Is there a role for chemotherapy in prostate cancer?

Overcoming ABCB1 mediated multidrug resistance in castration resistant prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in American men. PCa that relapses after hormonal therapies, referred to as castration resistant PCa (CRPC), often presents with metastases (mCRPC) that are the major cause of mortality. The few available therapies for mCRPC patients include taxanes docetaxel (DTX) and cabazitaxel (CBZ). However, development of resistance limits their clinical use. Mechanistically, resistance arises through upregulation of multidrug resistance (MDR) proteins such as MDR1/ABCB1, making ABCB1 an attractive therapeutic target. Yet, ABCB1 inhibitors failed to be clinically useful due to low specificity and toxicity issues. To study taxanes resistance, we produced CBZ resistant C4-2B cells (RC4-2B) and documented resistance to both CBZ and DTX in cell culture and in 3D prostaspheres settings. RNAseq identified increased expression of ABCB1 in RC4-2B, that was confirmed by immunoblotting and immunofluorescent analysis. ABCB1-specific inhibitor elacridar reversed CBZ and DTX resistance in RC4-2B cells, confirming ABCB1-mediated resistance mechanism. In a cell-based screen using a curated library of FDA-approved cytotoxic drugs, we found that DNA damaging compounds Camptothecin (CPT) and Cytarabine (Ara-C) overcame resistance as seen by similar cytotoxicity in parental C4-2B and resistant RC4-2B. Further, these compounds were cytotoxic to multiple PC cells resistant to taxanes with high ABCB1 expression and, therefore, can be used to conquer the acquired resistance to taxanes in PCa. Finally, inhibition of CDK4/6 kinases with small molecule inhibitors (CDK4/6i) potentiated cytotoxic effect of CPT or Ara-C in both parental and resistant cells. Overall, our findings indicate that DNA damaging agents CPT and Ara-C alone or in combination with CDK4/6i can be suggested as a new treatment regimen in CRPC patients, including those that are resistant to taxanes.

Itraconazole Reverts ABCB1-Mediated Docetaxel Resistance in Prostate Cancer

Docetaxel (DTX) was the first chemotherapeutic agent to demonstrate significant efficacy in the treatment of men with metastatic castration-resistant prostate cancer. However, response to DTX is generally short-lived, and relapse eventually occurs due to emergence of drug-resistance. We previously established two DTX-resistant prostate cancer cell lines, LNCaP^R and C4-2B^R, derived from the androgen‐dependent LNCaP cell line, and from the LNCaP lineage-derived androgen-independent C4-2B sub-line, respectively. Using an unbiased drug screen, we identify itraconazole (ITZ), an oral antifungal drug, as a compound that can efficiently re-sensitize drug-resistant LNCaP^R and C4-2B^R prostate cancer cells to DTX treatment. ITZ can re-sensitize multiple DTX-resistant cell models, not only in prostate cancer derived cells, such as PC-3 and DU145, but also in docetaxel-resistant breast cancer cells. This effect is dependent on expression of ATP-binding cassette (ABC) transporter protein ABCB1, also known as P-glycoprotein (P-gp). Molecular modeling of ITZ bound to ABCB1, indicates that ITZ binds tightly to the inward-facing form of ABCB1 thereby inhibiting the transport of DTX. Our results suggest that ITZ may provide a feasible approach to re-sensitization of DTX resistant cells, which would add to the life-prolonging effects of DTX in men with metastatic castration-resistant prostate cancer.

