Does COVID-19 cause or worsen LUT dysfunction, what are the mechanisms and possible treatments? ICI-RS 2023.

INTRODUCTION: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) and produced a worldwide pandemic in 2020. There have been 770,875,433 confirmed cases and 6,959,316 attributed deaths worldwide until September 19, 2023. The virus can also affect the lower urinary tract (LUT) leading to bladder inflammation and producing lower urinary tract symptoms (LUTS) in both the acute and chronic phases of disease. METHODS: At the 2023 meeting of the International Consultation on Incontinence-Research Society (ICI-RS), the literature relating to COVID-19 and bladder dysfunction was reviewed. The LUTS reported, as well as the pathophysiology of these bladder symptoms, were the subject of considerable discussion. A number of different topics were discussed including lower LUTS reported in COVID-19, how SARS-CoV-2 may infect and affect the urinary tract, and proposed mechanisms for how viral infection result in new, worsened, and in some persisting LUTS. CONCLUSIONS: The workshop discussed the interaction between the virus and the immune system, covering current evidence supporting theories underlying the causes of acute and chronic LUTS related to COVID-19 infection. Research questions for further investigation were suggested and identified.

Can we predict whether a man with acute or chronic urinary retention will void after bladder outflow resistance reduction surgery? ICI-RS 2023.

AIMS: To address the predictive factors of a successful voiding after bladder outflow resistance reduction surgery (BORRS) in men presenting with acute or chronic urinary retention (UR). METHODS: A think tank (TT) of ICI-RS was gathered in 2023, Bristol, UK, to discuss several aspects of the problem, such as the pathophysiology of UR, the clinical and urodynamic evaluation of men with UR and whether it is possible to predict which men will be able to successfully void after treatment with contemporary surgical options. RESULTS: The TT agreed that successful voiding after BORRS depends on several factors but that a strong recommendation cannot be made regarding preoperative evaluation and whether there are predictive factors of success because of the heterogeneity of patients and methodology in published trials. The diagnosis of obstruction in men with UR may be challenging when there is apparent reduced detrusor contraction during urodynamic studies. Even in the absence of bladder contractility there is documentation of such cases that have voided adequately after BORRS. Still, detrusor underactivity and inadequate relief of prostatic obstruction are the main causes of an unsuccessful voiding after BORRS. Conventional resection and enucleation methods remain the most successful surgeries in relieving UR in men, whereas the efficacy of minimally invasive surgical treatments needs to be assessed further. CONCLUSION: Research is needed to understand the pathophysiology of UR and the predictors of successful voiding after different types of BORRS in men with UR.

Can we predict and manage persistent storage and voiding LUTS following bladder outflow resistance reduction surgery in men? ICI-RS 2023.

AIMS: Lower urinary tract symptoms (LUTS) persist in up to 50% of patients after bladder outflow resistance reduction surgery (BORRS) in men. Our think tank aims to address the predictive factors for persistent LUTS after BORRS and to propose the recommendations for future research to enable improved better patient counseling and selection by more accurate prediction of treatment outcome. METHODS: A think tank of ICI-RS gathered in 2023, Bristol, UK, to discuss the pre and postsurgical clinical and urodynamic evaluation of men undergoing BORRS and whether it is possible to predict which men will have persistent LUTS after BORRS. RESULTS: Our think tank agrees that due to the multifactorial, and still not fully understood, etiology of male LUTS it is not possible to precisely predict in many men who will have persistent LUTS after BORRS. However, severe storage symptoms (overactive bladder, OAB) in association with low volume and high amplitude detrusor overactivity and low bladder capacity in preoperative urodynamics, increase the likelihood of persistent OAB/storage symptoms after BORRS. Furthermore, patients who are clearly obstructed and have good bladder contractility on preoperative pressure flow studies do better postoperatively compared to their counterparts. However, the benefit of pressure flow studies is decreased in patients who do not acceptably void during the study. Poor voiding after BORRS may occur due to persistent obstruction or detrusor underactivity. CONCLUSION: Future research is needed to increase our understanding of why male LUTS persist after surgery, and to enable better patient selection and more precise patient counseling before BORRS.

