Effect of dual inhibition of the Src and insulin-like growth factor-1 receptor (IGF-1R) pathways on antitumor effects in prostate cancer (PCa)

21

Background: The Src and IGF-1R axes are aberrantly activated in both PCa and the microenvironment of bone metastases. Dasatinib and BMS-754807 are clinically promising small molecule inhibitors with high potency against Src family kinases and IGF-1R, respectively. The aim of this study was to establish antitumor co-operativity by combining IGF-1R and Src blockade in a preclinical PCa model.

Methods: LNCaP and PC3 cells were used as models for androgen-dependent and independent PCa, respectively. Inhibition of Src and IGF-1R pathways was accomplished by pharmacologic agents (dasatinib against Src and BMS-754807 against IGF-1R) as well as by shRNA. Serum IGF-1 levels were measured in patients (pts) with castration-resistant PCa (CRPC) treated with dasatinib and docetaxel in a phase II trial.

Results: Src inhibition decreased proliferation of PCa cells, and migration in modified Boyden Chamber and wound assays. In contrast, IGF-1R blockade induced apoptosis (increased Sub-G1 fraction cells, Annexin-V(+) cells and PARP cleavage). Phosphorylation of Akt was partially inhibited by either drug alone and almost completely abrogated by the combination. Intraprostatic injection of shIGF-1R or shSrc PC3 cells in nude mice led to an 83% and 60% decrease in tumor size compared to control shRNA, respectively. In both cell lines, all observed antitumor effects were enhanced when dual blockade was used, relative to blocking the Src or IGF-1R pathway alone. In 9/19 (47%) pts with CRPC, treatment with dasatinib resulted in a compensatory increase of serum IGF-1 levels.

Conclusions: Dual inhibition of Src and IGF-1R is effective and complementary in PCa, mediated, in part, through inhibition of the downstream target Akt. In about half of pts treated with dasatinib, an increase in soluble IGF-1 levels was observed, indicating there is a compensatory upregulation of survival pathways that might be abrogated by dual inhibition of Src and IGF-1R. The combination of dasatinib and BMS-754807 may be a rational therapeutic approach in PCa by blocking complementary processes of tumor growth and progression.

[Table: see text]

Caveolin-1 as a biomarker of Src family kinase/Abl inhibition in castrate-resistant prostate cancer

45

Background: Bone metastases cause significant morbidity in men with castrate-resistant prostate cancer (CRPC). Caveolin-1 (Cav-1), a Src kinase substrate, is overexpressed in primary prostate cancer (PCa) and in PCa bone metastases. In addition, PCa-derived and secreted Cav-1 contributes to malignant progression. We reasoned that Cav-1 may serve as a biomarker of dasatinib (a Src family kinase [SFK]/Abl inhibitor) activity in CRPC patients enrolled in a phase II clinical trial of docetaxel plus dasatinib.

Methods: Levels of prostate-specific antigen (PSA), Cav-1, and markers of bone turnover were measured from baseline and cycle-2, day-1 samples from patients (n = 32) enrolled in this trial. Changes in these markers were stratified by response (responders [R] vs. nonresponders [NR]) and by predominant disease site (lymph node vs. bone). We evaluated Cav-1 expression in human PCa bone metastases samples from trial patients by immunohistochemistry. In parallel, Cav-1 secretion in response to dasatinib treatment was analyzed in PCa cells and osteoblasts.

Results: Serum Cav-1 levels correlated directly with PSA levels in responding patients with node-positive disease (R vs. NR, p = 0.08) but correlated inversely in responding patients with bone-predominant disease (R vs. NR, p = 0.001). Serum from a separate cohort of patients treated with docetaxel only showed no effect on serum Cav-1 levels (R vs. NR, p = 0.85). Levels of Cav-1 were high in the active OBLs in bone specimens with PCa metastases, but not in bone specimens without metastases. Dasatinib treatment led to reduced secretion of Cav-1 in PC-3 and DU145 PCa cells but to increased secretion of Cav-1 in primary mouse osteoblasts or pre-osteoblast MC3T3-E1 cells.

Conclusions: Our results suggest that serum Cav-1 serves as a novel discriminating biomarker for SFK/Abl inhibition in both node-positive and bone-metastatic CRPC. The expression of Cav-1 in OBLs of patients with PCa bone metastases suggests that tumor-associated OBLs are an important source of Cav-1 production in bone marrow. Our data provide evidence that the increase in serum Cav-1 in these patients with bone disease likely occurs through a direct effect of dasatinib on osteoblasts.

