Synaptotagmin-7 outperforms synaptotagmin-1 to promote the formation of large, stable fusion pores via robust membrane penetration.

Synaptotagmin-1 and synaptotagmin-7 are two prominent calcium sensors that regulate exocytosis in neuronal and neuroendocrine cells. Upon binding calcium, both proteins partially penetrate lipid bilayers that bear anionic phospholipids, but the specific underlying mechanisms that enable them to trigger exocytosis remain controversial. Here, we examine the biophysical properties of these two synaptotagmin isoforms and compare their interactions with phospholipid membranes. We discover that synaptotagmin-1-membrane interactions are greatly influenced by membrane order; tight packing of phosphatidylserine inhibits binding due to impaired membrane penetration. In contrast, synaptotagmin-7 exhibits robust membrane binding and penetration activity regardless of phospholipid acyl chain structure. Thus, synaptotagmin-7 is a super-penetrator. We exploit these observations to specifically isolate and examine the role of membrane penetration in synaptotagmin function. Using nanodisc-black lipid membrane electrophysiology, we demonstrate that membrane penetration is a critical component that underlies how synaptotagmin proteins regulate reconstituted, exocytic fusion pores in response to calcium.

Pretest Video Education Versus Genetic Counseling for Patients With Prostate Cancer: ProGen, A Multisite Randomized Controlled Trial.

PURPOSE: Germline genetic testing (GT) is recommended for men with prostate cancer (PC), but testing through traditional models is limited. The ProGen study examined a novel model aimed at providing access to GT while promoting education and informed consent. METHODS: Men with potentially lethal PC (metastatic, localized with a Gleason score of ≥8, persistent prostate-specific antigen after local therapy), diagnosis age ≤55 years, previous malignancy, and family history suggestive of a pathogenic variant (PV) and/or at oncologist's discretion were randomly assigned 3:1 to video education (VE) or in-person genetic counseling (GC). Participants had 67 genes analyzed (Ambry), with results disclosed via telephone by a genetic counselor. Outcomes included GT consent, GT completion, PV prevalence, and survey measures of satisfaction, psychological impact, genetics knowledge, and family communication. Two-sided Fisher's exact tests were used for between-arm comparisons. RESULTS: Over a 2-year period, 662 participants at three sites were randomly assigned and pretest VE (n = 498) or GC (n = 164) was completed by 604 participants (VE, 93.1%; GC, 88.8%), of whom 596 participants (VE, 98.9%; GC, 97.9%) consented to GT and 591 participants completed GT (VE, 99.3%; GC, 98.6%). These differences were not statistically significant although subtle differences in satisfaction and psychological impact were. Notably, 84 PVs were identified in 78 participants (13.2%), with BRCA1/2 PV comprising 32% of participants with a positive result (BRCA2 n = 21, BRCA1 n = 4). CONCLUSION: Both VE and traditional GC yielded high GT uptake without significant differences in outcome measures of completion, GT uptake, genetics knowledge, and family communication. The increased demand for GT with limited genetics resources supports consideration of pretest VE for patients with PC.

Mitochondrial metabolism in primary and metastatic human kidney cancers.

Most kidney cancers display evidence of metabolic dysfunction1-4 but how this relates to cancer progression in humans is unknown. We used a multidisciplinary approach to infuse 13C-labeled nutrients during surgical tumour resection in over 70 patients with kidney cancer. Labeling from [U-13C]glucose varies across cancer subtypes, indicating that the kidney environment alone cannot account for all metabolic reprogramming in these tumours. Compared to the adjacent kidney, clear cell renal cell carcinomas (ccRCC) display suppressed labelling of tricarboxylic acid (TCA) cycle intermediates in vivo and in organotypic slices cultured ex vivo, indicating that suppressed labeling is tissue intrinsic. Infusions of [1,2-13C]acetate and [U-13C]glutamine in patients, coupled with respiratory flux of mitochondria isolated from kidney and tumour tissue, reveal primary defects in mitochondrial function in human ccRCC. However, ccRCC metastases unexpectedly have enhanced labeling of TCA cycle intermediates compared to primary ccRCCs, indicating a divergent metabolic program during ccRCC metastasis in patients. In mice, stimulating respiration in ccRCC cells is sufficient to promote metastatic colonization. Altogether, these findings indicate that metabolic properties evolve during human kidney cancer progression, and suggest that mitochondrial respiration may be limiting for ccRCC metastasis but not for ccRCC growth at the site of origin.