Quantitative Phosphoproteomics Analysis Uncovers PAK2- and CDK1-Mediated Malignant Signaling Pathways in Clear Cell Renal Cell Carcinoma.

Clear cell Renal Cell Carcinoma (ccRCC) is among the 10 most common cancers in both men and women and causes more than 140,000 deaths worldwide every year. In order to elucidate the underlying molecular mechanisms orchestrated by phosphorylation modifications, we performed a comprehensive quantitative phosphoproteomics characterization of ccRCC tumor and normal adjacent tissues. Here, we identified 16,253 phosphopeptides, of which more than 9000 were singly quantified. Our in-depth analysis revealed 600 phosphopeptides to be significantly differentially regulated between tumor and normal tissues. Moreover, our data revealed that significantly up-regulated phosphoproteins are associated with protein synthesis and cytoskeletal re-organization which suggests proliferative and migratory behavior of renal tumors. This is supported by a mesenchymal profile of ccRCC phosphorylation events. Our rigorous characterization of the renal phosphoproteome also suggests that both epidermal growth factor receptor and vascular endothelial growth factor receptor are important mediators of phospho signaling in RCC pathogenesis. Furthermore, we determined the kinases p21-activated kinase 2, cyclin-dependent kinase 1 and c-Jun N-terminal kinase 1 to be master kinases that are responsible for phosphorylation of many substrates associated with cell proliferation, inflammation and migration. Moreover, high expression of p21-activated kinase 2 is associated with worse survival outcome of ccRCC patients. These master kinases are targetable by inhibitory drugs such as fostamatinib, minocycline, tamoxifen and bosutinib which can serve as novel therapeutic agents for ccRCC treatment.

The efficacy of palbociclib and ribociclib in the first-line treatment of metastatic hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer in male patients: a Turkish oncology group (TOG) study.

INTRODUCTION: Male breast cancer, comprising approximately 1% of all breast cancer cases, often leads to the exclusion of male patients as a criterion in clinical trials. While the efficacy of Cyclin-dependent kinases 4 and 6 (CDK 4/6) inhibitors has been established in metastatic hormone receptor-positive (HR +) and human epidermal growth factor receptor 2-negative (HER2 -) breast cancer in women, limited data exist on their effectiveness in male patients. We aimed to evaluate the efficacy and safety of palbociclib or ribociclib in male patients with breast cancer. METHODS: This study is a multicenter, retrospective study. We included male patients with HR + and HER2-metastatic breast cancer who received palbociclib or ribociclib as first-line treatment. Our primary endpoints were progression-free survival (PFS), overall response rates (ORR), and drug-related adverse effects. RESULTS: A total of 46 male patients from 27 institutions were enrolled. The median age at initiation of CDK 4/6 inhibitors was 63.64 ± 13.69 years, with a median follow-up of 21.33 (95% CI 14.92-27.74) months. The ORR were 84% for palbociclib and 76.2% for ribociclib. The mPFS for the entire cohort was 28.06 months (95% CI 18.70-37.42). No significant difference in PFS was observed between palbociclib and ribociclib (mPFS: 24.46 months (95% CI 11.51-37.42) vs 28.33 months (95% CI 14.77-41.88), respectively, p = 0.211). No new adverse events were reported. DISCUSSION: This study demonstrates that palbociclib and ribociclib are effective and safe options for first-line treatment in male patients with HR + /HER2 - metastatic breast cancer. However, further prospective studies are warranted to establish their efficacy in this population.

Efficacy of subsequent treatments in patients with hormone-positive advanced breast cancer who had disease progression under CDK 4/6 inhibitor therapy.

