Advances in Molecular Regulation of Prostate Cancer Cells by Top Natural Products of Malaysia

Prostate cancer (PCa) remains both a global health burden and a scientific challenge. We present a review of the molecular targets driving current drug discovery to fight this disease. Moreover, the preventable nature of most PCa cases represents an opportunity for phytochemicals as chemopreventive when adequately integrated into nutritional interventions. With a renovated interest in natural remedies as a commodity and their essential role in cancer drug discovery, Malaysia is looking towards capitalizing on its mega biodiversity, which includes the oldest rainforest in the world and an estimated 1200 medicinal plants. We here explore whether the list of top Malay plants prioritized by the Malaysian government may fulfill the potential of becoming newer, sustainable sources of prostate cancer chemotherapy. These include Andrographis paniculate, Centella asiatica, Clinacanthus nutans, Eurycoma longifolia, Ficus deltoidea, Hibiscus sabdariffa, Marantodes pumilum (syn. Labisia pumila), Morinda citrifolia, Orthosiphon aristatus, and Phyllanthus niruri. Our review highlights the importance of resistance factors such as Smac/DIABLO in cancer progression, the role of the CXCL12/CXCR4 axis in cancer metastasis, and the regulation of PCa cells by some promising terpenes (andrographolide, Asiatic acid, rosmarinic acid), flavonoids (isovitexin, gossypin, sinensetin), and alkylresorcinols (labisiaquinones) among others.

Oligometastatic prostate cancer: Reality or figment of imagination?

The term “oligometastatic prostate cancer” refers to a heterogeneous group of disease states currently defined solely on the basis of clinical features. Oligorecurrent disease, de novo oligometastases, and oligoprogressive disease likely have unique biologic underpinnings and natural histories. Evidence suggesting the existence of a subset of patients who harbor prostate cancer with limited metastatic potential currently includes disparate and overwhelmingly retrospective reports. Nevertheless, emerging prospective data have corroborated the “better‐than‐expected,” retrospectively observed outcomes, particularly in the setting of oligorecurrent prostate cancer. Improved functional imaging with prostate‐specific membrane antigen‐targeted strategies may enhance the identification of patients with oligometastatic prostate cancer in the short term. In the long term, refinement of the oligometastatic case definition likely will require biologic risk‐stratification schemes. To determine optimal treatment strategies and identify patients most likely to benefit from metastasis‐directed therapy, future efforts should focus on conducting high‐quality, prospective trials with much‐needed molecular correlative studies.

The term “oligometastatic prostate cancer” currently refers to a heterogeneous group of clinically defined disease states. To improve patient risk stratification and determine optimal treatment strategies, future efforts should focus on conducting prospective trials and determining a biologic categorization of patients with limited metastatic potential.

The change of PSA doubling time and its association with disease progression in patients with biochemically relapsed prostate cancer treated with intermittent androgen deprivation

BACKGROUND

We sought to determine the change of PSA doubling time (PSADT) and its association with disease progression during intermittent androgen deprivation (IAD) therapy for prostate cancer.

METHODS

Data were retrospectively analyzed in 96 patients with biochemically relapsed prostate cancer (BRPC) treated with IAD since 1995. IAD consisted of LHRH-agonists ± antiandrogen given usually at PSA threshold (ng/ml) of 10-20, for 6-9 months. Cycles were repeated until the development of castration resistance. Mixed effects model was used to study PSADT change over cycles. Multivariate cox regression model was used to identify outcome-associated variables.

RESULTS

Patients received a mean of 2.8 treatment cycles over a mean follow-up time of 71 months. Fifty-seven (59%) remain on treatment and 39 (41%) developed PSA refractoriness (n = 8) or positive scans (n = 31). First off treatment interval PSADT (median 2.3 months) was significantly shorter than the baseline (median 7.34) but remained stable in subsequent cycles. Off treatment interval PSADT adjusted for testosterone recovery (median 3.7) was significantly longer than that based on all PSA determinations (median 2). Factors associated with disease progression were pre-treatment PSADT (≥6 vs. <6), first off treatment interval PSADT (≥3 vs. <3), and PSA nadir during the first treatment interval (<0.1 vs. ≥0.1).