No significant financial relationships to disclose.

Hyperthyroidism in men with germ cell tumors and high levels of beta-human chorionic gonadotropin

A retrospective review was done on all high volume choriocarcinomas and other germ cell tumors of men with serum beta-human chorionic gonadotropin (beta-HCG) levels greater than 50,000 mIU/ml to determine the incidence and characteristics of hyperthyroidism in this setting. Nineteen patients were identified with high beta-HCG levels, but because 2 did not have thyroid function tests performed, the cases of only 17 patients were evaluable. Of these, 14 (82%) had primary testicular carcinoma and 3 (18%) had extragonadal tumors. Beta-HCG levels on presentation ranged from 80,000 to 3,058,000 mIU/ml, with a median of 243,500 mIU/ml. Seven of the 17 evaluable cases (41%) had T4 serum levels higher than 12 micrograms/dl (normal level 4 to 12 micrograms/dl) with a median value of 15.4 micrograms/dl (range, 12.6 to 33.5 micrograms/dl); serum T4 levels correlated with beta-HCG levels (r = 0.84). All seven patients with elevated T4 levels had beta-HCG values greater than 200,000 mIU/ml, and three of these seven had clinical manifestations that could be attributed to an elevated serum T4; only one patient required specific antithyroid treatment; and after control of primary disease, all other patients had normalization of thyroid function. The most common manifestations of hyperthyroidism in our series were tachycardia, hypertension, and a systolic flow murmur; none of the patients had thyroid gland enlargement. We conclude that subclinical hyperthyroidism is a relatively common phenomenon in germ cell tumors of men with high levels of beta-HCG and that control of the primary disease results in serum T4 level normalization.

Phase II multicenter study of chemotherapy (chemo)-naive castration-resistant prostate cancer (CRPC) not exposed to ketoconazole (keto), treated with abiraterone acetate (AA) plus prednisone

5046

Background: AA is a potent inhibitor of the enzyme CYP17, a major contributor to androgen biosynthesis. Keto is also known to inhibit this enzyme but AA is many-fold stronger in its action. 33 pts with progressive metastatic disease, normal organ function, ECOG performance status (PS) 0–1, and no prior chemo were enrolled. Pts with prior keto treatment were excluded. AA (1000 mg qd) plus prednisone (5mg bid) were administered orally in 28 day cycles. Methods: Results: At baseline median age was 71.0 (range 52–85) yrs and median PSA was 24.7 (range 7.1–1110.0) ng/mL;19/26 pts (73%) had an ECOG PS of 0 and 7/26 (27%) had PS of 1; the median number of prior hormonal therapies was 2; all pts were on LHRHa and 73% of pts had received anti-androgen, all of whom had undergone prior anti-androgen withdrawal. Pts were evaluated at each cycle for PSA response according to PSAWG criteria. 27 pts have available data for PSA response. Total maximal PSA declines of ≥30%, ≥50%, ≥90% were observed in 89% (24/27), 85% (23/27) and 41% (11/27) pts, respectively. Week 12 PSA declines displayed a similar and sustained trend: ≥30%, ≥50% and ≥90% PSA decline in 82%, 78%, and 26% of pts. Post-treatment ECOG PS score was 0 in 24 (92%) pts: 19% experienced improvement in PS (PS 1 to 0 in 5 pts) and 19/19 pts maintained a PS of 0; Median time to PSA progression has not been reached. Majority of adverse events were grades 1–2. Incidence of hypokalemia - 12%; HTN - 6%; edema - 15%. One pt experienced a grade 3 drug-related HTN. Conclusions: Abiraterone acetate plus prednisone has significant anti-cancer activity in patients with metastatic CRPC not previously treated with ketoconazole or chemotherapy, as demonstrated by declines in PSA and improvement in performance status, and is well-tolerated.