BACKGROUND: There is no standard treatment recommended at category 1 level in international guidelines for subsequent therapy after cyclin-dependent kinase 4/6 inhibitor (CDK4/6) based therapy. We aimed to evaluate which subsequent treatment oncologists prefer in patients with disease progression under CDKi. In addition, we aimed to show the effectiveness of systemic treatments after CDKi and whether there is a survival difference between hormonal treatments (monotherapy vs. mTOR-based). METHODS: A total of 609 patients from 53 centers were included in the study. Progression-free-survivals (PFS) of subsequent treatments (chemotherapy (CT, n:434) or endocrine therapy (ET, n:175)) after CDKi were calculated. Patients were evaluated in three groups as those who received CDKi in first-line (group A, n:202), second-line (group B, n: 153) and ≥ 3rd-line (group C, n: 254). PFS was compared according to the use of ET and CT. In addition, ET was compared as monotherapy versus everolimus-based combination therapy. RESULTS: The median duration of CDKi in the ET arms of Group A, B, and C was 17.0, 11.0, and 8.5 months in respectively; it was 9.0, 7.0, and 5.0 months in the CT arm. Median PFS after CDKi was 9.5 (5.0-14.0) months in the ET arm of group A, and 5.3 (3.9-6.8) months in the CT arm (p = 0.073). It was 6.7 (5.8-7.7) months in the ET arm of group B, and 5.7 (4.6-6.7) months in the CT arm (p = 0.311). It was 5.3 (2.5-8.0) months in the ET arm of group C and 4.0 (3.5-4.6) months in the CT arm (p = 0.434). Patients who received ET after CDKi were compared as those who received everolimus-based combination therapy versus those who received monotherapy ET: the median PFS in group A, B, and C was 11.0 vs. 5.9 (p = 0.047), 6.7 vs. 5.0 (p = 0.164), 6.7 vs. 3.9 (p = 0.763) months. CONCLUSION: Physicians preferred CT rather than ET in patients with early progression under CDKi. It has been shown that subsequent ET after CDKi can be as effective as CT. It was also observed that better PFS could be achieved with the subsequent everolimus-based treatments after first-line CDKi compared to monotherapy ET.

Elastic network modeling of cellular networks unveils sensor and effector genes that control information flow.

The high-level organization of the cell is embedded in indirect relationships that connect distinct cellular processes. Existing computational approaches for detecting indirect relationships between genes typically consist of propagating abstract information through network representations of the cell. However, the selection of genes to serve as the source of propagation is inherently biased by prior knowledge. Here, we sought to derive an unbiased view of the high-level organization of the cell by identifying the genes that propagate and receive information most effectively in the cell, and the indirect relationships between these genes. To this aim, we adapted a perturbation-response scanning strategy initially developed for identifying allosteric interactions within proteins. We deployed this strategy onto an elastic network model of the yeast genetic interaction profile similarity network. This network revealed a superior propensity for information propagation relative to simulated networks with similar topology. Perturbation-response scanning identified the major distributors and receivers of information in the network, named effector and sensor genes, respectively. Effectors formed dense clusters centrally integrated into the network, whereas sensors formed loosely connected antenna-shaped clusters and contained genes with previously characterized involvement in signal transduction. We propose that indirect relationships between effector and sensor clusters represent major paths of information flow between distinct cellular processes. Genetic similarity networks for fission yeast and human displayed similarly strong propensities for information propagation and clusters of effector and sensor genes, suggesting that the global architecture enabling indirect relationships is evolutionarily conserved across species. Our results demonstrate that elastic network modeling of cellular networks constitutes a promising strategy to probe the high-level organization and cooperativity in the cell.

Evaluation of new treatments for benign prostatic obstruction: ICI-RS 2023.

AIMS: To address how invasive therapies for benign prostatic obstruction (BPO) have been evaluated, what their effect is on BPO, if they can prevent progression to BPO and how new therapies need to be evaluated before implementation into clinical practice. METHODS: The think tank conducted a literature review and looked at the previous and current American Urological Association, European Association of Urology and the International Consultation on Urological Diseases guidelines to see what procedures have been used to treat BPO. They then assessed whether trials have been conducted before implementation of the procedures and whether they have been compared to a "gold" standard treatment. The use of urodynamics has also been addressed in the think tank in relation the clinical trials as well as terminology. RESULTS: Guidelines vary in the use of terminology when it comes to BPO with some continuing to use the term benign prostatic hyperplasia (BPH). There are several procedures for example, TUNA, which have become obsolete although continues to be mentioned in the guidelines until recently. Majority of procedures have been introduced without comparing to "gold" standard treatment and without any long-term data. There continues to be many unknowns with regard to the success of some of the BPO procedures and why some of the adverse events develop. CONCLUSION: There needs to be more robust long-term clinical trials conducted of new BPO therapies, with men who have both lower urinary tract symptoms and urinary retention, before introduction into clinical practice.

