Phosphorylated Akt up-regulates angiotensin II type-1 receptor expression in castration resistant prostate cancer

Selective killing of castration-resistant prostate cancer cells by formycin A via the ATF4-CHOP axis

Prostate cancer is initially androgen-dependent but often relapses to an androgen-independent state called castration-resistant prostate cancer (CRPC). Currently approved therapies have limited efficacy against CRPC, highlighting the need for novel therapeutic strategies. To address this need, we conducted a drug screen in our previously established aggressive CRPC cell model. We found that formycin A induced cell death in CRPC model cells but not in parental prostate cancer cells. In addition, formycin A upregulated death receptor 5 through the induction of endoplasmic reticulum stress, activating the "extrinsic" apoptosis pathway in CRPC model cells. Moreover, formycin A showed in vivo antitumor efficacy against CRPC xenografts in castrated nude mice. Thus, our findings highlight the potential of formycin A as a CRPC therapeutic.

Influence of response to prior docetaxel on sensitivity to cabazitaxel in prostate cancer patients with PTEN alterations

The purpose of this study was to investigate factors predicting the sensitivity to cabazitaxel therapy in metastatic castration‐resistant prostate cancer (mCRPC) patients with phosphatase and tensin homolog deleted from chromosome 10 (PTEN) alterations. This single‐institution, retrospective study included 12 mCRPC patients with PTEN alterations who had received cabazitaxel therapy. Five patients (41%) responded to cabazitaxel therapy with a prostate‐specific antigen (PSA) level decline of ≥30% from baseline, and all of them had responded to prior docetaxel therapy with a PSA decline of ≥30%. None of the patients with a poor response to prior docetaxel therapy responded well to cabazitaxel therapy. Of the seven patients who did not respond to cabazitaxel and whose PSA declined from baseline was <30%, five (71%) were also refractory to prior docetaxel therapy. The PSA responses to docetaxel and cabazitaxel were significantly correlated (p = 0.027). Kaplan–Meier analysis revealed that progression‐free survival (PFS) for cabazitaxel was significantly shorter for prior docetaxel nonresponders (3.3 versus 9.1 months, p = 0.028). Multivariate analysis revealed that a poor response to prior docetaxel (PSA decline < 30%) (hazard ratio [HR] = 6.382, 95% confidence interval [CI] 1.172–34.750, p = 0.032) and baseline PSA of ≥20 ng/ml (HR = 33.584, 95% CI 2.332–483.671, p = 0.010) were independent prognostic factors for PFS with cabazitaxel therapy. These results demonstrate cross‐resistance between docetaxel and cabazitaxel. The response to prior docetaxel therapy can influence the sensitivity to cabazitaxel therapy in mCRPC patients with PTEN alterations.

Integrative Exome Sequencing Analysis in Castration-Resistant Prostate Cancer in Chinese Population

BACKGROUND

Castration-resistant Prostate Cancer (CRPC) is a fatal disease with rapid growth. The malignancy usually presents with metastasis and poor prognosis, and causes 100% mortality. Therefore, the treatment of CRPC is extremely challenging, and its pathogenesis need to be elucidated urgently.

OBJECTIVE

The high throughput sequencing technology was used to sequence the whole exome associated with CRPC, to explore the molecular mechanism of CRPC, and to find the potential therapeutic targets.

METHODS

We performed whole-exome sequencing of FFPE tissue from 11 Chinese adult male patients. Genomic DNA was fragmented and enriched for whole-exome sequencing using the QiAamp DNA FFPE Tissue KIT, sequenced on an Illumina HiSeq2000 platform, and the relevant genes were analyzed using biological information. Finally, immunohistochemistry method was used to detect the phosphorylation level of LATS1 in CRPC tissues of MST1 mutant and non-mutant patients.

RESULTS

We have screened 85 significant mutant genes with relatively high mutation rates of TP53, AR, KMT2, DMAPK1, PIK3R1, SH2B3, WHSC1, KMT2D, MST1 and MAPK1. We first found that MST1 has multiple mutations in CRPC patients, and the MST1 plays an important role in the Hippo pathway. Immunohistochemistry results showed that the phosphorylation level of LATS1 in the mutant patients was significantly lower than that in the non-mutant patients.

