Signal transduction targets in androgen-independent prostate cancer

Prostate cancer (PCa) first manifests as an androgen-dependent disease. Thus, androgen-deprivation therapy is a standard regimen for patients with metastatic PCa. Despite the initial success of androgen-deprivation therapy, PCa inevitably progresses from being androgen dependent (AD) to androgen independent (AI), and this marks the poor prognosis of this disease. Relapse of AIPCa becomes life threatening and accounts for the majority of mortality of PCa patients. Currently, no effective therapy is available for controlling AIPCa. Therefore, the challenge in providing a new intervention is to understand the fundamental changes that occur in AIPCa. Increasing evidence indicates that, under androgen-deprived milieu, several signal networks elicited by peptide growth factors dictate the AI phenotype of PCa. This review covers the latest studies investigating the potential involvement of autocrine growth factors in cell proliferation, survival, metastasis, and the reciprocal interaction with the androgen receptor pathway. In addition, loss of the negative feedback mechanism of the signal cascade further amplifies the effect of growth factors, and thus contributes significantly to the onset of AIPCa. The understanding of the signal target(s) in AIPCa should provide the new markers for prognosis and a new strategy for prevention and therapy.     

Treatment of androgen-independent, hormone-refractory prostate cancer with docetaxel in Japanese patients

Background Although patients with prostate cancer with metastatic lesions initially respond to androgen ablation therapy, most patients ultimately develop a hormone-refractory state. Effective treatment for men with hormone-refractory prostate cancer (HRPC) has not been established. We performed a clinical study of docetaxel in HRPC patients, and evaluated its efficacy.Methods Nine patients with HRPC were administered 55 mg/m² docetaxel, every 3 weeks, simultaneously with hormonal therapy, with a luteinizing hormone-releasing hormone analog, and daily oral dexamethasone. Change in serum prostate-specific antigen (PSA) was determined as the primary endpoint.Results The mean age of the patients was 64 years (range, 49 to 76 years). Median follow-up time was 8.5 months (range, 5.3 to 16.7 months). In eight patients whose pretreatment serum PSA was elevated, six patients (75.0%) had a PSA decline of more than 50%, and four (50.0%) had a PSA decline of more than 75%. Median time to progression for all patients was 7.9 months (range, 0.0 to 11.6 months; 95% confidence interval [CI], 0.0 to 26.3). The median overall survival was 8.5 months (range, 5.3 to 16.7 months; 95% CI, 8.1 to 13.8). Four of six patients (66.7%) with pain before treatment obtained pain relief and were able to discontinue analgesic agents. This regimen was well tolerated. Grade 3 or 4 neutropenia or leukocytopenia without fever was seen in three patients (33.3%). Only one patient required administration of granulocyte-colony stimulating factor because of neutropenia. No other grade 3 or 4 toxicity was observed.Conclusion Docetaxel was an active agent in Japanese HRPC patients, and was well tolerated in this population. To establish its efficacy and safety in Japanese HRPC patients, a large-scale study in Japan is warranted.     

Mitochondrial apoptosis: killing cancer using the enemy within

Apoptotic cell death inhibits oncogenesis at multiple stages, ranging from transformation to metastasis. Consequently, in order for cancer to develop and progress, apoptosis must be inhibited. Cell death also plays major roles in cancer treatment, serving as the main effector function of many anti-cancer therapies. In this review, we discuss the role of apoptosis in the development and treatment of cancer. Specifically, we focus upon the mitochondrial pathway of apoptosis—the most commonly deregulated form of cell death in cancer. In this process, mitochondrial outer membrane permeabilisation or MOMP represents the defining event that irrevocably commits a cell to die. We provide an overview of how this pathway is regulated by BCL-2 family proteins and describe ways in which cancer cells can block it. Finally, we discuss exciting new approaches aimed at specifically inducing mitochondrial apoptosis in cancer cells, outlining their potential pitfalls, while highlighting their considerable therapeutic promise.     

Intermittent chemotherapy in metastatic androgen-independent prostate cancer

Intermittent use of chemotherapy for androgen-independent prostate cancer (AIPC) instead of treatment until disease progression may reduce toxicity. We prospectively tested this approach in eight AIPC patients responding to calcitriol plus docetaxel who reached a serum prostate-specific antigen (PSA) <4 ng ml(-1). Chemotherapy was suspended until a rise in PSA>/=50% and 1 ng ml(-1). The median duration of treatment holiday was 20 weeks (13-43+weeks) and all patients retained sensitivity to re-treatment. Chemotherapy holiday was associated with an improvement of fatigue (P=0.05). Intermittent chemotherapy for AIPC is feasible and deserves further study.     