Outcomes of penile inversion vaginoplasty and robotic-assisted peritoneal flap vaginoplasty in obese and nonobese patients.

AIM: To explore the impact of body mass index (BMI) on the outcomes of gender-affirming vaginoplasty. METHODS: A cohort consisting of all gender-affirming vaginoplasties in our practice between September 27th, 2018, and September 1st, 2022 were identified, and data were retrospectively collected. Patients were classified as obese if their BMI was ≥30 kg/m2 at the time of surgery and nonobese if their BMI was <30 kg/m2 . Complications were assigned a Clavien-Dindo grade and grouped as Grade ≥2 versus Grade ≤1. Patient-reported functional outcomes of intact erogenous sensation, tactile sensation, ability to achieve penetrative vaginal intercourse, and cosmetic satisfaction were assessed. RESULTS: A total of 58 patients with a mean follow-up time of 6.9 months were included. Seventeen patients (mean BMI = 36.8 kg/m2 ) were classified as obese and 41 patients (mean BMI = 25.1 kg/m2 ) were classified as nonobese. No significant differences in outcomes were identified in the obese versus nonobese groups in terms of the incidence of complications. Patient-reported functional outcomes did not differ significantly between the two groups. CONCLUSIONS: Similar results can be achieved with gender-affirming vaginoplasty in obese patients when compared to their nonobese counterparts. Eligibility for this procedure should not be restricted based on BMI alone.

Gender-affirming vaginoplasty: Technical considerations in patients with genital skin deficiency.

INTRODUCTION: Gender dysphoria affects over 1 million American adults. Vaginoplasty is a critical step in gender affirmation, and many patients have insufficient genital skin for full-depth penile inversion vaginoplasty (PIV). We reviewed the literature for technical considerations addressing this and present our data supporting the use of peritoneal flaps (Davydov technique). MATERIALS AND METHODS: A comprehensive review of modern literature was conducted. Second, we present a retrospective case review of our experience with PIV, including data from procedures utilizing peritoneal flaps. RESULTS: We identified 20 original articles, including retrospective and prospective case and cohort studies. Approaches included the application of local soft tissue grafts and flaps, peritoneal flaps, and intestinal segments. Between June 2018 and February 2021, 47 patients at our institution, underwent PIV for the treatment of gender dysphoria. Nineteen of those patients underwent robotic-assisted peritoneal flap procedure in addition to PIV. In this cohort, the mean follow-up was 200.6 ± 124.8 days. Mean neovaginal depth was 13.1 ± 3.0 cm intra-operatively and 11.0 cm at the last follow-up. Twenty-six percent of complications were Clavien Grade 1 or 2; others included wound dehiscence (30.4%), perianal and urethral fistula (13.0%), and neovaginal stenosis (8.7%). The majority of patients reported satisfactory results in terms of sexual function with intact tactile and erogenous sensation. Almost half were able to have penetrative vaginal intercourse at the last follow-up. We did not aim to perform statistical calculations to compare the outcomes of PIV with and without robotic-assisted peritoneal flap augmentation, as the groups were not constructed in that manner. However, it is evident that anatomical and functional results as well as the distribution of postoperative complications seem similar. CONCLUSION: Vaginoplasty is indicated in a growing population of patients with a wide range of medical histories and anatomic variations. Genitourinary reconstructive surgeons must have several methods to achieve full-depth vaginoplasty in cases of inadequate genital skin. Peritoneal flaps serve as a versatile, safe, and functionally advantageous solution.

Treatment efficacy of ribociclib or palbociclib plus letrozole in hormone receptor-positive/HER2-negative metastatic breast cancer.

