Improving and predicting radiosensitivity in muscle invasive bladder cancer

Radiation Treatment Timing and Dose Delivery: Effects on Bladder Cancer Cells in 3D in Vitro Culture

While radical cystectomy remains the primary treatment of choice for bladder cancer, increased evidence supports the use of bladder-preservation strategies based on adjuvant radiotherapy. This highlights the need for a better understanding of bladder cancer radiosensitivity to different types of treatment deliveries. The purpose of this study is to analyze the effect of treatment time, dose and fractionation on the number and sizes of grown three-dimensional (3D) bladder cancer spheres, and to assess the capacity of the linear-quadratic model in describing the response of cells cultured in 3D. 3D MatrigelTM-based cultures were employed to enrich for cancer stem cells (CSCs) from three human bladder cancer cell lines, RT4, T24 and UM-UC-3. Three single dose radiation treatments were performed at different time points after plating, and sphere number and sizes were assessed. Anti-CD44 immunofluorescence, clonogenic assay and anti-γH2AX staining were also performed to analyze the cell lines’ radiosensitivity. The radiosensitivity of spheres was dependent on the treatment timing after plating. Current linear quadratic dose fractionation models were shown to over-estimate radiosensitivity in 3D models. Our results showed the importance of treatment timing on the radio-response of bladder cancer spheres. We also demonstrated that bladder cancer spheres are more resistant to dose-fractionation than the estimation from the theoretical linear-quadratic model.

Radiosensitizing Effect of Curcumin on Human Bladder Cancer Cell Lines: Impact on DNA Repair Mechanisms

Chemo-radiotherapy is one of the promising approaches to treat bladder cancer, but its effectiveness is limited to sensitive patients. Polyphenol curcumin has shown anticancer and radiosensitizing potentials, but the mechanism is not fully understood. Here, the In Vitro response of UM-UC5 and UM-UC6 bladder cell lines to curcumin and radiation treatments was evaluated. The effect of curcumin on the DNA double-strand breaks repair system after treatment with ionizing radiation (2 Gy) was determined by immunofluorescence. Cell viability, proliferation, and survival were performed using trypan blue, MTT, clonogenic, and sphere-forming assays. The migratory ability of both cells was assessed by wound healing. We showed that curcumin treatment increased the radiosensitivity by modifying the DNA double-strand breaks repair kinetics of the most radioresistant cells UM-UC6 without affecting the radiosensitive UM-UC5. Moreover, UM-UC6 cell survival and proliferation was significantly decreased after the combination of curcumin with radiation. Bladder cell migration was also inhibited considerably. Curcumin was also shown to reduce the number and the volume of bladder cancer spheres of both cell lines. This study revealed that curcumin was able to radiosensitize resistant bladder cell line without affecting the sensitive one with minimal side effects through enhancing DNA damage signaling and repair pathway.

Evaluation of the Major Steps in the Conventional Protocol for the Alkaline Comet Assay

Single cell gel electrophoresis, also known as the comet assay, has become a widespread DNA damage assessment tool due to its sensitivity, adaptability, low cost, ease of use, and reliability. Despite these benefits, this assay has shortcomings, such as long assay running time, the manipulation of multiple slides, individually, through numerous process steps, the challenge of working in a darkened environment, and reportedly considerable inter- and intra-laboratory variation. All researchers typically perform the comet assay based upon a common core approach; however, it appears that some steps in this core have little proven basis, and may exist, partly, out of convenience, or dogma. The aim of this study was to critically re-evaluate key steps in the comet assay, using our laboratory's protocol as a model, firstly to understand the scientific basis for why certain steps in the protocol are performed in a particular manner, and secondly to simplify the assay, and decrease the cost and run time. Here, the shelf life of the lysis and neutralization buffers, the effect of temperature and incubation period during the lysis step, the necessity for drying the slides between the electrophoresis and staining step, and the need to perform the sample workup and electrophoresis steps under subdued light were all evaluated.