[Table: see text]

Differential gene expression in preoperative study of selenium and vitamin E chemoprevention in prostate cancer

1523

Background: To identify genes that distinguish between treatments, tumor types, and their interaction, we undertook a microarray analysis of tissue in a preoperative chemoprevention study of L-selenomethionine (SeMet) and vitamin E (VE) in prostate cancer. Methods: Forty-eight men with prostate cancer were enrolled in a single-institution, double-blind, placebo-controlled trial that randomized patients into four groups receiving 200 μg SeMet, 400 IU VE, a combination of the two, or placebo (see 2006 ASCO abstract 1007). All patients also received a multivitamin and vitamin C (250 mg) daily. Modeled on the Selenium and Vitamin E Cancer Prevention Trial, this study included patients scheduled for prostatectomy within 3 to 6 wk of registration who had a prostate-specific antigen level <10 ng/mL within 3 mo of registration, clinical stage T1c/T2 disease, and a Gleason score =7. From core biopsy specimens, we isolated cancerous and noncancerous cells, tumor-adjacent stroma, and non-tumor adjacent stroma of 38 evaluable radical prostatectomy specimens using laser capture microdissection. The cDNA hybridized to oligonucleotide microarrays was generated from extracted RNA, which had undergone two rounds of linear amplification. Expression levels were extracted using the positional-dependent nearest-neighbor model, and after ANOVA model analysis, effects were contrasted using the approximate z-test with statistic z. The beta-uniform mixture model was used to analyze p values and control the false discovery rate. Ingenuity Pathway Analysis followed. Results: Differentially expressed genes were selected that were common in the combination and selenium arms or in the combination and VE arms: unique in tumor-69 in combination and selenium, 71 in combination and VE; unique in stroma-64 in combination and selenium, 45 in combination and VE; unique in normal tissue-48 in combination and selenium, 38 in combination and VE. Conclusions: This work demonstrates that gene expression may be correlated with specific therapeutic interventions, and this analysis indicates that dietary antioxidants modulate gene expression in human prostate cancer cells and pathways relevant to prostate carcinogenesis.

No significant financial relationships to disclose.

Preoperative platelet-derived growth factor receptor inhibitor therapy combined with docetaxel and androgen ablation in high-risk localized prostate cancer

5141

Background: Reduction in tumor interstitial fluid pressure with platelet-derived growth factor receptor (PDGFR) inhibitor therapy in experimental systems improves drug delivery and the therapeutic index of taxane chemotherapy (Pietras, Cancer Research, 2002). We hypothesized that PDGFR inhibitor therapy with imatinib mesylate combined with androgen ablation (AA) and docetaxel (D) induces pathological complete responses (pCR) in high-risk localized prostate adenocarcinoma (PC) prior to radical prostatectomy and pelvic lymph node dissection (RP). Methods: Thirty six men with PC ≥T2 disease or Gleason grade 8–10 or serum prostate-specific antigen (PSA) > 20 ng/ml or cT2b and PSA >10 ng/ml and Gleason 7 disease (AJCC, 1992), without radiological evidence of metastases, were planned to receive intramuscular leuprolide, imatinib 600mg orally daily, and weekly D 30 mg/m2 on D1, 8, 15, 22 q42 for three cycles (18 weeks) before RP [β (0.02, 1.98) prior on the possibility of pCR]. Unresectable pelvic nodal disease, post-operative PSA > 0.2 ng/ml or administration of post-operative radiation or AA were defined as treatment failure. Results: Between 6–03 and 9–04, 39 men were registered; median age 57 years (range, 44–71); 35 Caucasian, 2 Hispanic, 4 African-American. Risk factors included T3 disease (22/39), Gleason 8–10 disease (31/39), PSA > 20 ng/ml (12/39). Three men were ineligible or declined therapy; 29/36 (80%) received three cycles of therapy; 7/36 (20%) discontinued therapy related to toxicity. Grade 3–4 toxicity included rash (n=3), diarrhea (n=5), fatigue (n=3), neutropenia (n=2), hepatic (n=1). Severe or unexpected surgical complications were not encountered. No pCRs were defined; 15/36 (42%) have PSA < 0.2 ng/ml [12/36 (33%), <0.1 ng/ml] at 24 months and 13/36 (36%) met definition for treatment failure. Conclusions: The addition of the PDGFR inhibitor imatinib to pre-operative AA and D, although feasible, did not induce pCR in PC.

[Table: see text]

Kidney Cancer

An estimated 38,890 Americans will be diagnosed with kidney cancer and 12,840 will die of this disease in the United States in 2006. Renal cell carcinoma (RCC) constitutes approximately 2% of all malignancies, with a median age at diagnosis of 65 years. Smoking and obesity are among the risk factors for RCC development, and tumor grade, local extent of the tumor, presence of regional nodal metastases, and evidence of metastatic disease at presentation are the most important prognostic determinants of 5-year survival. These guidelines discuss evaluation, staging, treatment, and management after treatment.