Background: Ribociclib, palbociclib and abemaciclib are currently approved CDK4/6 inhibitors along with aromatase inhibitors as the first-line standard-of-care for patients with hormone receptor-positive, HER2-negative metastatic breast cancer. Methods: The authors report retrospective real-life data for 600 patients with estrogen receptor- and/or progesterone receptor-positive and HER2-negative metastatic breast cancer who were treated with ribociclib and palbociclib in combination with letrozole. Results & conclusion: The results demonstrated that the combination of palbociclib or ribociclib with letrozole has similar progression-free survival and overall survival benefit in real life for the patient group with similar clinical features. Specifically, endocrine sensitivity may be a factor to be considered in the treatment preference.

Histologically benign PI-RADS 4 and 5 lesions contain cancer-associated epigenetic alterations.

BACKGROUND: The detection rate of clinically significant prostate cancer has improved with the use of multiparametric magnetic resonance imaging (mpMRI). Yet, even with MRI-guided biopsy 15%-35% of high-risk lesions (Prostate Imaging-Reporting and Data System [PI-RADS] 4 and 5) are histologically benign. It is unclear if these false positives are due to diagnostic/sampling errors or pathophysiological alterations. To better understand this, we tested histologically benign PI-RAD 4 and 5 lesions for common malignant epigenetic alterations. MATERIALS AND METHODS: MRI-guided in-bore biopsy samples were collected from 45 patients with PI-RADS 4 (n = 31) or 5 (n = 14) lesions. Patients had a median clinical follow-up of 3.8 years. High-risk mpMRI patients were grouped based on their histology into biopsy positive for tumor (BPT; n = 28) or biopsy negative for tumor (BNT; n = 17). From these biopsy samples, DNA methylation of well-known tumor suppressor genes (APC, GSTP1, and RARß2) was quantified. RESULTS: Similar to previous work we observed high rates of promoter methylation at GSTP1 (92.7%), RARß2 (57.3%), and APC (37.8%) in malignant BPT samples but no methylation in benign TURP chips. Interestingly, similar to the malignant samples the BNT biopsies also had increased methylation at the promoter of GSTP1 (78.8%) and RARß2 (34.6%). However, despite these epigenetic alterations none of these BNT patients developed prostate cancer, and those who underwent repeat mpMRI (n = 8) demonstrated either radiological regression or stability. CONCLUSIONS: Histologically benign PI-RADS 4 and 5 lesions harbor prostate cancer-associated epigenetic alterations.

International Continence Society (ICS) report on the terminology for sexual health in men with lower urinary tract (LUT) and pelvic floor (PF) dysfunction.

INTRODUCTION: The terminology for sexual health in men with lower urinary tract (LUT) and pelvic floor (PF) dysfunction has not been defined and organized into a clinically based consensus terminology report. The aim of this terminology report is to provide a definitional document within this context that will assist clinical practice and research. METHODS: This report combines the input of the members of sexual health in men with LUT and PF Dysfunction working group of the International Continence Society (ICS), assisted at intervals by external referees. Appropriate core clinical categories and a sub-classification were developed to give coding to definitions. An extensive process of 18 rounds of internal and external review was involved to exhaustively examine each definition, with decision-making by collective opinion (consensus). The Committee retained evidence-based definitions, identified gaps, and updated or discarded outdated definitions. Expert opinions were used when evidence was insufficient or absent. RESULTS: A terminology report for sexual health in men with LUT and PF dysfunction, encompassing 198 (178 NEW) separate definitions, has been developed. It is clinically based with the most common diagnoses defined. Clarity and user-friendliness have been key aims to make it interpretable by practitioners and trainees in all the different speciality groups involved. Conservative and surgical managements are major additions and appropriate figures have been included to supplement and clarify the text. Emerging concepts and measurements, in use in the literature and offering further research potential, but requiring further validation, have been included as an appendix. Interval (5-10 years) review is anticipated to keep the document updated. CONCLUSION: A consensus-based terminology report for sexual health in men with LUT and PF dysfunction has been produced to aid clinical practice and research. The definitions that have been adopted are those that are most strongly supported by the literature at this time or are considered clinical principles or consensus of experts' opinions.

