Docetaxel, estramustine, and short-term androgen withdrawal for patients with biochemical failure after definitive local therapy for prostate cancer.

Over the past 10 years, men with prostate cancer have received earlier diagnoses and are undergoing prostatectomy and/or radiation therapy with curative intent; however, many men have increasing prostate-specific antigen (PSA) levels without evidence of local progression or metastatic disease during the first 2 years after definitive local therapy. Optimal treatment of men with PSA-only recurrent prostate cancer has not been established. This ongoing phase II trial is evaluating docetaxel (70 mg/m(2) administered intravenously over 1 hour on day 2 every 21 days for four cycles) and estramustine (10 mg/kg/d orally on days 1 to 5 every 21 days for four cycles) followed by bicalutamide and goserelin acetate in men with increasing PSA levels after prostatectomy and/or radiation therapy. Patients received pretreatment with dexamethasone, and after the third patient enrolled, patients received warfarin for prophylaxis against thrombosis. Colony-stimulating factor support was allowed. In preliminary results, 11 of 15 patients completed protocol chemotherapy; 12 of 15 patients achieved complete response (ie, normalization of PSA) after four cycles of chemotherapy. In addition, testosterone levels were reduced to the castrate range in all patients after chemotherapy. The regimen was generally well tolerated, and toxicities were mostly hematologic, with grade (3/4) neutropenia reported in approximately half of patients. Preliminary results of this phase II trial are encouraging, and enrollment is ongoing.

Prostate cancer in the older man.

Most men diagnosed with prostate cancer are more than 65 years of age. Therefore, a discussion of the issues surrounding the diagnosis, prevention, and treatment of prostate cancer in older men is, in many ways, a review of prostate cancer in general. Nonetheless, older patients with prostate cancer are often faced with a different set of problems than younger patients. For instance, if preventive strategies prove useful, they will have important implications for older men. Even a significant delay in diagnosis could greatly benefit the elderly population. Prostate-specific antigen (PSA) screening is controversial for men of any age but, for older men, screening may impart a risk to quality of life that may outweigh the potential advantages of diagnosis and treatment. Results of a large follow-up study of patients treated with radical prostatectomy suggest that even men with rising PSA values after surgery can have a relatively benign and protracted course. The survival rates noted in this study, however, were only for a select population of surgical patients, and, in fact, higher prostate cancer death rates have been observed for patients adopting the watchful waiting approach. Older men who request some form of primary therapy are increasingly being treated with brachytherapy, despite the lack of randomized trials demonstrating efficacy compared to external-beam radiation therapy, surgery, or watchful waiting. Contrary to an often-held view, older prostate cancer patients may have more morbidity from long-term testosterone suppression than younger patients. On the other hand, chemotherapy seems to be as well tolerated overall in older patients as in younger patients.

Prostatic intraepithelial neoplasia in mice expressing an androgen receptor transgene in prostate epithelium.

Prostate cancer (PCa) is an androgen dependent disease that can be treated by androgen ablation therapy, and clinical trials are under way to prevent PCa through the reduction of androgen receptor (AR) activity. However, there are no animal models of AR-mediated prostatic neoplasia, and it remains unclear whether the AR is a positive or negative regulator of cell growth in normal prostate secretory epithelium. To assess the direct effects of the AR in prostate epithelium, a murine AR transgene regulated by the rat probasin promoter (Pb) was used to generate transgenic mice expressing increased levels of AR protein in prostate secretory epithelium. The prostates in younger (<1 year) Pb-mAR transgenic mice were histologically normal, but Ki-67 immunostaining revealed marked increases in epithelial proliferation in ventral prostate and dorsolateral prostate. Older (>1 year) transgenic mice developed focal areas of intraepithelial neoplasia strongly resembling human high-grade prostatic intraepithelial neoplasia (PIN), a precursor to PCa. These results demonstrate that the AR is a positive regulator of cell growth in normal prostate epithelium and provide a model system of AR-stimulated PIN that can be used for assessing preventative hormonal therapies and for identifying secondary transforming events relevant to human PCa.

