Joseph Bucci

Acquisition of epithelial-mesenchymal transition and cancer stem cell phenotypes is associated with activation of the PI3K/Akt/mTOR pathway in prostate cancer radioresistance.

Radioresistance is a major challenge in prostate cancer (CaP) radiotherapy (RT). In this study, we investigated the role and association of epithelial–mesenchymal transition (EMT), cancer stem cells (CSCs) and the PI3K/Akt/mTOR signaling pathway in CaP radioresistance. We developed three novel CaP radioresistant (RR) cell lines (PC-3RR, DU145RR and LNCaPRR) by radiation treatment and confirmed their radioresistance using a clonogenic survival assay. Compared with untreated CaP-control cells, the CaP-RR cells had increased colony formation, invasion ability and spheroid formation capability (P<0.05). In addition, enhanced EMT/CSC phenotypes and activation of the checkpoint proteins (Chk1 and Chk2) and the PI3K/Akt/mTOR signaling pathway proteins were also found in CaP-RR cells using immunofluorescence, western blotting and quantitative real-time PCR (qRT-PCR). Furthermore, combination of a dual PI3K/mTOR inhibitor (BEZ235) with RT effectively increased radiosensitivity and induced more apoptosis in CaP-RR cells, concomitantly correlated with the reduced expression of EMT/CSC markers and the PI3K/Akt/mTOR signaling pathway proteins compared with RT alone. Our findings indicate that CaP radioresistance is associated with EMT and enhanced CSC phenotypes via activation of the PI3K/Akt/mTOR signaling pathway, and that the combination of BEZ235 with RT is a promising modality to overcome radioresistance in the treatment of CaP. This combination approach warrants future in vivo animal study and clinical trials.

PREDICTIVE FACTORS OF URINARY RETENTION FOLLOWING PROSTATE BRACHYTHERAPY

PURPOSEnTo evaluate the incidence and duration of urinary retention requiring catheterization and the factors predictive for these end points.nnnMETHODS AND MATERIALSnTwo hundred eighty-two patients treated with prostate brachytherapy alone were evaluated. Clinical and treatment-related factors examined included: age, baseline International Prostate Symptom Score (IPSS), presence of comorbidity, planning ultrasound target volume (PUTV), postimplant prostate CT scan volume, the CT:PUTV ratio, number of seeds inserted, number of needles used, use of neoadjuvant hormones, procedural physician, clinical stage, Gleason score, and pretreatment PSA. Dosimetric quality indicators were also examined.nnnRESULTSnUrinary obstruction after prostate brachytherapy developed in 43 (15%) patients. The median duration of catheter insertion was 21 days (mean 49, range 1-365). Univariate analysis demonstrated that presence of diabetes, preimplant volume, postimplant volume, CT:PUTV ratio, number of needles, and dosimetric parameters were predictive for catheterization. However, in multivariate analysis, only the baseline IPSS, CT:PUTV ratio, and presence of diabetes were significant independent predictive factors for catheterization.nnnCONCLUSIONnBaseline IPSS was the most important predictive factor for postimplantation catheterization. The extent of postimplant edema, as reflected by the CT:PUTV ratio, predicted for need and duration of catheterization. The presence of diabetes was predictive for catheterization, but may relate to the absence of prophylactic steroids, and therefore requires further evaluation.

PI3K/Akt/mTOR pathway inhibitors enhance radiosensitivity in radioresistant prostate cancer cells through inducing apoptosis, reducing autophagy, suppressing NHEJ and HR repair pathways.

The PI3K/Akt/mTOR pathway has a central role in cancer metastasis and radiotherapy. To develop effective therapeutics to improve radiosensitivity, understanding the possible pathways of radioresistance involved and the effects of a combination of the PI3K/Akt/mTOR inhibitors with radiotherapy on prostate cancer (CaP) radioresistant cells is needed. We found that compared with parent CaP cells, CaP-radioresistant cells demonstrated G0/G1 and S phase arrest, activation of cell cycle check point, autophagy and DNA repair pathway proteins, and inactivation of apoptotic proteins. We also demonstrated that compared with combination of single PI3K or mTOR inhibitors (BKM120 or Rapamycin) and radiation, low-dose of dual PI3K/mTOR inhibitors (BEZ235 or PI103) combined with radiation greatly improved treatment efficacy by repressing colony formation, inducing more apoptosis, leading to the arrest of the G2/M phase, increased double-strand break levels and less inactivation of cell cycle check point, autophagy and non-homologous end joining (NHEJ)/homologous recombination (HR) repair pathway proteins in CaP-radioresistant cells. This study describes the possible pathways associated with CaP radioresistance and demonstrates the putative mechanisms of the radiosensitization effect in CaP-resistant cells in the combination treatment. The findings from this study suggest that the combination of dual PI3K/Akt/mTOR inhibitors (BEZ235 or PI103) with radiotherapy is a promising modality for the treatment of CaP to overcome radioresistance.