Docetaxel and Doxorubicin Codelivery by Nanocarriers for Synergistic Treatment of Prostate Cancer

Combination chemotherapy has been proven to be an efficient strategy for the treatment of prostate cancer (PCA). However, the pharmacokinetic distinction between the relevant drugs is an insurmountable barrier to the realization of their synergistic use against cancer. To overcome the disadvantages of combination chemotherapy in the treatment of PCA, targeted nanoparticles (NPs), which can codeliver docetaxel (DOC) and doxorubicin (DOX) at optimal synergistic proportions, have been designed. In this study, the DOC and DOX codelivery nanoparticles (DDC NPs) were constructed by hyaluronic acid (HA) and cationic amphipathic starch (CSaSt) through a self-assembly process. Human PCA cell lines (PC-3, DU-145, and LNCap) and mouse models were then used for evaluation in vitro and in vivo, respectively, of delivery and antitumor effects. The DDC NPs were spherical with rough surfaces, and the size and zeta potential were 68.4 ± 7.1 nm and -22.8 ± 2.2 mV, respectively. The encapsulation efficiencies of DOC and DOX in the NPs were 96.1 ± 2.3% and 91.4 ± 3.7%, respectively, while the total drug loading was 9.1 ± 1.7%. Moreover, the ratio of DOC to DOX in the DDC NPs was approximately 1:400, which aligned with the optimal synergistic proportions of the drugs. The DDC NPs exhibited excellent loading capacities, performed sustained and enzymatic release, and were stable in PBS, medium, and serum. After investigations in vitro, the DDC NPs were as effective as the dual drug combination in terms of cytotoxicity, antimigration, and apoptosis. Internalization results indicated that the DDC NPs could effectively deliver and fully release the payloads into PCA cells, and the process was mediated by the ligand-receptor interaction of HA with the CD44 protein. Low toxicity in vivo was confirmed by acute toxicity and hemolytic assays. The distribution in vivo showed that DDC NPs could enhance the accumulation of drugs in tumors and decrease nonspecific accumulation in normal organs. More importantly, DDC NPs significantly promoted the curative effect of the DOC and DOX combination in the PCA cell xenograft mouse model, indicating that the drugs with NPs did indeed act synergistically. This study suggests that the DDC NPs possess noteworthy potential as prospects for the development of PCA clinical chemotherapy.

Schiff Base-Poloxamer P85 Combination Prevents Prostate Cancer Progression in C57/Bl6 Mice

BACKGROUND

Prostate cancer which is the second most common cause of death among men has a high incidence in recent years. Current therapeutic regimens should be improved to overcome drug resistance. At the metastatic stage, tumors become refractory to established chemotherapeutic treatments and cause serious problems at the clinics. Development of new drug molecules that are able to transport through the membrane easily and kill tumor cells rapidly is of great interest.

METHOD

In the current study, a novel Heterodinuclear copper(II)Mn(II) Schiff base complex combined with P85 was used for prostate cancer treatment in vivo. Tramp-C1 cells injected animals were subjected to chemotherapeutic formulation treatment and results were analyzed by toxicology analysis, tumor volume measurements, and histopathological analysis. 0.5 mg/kg Schiff base was selected and combined with 0.05% P85 according to the toxicology analysis showing the enzyme levels, blood parameters, and multiple organ toxicity.

RESULTS

Results demonstrated that Heterodinuclear copper(II)Mn(II) complex-P85 combination decreased tumor formation and tumor volume steadily over the course of experiments.

CONCLUSIONS

Overall, Heterodinuclear copper(II)Mn(II) complex-P85 exerted remarkable anti-cancer activity in vivo in C57/B16 mice. Prostate 76:1454-1463, 2016. © 2016 Wiley Periodicals, Inc.

Curcumin potentiates antitumor activity of 5-fluorouracil in a 3D alginate tumor microenvironment of colorectal cancer

BACKGROUND

To overcome the limitations of animal-based experiments, 3D culture models mimicking the tumor microenvironment in vivo are gaining attention. Herein, we investigated an alginate-based 3D scaffold for screening of 5-fluorouracil (5-FU) or/and curcumin on malignancy of colorectal cancer cells (CRC).

METHODS

The potentiation effects of curcumin on 5-FU against proliferation and metastasis of HCT116 cell and its corresponding isogenic 5-FU-chemoresistant cells (HCT116R) were examined in a 3D-alginate tumor model.