Defining the molecular action of HDAC inhibitors and synergism with androgen deprivation in ERG-positive prostate cancer

Gene fusions between prostate-specific, androgen responsive TMPRSS2 gene and oncogenic ETS factors, such as ERG, occur in up to 50% of all prostate cancers. We recently defined a gene signature that was characteristic to prostate cancers with ERG activation. This suggested epigenetic reprogramming, such as upregulation of histone deactylase 1 (HDAC1) gene and downregulation of its target genes. We then hypothesized that patients with ERG-positive prostate cancers may benefit from epigenetic therapy such as HDAC inhibition (HDACi), especially in combination with antiandrogens. Here, we exposed ERG-positive prostate cancer cell lines to HDAC inhibitors Trichostatin A (TSA), MS-275 and suberoylanilide hydroxamic acid (SAHA) with or without androgen deprivation. We explored the effects on cell phenotype, gene expression as well as ERG and androgen receptor (AR) signaling. When compared with 5 other prostate cell lines, ERG-positive VCaP and DuCap cells were extremely sensitive to HDACi, in particular TSA, showing synergy with concomitant androgen deprivation increasing apoptosis. Both of the HDAC inhibitors studied caused repression of the ERG-fusion gene, whereas the pan-HDAC inhibitor TSA prominently repressed the ERG-associated gene signature. Additionally, HDACi and flutamide caused retention of AR in the cytoplasm, indicating blockage of androgen signaling. Our results support the hypothesis that HDACi, especially in combination with androgen deprivation, is effective against TMPRSS2-ERG-fusion positive prostate cancer in vitro. Together with our previous in vivo observations of an "epigenetic reprogramming gene signature" in clinical ERG-positive prostate cancers, these studies provide mechanistic insights to ERG-associated tumorigenesis and suggest therapeutic paradigms to be tested in vivo.     

Phase II study of weekly docetaxel in symptomatic androgen-independent prostate cancer

Background:This study sought to dene the activity and toxicityof weekly docetaxel in patients with androgen-independentprostate cancer and cancer-related pain. Patients and methods:Patients and methods: Twenty-ve patients were treatedwith docetaxel 36 mg/m 2 i.v. administered weekly for sixconsecutive weeks followed by two weeks without treatment.This eight-week treatment cycle was repeated until progressionor unacceptable toxicity. Endpoints included palliative re-sponse (a 2-point reduction on the 6-point Present Pain Inten-sity scale without an increase in analgesic consumption or a50% decrease in analgesic use without an increase in pain),PSA response (a 50% decrease maintained at least four weeks),measurable disease response, survival, and toxicity. Results:Twelve of 25 patients (48%, 95% condence inter-val (95% CI): 28%-68%) had a palliative response. Eleven ofthe 24 patients who entered with an elevated PSA (46%, 95%CI: 25%-67%) had a PSA response. Two of ve patients withmeasurable disease had a partial response. Toxicity of therapywas modest with no treatment-related mortality. Twenty-vepercent of patients experienced a grade 3 or 4 hematologictoxicity and 36% of patients experienced a grade 3 non-hema-tologic toxicity. Conclusions:Weekly docetaxel is well tolerated in patientswith androgen-independent prostate cancer and has signi-cant activity as measured by relief of pain, reduction in PSA,and reduction in measurable disease.     

ERK inhibitor PD98059 enhances docetaxel-induced apoptosis of androgen-independent human prostate cancer cells

