign prostatic hyperplasia. Some of the drugs in this class, notably the quinazoline derivatives, have been found to display cytotoxic properties, identifying them as potential options in the treatment of cancer. This review will examine the currently available evidence that investigates the cytotoxic and anti-cancer properties of these agents, the mechanisms behind these properties and how the alpha-1 blockers fit within current cancer therapies. It aims to answer the question of whether these agents can go from the laboratory bench top into cancer clinics.

A Pilot retrospective analysis of alpha-blockers on recurrence in men with localised prostate cancer treated with radiotherapy

While alpha-blockers are commonly used to reduce lower urinary tract symptoms in prostate cancer patients receiving radiotherapy, their impact on response to radiotherapy remains unknown. Therefore, this pilot study aimed to retrospectively determine if alpha-blockers use, influenced response to radiotherapy for localised prostate cancer. In total, 303 prostate cancer patients were included, consisting of 84 control (alpha-blocker naïve), 72 tamsulosin and 147 prazosin patients. The main outcomes measured were relapse rates (%), time to biochemical relapse (months) and PSA velocity (ng/mL/year). Recurrence free survival was calculated using Kaplan-Meier analysis. Prazosin significantly reduced biochemical relapse at both two and five-years (2.72%, 8.84%) compared to control (22.61%, 34.52%). Recurrence free survival was also significantly higher in the prazosin group. This remained after multivariable analysis (HR: 0.09, 95% CI: 0.04-0.26, p < 0.001). Patients receiving prazosin had a 3.9 times lower relative risk of biochemical relapse compared to control. Although not statistically significant, tamsulosin and prazosin extended recurrence free survival by 13.15 and 9.21 months respectively. We show for the first time that prazosin may reduce risk of prostate cancer recurrence and delay time to biochemical relapse and provides justification for prospective studies to examine its potential as an adjunct treatment option for localised prostate cancer.

HERG channel and cancer: A mechanistic review of carcinogenic processes and therapeutic potential

The human ether-à-go-go related gene (HERG) encodes the alpha subunit of Kv11.1, which is a voltage-gated K⁺ channel protein mainly expressed in heart and brain tissue. HERG plays critical role in cardiac repolarization, and mutations in HERG can cause long QT syndrome. More recently, evidence has emerged that HERG channels are aberrantly expressed in many kinds of cancer cells and play important roles in cancer progression. HERG could therefore be a potential biomarker for cancer and a possible molecular target for anticancer drug design. HERG affects a number of cellular processes, including cell proliferation, apoptosis, angiogenesis and migration, any of which could be affected by dysregulation of HERG. This review provides an overview of available information on HERG channel as it relates to cancer, with focus on the mechanism by which HERG influences cancer progression. Molecular docking attempts suggest two possible protein-protein interactions of HERG with the ß1-integrin receptor and the transcription factor STAT-1 as novel HERG-directed therapeutic targeting which avoids possible cardiotoxicity. The role of epigenetics in regulating HERG channel expression and activity in cancer will also be discussed. Finally, given its inherent extracellular accessibility as an ion channel, we discuss regulatory roles of this molecule in cancer physiology and therapeutic potential. Future research should be directed to explore the possibilities of therapeutic interventions targeting HERG channels while minding possible complications.

Herbal formula YGJDSJ inhibits anchorage-independent growth and induces anoikis in hepatocellular carcinoma Bel-7402 cells

Background

Based on clinical medications and related studies, we established a Yang-Gan Jie-Du Sang-Jie (YGJDSJ) herbal formula for hepatocarcinoma treatment. In present study, we evaluated the anti-cancer potential of YGJDSJ on suspension-grown human hepatocellular carcinoma Bel-7402 cells.

Methods

Bel-7402 cells were cultured in poly(2-hydroxyethyl methacrylate) (poly-HEMA) coated plates and treated with YGJDSJ. Anchorage-independent cell growth was detected by cell Counting Kit-8 (CCK-8) assay and soft agar colony formation assay. Anoikis was detected by ethdium homodimer-1 (EthD-1) staining and flow cytometry analysis. Caspases activities were detected by the cleavage of chromogenic substrate. Reactive oxygen species (ROS) was detected by 2′,7′-dichlorofluorescin diacetate (DCFH-DA) staining. Protein expression and phosphorylation was identified by western blot. Protein expression was knocked-down by siRNA.