Emergence of BRCA Reversion Mutations in Patients with Metastatic Castration-resistant Prostate Cancer After Treatment with Rucaparib.

BACKGROUND: Poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors are approved in the USA for the treatment of patients with BRCA1 or BRCA2 (BRCA) mutated (BRCA+) metastatic castration-resistant prostate cancer (mCRPC). BRCA reversion mutations are a known mechanism of acquired resistance to PARP inhibitors in multiple cancer types, although their impact and prevalence in mCRPC remain unknown. OBJECTIVE: To examine the prevalence of BRCA reversion mutations in the plasma of patients with BRCA+ mCRPC after progression on rucaparib. DESIGN, SETTING, AND PARTICIPANTS: Men with BRCA+ mCRPC enrolled in Trial of Rucaparib in Prostate Indications 2 (TRITON2) were treated with rucaparib after progressing on one to two lines of androgen receptor-directed and one taxane-based therapy. Cell-free DNA from the plasma of 100 patients, collected at the end of treatment after confirmed progression before May 5, 2020, was queried for BRCA reversion mutations using next-generation sequencing (NGS). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The association of clinical efficacy and postprogression genomics was measured in 100 patients with BRCA+ mCRPC treated with rucaparib. RESULTS AND LIMITATIONS: No baseline BRCA reversion mutations were observed in 100 BRCA+ patients. NGS identified somatic BRCA reversion mutations in 39% (39/100) of patients after progression. Reversion rates were similar for BRCA2 and BRCA1, irrespective of germline or somatic status, but higher in samples with a high tumor DNA fraction. Most patients with reversions (74%, 29/39) had two or more reversion mutations occurring subclonally at lower allele frequencies than the original BRCA mutations. The incidence of BRCA reversion mutations increased with the duration of rucaparib treatment. The frequency of reversion mutations was higher in patients with an objective (58%) or a prostate-specific antigen (69%) response compared with those without either (39% and 29%, respectively). CONCLUSIONS: These findings suggest that BRCA reversion mutations are a significant mechanism of acquired resistance to rucaparib in patients with BRCA+ mCRPC, with evidence of subclonal convergence promoting systemic resistance. PATIENT SUMMARY: Men with BRCA mutated metastatic castration-resistant prostate cancer enrolled in TRITON2 were treated with rucaparib after progressing on one to two lines of androgen receptor-directed and one taxane-based therapy. Cell-free DNA from the plasma of 100 patients, collected after radiographic or prostate-specific antigen progression before May 5, 2020, was analyzed by next-generation sequencing and queried for BRCA reversion mutations.

Stereotactic Ablative Radiation for Systemic Therapy-naïve Oligometastatic Kidney Cancer.