Epithelial cell adhesion molecule (EpCAM) is associated with prostate cancer metastasis and chemo/radioresistance via the PI3K/Akt/mTOR signaling pathway

Prostate cancer (CaP) is the second leading malignancy in men. The role of epithelial cell adhesion molecule (EpCAM), also known as CD326, in CaP progression and therapeutic resistance is still uncertain. Here, we aimed to investigate the roles of EpCAM in CaP metastasis and chemo/radioresistance. Expression of EpCAM in CaP cell lines and human CaP tissues was assessed using immunofluorescence and immunohistochemistry, respectively. EpCAM was knocked down (KD) in PC-3, DU145 and LNCaP-C4-2B cells using small interfering RNA (siRNA), and KD results were confirmed by confocal microscope, Western blotting and quantitative real time polymerase chain reaction (qRT-PCR). Cell growth was evaluated by proliferation and colony formation assays. The invasive potential was assessed using a matrigel chamber assay. Tumorigenesis potential was measured by a sphere formation assay. Chemo-/radiosensitivity were measured using a colony formation assay. Over-expression of EpCAM was found in primary CaP tissues and lymph node metastases including cancer cells and surrounding stromal cells. KD of EpCAM suppressed CaP proliferation and invasive ability, reduced sphere formation, enhanced chemo-/radiosensitivity, and down-regulated E-cadherin, p-Akt, p-mTOR, p-4EBP1 and p-S6K expression in CaP cells. Our findings suggest that EpCAM plays an important role in CaP proliferation, invasion, metastasis and chemo-/radioresistance associated with the activation of the PI3K/Akt/mTOR signaling pathway and is a novel therapeutic target to sensitize CaP cells to chemo-/radiotherapy.

CD44 variant 6 is associated with prostate cancer metastasis and chemo‐/radioresistance

Prostate cancer (CaP) is the second leading malignancy in older men in Western countries. The role of CD44 variant 6 (CD44v6) in CaP progression and therapeutic resistance is still uncertain. Here, we investigated the roles of CD44v6 in CaP metastasis and chemo/radioresistance. Expression of CD44v6 in metastatic CaP cell lines, human primary CaP tissues and lymph node metastases was assessed using immunofluorescence and immunohistochemistry, respectively.

Emerging roles of radioresistance in prostate cancer metastasis and radiation therapy

Radiation therapy (RT) continues to be one of the most popular treatment options for localized prostate cancer (CaP). Local CaP recurrence after RT is a pattern of treatment failure attributable to radioresistance of cancer cells. One major obstacle to RT is that there is a limit to the amount of radiation that can be safely delivered to the target organ. Recent results indicate that phosphoinositide 3-kinase (PI3K)/Akt/phosphatase and tensin homolog (PTEN)/mammalian target of rapamycin (mTOR) signaling pathway, autophagy, epithelial–mesenchymal transition (EMT) and cancer stem cells (CSCs) are involved in CaP metastasis and radioresistance. Emerging evidence also suggests that combining a radiosensitizer with RT increases the efficacy of CaP treatment. Understanding the mechanisms of radioresistance will help to overcome recurrence after RT in CaP patients and prevent metastasis. In this review, we discuss the novel findings of PI3K/Akt/PTEN/mTOR signaling pathway, autophagy, EMT and CSCs in the regulation of CaP metastasis and radioresistance, and focus on combination of radiosensitizers with RT in the treatment of CaP in preclinical studies to explore novel approaches for future clinical trials.