For the most recent version of the guidelines, please visit NCCN.org

Testicular Cancer

An estimated 8250 new cases of testicular cancer will be diagnosed in the United States in 2006, with germ cell tumors (GCTs) constituting 95% of the malignant tumors arising in the testes. Although GCTs are relatively uncommon tumors, they are the most common solid tumor in men between the ages of 15 and 34 years. The worldwide incidence of these tumors has more than doubled in the past 40 years. More than 90% of all patients diagnosed with GCTs are cured, including 70% to 80% of patients with advanced tumors who are treated with chemotherapy. Standard therapy has been established at essentially all stages of management and must be closely followed to ensure the potential for cure.

For the most recent version of the guidelines, please visit NCCN.org

A preoperative model evaluating the tissue effects of chemopreventive agents in low-volume prostate cancer

1007

Background: To identify and assess biomarkers modulated by prostate cancer chemopreventive agents, we created a model that, by exploiting the time between histologic diagnosis of prostate cancer and definitive therapy (prostatectomy), expedites tissue cross comparison and confronts the multifocality and multizonal heterogeneity of prostate cancer. Methods: Between February 2001 and April 2002, 48 presurgical patients were enrolled in a single-institution, randomized, double-blind trial of vitamin E (VE) and L-selenomethionine (SeMET) based on the framework of the ongoing Selenium and Vitamin E Cancer Prevention Trial. Patients were treated with 400 IU VE, 200 μg SeMET, a combination of VE and SeMET, or placebo for 3 to 6 weeks before prostatectomy. All patients also received a multivitamin and vitamin C 250 mg each day. Ex vivo simulated sextant biopsies on the radical prostatectomy specimen (RPS) were performed, and 36 of 39 evaluable patients had RPS sections that were suitable for pathologic evaluation. Blood components were collected at baseline and prior to prostatectomy. We derived an apoptotic index (AI) morphologically and a proliferation index (PI) by using immunohistochemistry and counting Ki-67-positive nuclei. Cells were counted and identified by cell type (normal and cancerous) and by zone (peripheral [PZ], transition [TZ], and central [CZ]). Results: In normal epithelial cells when the Wilcoxon rank sum test was used to compare AI and PI changes between groups, the AI was higher in the TZ than in the CZ, a difference independent of treatment effects (p = .01). Between the largest PZ and TZ tumor foci, a statistically significant difference in PI was observed (p = .006). Using a multiple linear regression model fitted for AI from the largest RPS PZ tumor focus, we found a statistically significant difference between the SeMET group and the placebo group (p = .02). Conclusions: Besides introducing new findings, the clinicopathologic model proved itself a platform for biomarker discovery by leveraging molecular technologies to full advantage, including serum protein profiling (Kim et al., CEBP 2005) and gene expression profiling of different cell types. Supported by NIH grant CA88761.

No significant financial relationships to disclose.

A meta-analysis of individual patient data from randomized trials assessing chemotherapy with and without estramustine in patients with castration-refractory prostate cancer

4561

Background: Estramustine phosphate is a mustard-estradiol conjugate, with evidence of both hormonal and non-hormonal effects. In phase II trials, the response rates of microtubule inhibitors are increased when combined with estramustine. Morbidity includes notably thrombosis in about 7% of cases. Whether combining estramustine with chemotherapy increases survival in castration-refractory prostate cancer (CRPC) is still controversial. Methods: Data from all published and unpublished prospective randomized trials assessing chemotherapy + estramustine versus chemotherapy alone in CRPC were sought using electronic database searching, hand searching, and by contacting experts in the field. The primary endpoint was overall survival (OS). The analysis was performed on an intention-to-treat basis. The stratified logrank test was used and an overall hazard ratio (HR) was computed using a fixed effect model. χ2 heterogeneity tests were used to test for statistical heterogeneity. All p-values were two-sided. Multivariate analysis was performed using a Cox model stratified by trial. Results: Individual data were obtained from all 5 randomized trials conducted in the PSA era that had been identified (n = 610). The control arms consisted of docetaxel (1), paclitaxel (1), ixabepilone (1), and vinblastine (2). With a median follow-up of 2.8 years, 510 deaths had occurred. OS was significantly better in the estramustine arm (HR = 0.82 [95% CI: 0.69–0.97]; p = 0.02). Overall, the risk reduction (RR) of death related to estramustine was 18% (± 8). There was no significant interaction (p = 0.66) between the RR of trials using vinblastine (RR = 15% [± 12]) and in those using taxanes or ixabepilone (RR = 21% [± 11]). The estimated 1-year OS rate was 57% and 50% in the estramustine arm and in the control arm, respectively. The 18-months OS rate was 43% and 35%, respectively. There was no interaction between the effect of estramustine and age, performance status, or serum PSA in the Cox model. Conclusions: Combining estramustine with chemotherapy increases OS over chemotherapy alone in patients with castration-refractory prostate cancer.