BACKGROUND: Evidence-based guidelines for the management of systemic therapy-naïve oligometastatic renal cell carcinoma (RCC) are lacking. OBJECTIVE: To evaluate the potential of stereotactic ablative radiotherapy (SAbR) to provide longitudinal disease control while preserving quality of life (QOL) in patients with systemic therapy-naïve oligometastatic RCC. DESIGN, SETTING, AND PARTICIPANTS: RCC patients with three or fewer extracranial metastases were eligible. SAbR was administered longitudinally to all upfront and, as applicable, subsequent metastases. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: This prospective phase II single-arm trial was powered to achieve a primary objective of freedom from systemic therapy for >1 yr in >60% of patients (using the Clopper and Pearson methodology). Secondary endpoints included progression-free survival (PFS), defined as the time from first SAbR to progression not amenable to SAbR (local failure at SAbR-treated sites, new metastases not amenable to SAbR, more than three new metastases, or brain metastases); patient-reported QOL metrics; local control (LC) rates; toxicity; cancer-specific survival (CSS); and overall survival (OS). RESULTS AND LIMITATIONS: Twenty-three patients received SAbR to 33 initial and 57 total sites. The median follow-up was 21.7 mo (interquartile range 16.3-30.3). Exceeding the prespecified 60% benchmark, freedom from systemic therapy at 1 yr was 91.3% (95% confidence interval [CI]: 69.5, 97.8). One-year PFS was 82.6% (95% CI: 60.1, 93.1). QOL was largely unaffected. LC was 100%. There were no grade 3/4 toxicities, but there was one death due to immune-related colitis 3 mo after SAbR while on subsequent checkpoint inhibitor therapy, where a SAbR contribution could not be excluded. One-year OS was 95.7% (95% CI: 72.9, 99.4); one-year CSS was 100%. CONCLUSIONS: SAbR for oligometastatic RCC was associated with meaningful longitudinal disease control while preserving QOL. These data support further evaluation of SAbR for systemic therapy-naïve oligometastatic RCC. PATIENT SUMMARY: Sequential stereotactic radiation therapy can safely and effectively control metastatic kidney cancer with limited spread for over a year without compromising patients' quality of life.

Phase II Trial of Sipuleucel-T and Stereotactic Ablative Body Radiation for Patients with Metastatic Castrate-Resistant Prostate Cancer.

(1) We hypothesized that adding concurrent stereotactic ablative radiotherapy (SAbR) would increase the time to progression in patients with metastatic castrate-resistant prostate cancer (mCRPCA) treated with sipuleucel-T. (2) Patients with a history of prostate cancer (PC), radiographic evidence of metastatic disease, and rising prostate-specific antigen (PSA) > 0.2 ng/dL on castrate testosterone levels were enrolled in this single-arm phase II clinical trial and treated with sipuleucel-T and SAbR. The primary endpoint was time to progression (TTP). Cellular and humoral responses were measured using ELISpot and Luminex multiplex assays, respectively. (3) Twenty patients with mCRPC were enrolled and treated with SAbR to 1−3 sites. Treatment was well tolerated with 51, 8, and 4 treatment-related grade 1, 2, and 3 toxicities, respectively, and no grade 4 or 5 adverse events. At a median follow-up of 15.5 months, the median TTP was 11.2 weeks (95% CI; 6.8−14.0 weeks). Median OS was 76.8 weeks (95% CI; 41.6−130.8 weeks). This regimen induced both humoral and cellular immune responses. Baseline M-MDSC levels were elevated in mCRPC patients compared to healthy donors (p = 0.004) and a decline in M-MDSC was associated with biochemical response (p = 0.044). Responders had lower baseline uric acid levels (p = 0.05). No clear correlation with radiographic response was observed. (4) While the regimen was safe, the PC-antigen-specific immune response induced by SAbR did not yield a synergistic clinical benefit for patients treated with sipuleucel-T compared to the historically reported outcomes.

Pyruvate Kinase M1 Suppresses Development and Progression of Prostate Adenocarcinoma.

SIGNIFICANCE: Differential expression of PKM1 and PKM2 impacts prostate tumorigenesis and suggests a potential therapeutic vulnerability in prostate cancer.

The complexin C-terminal amphipathic helix stabilizes the fusion pore open state by sculpting membranes.