Targeting PI3K/Akt/mTOR signaling pathway in the treatment of prostate cancer radioresistance

The phosphatidylinositol-3-kinase/Akt and the mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is one of the most frequently activated signaling pathways in prostate cancer (CaP) and other cancers, and responsible for the survival, metastasis and therapeutic resistance. Recent advances in radiation therapy indicate that activation of this pathway is closely associated with cancer radioresistance, which is a major challenge for the current CaP radiation treatment. Therefore, targeting this pathway by inhibitors to enhance radiosensitivity has great potential for clinical benefits of CaP patients. In this review, we summarize the recent findings in the PI3K/Akt/mTOR pathway in CaP radiotherapy research and discuss the potential use of the PI3K/Akt/mTOR pathway inhibitors as radiosensitizers in the treatment of CaP radioresistance in preclinical studies to explore novel approaches for future clinical trials.

Cancer stem cells and signaling pathways in radioresistance

Radiation therapy (RT) is one of the most important strategies in cancer treatment. Radioresistance (the failure to RT) results in locoregional recurrence and metastasis. Therefore, it is critically important to investigate the mechanisms leading to cancer radioresistance to overcome this problem and increase patients survival. Currently, the majority of the radioresistance-associated researches have focused on preclinical studies. Although the exact mechanisms of cancer radioresistance have not been fully uncovered, accumulating evidence supports that cancer stem cells (CSCs) and different signaling pathways play important roles in regulating radiation response and radioresistance. Therefore, targeting CSCs or signaling pathway proteins may hold promise for developing novel combination modalities and overcoming radioresistance. The present review focuses on the key evidence of CSC markers and several important signaling pathways in cancer radioresistance and explores innovative approaches for future radiation treatment.

Iodine-125 prostate seed brachytherapy in renal transplant recipients: an analysis of oncological outcomes and toxicity profile.

Purpose Prostate cancer is among the most common non-cutaneous neoplasms affecting renal transplant recipients (RTRs). Available treatments including radical prostatectomy and external beam radiotherapy carry a risk of damage to the transplanted kidney, ureters, or bladder. We assessed the safety and efficacy of Iodine-125 (125I) prostate seed brachytherapy as an alternative to surgery and radiotherapy in these individuals. Material and methods We retrospectively reviewed our brachytherapy database to identify patients with a prior history of renal transplantation, who had undergone seed implantation for localized prostate cancer. Long term PSA control and treatment related toxicity, including graft dysfunction, urinary, rectal, and sexual complications, were assessed and compared with published outcomes for surgery and external beam radiotherapy. Results Of 1054 patients treated with permanent seed implantation from 2002-2012, we identified four who had a prior history of renal transplantation. Mean time from renal transplantation to prostate cancer diagnosis was 13 years. Mean follow-up after seed implantation was 44 months (range 12-60 months). All four patients remain free of PSA progression. No peri-operative complications were experienced following seed implantation, and all four patients continued to have normal graft function. Long term urinary and rectal function scores were comparable to reported outcomes for seed brachytherapy in the non-transplant population. Conclusions 125I prostate seed brachytherapy is associated with high rates of biochemical control and minimal toxicity to the renal graft in RTRs. This treatment should be considered as an alternative to surgery in managing RTRs with localized prostate cancer.

Proteomics discovery of radioresistant cancer biomarkers for radiotherapy

Radiotherapy (RT) is one of the most important strategies in cancer treatment. Radioresistance is a major challenge to RT and results in locoregional recurrence and metastasis. Thus, there is a great interest in investigating biomarkers to distinguish radiosensitive from radioresistant (RR) cancer patients. The development of proteomic techniques has sparked new searches for novel proteins for cancer biomarker discovery. Modern proteomic techniques allow for a high-throughput analysis of samples with the visualization and quantification of thousands of potential protein and peptide markers. The discovery of RR biomarkers can provide a clue for predicting RT response and discover therapeutic targets for developing personalised medicine of individual patients. In the past decade, emerging advanced proteomic technologies have been performed to identify radiation-related biomarkers in human cancers. This review discusses the mass spectrometry (MS)-based proteomic techniques in RR cancer biomarker discovery, summarises RR biomarkers identified in cancers from proteomics-based findings and explores potential values of RR biomarkers for future clinical trials.