[Table: see text]

Integrated therapy for locally advanced bladder cancer: final report of a randomized trial of cystectomy plus adjuvant M-VAC versus cystectomy with both preoperative and postoperative M-VAC

PURPOSE

We conducted a phase III trial to investigate the timing of chemotherapy with respect to surgery for patients with resectable but high-risk urothelial cancer. The trial was also designed to evaluate the accuracy of clinical staging in patients with locally advanced cancer and the prognostic significance of chemotherapy-induced downstaging.

PATIENTS AND METHODS

A total of 140 uniformly evaluated patients with locally advanced urothelial cancer were studied. Planned treatment was five cycles of chemotherapy (M-VAC: methotrexate, vinblastine, doxorubicin, and cisplatin) plus radical cystectomy and pelvic lymph node dissection. Patients were randomly assigned to receive either two courses of neoadjuvant M-VAC followed by surgery plus three additional cycles of chemotherapy, or, alternatively, to have initial cystectomy followed by five cycles of adjuvant chemotherapy.

RESULTS

There were no significant differences in outcome between the two groups. By intent-to-treat, 81 patients (58%) remain disease-free, with median follow-up of 6.8 years. We confirmed a high rate of clinical understaging in this cohort, especially among patients showing lymphovascular invasion on biopsy. Patients with no residual muscle-invasive disease at cystectomy after neoadjuvant chemotherapy were likely to be cured.

CONCLUSION

These results lend further support to the impression from small randomized trials that, in a high-risk cohort, there is an improved cure fraction by the combination of multiagent chemotherapy and surgery, although we found no preferred sequence. Importantly, it is possible to select appropriate patients for such therapy on the basis of clinical staging information. These results establish a benchmark of outcome for this cohort.

Restoration of bax in prostate cancer suppresses tumor growth and augments therapeutic cell death induction

BACKGROUND

Cancer cells are characterized by multiple genetic defects which result in altered rates of cell division, cell death and ability to differentiate. These same molecular alterations may also contribute to therapeutic resistance. We examined the potential contribution of the pro-apoptotic gene, bax, to suppressing the growth of prostate cancer cells.

MATERIALS AND METHODS

The bax-deficient DU145 prostate cancer cell line was transfected with a hemagluttinin-tagged bax (HA-bax) vector to generate stable expressing bax clones.

RESULTS

Ha-bax clones exhibited a significant reduction in tumor growth compared to vector control and parental cells when xenografted into nude mice. HA-bax clones were significantly more sensitive to cell death induction by cis-diamminedichloroplatinum, etoposide, doxorubicin and gamma-radiation than vector control cells. Sensitivity to paclitaxel remained unaltered in the Ha-bax cells.

CONCLUSION

These findings suggest that bax may possess a tumor suppressor function in prostatic glandular epithelial cells and be an important determinant of sensitivity to therapeutic cell death induction.

Randomized phase 2 trial of ketoconazole and ketoconazole/doxorubicin in androgen independent prostate cancer

Eighty-nine patients with progressive prostate cancer despite suppression of testosterone and withdrawal of anti-androgens were studied. This was a relatively advanced population, with 63 of 89 having either osseous metastases (mets) beyond the axial skeleton or visceral mets. Patients were randomly assigned to receive either ketoconazole alone, or ketoconazole with weekly doxorubicin. All patients received replacement hydrocortisone. The primary endpoints were response and survival. Based on PSA reduction criteria (>/= 80% maintained for at least 8 weeks), 14 of 45 patients (31%) in the single-agent ketoconazole arm responded. Sixteen of 44 patients (36%) in the combination ketoconazole/doxorubicin arm responded. There were no important differences between the two treatments in any outcome measure. The median overall survival for all patients was 12.5 months; median time to progression was 3.3 months. Toxicity was significant with both regimens, and more severe in the doxorubicin arm. Fully 20% of patients in each arm discontinued therapy due to intolerable side effects.Each of these regimens is toxic, and produced responses in fewer than half of treated patients. Although the observed median survival does compare favorably with reports from similar cohorts treated in the community, the potential benefit is only modest. In our view, neither of these regimens is sufficiently promising to justify phase 3 evaluation.