Loss of IFN-gamma production by invariant NK T cells in advanced cancer.

Invariant NK T cells express certain NK cell receptors and an invariant TCRalpha chain specific for the MHC class I-like CD1d protein. These invariant NK T cells can regulate diverse immune responses in mice, including antitumor responses, through mechanisms including rapid production of IL-4 and IFN-gamma, but their physiological functions remain uncertain. Invariant NK T cells were markedly decreased in peripheral blood from advanced prostate cancer patients, and their ex vivo expansion with a CD1d-presented lipid Ag (alpha-galactosylceramide) was diminished compared with healthy donors. Invariant NK T cells from healthy donors produced high levels of both IFN-gamma and IL-4. In contrast, whereas invariant NK T cells from prostate cancer patients also produced IL-4, they had diminished IFN-gamma production and a striking decrease in their IFN-gamma:IL-4 ratio. The IFN-gamma deficit was specific to the invariant NK T cells, as bulk T cells from prostate cancer patients produced normal levels of IFN-gamma and IL-4. These findings support an immunoregulatory function for invariant NK T cells in humans mediated by differential production of Th1 vs Th2 cytokines. They further indicate that antitumor responses may be suppressed by the marked Th2 bias of invariant NK T cells in advanced cancer patients.

Is the flare phenomenon clinically significant?

OBJECTIVES: The existing luteinizing hormone-releasing hormone (LHRH) analogs have been the preferred method of inducing androgen deprivation for prostate cancer for over a decade. These agents are well known to cause a surge in serum testosterone levels during the first week of therapy. However, there are wide discrepancies in reports of the frequency and severity of acute clinical progression or clinical flare that might result from the testosterone surge. Also, there is not a clear consensus as to whether antiandrogens should be routinely given to all patients during the first month of LHRH therapy to prevent flare responses. METHODS: Clinical trials involving LHRH analog therapy for prostate cancer were reviewed, and the frequency of clinical flare responses noted. Particular attention was given to the kinds of clinical problems associated with the flare response. The use of LHRH analog therapy in treatment of patients with prostate cancer for indications other than overt metastatic disease is discussed, because this is becoming a much more common use of these agents. This article analyzes 2 placebo-controlled, double-blind trials testing the effectiveness of existing antiandrogens in ameliorating flare responses. RESULTS: The use of LHRH analogs for patients with stage D2 disease can be associated with clinical flare in approximately 10% of D2 patients. In addition to bone pain, cord compression, and bladder outlet obstruction, another potentially severe side effect is cardiovascular risk arising presumably from hypercoagulability associated with a rapid increase in tumor burden. In clinical series involving D2 patients, the frequency of clinical flare greatly varies, probably because of the level of scrutiny of the investigator and/or the prostate-cancer tumor burden present at the initiation of therapy. Concomitant antiandrogen therapy reduces, but does not totally eliminate, the flare responses in patients at high risk for flare. Treating prostate cancer in the D0 stage or in the neoadjuvant setting will result in biochemical evidence of testosterone surge, but these patients are at very little risk for clinical flare responses. CONCLUSIONS: There is a wide variation in the reported frequency of clinical flare responses from LHRH analogs during the initial treatment of patients with stage D2 disease. The risk-to-benefit ratio, especially in patients with symptomatic bone metastasis, would dictate routine use of antiandrogen therapy for the first month of LHRH analog treatment. For patients at risk for cord compression, other means of ablating testosterone might be considered, such as ketoconazole, orchiectomy, or LHRH antagonists. Clinical flare responses, as opposed to biochemical flare responses, are very rare during LHRH analog therapy for stage D0 disease and/or in the setting of neoadjuvant hormonal therapy.

Target-directed enediynes: designed estramycins.

The goal of selective targeting of enediyne cytotoxins has been investigated using estrogenic delivery vehicles. A series of estrogen-enediyne conjugates were assembled, and affinity for human estrogen receptor [hERalpha] was determined. The most promising candidate induced receptor degradation following Bergman cycloaromatization and caused inhibition of estrogen-induced transcription in T47-D human breast cancer cells.