Neurotransmitter release is mediated by proteins that drive synaptic vesicle fusion with the presynaptic plasma membrane. While soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) form the core of the fusion apparatus, additional proteins play key roles in the fusion pathway. Here, we report that the C-terminal amphipathic helix of the mammalian accessory protein, complexin (Cpx), exerts profound effects on membranes, including the formation of pores and the efficient budding and fission of vesicles. Using nanodisc-black lipid membrane electrophysiology, we demonstrate that the membrane remodeling activity of Cpx modulates the structure and stability of recombinant exocytic fusion pores. Cpx had particularly strong effects on pores formed by small numbers of SNAREs. Under these conditions, Cpx increased the current through individual pores 3.5-fold, and increased the open time fraction from roughly 0.1 to 1.0. We propose that the membrane sculpting activity of Cpx contributes to the phospholipid rearrangements that underlie fusion by stabilizing highly curved membrane fusion intermediates.

Phase II Trial of Stereotactic Ablative Radiation for Oligoprogressive Metastatic Kidney Cancer.

BACKGROUND: Patients with metastatic renal cell carcinoma (mRCC) treated with systemic therapy sometimes progress at limited sites.The best treatment approach for patients with oligoprogression remains unclear. OBJECTIVE: To determine the ability of stereotactic ablative radiation (SAbR) to extend ongoing systemic therapy in mRCC patients with oligoprogression. DESIGN, SETTING, AND PARTICIPANTS: A single-arm phase II clinical trial was conducted at a university medical center and county hospital, including 20 patients with mRCC on first- to fourth-line systemic therapy with three or fewer sites of progression (including new sites) involving ≤30% of all sites. INTERVENTION: SAbR to oligoprogressing metastases at outset and longitudinally, while radiated sites remain controlled and overall disease oligoprogressive. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary objective was to extend ongoing systemic therapy by >6 mo in >40% of patients. Secondary endpoints included overall survival, toxicity, and patient-reported quality of life. RESULTS AND LIMITATIONS: Twenty patients were enrolled. Upfront and sequential SAbR was administered to a total of 37 sites. The local control rate was 100%. At a median follow-up of 10.4 mo (interquartile range: 5.8-16.4), SAbR extended the duration of the ongoing systemic therapy by >6 mo in 14 patients (70%, 95% confidence interval [CI]: 49.9-90.1). The median time from SAbR to the onset of new systemic therapy or death was 11.1 mo (95% CI: 4.5-19.3). The median duration of SAbR-aided systemic therapy was 24.4 mo (95% CI: 15.3-42.2). Median overall survival was not reached. One patient developed grade 3 gastrointestinal toxicity possibly related to treatment. There was no significant decline in quality of life. Limitations include nonrandomized design and a small patient cohort. CONCLUSIONS: SAbR extended the duration of the ongoing systemic therapy for patients with oligoprogressive mRCC without undermining quality of life. These data support the evaluation of SAbR for oligoprogressive mRCC in a prospective randomized clinical trial. PATIENT SUMMARY: Patients with metastatic kidney cancer on systemic therapy but progressing at limited sites may benefit from focused radiation to progressive sites. Focused radiation was safe and effective, and extended the duration of the ongoing systemic therapy.

Disparities in Pre-Orchiectomy Sperm Cryopreservation Among Testicular Cancer Patients at a Public Safety Net Hospital and a Private Tertiary Care Center.

OBJECTIVE: To compare pre-orchiectomy sperm cryopreservation use in testicular cancer patients at a private tertiary care academic center and an affiliated public safety-net hospital. METHODS: This was a retrospective cohort study of patients who underwent radical orchiectomy for testicular cancer at a private tertiary-care hospital, which cared primarily for patients with private health insurance, and at a public "safety-net" facility, which cared for patients regardless of insurance status. Clinical and demographic predictors of cryopreservation use prior to orchiectomy were determined by chart review. RESULTS: A total of 201 patients formed the study cohort, 106 (53%) at the safety-net hospital and 95 (47%) at the private hospital. Safety net patients were more likely to be non-White (82% vs 15%, P < 0.001), uninsured (80% vs 12%, P < 0.001), Spanish speaking (38% vs 5.6%, P < 0.001), and to reside in areas in the bottom quartile of income (41% vs 5.6%, P < 0.001). On multivariable analysis, treatment at the private tertiary care center was strongly associated with use of cryopreservation (OR 5.60, 95% CI 1.74 - 20.4, P = 0.005, though the effects of specific demographic factors could not be elucidated due to collinearity. CONCLUSION: Among patients with testicular cancer, disparities exist in use of sperm cryopreservation between the private and safety-net settings. Barriers to the use of cryopreservation in the safety-net population should be sought and addressed.