Anticancer drugs docetaxel and vinorelbine suppress cell growth by altering microtubule assembly and activating the proapoptotic signal pathway. Vinorelbine and docetaxel have been approved for treating several advanced cancers. However, their efficacy in the management of advanced hormone-refractory prostate cancer remains to be clarified. Microtubule damage by some anticancer drugs can activate the ERK survival pathway, which conversely compromises chemotherapeutic efficacy. We analyzed the effect of ERK inhibitors PD98059 and U0126 on vinorelbine- and docetaxel-induced cell growth suppression of androgen-independent prostate cancer cells. In androgen-independent C-81 LNCaP cells, inhibition of ERK by PD98059, but not U0126, plus docetaxel resulted in enhanced growth suppression by an additional 20% compared to the sum of each agent alone (p < 0.02). The combination treatment of docetaxel plus PD98059 also increased cellular apoptosis, which was in part due to the inactivation of Bcl-2 by increasing phosphorylated Bcl-2 by more than 6-fold and Bax expression by 3-fold over each agent alone. At these dosages, docetaxel alone caused only marginal phosphorylation of Bcl-2 (10%). Docetaxel plus U0126 had only 20% added effect on Bcl-2 phosphorylation compared to docetaxel alone. Nevertheless, both U0126 and PD98059 exhibited an enhanced effect on docetaxel-induced growth suppression in PC-3 cells. No enhanced effect was observed for vinorelbine plus PD98059 or U0126. Thus, the combination therapy of docetaxel plus PD98059 may represent a new anticancer strategy, requiring lower drug dosages compared to docetaxel monotherapy. This may lower the cytotoxicity and enhance tumor suppression in vivo. This finding of a combination effect could be of potential clinical importance in treating hormone-refractory prostate cancer.     

The role of Src in prostate cancer.

The Src family kinases (SFKs) are the largest family of nonreceptor protein tyrosine kinases and are responsible for signal transduction during many cellular activities, including differentiation, adhesion, and migration. Aberrant Src/SFK activity has been widely implicated in cancer development. Several lines of evidence indicate a role for SFKs in the development of prostate cancer, e.g. SFK overexpression in prostate cancer cell lines and tissues and reduced cancer cell proliferation, invasion, and migration following Src inhibition. In particular, Src may be involved in androgen-independent growth during advanced stages of disease. Src signaling is also a key pathway during normal and dysregulated bone functioning, and bone metastases are responsible for substantial morbidity in advanced prostate cancer. Src/SFK inhibition therefore represents a potentially useful therapeutic strategy for patients with various stages of prostate cancer. To date, four Src inhibitors have reached clinical trials. Of these, the broadest range of in vitro prostate cancer data are available for dasatinib, which inhibits several SFKs as well as other tyrosine kinases. Src inhibitors may be specifically evaluated in prostate cancer clinical trials in the near future.     

雄激素非依赖性前列腺癌DU145细胞中TRPM8和TRPA1的表达及活性研究

目的 探讨TRPM8和TRPA1在雄激素非依赖性前列腺癌DU145细胞中是否表达,以及薄荷醇是否通过作用于TRPM8通道来影响DU145细胞的生物学行为.方法 采用Nested RT-PCR实验、Western Blot实验和免疫组织化学法从不同水平(mRNA水平、蛋白水平)以及直观观察层面检测TRPM8和TRPA1在DU145细胞中的表达;采用Ca2+成像实验观察薄荷醇能否诱导DU145细胞内Ca2+浓度的变化;采用MTT法检测梯度浓度的薄荷醇对DU145细胞增殖能力的影响.结果 Nested RT-PCR实验、Western Blot实验和免疫组织化学法结果证明,在DU145细胞中检测到TRPM8表达,而未检测到TRPA1表达.Ca2+成像实验结果显示,在37℃环境下细胞荧光非常弱,加入薄荷醇后细胞内Ca2+荧光强度急剧升高.MTT法检测结果显示,与未经薄荷醇处理的对照组相比不同浓度(25、50、75、100μmol/L)薄荷醇处理组的细胞增殖率均下降(P﹤0.05).经BCTC预处理20 min,薄荷醇所致的细胞增殖抑制被部分恢复(P﹤0.05).结论 雄激素非依赖性前列腺癌DU145细胞中有大量的具有生物活性的TRPM8通道蛋白表达,而可同被薄荷醇激活的TRPA1却未被检测到表达.薄荷醇可激活DU145细胞中的TRPM8通道诱导Ca2+荧光强度急剧升高,抑制DU145细胞的增殖.     

Chemotherapy in advanced androgen-independent prostate cancer 1990-1999: a decade of progress?