Assessing Radiosensitivity of Bladder Cancer in vitro: A 2D vs. 3D Approach

Background: Bladder cancer is the fourth most commonly diagnosed cancer among males worldwide. Current treatment strategies established for bladder cancer mainly consist of cystectomy yet advances in radiation therapy have pointed to the value of organ-preserving strategies in preserving patients' quality of life. Aim: To study and compare the radiosensitivity in two-dimension (2D) and physiologically-relevant three-dimension (3D) in vitro culture of three human bladder cancer cell lines, RT4, T24, and UM-UC-3. Materials and Methods: Clonogenic assay was performed to assess cells' radiosensitivity in 2D. Employing the 3D Matrigel™-based cultures to enrich for cancer stem cells (CSCs) allowed us to assess the survival of this subpopulation of cells via evaluating the number, i.e., sphere forming unit (SFU), and the sizes of cultured spheres, formed from cells exposed to different radiation doses compared to non-irradiated cells. Results: Irradiating cells with increasing radiation doses revealed highest survival rates with RT4 cells in 2D, followed by T24 and UM-UC-3. In 3D, however, UM-UC-3 cells were shown to be the most radio-resistant as evidenced by the number of spheres formed, yet they displayed the least efficient volume reduction/regression (VR), whilst the volume decreased significantly for both RT4 and T24 cells. Sphere VR and sphere ratio (SR) values were then plotted against each other demonstrating a linear correlation between volume and number with RT4 and UM-UC-3 cell lines, but not T24. Lastly, multiple regression model was employed to evaluate the possibility of obtaining a function combining both 3D parameters, SR and VR, with the surviving fraction (SF) in 2D, and showed a linear regression for T24 cells only, with a correlation coefficient of 0.97 for the combined parameters. Conclusion: We were able to radiobiologically characterize 3 human bladder cancer cell lines showing differential effects of radiation between 2D and 3D culture systems, paving the way for achieving better assessment of radiosensitivity of bladder cancer in vitro.

A review of plan library approaches in adaptive radiotherapy of bladder cancer

BACKGROUND

Large variations in the shape and size of the bladder volume are commonly observed in bladder cancer radiotherapy (RT). The clinical target volume (CTV) is therefore frequently inadequately treated and large isotropic margins are inappropriate in terms of dose to organs at risk (OAR); thereby making adaptive radiotherapy (ART) attractive for this tumour site. There are various methods of ART delivery, however, for bladder cancer, plan libraries are frequently used.

MATERIAL AND METHODS

A review of published studies on plan libraries for bladder cancer using four databases (Pubmed, Science Direct, Embase and Cochrane Library) was conducted. The endpoints selected were accuracy and feasibility of initiation of a plan library strategy into a RT department.

RESULTS

Twenty-four articles were included in this review. The majority of studies reported improvement in accuracy with 10 studies showing an improvement in planning target volume (PTV) and CTV coverage with plan libraries, some by up to 24%. Seventeen studies showed a dose reduction to OARs, particularly the small bowel V45Gy, V40Gy, V30Gy and V10Gy, and the rectal V30Gy. However, the occurrence of no suitable plan was reported in six studies, with three studies showing no significant difference between adaptive and non-adaptive strategies in terms of target coverage. In addition, inter-observer variability in plan selection appears to remain problematic. The additional resources, education and technology required for the initiation of plan library selection for bladder cancer may hinder its routine clinical implementation, with eight studies illustrating increased treatment time required.

CONCLUSIONS

While there is a growing body of evidence in support of plan libraries for bladder RT, many studies differed in their delivery approach. The advent of the clinical use of the MRI-linear accelerator will provide RT departments with the opportunity to consider daily online adaption for bladder cancer as an alternate to plan library approaches.