CONCLUSION

We speculate that MST1 would be a new potential target for the treatment of CRPC by regulating Hippo signaling pathway. The results provided an important clue to the molecular mechanism of CRPC.

TUBB3 Reverses Resistance to Docetaxel and Cabazitaxel in Prostate Cancer

Recent studies have reported that TUBB3 overexpression is involved in docetaxel (DTX) resistance in prostate cancer (PCa). The aim of this study was to clarify the role of TUBB3 in DTX and cabazitaxel (CBZ) resistance, and cross-resistance between DTX and CBZ in PCa. We analyzed the effect of TUBB3 knockdown on DTX and CBZ resistance and examined the interaction between TUBB3 and PTEN. We also investigated the role of phosphoinositide 3-kinases (PI3K) inhibitor (LY294002) in DTX and CBZ resistance. TUBB3 expression was upregulated in DTX-resistant and CBZ-resistant cells. TUBB3 knockdown re-sensitized DTX-resistant cells to DTX and CBZ-resistant cells to CBZ. Additionally, TUBB3 knockdown re-sensitized DTX-resistant cell lines to CBZ, indicating that TUBB3 mediates cross-resistance between DTX and CBZ. Knockdown of TUBB3 enhanced PTEN expression, and PTEN knockout enhanced TUBB3 expression. LY294002 suppressed TUBB3 expression in DTX-resistant and CBZ-resistant cell lines. LY294002 re-sensitized DTX-resistant cell lines to DTX and CBZ-resistant cell lines to CBZ. These results suggest that TUBB3 is involved in DTX resistance and CBZ resistance. A combination of LY294002/DTX and that of LY294002/CBZ could be potential strategies for PCa treatment.

Reactive oxygen species induction by cabazitaxel through inhibiting Sestrin-3 in castration resistant prostate cancer

Reactive oxygen species (ROS) production induced by taxanes in cancer cells may influence the taxane-induced cell death or the drug resistance. We investigated the correlation between the cytotoxic effect of taxanes and ROS production in human castration-resistant prostate cancer (CRPC) cell lines. Three human prostate cancer cell lines were treated with increasing concentrations of docetaxel or cabazitaxel in vitro. Cabazitaxel showed significantly higher cytotoxic efficacy than docetaxel in human CRPC cells, accompanied by elevated ROS production detected by FACS analysis. To investigate whether cabazitaxel-mediated cell death was caused by the ROS generation induced by cabazitaxel, we treated CRPC cells in the presence of antioxidant NAC. NAC reduced the cytotoxic effect induced by cabazitaxel. We found that ROS elimination by Sestrin-3 (SESN3) was significantly inhibited by cabazitaxel, but not by docetaxel. These results indicate higher sensitivity of human CRPC to cabazitaxel compared to docetaxel involves ROS production through inhibiting the expression of antioxidant enzyme SESN3.

Limited in vitro efficacy of CYP17A1 inhibition on human castration resistant prostate cancer

Although accumulating evidence indicates high expression of CYP17A1(P45017A1) allows castration resistant prostate cancer (CRPC) to maintain high intratumoral androgen levels, the potential P45017A1 activity has not been characterized yet. The aim of this study was to examine the potential CYP17A1 activity including 17α-hydroxylase and 17,20-lyase activities in human CRPC and the effect of a CYP17A inhibitor. We used three human CRPC cell lines: C4-2 and C4-2AT6 which was established from C4-2 under androgen ablation conditions for 6months, and PC3. To ascertain the potential CYP17A1 activity, we cultured with the steroid precursors: (13)C-[2,3,4]-progesterone (13C-Prog), and analyzed the sequential biosynthesis (13)C-[2,3,4]-17-hydroxyprogesterone (13C-17OHP) and (13)C-[2,3,4]-androstenedione(13C-Adione) by liquid chromatography/mass spectrometry (LC/MS/MS).The C4-2AT6 cells showed significantly higher CYP17A1 expression than C4-2 cells (p<0.001). LC/MS/MS analysis enabled us to detect the 13C-17-OHP and 13C-A-dione in these cell lines. The concentration ratio of 13C-Adione/13C-17OHP (Adione-17OHP ratio), which is thought to reflect the differences between 17-hydroxylase and 17,20-lyase activities, was then determined. The Adione-17OHP ratio in C4-2AT6 cells was significantly higher than that of C4-2 cells (p<0.001). Abiraterone were able to inhibit the CYP17A activities, although abiraterone did not have anti-proliferative effects on C4-2 and C4-2AT6 cells at clinically achievable concentrations of <1000nM in vitro. The present study clearly demonstrates CRPC have the dual activities of CYP17A1 mediated by 17-hydroxylase activity and 17,20-lyase activity. Abiraterone doesn't have an in vitro anti-proliferative efficacy in CRPC cells, suggesting limited efficacy in vitro.