Results

YGJDSJ inhibited the proliferation of Bel-7402 cells in poly-HEMA coated plates and anchorage-independent growth of Bel-7402 cells in soft agar. YGJDSJ also induced anoikis in Bel-7402 cells as indicated by EthD-1 staining and flow cytometry analysis. YGJDSJ activated caspase-3, − 8, and − 9 in suspension-grown Bel-7402 cells. The pan-caspase inhibitor Z-VAD-FMK significantly abrogated the effects of YGJDSJ on anoikis in suspension-grown Bel-7402 cells. In addition, YGJDSJ increased ROS in suspension-grown Bel-7402 cells. The ROS scavenger N-acetyl-L-cysteine (NAC) partially attenuated YGJDSJ-induced activation of caspase-3, − 8 and − 9 and anoikis in suspension-grown Bel-7402 cells. Furthermore, YGJDSJ inhibited expression and phosphorylation of protein tyrosine kinase 2 (PTK2) in suspension-grown Bel-7402 cells. Over-expression of PTK2 significantly abrogated YGJDSJ induced anoikis.

Conclusions

YGJDSJ inhibits anchorage-independent growth and induce caspase-mediated anoikis in Bel-7402 cells, and may relate to ROS generation and PTK2 downregulation.

The Role of α1-Adrenoceptor Antagonists in the Treatment of Prostate and Other Cancers

This review evaluates the role of α-adrenoceptor antagonists as a potential treatment of prostate cancer (PCa). Cochrane, Google Scholar and Pubmed were accessed to retrieve sixty-two articles for analysis. In vitro studies demonstrate that doxazosin, prazosin and terazosin (quinazoline α-antagonists) induce apoptosis, decrease cell growth, and proliferation in PC-3, LNCaP and DU-145 cell lines. Similarly, the piperazine based naftopidil induced cell cycle arrest and death in LNCaP-E9 cell lines. In contrast, sulphonamide based tamsulosin did not exhibit these effects. In vivo data was consistent with in vitro findings as the quinazoline based α-antagonists prevented angiogenesis and decreased tumour mass in mice models of PCa. Mechanistically the cytotoxic and antitumor effects of the α-antagonists appear largely independent of α 1-blockade. The proposed targets include: VEGF, EGFR, HER2/Neu, caspase 8/3, topoisomerase 1 and other mitochondrial apoptotic inducing factors. These cytotoxic effects could not be evaluated in human studies as prospective trial data is lacking. However, retrospective studies show a decreased incidence of PCa in males exposed to α-antagonists. As human data evaluating the use of α-antagonists as treatments are lacking; well designed, prospective clinical trials are needed to conclusively demonstrate the anticancer properties of quinazoline based α-antagonists in PCa and other cancers.

Relative cytotoxic potencies and cell death mechanisms of α1 -adrenoceptor antagonists in prostate cancer cell lines

BACKGROUND

Some α1 -adrenoceptor antagonists possess anti-cancer actions that are independent of α1 -adrenoceptors and the aim of these studies was to assess the relative cytotoxic potencies of α1 -adrenoceptor antagonists and the mechanisms involved in these actions.

METHODS

PC-3 and LNCap human prostate cancer cells were exposed to α1 -adrenoceptor antagonists (0.01-100 μM) and cell survival assessed after 24-72 hr. The levels of apoptosis, autophagy and stress related proteins were also determined.

RESULTS

The relative cytotoxic potency order was prazosin = doxazosin > terazosin = silodosin = alfuzosin > tamsulosin on both cell types, but LNCaP cells were significantly more sensitive to these effects than PC-3 cells. Prazosin and doxazosin increased levels of apoptotsis and autophagy in both cell lines, and activated EphA2 receptors in PC-3 cells. Autophagy contributed to survival of LNCaP, but promoted cell death in PC-3 cells. Treatment with prazosin (30 μM) altered the expression of several cell stress-related proteins: elevating phospho-p38α and reducing S6 kinase in both cell lines. Surprisingly some proteins were differentially affected in the two prostate cancer cell lines: Akt and p27 increasing and HIF-1α decreasing in LNCap cells but not PC-3, while ADAMTS1 was increased in PC-3 cells only.

