Renal cell carcinoma histologic subtypes exhibit distinct transcriptional profiles.

Molecular profiling of clear cell renal cell carcinoma (ccRCC) tumors of patients in a clinical trial has identified distinct transcriptomic signatures with predictive value, yet data in non-clear cell variants (nccRCC) are lacking. We examined the transcriptional profiles of RCC tumors representing key molecular pathways, from a multi-institutional, real-world patient cohort, including ccRCC and centrally reviewed nccRCC samples. ccRCC had increased angiogenesis signature scores compared with the heterogeneous group of nccRCC tumors, while cell cycle, fatty acid oxidation/AMPK signaling, and fatty acid synthesis/pentose phosphate signature scores were increased in one or more nccRCC subtypes. Among both ccRCC and nccRCC tumors, T effector scores statistically correlated with increased immune cell infiltration and were more commonly associated with immunotherapy-related markers (PD-L1+/TMBhi/MSIhi). In conclusion, this study provides evidence of differential gene transcriptional profiles among ccRCC versus nccRCC tumors, providing insights for optimizing personalized and histology-specific therapeutic strategies for patients with advanced RCC.

Analysis of treatment of muscle invasive bladder cancer using the national cancer database: Factors associated with receipt of aggressive therapy.

OBJECTIVES: To characterize the treatments received by muscle-invasive bladder cancer (MIBC) patients, analyze their use according to sociodemographic, clinical, pathologic, and facility variables, and identify possibilities for improvement in care, with the understanding that patients with MIBC face a potentially lethal disease, yet often do not receive guideline-concordant potentially curative therapies. MATERIALS AND METHODS: Using the National Cancer Data Base (NCDB), we analyzed 102,119 patients with MIBC diagnosed from 2009 to 2018. Treatments included cystectomy, radiation, chemotherapy (CT), or observation. Treatments including cystectomy or radiotherapy (RT) ≥50 Gy were considered aggressive therapy (AT). A multivariable generalized estimating equation model was used to assess the impact of the independent variables with receiving AT, using SAS version 9.4. RESULTS: The median age was 73 years, with 72.9% male, 84.3% White, and 7.1% Black. Stage distribution was 59.4% stage II, 23.0% stage III, and 17.6% stage IV. Overall, 55.2% of patients received AT, while 41.1% did not, with 26.6% receiving observation alone after transurethral resection of bladder tumor. 45.4% received cystectomy, 9.8% received RT, and 12.8% received CT as primary treatment. Notably, over 30% of patients ages 50 to 70 did not receive aggressive therapy. On multivariate analysis, factors associated with nonreceipt of AT included age >70 (OR < 0.79, P < 0.0001), Black race (OR 0.70, P < 0.0001), underinsured status (OR 0.62, P < 0.0001), high comorbidity (OR 0.74, P < 0.0001), and treatment at low volume (OR 0.72 P < 0.0001) or nonacademic cancer program (OR 0.54, P < 0.0001). Long-term trends included increases in utilization of perioperative CT (17.5% in 2009 to 46.7% in 2018, P < 0.001), and chemoradiation (5.4% in 2009 to 8.8% in 2018, P < 0.001). Using Cox regression analysis to control for confounding variables, receipt of aggressive therapy was associated with improved overall survival. CONCLUSIONS: Over a third of patients did not receive AT for MIBC, with many of these patients seemingly eligible by age and comorbidity status. Prospective studies are needed to determine why these patients do not receive AT. A better understanding of patient vs. access to care vs. provider factors will help to focus efforts to improve care for MIBC patients.

Efficient Synergistic Antibacterial Activity of α-MSH Using Chitosan-Based Versatile Nanoconjugates.

The application of antimicrobial peptides has emerged as an alternative therapeutic tool to encounter against multidrug resistance of different pathogenic organisms. α-Melanocyte stimulating hormone (α-MSH), an endogenous neuropeptide, is found to be efficient in eradicating infection of various kinds of Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA). However, the chemical stability and efficient delivery of these biopharmaceuticals (i.e., α-MSH) to bacterial cells with a significant antibacterial effect remains a key challenge. To address this issue, we have developed a chitosan-cholesterol polymer using a single-step, one-pot, and simple chemical conjugation technique, where α-MSH is loaded with a significantly high amount (37.7%), and the final product is obtained as chitosan-cholesterol α-MSH polymer-drug nanoconjugates. A staphylococcal growth inhibition experiment was performed using chitosan-cholesterol α-MSH and individual controls. α-MSH and chitosan-cholesterol both show bacterial growth inhibition by a magnitude of 50 and 79%, respectively. The killing efficiency of polymer-drug nanoconjugates was very drastic, and almost no bacterial colony was observed (∼100% inhibition) after overnight incubation. Phenotypic alternation was observed in the presence of α-MSH causing changes in the cell structure and shape, indicating stress on Staphylococcus aureus. As a further consequence, vigorous cell lysis with concomitant release of the cellular material in the nearby medium was observed after treatment of chitosan-cholesterol α-MSH nanoconjugates. This vigorous lysis of the cell structure is associated with extensive aggregation of the bacterial cells evident in scanning electron microscopy (SEM). The dose-response experiment was performed with various concentrations of chitosan-cholesterol α-MSH nanoconjugates to decipher the degree of the bactericidal effect. The concentration of α-MSH as low as 1 pM also shows significant inhibition of bacterial growth (∼40% growth inhibition) of Staphylococcus aureus. Despite playing an important role in inhibiting bacterial growth, our investigation on hemolytic assay shows that chitosan-cholesterol α-MSH is significantly nontoxic at a wide range of concentrations. In a nutshell, our analysis demonstrated novel antimicrobial activity of nanoparticle-conjugated α-MSH, which could be used as future therapeutics against multidrug-resistant Staphylococcus aureus and other types of bacterial cells.