Synaptotagmin 1 oligomerization via the juxtamembrane linker regulates spontaneous and evoked neurotransmitter release.

Synaptotagmin 1 (syt1) is a Ca2+ sensor that regulates synaptic vesicle exocytosis. Cell-based experiments suggest that syt1 functions as a multimer; however, biochemical and electron microscopy studies have yielded contradictory findings regarding putative self-association. Here, we performed dynamic light scattering on syt1 in solution, followed by electron microscopy, and we used atomic force microscopy to study syt1 self-association on supported lipid bilayers under aqueous conditions. Ring-like multimers were clearly observed. Multimerization was enhanced by Ca2+ and required anionic phospholipids. Large ring-like structures (∼180 nm) were reduced to smaller rings (∼30 nm) upon neutralization of a cluster of juxtamembrane lysine residues; further substitution of residues in the second C2-domain completely abolished self-association. When expressed in neurons, syt1 mutants with graded reductions in self-association activity exhibited concomitant reductions in 1) clamping spontaneous release and 2) triggering and synchronizing evoked release. Thus, the juxtamembrane linker of syt1 plays a crucial role in exocytosis by mediating multimerization.

Prophylaxis Against Thromboembolic Events During Chemotherapy for Germ Cell Cancer.

INTRODUCTION: Patients with advanced germ cell tumors (GCT) receiving cisplatin-based chemotherapy have high rates of thromboembolic events (TEE) which can negatively affect their overall survival. While primary TEE prophylaxis during chemotherapy may prevent these events, it is unclear which patients will benefit in this setting. MATERIALS AND METHODS: A review of PubMed/Medline was conducted in December 2020 and all pertinent articles were evaluated for relevancy and quality of data for inclusion in the review. RESULTS: Studies on patients receiving initial cisplatin-based chemotherapy for advanced GCT have reported up to a 19% rate of TEE. This high rate may be associated with multiple factors including retroperitoneal lymphadenopathy, advanced clinical stage, high risk Khorana scores and presence of a central line. Large phase III clinical trials have demonstrated the benefit of low-molecular-weight-heparin and direct oral anticoagulants for primary prophylaxis and against recurrent TEE. However, primary prophylaxis is currently underutilized with GCT patients starting chemotherapy. CONCLUSION: Precise models to predict TEE risk and consideration of anticoagulation are difficult to develop owing to the relatively uncommon nature of GCT and lack of representation in primary TEE prophylaxis clinical trials. Despite these limitations, we believe that the benefits of prophylactic anticoagulation outweigh the risk of major bleeding in select GCT patients with higher risk of TEE. We have developed a simple algorithm to help guide TEE prophylaxis selection based on patient factors and route of chemotherapy administration. Given the high rate of TEE in GCT patients, we believe better utilization of primary prophylaxis in patient starting cisplatin-based chemotherapy will have clinical benefit.

Stereotactic Ablative Radiation Therapy for Oligoprogressive Renal Cell Carcinoma.