CONCLUSIONS

Prazosin and doxazosin demonstrated cytotoxic actions on both castration-resistant PC-3 and androgen-sensitive LNCap prostate cancer cells. The mechanisms involved included changes in a number of proliferation and apoptosis regulatory proteins. The role of autophagy depended on the cell type, but contributed to cell death in PC3 cells.

Antitumor action of α(1)-adrenoceptor blockers on human bladder, prostate and renal cancer cells

The present study investigated the antitumor action of α(1)-adrenoceptor blockers on human bladder, prostate and renal cancer cells. For bladder cancer cell lines used here such as 253J, 5637, KK-47, T24 and UM-UC-3 cells, prazosin, a selective α(1)-adrenoceptor blocker, reduced cell viability at concentrations more than 30 µmol/l. Likewise, naftopidil, a blocker of α(1A)- and α(1D)-adrenoceptors, reduced cell viability for all the bladder cancer cells used here in a concentration (10-100 µmol/l)-dependent manner, with a much greater advantage than prazosin. Naftopidil also reduced cell viability for human prostate cancer cell lines such as DU145, LNCap and PC-3 cells and ACHN human renal cancer cells, with a much higher potential than prazosin. Thus, the results of the present study suggest that naftopidil could be a beneficial antitumor drug for the treatment of urological cancers.

Novel roles for hERG K(+) channels in cell proliferation and apoptosis

The human ether-a-go-go-related gene potassium channel (hERG, Kv11.1, KCNH2) has an essential role in cardiac action potential repolarization. Electrical dysfunction of the voltage-sensitive ion channel is associated with potentially lethal ventricular arrhythmias in humans. hERG K⁺ channels are also expressed in a variety of cancer cells where they control cell proliferation and apoptosis. In this review, we discuss molecular mechanisms of hERG-associated cell cycle regulation and cell death. In addition, the significance of hERG K⁺ channels as future drug target in anticancer therapy is highlighted.

Prazosin induces p53-mediated autophagic cell death in H9C2 cells

Prazosin, a quinazoline-based α(1)-adrenoceptor antagonist, is known to induce cell death, and this effect is independent of its α-blockade activity. However, the detailed molecular mechanisms involved are still not fully understood. In this study, we found that prazosin, but not doxazosin, could induce patterns of autophagy in H9C2 cells, including intracellular vacuole formation, microtubule-associated protein 1 light chain 3 (LC3) conversion, and acidic vesicular organelle (AVO) augmentation. Western blot analysis of phosphorylated proteins showed that exposure to prazosin increased the levels of phospho-p53 and phospho-adenosine monophosphate-activated protein kinase (AMPK) but dramatically decreased the levels of phospho-mammalian target of rapamycin (mTOR), phospho-protein kinase B (Akt), and phospho-ribosomal protein S6 kinase (p70S6K). Furthermore, although pretreatments with the pharmacological autophagy inhibitor 3-methyladenine and the p53 inhibitor pifithrin-α suppressed prazosin-induced AVO formation, they did not reverse prazosin-induced decline in cell viability but enhanced prazosin-induced caspase-3 activation. From these results we suggest that prazosin induces autophagic cell death via a p53-mediated mechanism. When the autophagy pathway was inhibited, prazosin still induced programmed cell death, at least in part through apoptotic caspase-3 cascade enhancement. Thus, our results indicate a potential new target in prazosin-induced cell death.