A multi-institutional phase ii study of SU101, a platelet-derived growth factor receptor inhibitor, for patients with hormone-refractory prostate cancer.

In a multi-institutional Phase II trial, we evaluated the efficacy of a platelet-derived growth factor receptor (PDGF-r) inhibitor, SU101, in patients with hormonerefractory prostate cancer. The patients received a 4-day i.v. loading dose of SU101 at 400 mg/m(2) for 4 consecutive days, followed by 10 weekly infusions at 400 mg/m(2). The primary study end points were a decline in prostate-specific antigen (PSA) and a decrease in measurable tumor. Secondary end points were time to progression and an effect on pain as measured by the Brief Pain Survey. Expression of PDGF-r was examined in both metastatic and archival primary prostate tumor samples. Forty-four patients were enrolled at four centers. The median age was 72 years, the median PSA was 223 ng/ml, and 21 patients had at least one prior chemotherapy. Thirty-nine patients are evaluable for PSA, and three patients demonstrated a PSA decline >50% from baseline (55-99.9% decrease). The median time to progression was 90 days. Of 19 patients evaluable for measurable disease, 1 patient had a partial response. Nine of 35 evaluable patients had significant improvement in pain. The most frequent adverse events were asthenia (75%), nausea (55%), anorexia (50%), and anemia (41%). PDGF-r expression was detected in 80% of the metastases and 88% of primary prostate cancers. The results of this trial may warrant further clinical studies with other PDGF-r inhibitors.

Towards enzyme activated antiprostatic agents.

A prodrug conjugate designed to undergo activation by enzymatic prostate specific antigen has been synthesized. The prodrug system undergoes activation with PSA or alpha-chymotrypsin, and shows selective cytotoxicity in a PSA secreting cell line.

A phase I trial of a recombinant vaccinia virus expressing prostate-specific antigen in advanced prostate cancer.

A recombinant vaccinia virus encoding human prostate-specific antigen (rV-PSA) was administered as three consecutive monthly doses to 33 men with rising PSA levels after radical prostatectomy, radiation therapy, both, or metastatic disease at presentation. Dose levels were 2.65 x 10(6), 2.65 x 10(7), and 2.65 x 10(8) plaque forming units. Ten patients who received the highest dose also received 250 microg/m2 granulocyte-macrophage colony-stimulating factor (GM-CSF) as an immunostimulatory adjunct. No patient experienced any virus-related effects beyond grade I cutaneous toxicity. Pustule formation and/or erythema occurred after the first dose in all 27 men who received > or =2.65 x 10(7) plaque forming units. GM-CSF administration was associated with fevers and myalgias of grade 2 or lower in 9 of 10 patients. PSA levels in 14 of 33 men treated with rV-PSA with or without GM-CSF were stable for at least 6 months after primary immunization. Nine patients remained stable for 11-25 months; six of these remain progression free with stable PSA levels. Immunological studies demonstrated a specific T-cell response to PSA-3, a 9-mer peptide derived from PSA. rV-PSA is safe and can elicit clinical and immune responses, and certain patients remain without evidence of clinical progression for up to 21 months or longer.

Eligibility and response guidelines for phase II clinical trials in androgen-independent prostate cancer: recommendations from the Prostate-Specific Antigen Working Group.