PURPOSE: Oligoprogression, defined as limited sites of progression on systemic therapy, in patients with metastatic renal cell carcinoma (mRCC) is not uncommon, possibly because of inter- and intratumoral heterogeneity. We evaluated the effect of stereotactic ablative radiation therapy (SAbR) for longitudinal control of oligoprogressive mRCC. METHODS AND MATERIALS: Patients with extracranial mRCC were included in this retrospective analysis if they progressed in ≤3 sites on systemic therapy while demonstrating response/stability at other sites and received SAbR to all progressing sites without switching systemic therapy. Our primary endpoint was modified progression-free survival (mPFS), which we calculated from the start of SAbR to the start of a subsequent systemic therapy, death, or loss to follow-up. RESULTS: We identified 36 patients with a median follow-up of 20.4 months (interquartile range, 10.9-29.4). Forty-three sites were treated with SAbR with a median dose of 36 Gy (range, 18-50) in 3 fractions (range, 1-5). Median time to SAbR from the start of systemic therapy was 11.4 months (interquartile range, 6.1-17.1). Median mPFS was 9.2 months (95% confidence interval [CI], 5.9-13.2). Patients receiving SAbR while on immunotherapy exhibited a longer median mPFS (>28.4 months, log-rank P = .0001) than patients not on immunotherapy (9.2 months). Median overall survival from SAbR administration was 43.4 months (95% CI, 21.5-not Reached). The 1-year local control rate was 93% (95% CI, 78.7-97.5). Most SAbR-related toxicities were grade 1 to 2 (33% of patients), with one grade 5 hemoptysis event possibly related to SAbR or disease progression. CONCLUSIONS: SAbR has the potential to extend the the duration of current systemic therapy for selected patients with mRCC, preserving subsequent therapies for later administration possibly enabling longer treatment duration.

Synaptotagmin 7 is targeted to the axonal plasma membrane through γ-secretase processing to promote synaptic vesicle docking in mouse hippocampal neurons.

Synaptotagmin 7 (SYT7) has emerged as a key regulator of presynaptic function, but its localization and precise role in the synaptic vesicle cycle remain the subject of debate. Here, we used iGluSnFR to optically interrogate glutamate release, at the single-bouton level, in SYT7KO-dissociated mouse hippocampal neurons. We analyzed asynchronous release, paired-pulse facilitation, and synaptic vesicle replenishment and found that SYT7 contributes to each of these processes to different degrees. 'Zap-and-freeze' electron microscopy revealed that a loss of SYT7 diminishes docking of synaptic vesicles after a stimulus and inhibits the recovery of depleted synaptic vesicles after a stimulus train. SYT7 supports these functions from the axonal plasma membrane, where its localization and stability require both γ-secretase-mediated cleavage and palmitoylation. In summary, SYT7 is a peripheral membrane protein that controls multiple modes of synaptic vesicle (SV) exocytosis and plasticity, in part, through enhancing activity-dependent docking of SVs.

Outcome and Immune Correlates of a Phase II Trial of High-Dose Interleukin-2 and Stereotactic Ablative Radiotherapy for Metastatic Renal Cell Carcinoma.

PURPOSE: This phase II clinical trial evaluated whether the addition of stereotactic ablative radiotherapy (SAbR), which may promote tumor antigen presentation, improves the overall response rate (ORR) to high-dose IL2 (HD IL2) in metastatic renal cell carcinoma (mRCC). PATIENTS AND METHODS: Patients with pathologic evidence of clear cell renal cell carcinoma (RCC) and radiographic evidence of metastasis were enrolled in this single-arm trial and were treated with SAbR, followed by HD IL2. ORR was assessed based on nonirradiated metastases. Secondary endpoints included overall survival (OS), progression-free survival (PFS), toxicity, and treatment-related tumor-specific immune response. Correlative studies involved whole-exome and transcriptome sequencing, T-cell receptor sequencing, cytokine analysis, and mass cytometry on patient samples. RESULTS: Thirty ethnically diverse mRCC patients were enrolled. A median of two metastases were treated with SAbR. Among 25 patients evaluable by RECIST v1.1, ORR was 16% with 8% complete responses. Median OS was 37 months. Treatment-related adverse events (AE) included 22 grade ≥3 events that were not dissimilar from HD IL2 alone. There were no grade 5 AEs. A correlation was observed between SAbR to lung metastases and improved PFS (P = 0.0165). Clinical benefit correlated with frameshift mutational load, mast cell tumor infiltration, decreased circulating tumor-associated T-cell clones, and T-cell clonal expansion. Higher regulatory/CD8+ T-cell ratios at baseline in the tumor and periphery correlated with no clinical benefit. CONCLUSIONS: Adding SAbR did not improve the response rate to HD IL2 in patients with mRCC in this study. Tissue analyses suggest a possible correlation between frameshift mutation load as well as tumor immune infiltrates and clinical outcomes.