Transforming growth factor-beta type I receptor/ALK5 contributes to doxazosin-induced apoptosis in H9C2 cells

The mechanism of doxazosin-induced apoptosis through alpha(1)-adrenoceptor-independent pathway has been reported in various types of cell models. However, the molecular events involved in this effect are still not fully discovered. In present study, we proposed that the transforming growth factor-beta type I receptor (TbetaRI/ALK5) may contribute to the doxazosin-induced apoptosis in H9C2 cardiomyoblasts. Via the detection of cell viability, apoptotic nuclei, and caspase-3 activity, we found that doxazosin induced concentration- and time-dependent apoptosis in H9C2 cells. The cell apoptosis induced by 30 muM doxazosin was exacerbated by the addition of 10 ng/ml transforming growth factor-beta1 (TGF-beta1). Doxazosin or TGF-beta1 alone respectively elevated p38 mitogen-activated protein kinases (MAPK) and Smad3 protein phosphorylation in H9C2 cells. However, the cotreatment of doxazosin and TGF-beta1 attenuated the TGF-beta1-induced Smad3 protein phosphorylation and increased doxazosin-induced p38 MAPK protein phosphorylation. Furthermore, inhibitors of TbetaRI/ALK5 (SB431542) and p38 MAPK (SB202190) or TbetaRI/ALK5 knockdown all dramatically reduced the doxazosin-induced apoptosis in H9C2 cells. In conclusion, our results demonstrated that TbetaRI/ALK5-p38 MAPK phosphorylation signaling pathway could contribute to doxazosin-induced cell apoptosis, which could be further enhanced by TGF-beta1 in association with attenuating Smad3 phosphorylation in H9C2 cells.

Induction of apoptosis of detached oral squamous cell carcinoma cells by safingol. Possible role of Bim, focal adhesion kinase and endonuclease G

The protein kinase C (PKC) inhibitor safingol increased rounding and detachment of human oral squamous cell carcinoma (SCC) cells in monolayer cultures. When dissociated cells were incubated in the presence of safingol, cell adhesion was prevented and cell viability was lost gradually, while most cells survived in the absence of safingol even if their attachment was blocked by coating the culture plates with polyhydroxyethyl methacrylate. Flow cytometric analysis and agarose gel electrophoresis of cellular DNA revealed an increase in the proportion of sub-G(1) cells and DNA fragmentation, indicating that safingol induced apoptosis of dissociated cells. During the induction of apoptosis in cell suspensions by safingol, there was an increase of the pro-apoptotic BH-3 only protein Bim and decrease of pro-survival Bcl-2 family proteins Bcl-xL and mitochondrial pro-apoptogenic factor endonuclease G translocated to the nucleus. The level of phosphorylated focal adhesion kinase (FAK) required for cell survival also rapidly decreased, followed by a decrease in the protein level. The introduction of siRNA against PKCalpha into SAS cells resulted in an increase of Bim, a decrease of Bcl-xL, the translocation of endonuclease G, and a decrease in the phosphorylation of FAK. These results suggest that Bim, Bcl-xL, FAK and endonuclease G are involved in safingol-induced apoptosis of detached oral SCC cells. Safingol can be used to induce apoptosis with cell detachment, anoikis, of oral SCC cells.

Involvement of transcription factor activator protein-2alpha in doxazosin-induced HeLa cell apoptosis

AIM

To investigate the pro-apoptotic effects of alpha1-adrenergic inhibitor doxazosin in HeLa cells and the potential involvement of transcription factor activator protein-2alpha (AP-2alpha) in doxazosin-induced apoptosis.

METHODS

The HeLa cells were exposed to various concentrations of doxazosin for 16 h. Apoptosis was detected using a DNA fragmentation assay, Hoechst 33258 staining, and flow cytometric analysis. The expression of AP-2alpha and caspase-3 was detected by relative quantitative RT-PCR and Western blot assays, respectively. After the respective transfections of the HeLa cells with AP-2alpha overexpressing constructs and an antisense oligonucleotide against AP-2alpha, apoptosis was assessed by flow cytometric analysis, and the expression of AP-2alpha and caspase-3 was detected by relative quantitative RT-PCR and Western blot assays. The colorimetric assay was performed to detect the caspase-3 activity.