MRE11 expression is predictive of cause-specific survival following radical radiotherapy for muscle-invasive bladder cancer

Radical radiotherapy and surgery achieve similar cure rates in muscle-invasive bladder cancer, but the choice of which treatment would be most beneficial cannot currently be predicted for individual patients. The primary aim of this study was to assess whether expression of any of a panel of DNA damage signaling proteins in tumor samples taken before irradiation could be used as a predictive marker of radiotherapy response, or rather was prognostic. Protein expression of MRE11, RAD50, NBS1, ATM, and H2AX was studied by immunohistochemistry in pretreatment tumor specimens from two cohorts of bladder cancer patients (validation cohort prospectively acquired) treated with radical radiotherapy and one cohort of cystectomy patients. In the radiotherapy test cohort (n = 86), low tumor MRE11 expression was associated with worse cancer-specific survival compared with high expression [43.1% versus 68.7% 3-year cause-specific survival (CSS), P = 0.012] by Kaplan-Meier analysis. This was confirmed in the radiotherapy validation cohort (n = 93; 43.0% versus 71.2%, P = 0.020). However, in the cystectomy cohort (n = 88), MRE11 expression was not associated with cancer-specific survival, commensurate with MRE11 being a predictive marker. High MRE11 expression in the combined radiotherapy cohort had a significantly better cancer-specific survival compared with the high-expression cystectomy cohort (69.9% versus 53.8% 3-year CSS, P = 0.021). In this validated immunohistochemistry study, MRE11 protein expression was shown and confirmed as a predictive factor associated with survival following bladder cancer radiotherapy, justifying its inclusion in subsequent trial designs. MRE11 expression may ultimately allow patient selection for radiotherapy or cystectomy, thus improving overall cure rates.

Challenges in the treatment of bladder cancer

Seventy to eighty percent of patients with newly-diagnosed bladder cancer will present with superficial tumors (Ta, Tis or T(1)). There is, however, a continuum between superficial and muscle-invasive cancer, with the advanced cases usually associated with less-differentiated histology and aneuploidy. Common sites of metastasis include regional lymph nodes, bone, lung, skin and liver. From the low cure rates achieved with radical cystectomy, there is strong evidence that bladder cancer, from the outset, is a systemic disease. The limitations of local treatment are well-documented: a local control rate of 30% with radiation treatment, and 50-70% with radical cystectomy; and no improvement in surgical cure was seen with the use of preoperative radiation. Over the past 30 years, since the initial reports of the effectiveness of cisplatin in the treatment of advanced bladder cancer, there has been a steady flow of chemotherapeutic agents, singly and in combination, shown to be effective in the treatment of this tumor. While response rates and CR rates have increased with the use of combination chemotherapy, this has not translated into survival in advanced disease of greater than 16 months. While the search for more effective agents and combinations continues, attention has also been given to the roles of neoadjuvant and adjuvant chemotherapy in an effort to improve the cure rate achieved with surgery alone. Although radical cystectomy, with continent diversion or neobladder construction in selected cases remains the standard of care in the United States for patients with muscle-invasive bladder cancer, several groups have explored therapeutic strategies that aim at bladder preservation. Early approaches with the goal of bladder preservation consisted of radiation treatment as monotherapy (largely abandoned) or aggressive TURBT for smaller tumors. Over the past 20 years, the Massachusetts General Hospital (MGH) and the Radiation Therapy Oncology Group (RTOG) have studied patients with muscle-invading bladder cancer utilizing tri-modality treatment: a visibly complete transurethral resection followed by radiation with concurrent radiosensitizing chemotherapy and, subsequently, adjuvant chemotherapy. Thus, chemotherapy has been used in two phases of treatment (1) as radiosensitizers, given concurrently with radiation treatment and (2) as adjuvant treatment, recognizing that survival will only be improved by the successful treatment of micrometastases. Based on preliminary information from reports of the effectiveness of gemcitabine/cisplatin in advanced disease, that combination was chosen as the adjuvant regimen in one of our earlier protocols, recently completed and reported. Our current protocol utilizes the Bellmunt regimen as our adjuvant program with the highest RR in advanced disease. This study is ongoing, with early reports of tolerance of the three-drug regimen encouraging. The treatment options for muscularis propria-invasive bladder tumors can broadly be divided into those that spare the bladder and those that involve removing it. In the United States, radical cystectomy with pelvic lymph node dissection is the standard method used to treat patients with this tumor.