CONCLUSIONS

During IAD for BRPC, PSADT becomes shorter, and is associated with testosterone recovery. PSADT before treatment and during the first off treatment interval is associated with disease progression. If prospectively validated these data may guide treatment with IAD and clinical trial design.

Long-term overall survival and metastasis-free survival for men with prostate-specific antigen-recurrent prostate cancer after prostatectomy: analysis of the Center for Prostate Disease Research National Database

OBJECTIVE

• To describe metastasis-free survival (MFS) and overall survival (OS) among men with prostate-specific antigen (PSA)-recurrent prostate cancer after radical prostatectomy who did not receive additional therapy until metastasis, using a multicentre database capturing a wide ethnic mix.

PATIENTS AND METHODS

• A retrospective analysis of the Center for Prostate Disease Research National Database (comprised of five US military hospitals and one civilian centre) was performed for patients with PSA relapse (≥ 0.2 ng/mL) after radical prostatectomy who had no additional therapy until the time of radiographic metastatic disease. • We investigated factors influencing metastasis and all-cause mortality using univariate and multivariate Cox regression analysis.

RESULTS

• There were a total of 346 men who underwent radical prostatectomy between May 1983 and November 2008 and fulfilled the entry criteria. All patients had information on survival and 190 men had information on metastasis. Among patients with survival data (n= 346), 10-year OS was 79% after a median follow-up of 8.6 years from biochemical recurrence. • Among men with metastasis data (n= 190), 10-year MFS was 46% after a median follow-up of 7.5 years. • In Cox regressions, four clinical factors (Gleason score, pathological stage, time to PSA relapse and PSA doubling time), as well as age, were predictive of OS and/or MFS in univariate analysis, although only PSA doubling time (≥ 9 vs 3-8.9 vs <3 months) remained independently predictive of these outcomes in multivariate analysis (P < 0.001).

CONCLUSIONS

• This multicentre multi-ethnic dataset shows that OS and MFS can be extensive for men with PSA-recurrent prostate cancer, even in the absence of further therapy before metastasis. • This unique patient cohort, the second largest of its type after the Johns Hopkins cohort, confirms that PSA doubling time is the strongest determinant of OS and MFS in men with PSA-recurrent disease. • Longer follow-up and more events will be required to determine whether other variables may also contribute to these outcomes.

Lenalidomide in nonmetastatic biochemically relapsed prostate cancer: results of a phase I/II double-blinded, randomized study

PURPOSE

To evaluate the safety and activity of 6 months of treatment with lenalidomide at 5 or 25 mg/d in nonmetastatic biochemically relapsed prostate cancer.

EXPERIMENTAL DESIGN

Sixty men with non-castrate, nonmetastatic, biochemically relapsed prostate cancer were stratified by prostate-specific antigen (PSA) doubling time, surgery/radiation therapy, prior androgen deprivation therapy (ADT), and randomized to lenalidomide 5 mg (n = 26) or 25 mg/d (n = 34) for 3 weeks repeated monthly for 6 months or until dose-limiting toxicity or disease progression. Toxicity was evaluated monthly, and PSAs and X-rays/scans every 6 months. Study size was determined to detect a progression rate of 40% at 6 months in either arm with 85% power (compared with a rate of 80% in the population receiving no treatment). Changes in PSA slopes were calculated using the regression of the log PSA for each patient before and during the initial 6 months and compared by t test.

RESULTS

Baseline variables were balanced between arms. Grade 3/4 toxicity rates were 12% (n = 3) with 5 mg and 29% (n = 10) with 25 mg (P = 0.1), most commonly neutropenia (five patients, all on 25 mg). Two patients per arm had thromboembolic events. The change in PSA slope was greater with 25 mg versus 5 mg [-0.172 (-0.24 to -0.11) versus -0.033 (-0.11 to 0.04); P = 0.005]. With a mean follow-up of 31.4 months (range 14-44), five patients on 25 mg and one patient on 5 mg remain on the study.

CONCLUSIONS

Lenalidomide has acceptable toxicity and is associated with long-term disease stabilization and PSA declines. Randomized studies evaluating conventional clinical disease end points in this patient population are planned.