Cholesterol stabilizes recombinant exocytic fusion pores by altering membrane bending rigidity.

SNARE-mediated membrane fusion proceeds via the formation of a fusion pore. This intermediate structure is highly dynamic and can flicker between open and closed states. In cells, cholesterol has been reported to affect SNARE-mediated exocytosis and fusion pore dynamics. Here, we address the question of whether cholesterol directly affects the flickering rate of reconstituted fusion pores in vitro. These experiments were enabled by the recent development of a nanodisc⋅black lipid membrane recording system that monitors dynamic transitions between the open and closed states of nascent recombinant pores with submillisecond time resolution. The fusion pores formed between nanodiscs that bore the vesicular SNARE synaptobrevin 2 and black lipid membranes that harbored the target membrane SNAREs syntaxin 1A and SNAP-25B were markedly affected by cholesterol. These effects include strong reductions in flickering out of the open state, resulting in a significant increase in the open dwell-time. We attributed these effects to the known role of cholesterol in altering the elastic properties of lipid bilayers because manipulation of phospholipids to increase membrane stiffness mirrored the effects of cholesterol. In contrast to the observed effects on pore kinetics, cholesterol had no effect on the current that passed through individual pores and, hence, did not affect pore size. In conclusion, our results show that cholesterol dramatically stabilizes fusion pores in the open state by increasing membrane bending rigidity.

Beyond Amphiphilic Balance: Changing Subunit Stereochemistry Alters the Pore-Forming Activity of Nylon-3 Polymers.

Amphiphilic nylon-3 polymers have been reported to mimic the biological activities of natural antimicrobial peptides, with high potency against bacteria and minimal toxicity toward eukaryotic cells. Amphiphilic balance, determined by the proportions of hydrophilic and lipophilic subunits, is considered one of the most important features for achieving this activity profile for nylon-3 polymers and many other antimicrobial polymers. Insufficient hydrophobicity often correlates with weak activities against bacteria, whereas excessive hydrophobicity correlates with high toxicity toward eukaryotic cells. To ask whether factors beyond amphiphilic balance influence polymer activities, we synthesized and evaluated new nylon-3 polymers with two stereoisomeric subunits, each bearing an ethyl side chain and an aminomethyl side chain. Subunits that differ only in stereochemistry are predicted to contribute equally to amphiphilic balance, but we observed that the stereochemical difference correlates with significant changes in biological activity profile. Antibacterial activities were not strongly affected by subunit stereochemistry, but the ability to disrupt eukaryotic cell membranes varied considerably. Experiments with planar lipid bilayers and synthetic liposomes suggested that eukaryotic membrane disruption results from polymer-mediated formation of large pores. Collectively, our results suggest that factors other than amphiphilic balance influence the membrane activity profile of synthetic polymers. Subunits that differ in stereochemistry are likely to have distinct conformational propensities, which could potentially lead to differences in the average shapes of polymer chains, even when the subunits are heterochiral. These findings highlight a dimension of polymer design that should be considered more broadly in efforts to improve specificity and efficacy of antimicrobial polymers.

Congenital Adrenal Hyperplasia Causing Poor Response to Androgen Deprivation Therapy in Prostate Cancer.