RESULTS

Treatment with various concentrations of doxazosin for 16 h increased the apoptotic rate and total cell death rate of the HeLa cells in a dose-dependent manner and upregulated the expression of AP-2alpha and caspase-3 in a dose-dependent manner. A dose-dependent increase was observed in the caspase-3 activity. Overexpressing AP-2alpha led to the increased rate of doxazosin-induced apoptosis and the total cell death, whereas doxazosin-induced apoptosis and the total cell death in HeLa cells decreased by antisense AP-2alpha. Furthermore, overexpressing AP-2alpha increased the expression and activity of caspase-3, whereas antisense AP-2alpha in part abolished the increased effects of doxazosin on caspase-3 expression and activity.

CONCLUSION

Doxazosin induces apoptosis in HeLa cells in a dose-dependent manner, and transcription factor AP-2alpha is functionally involved in doxazosin-induced HeLa cell apoptosis.

Doxazosin-induced clusterin expression and apoptosis in prostate cancer cells

The purpose of this study was to correlate temporal expression of clusterin and apoptosis in androgen-independent human prostate cancer cells (PC-3) treated with 25 microM doxazosin. DNA fragmentation, reverse transcriptase polymerase chain reaction, and terminal transferase-mediated biotinylated 16-desoxy-uridene triphosphate nick-end labeling (TUNEL) assays were used to assess degree of apoptosis and temporal and spatial expression of clusterin mRNA and protein. DNA fragmentation was significant at 48 hours. Clusterin mRNA expression was 3-fold higher than control at 9 hours and was maintained over 48 hours. The TUNEL assay showed increasing percentage of apoptotic cells and presence of clusterin after doxazosin treatment. During doxazosin-induced apoptosis in PC3 cells, clusterin appeared to initially accumulate in the cytoplasm and protect against apoptosis; later, after its transport to the nucleus, clusterin was no longer able to suppress apoptosis.

Prazosin displays anticancer activity against human prostate cancers: targeting DNA and cell cycle

Quinazoline-based alpha1-adrenoceptor antagonists, in particular doxazosin and terazosin, are suggested to display antineoplastic activity against prostate cancers. However, there are few studies elucidating the effect of prazosin. In this study, prazosin displayed antiproliferative activity superior to that of other alpha1-blockers, including doxazosin, terazosin, tamsulosin, and phentolamine. Prazosin induced G2 checkpoint arrest and subsequent apoptosis in prostate cancer PC-3, DU-145, and LNCaP cells. In p53-null PC-3 cells, prazosin induced an increase in DNA strand breaks and ATM/ATR checkpoint pathways, leading to the activation of downstream signaling cascades, including Cdc25c phosphorylation at Ser216, nuclear export of Cdc25c, and cyclin-dependent kinase (Cdk) 1 phosphorylation at Tyr15. The data, together with sustained elevated cyclin A levels (other than cyclin B1 levels), suggested that Cdk1 activity was inactivated by prazosin. Moreover, prazosin triggered mitochondria-mediated and caspase-executed apoptotic pathways in PC-3 cells. The oral administration of prazosin significantly reduced tumor mass in PC-3-derived cancer xenografts in nude mice. In summary, we suggest that prazosin is a potential antitumor agent that induces cell apoptosis through the induction of DNA damage stress, leading to Cdk1 inactivation and G2 checkpoint arrest. Subsequently, mitochondria-mediated caspase cascades are triggered to induce apoptosis in PC-3 cells.

Nonreceptor tyrosine kinases in prostate cancer

BACKGROUND

Carcinoma of the prostate (CaP) is the most commonly diagnosed cancer in men in the United States. Signal transduction molecules such as tyrosine kinases play important roles in CaP. Src, a nonreceptor tyrosine kinase (NRTK) and the first proto-oncogene discovered is shown to participate in processes such as cell proliferation and migration in CaP. Underscoring NRTK's and, specifically, Src's importance in cancer is the recent approval by the US Food and Drug Administration of dasatinib, the first commercial Src inhibitor for clinical use in chronic myelogenous leukemia (CML). In this review we will focus on NRTKs and their roles in the biology of CaP.

MATERIALS AND METHODS

Publicly available literature from PubMed regarding the topic of members of NRTKs in CaP was searched and reviewed.

RESULTS

Src, FAK, JaK1/2, and ETK are involved in processes indispensable to the biology of CaP: cell growth, migration, invasion, angiogenesis, and apoptosis.