PURPOSE: Prostate-specific antigen (PSA) is a glycoprotein that is found almost exclusively in normal and neoplastic prostate cells. For patients with metastatic disease, changes in PSA will often antedate changes in bone scan. Furthermore, many but not all investigators have observed an association between a decline in PSA levels of 50% or greater and survival. Since the majority of phase II clinical trials for patients with androgen-independent prostate cancer (AIPC) have used PSA as a marker, we believed it was important for investigators to agree on definitions and values for a minimum set of parameters for eligibility and PSA declines and to develop a common approach to outcome analysis and reporting. We held a consensus conference with 26 leading investigators in the field of AIPC to define these parameters. RESULT: We defined four patient groups: (1) progressive measurable disease, (2) progressive bone metastasis, (3) stable metastases and a rising PSA, and (4) rising PSA and no other evidence of metastatic disease. The purpose of determining the number of patients whose PSA level drops in a phase II trial of AIPC is to guide the selection of agents for further testing and phase III trials. We propose that investigators report at a minimum a PSA decline of at least 50% and this must be confirmed by a second PSA value 4 or more weeks later. Patients may not demonstrate clinical or radiographic evidence of disease progression during this time period. Some investigators may want to report additional measures of PSA changes (ie, 75% decline, 90% decline). Response duration and the time to PSA progression may also be important clinical end point. CONCLUSION: Through this consensus conference, we believe we have developed practical guidelines for using PSA as a measurement of outcome. Furthermore, the use of common standards is important as we determine which agents should progress to randomized trials which will use survival as an end point.

Tyrosine kinases expressed in vivo by human prostate cancer bone marrow metastases and loss of the type 1 insulin-like growth factor receptor.

An important biological feature of prostate cancer (PCa) is its marked preference for bone marrow as a metastatic site. To identify factors that may support the growth of PCa in bone marrow, expression of receptor and nonreceptor tyrosine kinases by androgen-independent PCa bone marrow metastases was assessed. Bone marrow biopsies largely replaced by PCa were analyzed using reverse transcriptase-polymerase chain reaction amplification with degenerate primers that amplified the conserved kinase domain. Sequence analyses of the cloned products demonstrated expression of multiple kinases. Expression of the receptor and nonreceptor tyrosine kinases, alpha platelet-derived growth factor receptor and Jak 1, respectively, was confirmed by immunohistochemistry. In contrast, the type 1 insulin-like growth factor receptor, thought to play a role in PCa development, was lost in metastatic PCa. These results implicate several specific growth factors and signaling pathways in metastatic androgen-independent PCa and indicate that loss of the type 1 insulin-like growth factor receptor contributes to PCa progression.

Selection for androgen receptor mutations in prostate cancers treated with androgen antagonist.

The role of androgen receptor (AR) mutations in androgen-independent prostate cancer (PCa) was determined by examining AR transcripts and genes from a large series of bone marrow metastases. Mutations were found in 5 of 16 patients who received combined androgen blockade with the AR antagonist flutamide, and these mutant ARs were strongly stimulated by flutamide. In contrast, the single mutant AR found among 17 patients treated with androgen ablation monotherapy was not flutamide stimulated. Patients with flutamide-stimulated AR mutations responded to subsequent treatment with bicalutamide, an AR antagonist that blocks the mutant ARs. These findings demonstrate that AR mutations occur in response to strong selective pressure from flutamide treatment.

Loss of DNA mismatch repair facilitates reactivation of a reporter plasmid damaged by cisplatin.

In addition to recognizing and repairing mismatched bases in DNA, the mismatch repair (MMR) system also detects cisplatin DNA adducts and loss of MMR results in resistance to cisplatin. A comparison was made of the ability of MMR-proficient and -deficient cells to remove cisplatin adducts from their genome and to reactivate a transiently transfected plasmid that had previously been inactivated by cisplatin to express the firefly luciferase enzyme. MMR deficiency due to loss of hMLH1 function did not change the extent of platinum (Pt) accumulation or kinetics of removal from total cellular DNA. However, MMR-deficient cells, lacking either hMLH1 or hMSH2, generated twofold more luciferase activity from a cisplatin-damaged reporter plasmid than their MMR-proficient counterparts. Thus, detection of the cisplatin adducts by the MMR system reduced the efficiency of reactivation of the damaged luciferase gene compared to cells lacking this detector. The twofold reduction in reactivation efficiency was of the same order of magnitude as the difference in cisplatin sensitivity between the MMR-proficient and -deficient cells. We conclude that although MMR-proficient and -deficient cells remove Pt from their genome at equal rates, the loss of a functional MMR system facilitates the reactivation of a cisplatin-damaged reporter gene.