Can remote ischemic preconditioning counteract the renal functional deterioration attributable to partial nephrectomy under warm ischemia? Results of an animal study.

BACKGROUND: To investigate if remote ischemic preconditioning (RIPC) can offer any renoprotective value by counteracting the deleterious effect of partial nephrectomy (PN) under warm ischemia on renal function. METHODS: Four groups, each with 5 Wistar albino rats, were constructed; RIPC + PN, PN, RIPC and sham. Right nephrectomy was performed to constitute a solitary kidney model. RIPC denoted sequential clamping/declamping of the femoral artery/vein complex. PN was performed under warm-ischemia following RIPC. Blood samples were collected on multiple occasions until euthanasia on day 7. Immunoassays were conducted to measure the serum and tissues levels of kidney injury markers. Kidneys were examined histologically and morphometric analyzes were performed using digital scanning. RESULTS: IL-33 levels did not differ significantly between the groups. Serum levels of KIM-1, NGAL, and aldose reductase in RIPC + PN, PN and RIPC groups were significantly lower than that of sham group. Tissue biomarker levels were similar across groups. The observed trend in mean necrosis area of PN group was higher than that of RIPC + PN group (p > 0.05). The transitional zone between necrosis and healthy tissue showed a trend towards increasing width in the rats subjected to RIPC before PN vs. those who underwent PN without RIPC (p > 0.05). CONCLUSION: RIPC failed to counteract the renal functional consequences of PN under warm ischemia in a solitary kidney animal model. The supportive but marginal histological findings in favor of RIPC's renoprotective potential were not supplemented with the changes in serum and tissue biomarker levels.

Complications of urethral bulking therapy for female stress urinary incontinence.

AIMS: To review, report, and discuss the complications associated with urethral bulking therapy in female stress urinary incontinence. METHODS: An extensive nonsystematic literature review on complications associated with injectable bulking agents used in the clinical practice was conducted. We reviewed articles published in English and indexed in the PubMed, Embase, and Google Scholar databases. Original articles, case reports, and case series were taken into consideration. Data regarding the safety of injectable bulking agents and the complications associated with their utility within the context of urethral bulking therapy for female stress urinary incontinence were extracted and discussed. RESULTS: Approximately, 1/3 of the patients experience some type of a complication after urethral bulking therapy. The majority of these complications are of low grade, transient, do not necessitate additional surgical intervention, and amenable to treatment with conservative measures such as clean intermittent catheterization and antibiotics. However, more serious complications such as abscess formation, delayed hypersensitivity reactions, and vaginal erosion have been reported. Some of the injectable bulking agents have been withdrawn from the market because of their unfavorable adverse effect profile. CONCLUSIONS: Urethral bulking therapy can be considered as a low-risk procedure. However, it is not without complications which can be severe in rare instances. The search for the ideal urethral bulking agent is ongoing and future comparative studies assessing the safety and efficacy of these compounds in randomized controlled settings are warranted.

The real-life management of overactive bladder: Turkish Continence Society multicenter prospective cohort study with short-term outcome.

INTRODUCTION: Turkish Continence Society aimed to analyze how overactive bladder (OAB) is being managed in routine practice by the urologists in Turkey. MATERIAL AND METHODS: Fourteen urology departments were randomly selected to represent the whole population in this multicenter study. An online data entry and storage software was created for patient recruitment and data assessment. A survey including demographic data, daily habits, lower urinary tract symptoms, and Turkish-validated OAB-V8 and ICIQ-SF questionnaires were completed by all patients. Second part of the survey, including the questions about clinical evaluation and management of the patient, was completed by the treating physician. RESULTS: A total of 507 patients (394 female and 113 male) were included. Behavioral therapy was recommended to 73.2% of female and 81.4% of male patients although bladder diary was requested for 59.5% and 52.7% of the female and male patients, respectively. In the first visit, 86.1% of the female and 89.3% of the male patients were given antimuscarinics (P = .431). Antimuscarinic-related side effects occurred in 94.9% and 88.9% of the female and male patients, respectively (P = .937). However, the rate of medical treatment change due to antimuscarinic-related side effects was only 1.7% in female and 4.8% in male patients at the end of 4 months. CONCLUSIONS: Behavioral therapy and antimuscarinics were the preferred initial treatment modalities of OAB in concordance with the guidelines. Despite guideline recommendations, bladder diaries were not utilized in half of the patients. Insufficient efficacy appeared to be the main reason for treatment modification.