RESULTS

CRC cells encapsulated in alginate were able to proliferate in 3D-colonospheres in a vivo-like phenotype and invaded from alginate. During cultivation of cells in alginate, we could isolate 3 stages of cells, (1) alginate proliferating (2) invasive and (3) adherent cells. Tumor-promoting factors (CXCR4, MMP-9, NF-κB) were significantly increased in the proliferating and invasive compared to the adherent cells, however HCT116R cells overexpressed factors in comparison to the parental HCT116, suggesting an increase in malignancy behavior. In alginate, curcumin potentiated 5-FU-induced decreased capacity for proliferation, invasion and increased more sensitivity to 5-FU of HCT116R compared to the HCT116 cells. IC50 for HCT116 to 5-FU was 8nM, but co-treatment with 5 μM curcumin significantly reduced 5-FU concentrations in HCT116 and HCT116R cells (0.8nM, 0.1nM, respectively) and these effects were accompanied by down-regulation of NF-κB activation and NF-κB-regulated gene products.

CONCLUSIONS

Our results demonstrate that the alginate provides an excellent tumor microenvironment and indicate that curcumin potentiates and chemosensitizes HCT116R cells to 5-FU-based chemotherapy that may be useful for the treatment of CRC and to overcome drug resistance.

Acid ceramidase upregulation in prostate cancer: role in tumor development and implications for therapy

Bioactive sphingolipids, such as ceramide, sphingosine and sphingosine-1-phosphate are known bio-effector molecules which play important roles in various aspects of cancer biology including cell proliferation, growth arrest, apoptosis, metastasis, senescence and inflammation. Therefore, enzymes involved in ceramide metabolism are gaining recognition as being critical regulators of cancer cell growth and/or survival. We previously observed that the ceramide metabolizing enzyme, acid ceramidase (AC) is upregulated in tumor tissues. Studies have now concluded that this creates a dysfunctional ceramide pathway, which is responsible for tumor progression and resistance to chemotherapy and radiation. This suggests that development of small-molecule drugs that inhibit AC enzyme activity is a promising approach for improving standard cancer therapy and patient's clinical outcomes.

Targeting prostate cancer based on signal transduction and cell cycle pathways

Prostate cancer remains a leading cause of death in men despite increased capacity to diagnose at earlier stages. After prostate cancer has become hormone independent, which often occurs after hormonal ablation therapies, it is difficult to effectively treat. Prostate cancer may arise from mutations and dysregulation of various genes involved in regulation signal transduction (e.g., PTEN, Akt, etc.,) and the cell cycle (e.g., p53, p21(Cip1), p27(Kip1), Rb, etc.,). This review focuses on the aberrant interactions of signal transduction and cell cycle genes products and how they can contribute to prostate cancer and alter therapeutic effectiveness.

Pre-clinical evaluation of 1-nitroacridine derived chemotherapeutic agent that has preferential cytotoxic activity towards prostate cancer

Chemotherapy in prostate cancer (CaP) even as an adjunct has not been a success. In this communication, we report the pre-clinical efficacy of a nitroacridine derivative, C-1748 (9[2'-hydroxyethylamino]-4-methyl-1-nitroacridine) in CaP cell culture and human xenograft animal models. C-1748, a DNA intercalating agent has been derived from its precursor C-857 that was a potent anti-cancer drug, but failed clinical development due to "high" systemic toxicities. Chemical modifications such as the introduction of a "methyl" group imparted novel properties, the most interesting of which is the difference in the IC(50) values between LnCaP (22.5 nM), a CaP cell line and HL-60, a leukemia cell line (>100 nM). Using gammaH2AX as an intervention marker of DNA double strand breaks, we concluded that C-1748 is more efficacious in CaP cells than in HL-60 cells. In hormone dependent cells, the androgen receptor (AR) was identified as an additional target of C-1748. In xenograft studies, administration of C-1748 intra-peritoneally inhibited tumor growth by 80-90% with minimal toxicity. These studies identify C-1748 as a novel acridine drug that has a high therapeutic index and low cytotoxicity on myelocytic cells with potential for clinical development.