CONCLUSIONS

Src emerges as a common signaling and regulatory molecule in multiple biological processes in CaP. Src's relative importance in particular stages of CaP, however, required further definition. Continued investigation of NRTKs will increase our understanding of their biological function and potential role as new therapeutic targets.

Alpha1-, alpha2- and beta-adrenoceptors in the urinary bladder, urethra and prostate

1 We have systematically reviewed the presence, functional responses and regulation of alpha(1)-, alpha(2)- and beta-adrenoceptors in the bladder, urethra and prostate, with special emphasis on human tissues and receptor subtypes. 2 Alpha(1)-adrenoceptors are only poorly expressed and play a limited functional role in the detrusor. Alpha(1)-adrenoceptors, particularly their alpha(1A)-subtype, show a more pronounced expression and promote contraction of the bladder neck, urethra and prostate to enhance bladder outlet resistance, particularly in elderly men with enlarged prostates. Alpha(1)-adrenoceptor agonists are important in the treatment of symptoms of benign prostatic hyperplasia, but their beneficial effects may involve receptors within and outside the prostate. 3 Alpha(2)-adrenoceptors, mainly their alpha(2A)-subtype, are expressed in bladder, urethra and prostate. They mediate pre-junctional inhibition of neurotransmitter release and also a weak contractile effect in the urethra of some species, but not humans. Their overall post-junctional function in the lower urinary tract remains largely unclear. 4 Beta-adrenoceptors mediate relaxation of smooth muscle in the bladder, urethra and prostate. The available tools have limited the unequivocal identification of receptor subtypes at the protein and functional levels, but it appears that the beta(3)- and beta(2)-subtypes are important in the human bladder and urethra, respectively. Beta(3)-adrenoceptor agonists are promising drug candidates for the treatment of the overactive bladder. 5 We propose that the overall function of adrenoceptors in the lower urinary tract is to promote urinary continence. Further elucidation of the functional roles of their subtypes will help a better understanding of voiding dysfunction and its treatment.

PI3-K/Akt-mediated anoikis resistance of human osteosarcoma cells requires Src activation

Considerable advances in understanding the mechanisms associated with anoikis resistance of normal and malignant epithelial cells have been made. However, little is still known about the pathways involved in anoikis resistance of non-epithelial cells such as fibroblasts and sarcomas. Our results show that Src activity contributes to anoikis resistance of human osteosarcoma SAOS-2 cells. Src was found to be upregulated in anoikis resistant SAOS cells, and pharmacological inhibition of its activity resulted in the restoration of anoikis sensitivity. A normal pattern of dephosphorylation of FAK was observed upon cell detachment of both anoikis sensitive and resistant SAOS-2 cells, suggesting that FAK activity during anoikis resistance is not essential. The activity of Akt was found to be upregulated in anoikis resistant SAOSar cells and the pharmacological inhibition of PI3-K activity restored sensitivity to anoikis resistant cells, reconfirming the critical role of PI3-K/Akt pathway in cell survival. Furthermore, pharmacological inhibition of Src resulted in a decrease of Akt phosphorylation at Ser473. Altogether, these studies indicated a survival pathway mediated by the Src-dependent activation of the PI3-K/Akt pathway in a manner independent of FAK activity.

Elevated levels of cholesterol-rich lipid rafts in cancer cells are correlated with apoptosis sensitivity induced by cholesterol-depleting agents

Lipid rafts/caveolae are membrane platforms for signaling molecules that regulate various cellular functions, including cell survival. To better understand the role of rafts in tumor progression and therapeutics, we investigated the effect of raft disruption on cell viability and compared raft levels in human cancer cell lines versus their normal counterparts. Here, we report that cholesterol depletion using methyl-beta cyclodextrin caused anoikis-like apoptosis, which in A431 cells involved decreased raft levels, Bcl-xL down-regulation, caspase-3 activation, and Akt inactivation regardless of epidermal growth factor receptor activation. Cholesterol repletion replenished rafts on the cell surface and restored Akt activation and cell viability. Moreover, the breast cancer and the prostate cancer cell lines contained more lipid rafts and were more sensitive to cholesterol depletion-induced cell death than their normal counterparts. These results indicate that cancer cells contain increased levels of rafts and suggest a potential use of raft-modulating agents as anti-cancer drugs.