Increased substrate affinity in the Escherichia coli L28R dihydrofolate reductase mutant causes trimethoprim resistance.

Dihydrofolate reductase (DHFR) is a ubiquitous enzyme with an essential role in cell metabolism. DHFR catalyzes the reduction of dihydrofolate to tetrahydrofolate, which is a precursor for purine and thymidylate synthesis. Several DHFR targeting antifolate drugs including trimethoprim, a competitive antibacterial inhibitor, have therefore been developed and are clinically used. Evolution of resistance against antifolates is a common public health problem rendering these drugs ineffective. To combat the resistance problem, it is important to understand resistance-conferring changes in the DHFR structure and accordingly develop alternative strategies. Here, we structurally and dynamically characterize Escherichia coli DHFR in its wild type (WT) and trimethoprim resistant L28R mutant forms in the presence of the substrate and its inhibitor trimethoprim. We use molecular dynamics simulations to determine the conformational space, loop dynamics and hydrogen bond distributions at the active site of DHFR for the WT and the L28R mutant. We also report their experimental kcat, Km, and Ki values, accompanied by isothermal titration calorimetry measurements of DHFR that distinguish enthalpic and entropic contributions to trimethoprim binding. Although mutations that confer resistance to competitive inhibitors typically make enzymes more promiscuous and decrease affinity to both the substrate and the inhibitor, strikingly, we find that the L28R mutant has a unique resistance mechanism. While the binding affinity differences between the WT and the mutant for the inhibitor and the substrate are small, the newly formed extra hydrogen bonds with the aminobenzoyl glutamate tail of DHF in the L28R mutant leads to increased barriers for the dissociation of the substrate and the product. Therefore, the L28R mutant indirectly gains resistance by enjoying prolonged binding times in the enzyme-substrate complex. While this also leads to slower product release and decreases the catalytic rate of the L28R mutant, the overall effect is the maintenance of a sufficient product formation rate. Finally, the experimental and computational analyses together reveal the changes that occur in the energetic landscape of DHFR upon the resistance-conferring L28R mutation. We show that the negative entropy associated with the binding of trimethoprim in WT DHFR is due to water organization at the binding interface. Our study lays the framework to study structural changes in other trimethoprim resistant DHFR mutants.

Prostate-specific membrane antigen-based imaging in prostate cancer: impact on clinical decision making process.

BACKGROUND: There is an ongoing need for an accurate imaging modality which can be used for staging purposes, metastatic evaluation, predicting biologic aggresiveness and investigating recurrent disease in prostate cancer. Prostate specific membrane antigen, given its favorable molecular characteristics, holds a promise as an ideal target for prostate cancer-specific nuclear imaging. In this study, we evaluated our initial results of PSMA based PET/CT imaging in prostate cancer. METHODS: A total of 22 patients with a median age and serum PSA level of 68 years and 4.15 ng/ml, respectively underwent Ga-68 PSMA PET/CT in our hospital between Februrary and August 2014. Their charts were retrospectively reviewed in order to document the clinical characteristics, the indications for and the results of PSMA based imaging and the impact of Ga-68 PSMA PET/CT findings on disease management. RESULTS: The most common indications were rising PSA after local ± adjuvant treatment followed by staging and metastatic evaluation before definitive or salvage treatment. All except 2 patients had prostatic ± extraprostatic PSMA positive lesions. For those who had a positive result; treatment strategies were tailored accordingly. Above the PSA level of 2 ng/ml, none of the PSMA based nuclear imaging studies revealed negative results. CONCLUSIONS: PSMA based nuclear imaging has significantly impacted our way of handling patients with prostate cancer. Its preliminary performance in different clinical scenarios and ability to detect lesions even in low PSA values seems fairly promising and deserves to be supplemented with further clinical studies.