Androgen deprivation therapy (ADT) is recommended for the treatment of advanced prostate cancer. Inadequate suppression of testosterone while on ADT poses a clinical challenge and requires evaluation of multiple potential causes, including adrenal virilizing disorders. We present 2 cases of elderly patients with prostate cancer who had undiagnosed congenital adrenal hyperplasia (CAH) driving persistent testosterone elevation during ADT. The first patient is a 73-year-old man who underwent radical prostatectomy on initial diagnosis and was later started on ADT with leuprolide following tumor recurrence. He had a testosterone level of 294.4 ng/dL and prostate-specific antigen (PSA) level of 17.7 ng/mL despite leuprolide use. Additional workup revealed adrenal nodular hyperplasia, elevated 17-hydroxyprogesterone (19 910 ng/dL) and dehydroepiandrosterone sulfate (378 mcg/dL), and 2 mutations of the CYP21A2 gene consistent with simple virilizing CAH. The second patient is an 82-year-old man who received stereotactic radiation therapy at time of diagnosis. He had insufficient suppression of testosterone with evidence of metastatic disease despite treatment with leuprolide and subsequently degarelix. Laboratory workup revealed elevated 17-hydroxyprogesterone (4910 ng/dL) and dehydroepiandrosterone sulfate (312 mcg/dL). Based on clinical, radiographic and biochemical findings, the patient was diagnosed with nonclassic CAH. The first patient initiated glucocorticoid therapy, and the second patient was treated with the CYP17 inhibitor abiraterone in combination with glucocorticoids. Both patients experienced rapid decline in testosterone and PSA levels. Inadequate testosterone suppression during ADT should trigger evaluation for causes of persistent hyperandrogenemia. CAH can lead to hyperandrogenemia and pose challenges when treating patients with prostate cancer.

Overcoming sociodemographic factors in the care of patients with testicular cancer at a safety net hospital.

BACKGROUND: The objective of this study was to determine whether standardized treatment of germ cell tumors (GCTs) could overcome sociodemographic factors limiting patient care. METHODS: The records of all patients undergoing primary treatment for GCTs at both a public safety net hospital and an academic tertiary care center in the same metropolitan area were analyzed. Both institutions were managed by the same group of physicians in the context of multidisciplinary cancer care. Patients were grouped by care center; clinicopathologic features and outcomes were analyzed. RESULTS: Between 2006 and 2018, 106 and 95 patients underwent initial treatment for GCTs at the safety net hospital and the tertiary care center, respectively. Safety net patients were younger (29 vs 33 years; P = .005) and were more likely to be Hispanic (79% vs 11%), to be uninsured (80% vs 12%; P < .001), to present via the emergency department (76% vs 8%; P < .001), and to have metastatic (stage II/III) disease (42% vs 26%; P = .025). In a multivariable analysis, an absence of lymphovascular invasion (odds ratio [OR], 0.30; P = .008) and an embryonal carcinoma component (OR, 0.36; P = .02) were associated with decreased use of adjuvant treatment for stage I patients; hospital setting was not (OR, 0.67; P = .55). For patients with stage II/III nonseminomatous GCTs, there was no difference in the performance of postchemotherapy retroperitoneal lymph node dissection between the safety net hospital and the tertiary care center (52% vs 64%; P = .53). No difference in recurrence rates was observed between the cohorts (5% vs 6%; P = .76). CONCLUSIONS: Sociodemographic factors are often associated with adverse clinical outcomes in the treatment of GCTs; they may be overcome with integrated, standardized management of testicular cancer.

Resolving kinetic intermediates during the regulated assembly and disassembly of fusion pores.

The opening of a fusion pore during exocytosis creates the first aqueous connection between the lumen of a vesicle and the extracellular space. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate the formation of these dynamic structures, and their kinetic transitions are tightly regulated by accessory proteins at the synapse. Here, we utilize two single molecule approaches, nanodisc-based planar bilayer electrophysiology and single-molecule FRET, to address the relationship between SNARE complex assembly and rapid (micro-millisecond) fusion pore transitions, and to define the role of accessory proteins. Synaptotagmin (syt) 1, a major Ca2+-sensor for synaptic vesicle exocytosis, drove the formation of an intermediate: committed trans-SNARE complexes that form large, stable pores. Once open, these pores could only be closed by the action of the ATPase, NSF. Time-resolved measurements revealed that NSF-mediated pore closure occurred via a complex 'stuttering' mechanism. This simplified system thus reveals the dynamic formation and dissolution of fusion pores.