Background and purpose:A great number of clinical researchstudies have been reported in the field of chemotherapy for advancedandrogen-independent prostate cancer during the last ten years. The aims ofthe present review were to assess their impact on management of the diseaseand on survival of patients. Methods:The review of full published reports was facilited by theuse of a MEDLINE computer search. Results:Clinical research studies have focused on definingguidelines for eligibility criteria and accurate endpoints for patients to beenrolled onto clinical trials and developing new agents or combinationof drugs including estramustine phosphate. Any combination of currentchemotherapy has no impact on overall survival of patients. Among drugs indevelopment, only the promising activity observed with docetaxel deservesrandomized trials to assess its impact on survival. The major innovativeadvance of the 90s is the demonstration of the impact of chemotherapy(mitoxantrone + prednisone) on quality of life as compared to prednisonealone. A greater and longer-lasting improvement in quality of life along witha concomitant decrease in costs was observed. Conclusions:At the present time, chemotherapy should beconsidered as a palliative treatment in patients with symptomaticandrogen-independent disease. The enrollment of patients into clinical trialsdealing with quality of life as primary endpoint is strongly solicited. Astandard methodology should be used in phase II trials with a primary goal ofselection of agents which should progress to randomized trials using survivalas an endpoint. Hopefully new specific strategies targeted to reverse themolecular changes that underlie prostate tumorigenesis should rapidly impactthe multimodality management of AIPC in the third millenium.     

Suppression of ErbB-2 in androgen-independent human prostate cancer cells enhances cytotoxic effect by gemcitabine in an androgen-reduced environment

We examined the efficacy of combination treatments utilizing cytotoxic drugs plus inhibitors to members of the ErbB–ERK signal pathway in human prostate cancer (PCa) LNCaP C-81 cells. Under an androgen-reduced condition, 50 nM gemcitabine caused about 40% growth suppression on C-81 cells. Simultaneous treatment of gemcitabine plus 10 μM AG825 produced 60% suppression (p < 0.03); while, 85% growth inhibition (p < 0.02) was seen if AG825 was added to gemcitabine-treated cells after a 24 h-interval. Our data thus showed that in androgen-reduced conditions, inhibition of ErbB-2 increases the cytotoxic efficacy of gemcitabine in PCa cells. This finding has significant implications in the choice of drugs for combination therapy as well as the order of administration for treating cancer patients.     

An open-label phase II study of low-dose thalidomide in androgen-independent prostate cancer

The antiangiogenic effects of thalidomide have been assessed in clinical trials in patients with various solid and haematological malignancies. Thalidomide blocks the activity of angiogenic agents including bFGF, VEGF and IL-6. We undertook an open-label study using thalidomide 100 mg once daily for up to 6 months in 20 men with androgen-independent prostate cancer. The mean time of study was 109 days (median 107, range 4-184 days). Patients underwent regular measurement of prostate-specific antigen (PSA), urea and electrolytes, serum bFGF and VEGF. Three men (15%) showed a decline in serum PSA of at least 50%, sustained throughout treatment. Of 16 men treated for at least 2 months, six (37.5%) showed a fall in absolute PSA by a median of 48%. Increasing levels of serum bFGF and VEGF were associated with progressive disease; five of six men who demonstrated a fall in PSA also showed a decline in bFGF and VEGF levels, and three of four men with a rising PSA showed an increase in both growth factors. Adverse effects included constipation, morning drowsiness, dizziness and rash, and resulted in withdrawal from the study by three men. Evidence of peripheral sensory neuropathy was found in nine of 13 men before treatment. In the seven men who completed six months on thalidomide, subclinical evidence of peripheral neuropathy was found in four before treatment, but in all seven at repeat testing. The findings indicate that thalidomide may be an option for patients who have failed other forms of therapy, provided close follow-up is maintained for development of peripheral neuropathy.     

Multiple cycles of intermittent chemotherapy in metastatic androgen-independent prostate cancer

Recently, completed phase III studies demonstrated a survival benefit for a fixed number of cycles of docetaxel-containing chemotherapy treatment of androgen-independent prostate cancer (AIPC). Management of patients who respond well to initial chemotherapy for AIPC remains ill-defined. We previously reported that in a select group of such patients, retreatment with the same regimen was feasible and was associated with quality of life gains. Here, we report that multiple cycles of such intermittent chemotherapy are feasible. We prospectively tested intermittent chemotherapy in eight AIPC patients responding to calcitriol plus docetaxel who reached a serum prostate-specific antigen (PSA) <4 ng ml(-1) (22% of the 37 patients who were initially treated with this regimen). Chemotherapy was suspended until a rise in PSA > or =50% and 1 ng ml(-1). The median duration of the first treatment holiday was 20 weeks (13-74 weeks) and all patients retained sensitivity to retreatment. Four patients were eligible for a second chemotherapy holiday, and the median duration was 21 weeks (17-28 weeks). Two patients elected to take a third chemotherapy holiday, which lasted 10 and 28 weeks. The median time to treatment failure was 26.5 months (95% CI 23.6-29.4 months), and the median survival is 41 months (95% CI 33.7-48.3 months). Multiple cycles of intermittent chemotherapy interrupted by clinically meaningful treatment holidays are feasible in a subset of AIPC patients treated with this docetaxel-containing regimen. Intermittent chemotherapy for AIPC is feasible and deserves further study.     