Is DHT Production by 5α-Reductase Friend or Foe in Prostate Cancer?

The first advance in the history of studies on prostate cancer (PCa) and androgens was the development of treatment with castration and administration of estrogen by Charles B. Huggins, who won the Nobel Prize in Physiology and Medicine. Since then, and for 70 years, androgen deprivation therapy has been the standard therapy for advanced PCa and the center of studies on PCa. However, recent advances have shed light on the relationship between androgens and the development or the progression of PCa. The use of 5AR inhibitors to prevent progression of PCa continues to be widely discussed. Discussion has been fueled by the findings of two large randomized, placebo-controlled trials: the Prostate Cancer Prevention Trial with finasteride and the Reduction by Dutasteride of Prostate Cancer Events trial. Does the development of PCa or progression to castration-resistant PCa depend on dihydrotestosterone (DHT)? Here, we summarize and discuss recent topics of local androgen production of DHT in PCa.

A novel PI3K inhibitor displays potent preclinical activity against an androgen-independent and PTEN-deficient prostate cancer model established from the cell line PC3

Recent studies demonstrated that targeting the phosphatidylinositide 3-kinase (PI3K)/AKT signaling pathway is a major strategy for the treatment of androgen-independent prostate cancer. In the present study, we developed an analog BENC-511 from a recently reported PI3K inhibitor S14161 by structural optimization. Using PC3 and DU145 as the model cell lines, we found PTEN-deficient PC3 cells were more sensitive than PTEN-expressing DU145 ones in terms of cell proliferation, apoptosis, and caspase-3 activation. These findings were consistent with the inhibition on PI3K/AKT signals. BENC-511 preferably suppressed AKT activation in PC3 over DU145 cells. Notably, PTEN restoration attenuated BENC-511 induced apoptosis. Moreover, BENC-511 displayed great therapeutic efficacy in a PC3-derived prostate cancer model in nude mice. With an oral dosage of 50mg/kg, BENC-511 decreased tumor growth more than 50% in 27 days, which was accompanied with PARP cleavage, but did not show overt toxicity. This study lays a solid rationale for the development of BENC-511 as a drug for the treatment of PTEN-deficient and androgen-independent prostate cancers.

Expression and clinical significance of angiotensin II type 1 receptor in human hepatocellular carcinoma

This study aimed to investigate the expression of angiotensin II type 1 receptor (AT-1R) mRNA and the AT-1R protein in human primary hepatocellular carcinoma (PHC), and to attempt to elucidate their association with pathological and clinical characteristics. Fresh tumor and normal liver tissues were obtained from 44 patients with PHC following hepatectomies. AT-1R mRNA levels were quantitatively analyzed by quantitative polymerase chain reaction (qPCR) while the protein levels were assessed by immunohistochemistry. The expression levels of AT-1R were observed in hepatocellular carcinoma tissues and normal liver tissues. The level of AT-1R protein expression in normal liver tissues was higher compared with that in PHC tissues (P=0.0033). The AT-1R mRNA levels were higher in patients with negative hepatitis B virus surface antigen (HBsAg), normal α-fetoprotein (AFP) levels and high tumor differentiation, compared with those in patients with positive HBsAg (P=0.0005), upregulated AFP levels (P=0.0008) and poor tumor differentiation (P=0.0290). No significant correlation was identified between the expression levels of AT-1R mRNA and general characteristics such as gender, age, cirrhotic nodules, tumor size, tumor encapsulation, tumor number, carcinoma embolus, tumor metastasis or tumor recurrence. Downregulated levels of AT-1R mRNA and AT-1R protein may indicate a poor prognosis for patients with PHC.