Muscle-invasive urothelial cell carcinoma of the human bladder: multidirectional differentiation and ability to metastasize

Few published studies have addressed the correlation between multidirectional differentiation in muscle-invasive bladder cancer and its ability to metastasize. We demonstrated that histologic differentiation within a single tumor affects lymph node metastasis. We examined cystectomy specimens from 93 bladder tumors and 1085 lymph nodes. In this study, urothelial cell carcinomas (UCCs) with divergent differentiation, excluding pure divergent patterns such as squamous cell carcinoma and adenocarcinoma that tend toward a distinct biologic behavior, were subjected to histopathologic estimation. The positive lymph node ratio increased with the nonconventional differentiation number (NDN) within a tumor from 8.7% for an NDN of 0 (pure conventional UCCs) to 35.5% for an NDN of 2 or higher (mixed conventional and nonconventional [NC] UCCs showing >2 NC patterns). The positive lymph node number (PLN) was more than twice as high for an NDN of 3 or higher as compared with cases with an NDN of 0. Lymph node positivity (LP) was associated with the presence of micropapillary, lymphoma-like, plasmacytoid, giant cell, or clear cell-type tumors, and increasing PLN was associated with the presence of glandular, nested, lymphoma-like, plasmacytoid, or undifferentiated types in the primary tumor. By multivariate analysis, NDN status was determined to be an independent predictor of PLN (P = .032). Tumor stage had impact on LP (P = .002); however, in cases with a PLN of 4 or higher, the NDN became the only predictor of further dissemination (P = .016). No significant tumor grade impact on LP or PLN was found. Our results indicate that NC differentiation in the primary tumor is a good predictor of lymph node dissemination.

Usefulness of histologic homogeneity estimation of muscle-invasive urinary bladder cancer in an individual prognosis: a mapping study

OBJECTIVES

To examine the histologic homogeneity of muscle-invasive urothelial cell carcinoma of the bladder, with conventional and nonconventional (eg, squamous, glandular, or variants) differentiation, to assess its influence on prognosis.

METHODS

With organ mapping, we investigated 38 cystectomy specimens. Each entire bladder was cut into 88 slices according to an identical topographic scheme. From all the bladder slices, 1231 slices that included tumor were chosen for the histologic study. We examined the diagnostic significance, extension, and number of histologic differentiation types.

RESULTS

The extension of nonconventional differentiation, with any proportion of histologic type, had an unfavorable impact on survival time. The number of nonconventional differentiation types increases in the presence of a sarcomatoid, an undifferentiated, a nested, or a micropapillary pattern. The increased number of differentiation types had an unfavorable influence on survival time. Patients with a more than 80% classic urothelial cell carcinoma pattern had a favorable prognosis, which increased further with increasing percentages of this differentiation type.

CONCLUSIONS

Muscle-invasive urinary bladder cancers are not a homogenous group of tumors. Our results suggest that a precise assessment of the extension and number of histological differentiation types may be an individual prognostic factor. Conventional differentiation with at least 80% extension seems to be prognostically favorable. Nonconventional differentiation, especially with greater extension and a greater number of types, could imply a worse prognosis.

Expression and regulation of tumor suppressor gene maspin in human bladder cancer

Maspin is a member of serine protease inhibitor family with tumor suppressing activity for breast and prostate cancers, acting at the level of tumor invasion and metastasis. However, there have been no published data regarding the role of maspin in human bladder cancer. We evaluated maspin expression in 65 series of bladder cancer samples (22 transurethral resection (TUR) and 43 radical cystectomy) and studied the regulatory mechanism of maspin gene activation in bladder cancer cells. Maspin expression was immunohistochemically detected in four (18.2%) patients with TUR and 22 (51.2%) patients with radical cystectomy whereas no expression was observed in normal transitional cells located at tumor-free area in bladder. The maspin expression was significantly correlated with the development of muscle invasive bladder cancer (P=0.00008). Using a luciferase reporter system, maspin promoter activity was induced in the maspin-positive bladder cancer cell lines as well as maspin-negative RT4 cells. Furthermore, treatment with the DNA methyltransferase inhibitor, 5-aza-2' deoxycytidine, and histone deacetylase inhibitor, trichostatin A, led to re-expression of maspin in RT4 cells. Our results indicate that maspin may contribute to bladder cancer development and that DNA methylation and histone deacetylation may be important for regulating maspin gene activation in bladder cancer cells.