Supra-additive antitumor effect of sunitinib malate (SU11248, Sutent®) combined with docetaxel. A new therapeutic perspective in hormone refractory prostate cancer

PURPOSE

Physiological and molecular findings indicate over-expression of HER proteins and dysregulation of neo-angiogenesis during progression of advanced prostate cancer. The aim of this study was to test a novel rational therapeutic approach by combining docetaxel with an EGFR-targeting agent (cetuximab) and with an anti-angiogenic agent (sunitinib, SUTENT).

METHODS

Mice bearing well-established PC3 prostate tumors (mean tumor volume/treatment group approximately 250 mm(3)) were treated every week with vehicle alone (controls), sunitinib (40 mg/kg/day, 5 days/week for 3 weeks, 0.2 ml p.o.), cetuximab (0.2 mg/kg/day, 5 days/week for 3 weeks, 0.2 ml i.p.) and docetaxel (10 mg/kg, 1 day/week for 3 weeks, 0.2 ml i.p.).

RESULTS

Each drug, administered as a single-agent, demonstrated comparable and moderate effects on tumor growth with approximately 50 % inhibition at the end of the 3-week dosing schedule. Computed combination ratio (CR) values for tumor growth determined on days 61, 68 and 75 after cell implantation indicated supra-additive effects for the sunitinib-docetaxel (1.53, 1.15 and 1.47, respectively) and sunitinib-cetuximab combinations (1.2, 1.32 and 1.14, respectively), and suggested additive effects only for the sunitinib-cetuximab-docetaxel combination (CR = 1). The effects on tumor growth were accompanied by a parallel diminution in tumor cell proliferation (Ki 67) and tumor vascularization (von Willebrandt factor). There were significantly higher pro-apoptotic effects (caspase-3 cleavage) observed for the sunitinib-docetaxel and sunitinib-docetaxel-cetuximab as compared to the other conditions.

CONCLUSION

The supra-additive anti-tumor effect observed with the sunitinib-docetaxel combination might support innovative strategies in the management of advanced prostate cancer.

The Case for Adjuvant Therapy for Prostate Cancer

PURPOSE

The rationale for adjuvant therapy for prostate cancer was reviewed.

MATERIALS AND METHODS

A selective review of the successful experience with adjuvant therapy in other epithelial neoplasms is presented along with discussion of the increasing success of chemotherapy to improve outcomes in advanced prostate cancer.

RESULTS

Adjuvant therapy could be effective for prostate cancer if men with high risk features, such as Gleason score 8 or greater, prostate specific antigen more than 20 ng/ml, positive surgical margins with Gleason score 7 or greater, seminal vesicle invasion or positive lymph nodes, were selectively given additional therapy after primary surgery or radiation. These individuals are easily identified by routine pathological findings and precise recurrence risks can be calculated with available nomograms. For primary radiotherapy hormonal adjuvant treatment has now been shown to produce improved disease-free and overall survival. Adjuvant radiotherapy following prostatectomy decreases biochemical relapse and local disease recurrence. Adjuvant hormonal therapy after prostatectomy is also beneficial in select patients. Adjuvant chemotherapy now has a powerful rationale since it has been shown to improve survival in other common epithelial cancers, such as those of the breast, colon and lung. Newer agents produce significant response rates in patients with advanced metastatic prostate cancer, even prolonging overall survival.

CONCLUSIONS

Only through dedication to a multimodality approach with all disciplines, including surgical urology, radiation therapy and medical oncology, will the promise of adjuvant therapy for prostate cancer be fully realized.