Increased resistance to proteasome inhibitors in multiple myeloma mediated by cIAP2 - implications for a combinatorial treatment

Despite the introduction of new treatment options for multiple myeloma (MM), a majority of patients relapse due to the development of resistance. Unraveling new mechanisms underlying resistance could lead to identification of possible targets for combinatorial treatment. Using TRAF3 deleted/mutated MM cell lines, we evaluated the role of the cellular inhibitor of apoptosis 2 (cIAP2) in drug resistance and uncovered the plausible mechanisms underlying this resistance and possible strategies to overcome this by combinatorial treatment. In MM, cIAP2 is part of the gene signature of aberrant NF-κB signaling and is heterogeneously expressed amongst MM patients. In cIAP2 overexpressing cells a decreased sensitivity to the proteasome inhibitors bortezomib, MG132 and carfilzomib was observed. Gene expression analysis revealed that 440 genes were differentially expressed due to cIAP2 overexpression. Importantly, the data imply that cIAPs are rational targets for combinatorial treatment in the population of MM with deleted/mutated TRAF3. Indeed, we found that treatment with the IAP inhibitor AT-406 enhanced the anti-MM effect of bortezomib in the investigated cell lines. Taken together, our results show that cIAP2 is an important factor mediating bortezomib resistance in MM cells harboring TRAF3 deletion/mutation and therefore should be considered as a target for combinatorial treatment.     

Activation of SAPK/JNK by camptothecin sensitizes androgen-independent prostate cancer cells to Fas-induced apoptosis

We have previously shown that the androgen-independent prostate cancer cells DU145, despite expressing Fas and FasL, were resistant to anti-Fas-induced apoptosis, and that this resistance could be overcome by pretreating the cells with sublethal doses of camptothecin. Here, we provide evidence that SAPK/JNK activity is required for camptothecin sensitization to anti-Fas-induced apoptosis. Camptothecin, but not Fas ligation, was shown to activate SAPK/JNK in a time-dependent manner, and to induce c-Jun expression. The effects were more prominent in cells treated with both camptothecin and anti-Fas. The expression levels of MKP-1, a phosphatase which regulates SAPK/JNK and which has been implicated in prostate cancer resistance to apoptosis, remained unchanged. Inhibition of caspases had no effect on the SAPK/JNK activation, suggesting that this activation is an upstream event in the Fas-signalling pathway, and is independent of caspase activity. Antisense oligonucleotides targeted to JNK1 and JNK2 reversed the effect of camptothecin. These results suggest that stress kinase activation can significantly influence the fate of androgen-independent prostate cancer cells following Fas receptor ligation.     

蛋白酶体抑制剂用于肺癌骨转移治疗的研究

转移是癌症致死的主要原因,骨转移是排第三的好发部位.肺癌是排第四的嗜骨转移肿瘤.目前对于肺癌骨转移的治疗仪限于抑制骨破坏,不能促进新骨形成.在应用万珂治疗多发骨髓瘤的过程中,发现其可以治疗骨髓瘤骨病,既能抑制骨破坏,又能促进新骨的形成.能否将其用于肺癌乃至实体瘤骨转移的预防或治疗呢?本文就肿瘤骨转移现状及蛋白酶体抑制剂在多发性骨髓瘤骨病中作用做一综述,为将来蛋白酶体抑制剂用于实体瘤骨转移预防和治疗提供参考.     

PD-1/PD-L1抑制剂在前列腺癌免疫治疗中的研究进展

前列腺癌（prostate cancer,PCa）发病率呈逐年上升趋势,前列腺癌免疫治疗已成为继外科、放疗、化疗之后的第四种治疗方法。作为当今肿瘤免疫治疗领域最具有研究前景的免疫检查点抑制剂中的程序性死亡受体-1（programmed cell death-1,PD-1）/程序性死亡配体-1（programmed cell death-ligand1,PD-L1）抑制剂,通过阻断PD-1与其配体PD-L1结合,从而终止T细胞的负性调控信号,使T细胞的活性恢复,进而逆转肿瘤免疫逃逸机制,恢复自身免疫应答,最后起到抑制和杀伤肿瘤的作用。本文就目前应用于前列腺癌临床试验的PD-1/PD-L1抑制剂的现况和临床疗效研究进展进行综述。