High dose bicalutamide for androgen independent prostate cancer: effect of prior hormonal therapy.

PURPOSE: A pilot study of the antiandrogen bicalutamide at 150 mg. a day for androgen independent prostate cancer was performed. This study was based on the possibility that androgen independent cases might display responses to additional hormonal agents. MATERIALS AND METHODS: The study included 31 androgen independent cases with an increasing prostate specific antigen (PSA) and progressive disease. PSA measurements were used as the primary method of assessing response. However, PSA decline was also correlated with clinical status. RESULTS: Seven patients demonstrated PSA declines of greater than 50% for 2 months or more, for an overall response rate of 22.5%. Responses were observed almost exclusively in patients treated with long-term flutamide as part of a complete androgen blockade regimen (43% response rate) in contrast to patients treated with androgen deprivation without flutamide (6% response rate). Of the 7 PSA responding patients bicalutamide resulted in a significant improvement in performance status and a decrease in analgesic requirement in 4 and 3 remained asymptomatic. Bicalutamide at 150 mg. a day was well tolerated, with the most frequent side effect being mild exacerbation of hot flashes. CONCLUSIONS: Bicalutamide at this dose is modestly effective for some patients with androgen independent prostate cancer, particularly for those previously treated with long-term flutamide. This study indicates that previous antiandrogen therapy alters the response to subsequent hormonal agents.

Functional characterization of mutant androgen receptors from androgen-independent prostate cancer.

Mutations in the androgen receptor (AR), that alter steroid hormone specificity have been identified in a series of androgen-independent prostate cancers. To address the functional properties of these mutant ARs that may have contributed to their selection in vivo, responses to a series of steroid hormones and antiandrogens were assessed. CV-1 cells were cotransfected with wild-type or mutant ARs and a luciferase reporter plasmid regulated by an androgen-responsive element. Dose-response curves were analyzed for 5alpha-dihydrotestosterone, the most active androgen in normal prostate, and androstenedione, a major androgen derived from the adrenals. Although the mutant ARs responded to both of these steroids, the responses were equivalent to or less than the wild-type AR. In contrast, responses to flutamide, a competitive antagonist of the wild-type AR, were markedly increased by three of the mutations. Similar responses were observed with a second antiandrogen, nilutamide. Bicalutamide, another antiandrogen related to flutamide, remained an antagonist for these mutant ARs. Finally, flutamide was observed to be a weak partial agonist of the wild-type AR in this system. These results indicate that flutamide used in conjunction with androgen ablation therapy for prostate cancer may select for tumor cells with flutamide-inducible ARs.

Chromium(VI) treatment of normal human lung cells results in guanine-specific DNA polymerase arrest, DNA-DNA cross-links and S-phase blockade of cell cycle.

Previous studies have shown that in vitro treatment of a synthetic double-stranded DNA template with chromium(III), or chromium(VI) in the presence of ascorbate, resulted in guanine-specific DNA polymerase arrests that correlated strongly with DNA-DNA cross-linking. In vivo chromium(VI) undergoes a more complicated intracellular cascade of reductive metabolism than is achievable in an in vitro model. Moreover, in living cells, DNA is highly packaged in the form of chromatin which may alter the accessibility of DNA to chromium. A repetitive primer-extension assay was employed to determine whether chromium forms polymerase-arresting lesions in vivo. Normal human lung fibroblasts treated with chromium(VI) exhibited adduct levels of 0.13-0.92 mmol Cr/mol DNA-nucleotides in the total genome (0.26-1.84 Cr adducts/Kbp DNA) and DNA interstrand cross-links. Genomic DNA was isolated and alphoid sequences (1-5% of the genome) were used as a substrate for repetitive primer extension using Taq polymerase. The results showed a dose-dependent, guanine-specific, replication termination, even at low doses resulting in greater than 90% survival. The same treatment resulted in dose-dependent suppression of thymidine incorporation into DNA immediately after treatment. Thymidine incorporation increased during the first 6 h after the 2-h exposure, probably related to the repair of the single strand breaks, but then returned to high suppression levels at 24 h. The chromate treatments inhibited cell growth by specific blocking of the progression of cells through S-phase of the cell cycle. The results confirmed our studies in cell-free systems and taken together they strongly indicate that guanine-guanine DNA interstrand cross-links induced by chromate in living cells is the lesion responsible for blocking DNA replication processivity.