Synergistic cytotoxic interaction in hormone-refractory prostate cancer with the triple combination docetaxel–erlotinib and 5-fluoro-5′-deoxyuridine

The current reference treatment of hormone-refractory prostate cancer consists mainly of chemotherapy with docetaxel. To improve the management of advanced prostate cancer, one should examine the benefits of adding other agents to docetaxel. We examined the growth inhibitory effects of a triple combination, including the anti-epidermal growth factor receptor drug erlotinib, docetaxel and 5-fluoro-5'-deoxyuridine (the main intermediary metabolite of capecitabine), on the human prostate cancer cell lines PC3 and DU145, which are both devoid of androgen receptors. Marked synergistic cytotoxic effects were observed with the application of the double combination of erlotinib-5-fluoro-5'-deoxyuridine for both cell lines and to a lesser magnitude with the triple combination. For PC3 cells, all conditions resulted in synergistic interactions. The combination between erlotinib and docetaxel resulted in an approximately 50% reduction in thymidylate synthase activity (the molecular target of 5-fluorodeoxyuridine monophosphate, the active capecitabine anabolite) with an higher impact observed with DU145 cells than with PC3 cells. Neither erlotinib nor docetaxel alone displayed marked effects on thymidine phosphorylase activity (the enzyme that governs at the cellular level the final and crucial step in the activation cascade of capecitabine), in contrast to their combination that resulted in a strong increase in thymidine phosphorylase activity in PC3 cells. These data may serve as a rational basis for setting up clinical trials in advanced prostate cancer combining epidermal growth factor receptor-targeting agents like erlotinib together with docetaxel and capecitabine.

Evaluation of Calvert's Formula for Dosage Adjustment of Carboplatin in Japanese Patients with Hormone Refractory Prostate Cancer

For hormone refractory prostate carcinoma, a combination therapy of paclitaxel and carboplatin is used to expect life extension. We investigated the pharmacokinetics of carboplatin in Japanese prostate cancer patients (n=10, 55-72 years), and evaluated the usefulness of Calvert's formula in the individualized dosing adjustment. They were intravenously administered carboplatin (area under the free plasma concentration versus time curve (AUC)=5 mg.min/ml), following the intravenous administration of paclitaxel (175 mg/m(2)). The dosage of carboplatin for each patient was determined with Calvert's formula using individual creatinine clearance values. Plasma concentration of total platinum was measured sequentially and the pharmacokinetic parameters of carboplatin were determined in each patient. Plasma concentration of total carboplatin after intravenous infusion well fitted the two-compartment model. Carboplatin clearance was 62.0+/-12.7 ml/min (mean+/-S.D.), and linearly related to the individual creatinine clearance (r(2)=0.64, p<0.01). The actual AUC for total carboplatin was 8.20+/-1.11 mg.min/ml, and its inter-individual variability was decreased to 65% of that in carboplatin clearance, indicating the effectiveness of Calvert's formula for dosage adjustment of carboplatin. Leucopenia of grade 4 according to the National Cancer Institute's Common Toxicity Criteria was found in one patient, but no patient demonstrated thrombocytopenia. In conclusion, determining carboplatin dosage based on Calvert's formula decreased the inter-individual variability in the actual AUC compared with that in the carboplatin clearance, and a target AUC of 5 mg.min/ml of carboplatin was comparatively safe for Japanese patients with prostate cancer.

Recent advances on multiple tumorigenic cascades involved in prostatic cancer progression and targeting therapies

Recent advances on differently-expressed gene products and their functions during the progression from localized androgen-dependent states into androgen-independent and metastatic forms of prostate cancer are reported. The expression levels of numerous oncogenes and tumor suppressor genes in distinct prostatic cancer epithelial cell lines and tissues relative to normal prostate cells are described. This is carried out to identify the signaling elements that are altered during the initiation, progression and metastatic process of prostate cancer. Additional information on the interactions between certain deregulated signaling pathways such as androgen receptor (AR), estrogen receptors, epidermal growth factor receptor (EGFR), hedgehog and Wnt/beta-catenin cascades in controlling the proliferation, survival and invasion of tumor prostate epithelial cells during the disease progression is described. The emphasis is on the critical functions of the AR and EGF-EGFR systems at all stages during prostate carcinogenesis. Of therapeutic interest, new strategies for the diagnosis and treatment of localized and metastatic forms of prostate cancer by targeting multiple tumorigenic signaling elements are also reported.