Celecoxib induces anoikis in human colon carcinoma cells associated with the deregulation of focal adhesions and nuclear translocation of p130Cas

Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, is effective as chemopreventive against colon cancer and it is the only nonsteoroidal antiinflammatory drug approved by the FDA for adjuvant therapy in patients with familial adenomatous polyposis. It is also being evaluated, within Phase II and III clinical trials, in combination with standard chemotherapy to treat sporadic colorectal cancer. Nevertheless, its antitumor mechanism of action is still not fully understood. In this study, we have evaluated the in vitro growth inhibitory effect of celecoxib in colon carcinoma cells and analyzed its mechanism of action. We report that the deregulation of the focal adhesion assembly protein Crk-associated substrate 130 kDa (p130Cas) by celecoxib plays a relevant role in the cytotoxic effect of this drug. Thus, celecoxib induces the proteolysis of p130Cas and the nuclear translocation of the 31 kDa generated fragment leading to apoptosis. Furthermore, overexpression of wild-type p130Cas reverts, in part, the growth inhibitory effect of celecoxib. In contrast, FAK and AKT do not appear to be involved in this activity. Our data suggest, for the first time, that the antitumor mechanism of action of celecoxib includes the induction of anoikis, an effect that is not related to COX-2 inhibition. Besides providing new insights into the antitumor effect of celecoxib, this novel mechanism of action holds potential relevance in drug development. Indeed, our results open the possibility to develop new celecoxib derivatives that induce anoikis without COX-2 inhibition so as to avoid the cardiovascular toxicity recently described for the COX-2 inhibitors.

Quinazoline α1-Blockers: Are there any News about their Efficacy in Inhibiting Prostate Tumor Growth?

α1-adrenoceptor agonists have recently been recognized as growth factors for several cell types, including both stromal smooth muscle- and epithelial cells of the prostate gland, by triggering off a cascade of intracellular signal transduction pathway that controls cell proliferation. On the contrary, quinazoline α1 -blockers (doxazosin, terazosin, prazosin) inhibit cell kinetics and induce, above all, anoikis and apoptotic death of both stromal smooth muscle- and epithelial cells, through α1 -adrenoceptor-indipendent mechanisms, thus preventing or delaying prostate tumor growth.

Oral treatment of the TRAMP mice with doxazosin suppresses prostate tumor growth and metastasis

BACKGROUND

We used the TRAMP mouse model for testing the effect of oral doxazosin treatment on the in vivo prostate tumor growth and metastasis.

METHODS

Five groups of TRAMP mice at different ages were orally fed with 1 mg/kg of doxazosin or DMSO for 45-196 days. At the end of oral treatment, tumor weight was determined, and metastasis to multiple organs examined. The levels of MUC18, Bcl-2, Bax, caspase-3, poly (ADP-ribose) polymerase (PARP), phospho (Ser473)-AKT, and Ki-67 in the mouse prostate tumors were determined.

RESULTS

Oral treatment of the TRAMP mice with doxazosin for 45-81 days did not decrease the size of preexisting prostate tumors, but it limited the metastasis to peri-aortic lymph nodes. A prolonged treatment of TRAMP mice with doxazosin (156-196 days), if administered early, decreased the prostate tumor weight and completely suppressed metastasis. The doxazosin treatment did not further decrease the expression of an already low level of Bcl-2 in all prostate tumors, but it increased the expression of Bax, and the activation of caspase-3, and the cleavage of a downstream substrate, PARP. The treatment reduced the expression of MUC18, phospho (Ser473)-AKT, and Ki-67. The treatment in the early phase appeared to promote prostate tumor growth and increased the expression of a proliferative index, Ki-67.

CONCLUSIONS

Doxazosin, if administered early, may be useful for preventing the prostate tumor formation, and also for limiting or completely suppressing the metastasis of prostate cancer in the TRAMP model. The mechanism of doxazosin is consistent with the established hypothesis.