Treatment of metastatic prostate cancer. Lessons from the androgen receptor.

The exquisite hormonal dependence of prostate cancer continues to provide an opportunity and a challenge for oncologists. It is clear that future efforts in the laboratory should include determining the frequency and spectrum of AR mutations in AI prostate cancer, the development of more effective antiandrogens, and understanding in greater detail how the AR stimulates the growth of prostate cancers. These efforts may eventually lead to treatments that greatly reduce any stimulatory effects of the AR on prostate cells, possibly resulting in a significant improvement in disease-free survival and, perhaps in conjunction with other modalities, cure of some earlier stages of disease. And even for patients with advanced disease, because hormonal therapy is generally fairly well tolerated even in the typically older prostate cancer patient, defining the contribution of AR-mediated growth to AI disease will be critically important.

Effect of DNA conformation on cisplatin adduct formation.

The anticancer drug cis-diamminedichloroplatinum(II) (cisplatin) has been shown previously to form adducts preferentially within internucleosomal or linker DNA rather than to DNA within the nucleosome. To determine whether other "open" regions of chromatin have an increased affinity for cisplatin, adduct formation within specific chromatin domains was analyzed. There was a significant increase in cisplatin-DNA adduct formation for DNA associated with the nuclear matrix (NM) compared with other chromatin domains and total unfractionated DNA. In contrast, treatment of the same cells with trans-diamminedichloroplatinum(II) (transplatin) did not result in preferential adduct formation. These findings led to the hypothesis that it might be possible to alter DNA to make it a more favorable target for cisplatin. The effect of arginine butyrate on cisplatin-DNA adduct formation was analyzed in human cancer cells. The combination of arginine butyrate and cisplatin resulted in a concentration-responsive increase in cisplatin-DNA adduct formation in PC-3 cells and an overall increase in cisplatin-DNA adduct formation in three other human cancer cell lines. The same combination also resulted in a significant increase in drug-induced cytotoxicity at a low concentration of cisplatin. These results suggest that chromatin configuration can affect cisplatin adduct formation.

Mutation of the androgen-receptor gene in metastatic androgen-independent prostate cancer.

BACKGROUND: Metastatic prostate cancer is a leading cause of cancer-related death in men. The rate of response to androgen ablation is high, but most patients relapse as a result of the outgrowth of androgen-independent tumor cells. The androgen receptor, which binds testosterone and stimulates the transcription of androgen-responsive genes, regulates the growth of prostate cells. We analyzed the androgen-receptor genes from samples of metastatic androgen-independent prostate cancers to determine whether mutations in the gene have a role in androgen independence. METHODS: Complementary DNA was synthesized from metastatic prostate cancers in 10 patients with androgen-independent prostate cancer, and the expression of the androgen-receptor gene was estimated by amplification with the polymerase chain reaction. Exons B through H of the gene were cloned, and mutations were identified by DNA sequencing. The functional effects of the mutations were assessed in cells transfected with mutant genes. RESULTS: All androgen-independent tumors expressed high levels of androgen-receptor gene transcripts, relative to the levels expressed by an androgen-independent prostate-cancer cell line (LNCaP). Point mutations in the androgen-receptor gene were identified in metastatic cells from 5 of the 10 patients examined. One mutation was in the same codon as the mutation found previously in the androgen-independent prostate-cancer cell line. The mutations were not detected in the primary tumors from of the two patients. Functional studies of two of the mutant androgen receptors demonstrated that they could be activated by progesterone and estrogen. CONCLUSIONS: Most metastatic androgen-independent prostate cancers express high levels of androgen-receptor gene transcripts. Mutations in androgen-receptor genes are not uncommon and may provide a selective growth advantage after androgen ablation.