Human castration resistant prostate cancer rather prefer to decreased 5α-reductase activity

Physiologically relevant steroid 5α-reductase (SRD5A) activity that is essential for dihydrotestosterone (DHT) biosynthesis in human castration-resistant prostate cancer (CRPC) has not been fully characterized yet. In this study to ascertain the potential SRD5A activity, we cultured two human CRPC cell lines, C4-2 and C4-2AT6, with the steroid precursor: ¹³C-[2,3,4]-androstenedione (13C-Adione), and analyzed the sequential biosynthesis of ¹³C-[2,3,4]-testosterone (13C-T) and ¹³C-[2,3,4]-DHT (13C-DHT) by liquid chromatography/mass spectrometry (LC/MS/MS). The 13C-DHT/13C-T concentration ratio detected by LC/MS/MS in C4-2AT6 cells appeared to reflect the SRD5A activity. The ratio in C4-2AT6 was significantly lower than that in C4-2. An increased concentration of DHT did not have a positive effect on cell proliferation, rather it exhibited inhibitory effects. 5α-reductase inhibitors did not have any inhibitory effect at clinically achievable concentrations. These results indicate that CRPC cells may have an unknown regulation system to protect themselves from an androgenic suppressive effect mediated by SRD5A activity.

ETS1 transcriptional activity is increased in advanced prostate cancer and promotes the castrate-resistant phenotype

Advanced disease accounts for the majority of prostate cancer-related deaths and androgen deprivation therapy (ADT) is the standard of care for these patients. Many patients undergoing ADT become resistant to its effects and progress to castrate-resistant prostate cancer (CRPC). Current therapies for CRPC patients are inadequate, with progression-free survival rates as low as 2 months. The molecular events that promote CRPC are poorly understood. ETS (v-ets erythroblastosis virus E26 oncogene) transcription factors are regulators of carcinogenesis. Protein levels of the archetypical ETS factor, ETS1, are increased in clinical and latent prostate cancer relative to benign prostatic hyperplasia and normal prostate to promote multiple cancer-associated processes, such as energy metabolism, matrix degradation, survival, angiogenesis, migration and invasion. Our studies have found that ETS1 expression is highest in high-grade prostate cancer (Gleason 7 and above). Increased ETS1 expression and transcriptional activity promotes an aggressive and castrate-resistant phenotype in immortalized prostate cancer cells. Elevated AKT (v-akt murine thymoma viral oncogene homolog) activity was demonstrated to increase ETS1 protein levels specifically in castrate-resistant cells and exogenous ETS1 expression was sufficient to rescue invasive potential decreased by inhibition of AKT activity. Significantly, targeted androgen receptor activity altered ETS1 expression, which in turn altered the castrate-resistant phenotype. These data suggest a role for oncogenic ETS1 transcriptional activity in promoting aggressive prostate cancer and the castrate-resistant phenotype.

Regulation of monocyte chemoattractant protein-1 through angiotensin II type 1 receptor in prostate cancer

Monocyte chemoattractant protein-1 (MCP-1/CCL2) is reported to contribute to tumor progression and is regulated by the renin-angiotensin system in hypertensive disease. In this study, we investigated the clinical outcome of MCP-1 expression in patients with prostate cancer (CaP) and the regulation of MCP-1 through angiotensin II (AngII) type 1 receptor (AT1R) in CaP. Specimens were obtained from 138 CaP patients and analyzed by immunostaining for both MCP-1 and macrophages. We investigated the regulation of MCP-1 expression through AT1R both in vivo and in vitro using three human prostate cancer cell lines: LNCaP, C4-2, and C4-2AT6. Specimens with a high Gleason score (≥7) and a high pathological classification (≤pT3), and those with castration-resistant prostate cancer showed significantly higher MCP-1 expression and higher macrophage infiltration than low malignant potential CaP. High MCP-1 expression in CaP correlated significantly with high prostate-specific antigen (PSA) recurrence rates. AngII induced significantly higher MCP-1 levels in C4-2AT6 than in LNCaP, whereas AT1R blockade (ARB) inhibited MCP-1 production via the inhibition of the PI3K/Akt pathway in C4-2AT6. ARB also significantly suppressed MCP-1 expression in C4-2AT6 tumors. Our study is the first to demonstrate that both high MCP-1 expression and high macrophage infiltration in CaP specimens correlate with a high PSA recurrence rate and that ARB inhibits MCP-1 expression through the PI3K/Akt pathway and blocks macrophage infiltration in castration-resistant prostate cancer.