Mechanisms of tyrosine kinase inhibitor resistance in renal cell carcinoma.

Renal cell carcinoma (RCC), the most prevalent type of kidney cancer, is a significant cause of cancer morbidity and mortality worldwide. Antiangiogenic tyrosine kinase inhibitors (TKIs), in combination with immune checkpoint inhibitors (ICIs), are among the first-line treatment options for patients with advanced RCC. These therapies target the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase pathway and other kinases crucial to cancer proliferation, survival, and metastasis. TKIs have yielded substantial improvements in progression-free survival (PFS) and overall survival (OS) for patients with advanced RCC. However, nearly all patients eventually progress on these drugs as resistance develops. This review provides an overview of TKI resistance in RCC and explores different mechanisms of resistance, including upregulation of alternative proangiogenic pathways, epithelial-mesenchymal transition (EMT), decreased intracellular drug concentrations due to efflux pumps and lysosomal sequestration, alterations in the tumor microenvironment including bone marrow-derived cells (BMDCs) and tumor-associated fibroblasts (TAFs), and genetic factors such as single nucleotide polymorphisms (SNPs). A comprehensive understanding of these mechanisms opens the door to the development of innovative therapeutic approaches that can effectively overcome TKI resistance, thereby improving outcomes for patients with advanced RCC.

Emerging perioperative therapeutic approaches in muscle invasive bladder cancer.

Bladder cancer is a significant healthcare burden with more than 17,000 deaths in the United States in 2018. Patients who are diagnosed with muscle invasive bladder cancer (MIBC) have a high rate of micro-metastatic disease and have a much poorer prognosis compared with patients who have less advanced lesions. Historically, neoadjuvant administration of cisplatin-based therapy followed by surgery has been the mainstay of treatment. Unfortunately, of patients who come in with initially diagnosed MIBC, more than 50% are ineligible for traditional cisplatin-based therapy. Today, new modalities of treatment such as immune checkpoint inhibitors are beginning to radically improve outcomes in this population. The addition of immune checkpoint therapy to traditional chemotherapy appears to augment pathologic complete response rates in the bladder during surgery. Immunotherapy combinations also provide novel trimodality approaches with excellent outcomes in those pursuing non-surgical management. Pure immunotherapy approaches appear promising in the neoadjuvant and adjuvant setting, and the immune checkpoint inhibitor nivolumab is now approved in the adjuvant setting for high-risk patients. Antibody drug conjugates, such as enfortumab vedotin, and targeted therapies, such as infigratinib, are in trials in the perioperative setting. This review article summarizes the current evidence and likely future developments for the management of muscle invasive bladder cancer in 2022 and beyond.

Understanding the Uptake and Challenges of Genetic Testing Guidelines for Prostate Cancer Patients.

BACKGROUND: Multiple studies have confirmed a high prevalence of prognostic germline mutations in prostate cancer. In recognition, the NCCN guidelines and recommendations for genetic counselling (GC) in prostate cancer patients were expanded. METHODS: Data on prostate cancer patients at a single tertiary cancer center from January 2019 - June 2019 were queried. The cohort of patients from the queried list were evaluated for their eligibility for genetic testing. From the patients that were eligible for testing, the rate of referrals was ascertained. A 10-item questionnaire was concurrently sent to providers to understand germline genetic testing patterns and potential barriers. RESULTS: Only 39% of the eligible prostate cancer patients were referred, with testing completed in 11% with indications. 30% of providers reported they would be comfortable completing genetic counseling themselves. The identified barriers to provide genetic testing themselves were lack of time and expertise (50%). Other barriers included: lack of genetic counselor workforce (70%), lack of knowledge of genetic testing and the inadequate co-ordination of referrals (60%). CONCLUSION: In this retrospective study, many patients met the criteria for GC, however, the referrals for this patient population are inconsistent, and only a handful of the eligible patients completed testing. Identified barriers were provider's knowledge and comfort with guidelines and testing, systemic bottlenecks such as limited capacity of genetic counsellors, and the creation of improved workflows.

The structure-function analysis of Obg-like GTPase proteins along the evolutionary tree from bacteria to humans.

Obg proteins belong to P-loop guanine triphosphatase (GTPase) that are conserved from bacteria to humans. Like other GTPases, Obg cycles between guanine triphosphate (GTP) bound "on" state and guanine diphosphate (GDP)-bound "off" state, thereby controlling various cellular processes. Different members of this group have unique structural characteristics; a conserved glycine-rich N-terminal domain known as obg fold, a central conserved nucleotide binding domain, and a less conserved C-terminal domain of other functions. Obg is a ribosome dependent GTPase helps in ribosome maturation by interacting with several proteins of the 50S subunit of the ribosome. Obg proteins have been widely considered as a regulator of cellular functions, helping in DNA replication, cell division. Apart from that, this protein also takes part in various stress adaptation pathways like a stringent response, sporulation, and general stress response. In this particular review, the structural features of ObgE have been highlighted and how the structure plays important role in interacting with regulators like GTP, ppGpp that are crucial for executing biological function has been orchestrated. In particular, we believe that Obg-like proteins can provide a link between different global pathways that are necessary for fine-tuning cellular processes to maintain the cellular energy status.

Multi-institutional Analysis of the Clinical and Genomic Characteristics of Black Patients with Metastatic Hormone-Sensitive Prostate Cancer.

BACKGROUND: The outcomes of metastatic hormone-sensitive prostate cancer (mHSPC) have significantly improved through treatment intensification, yet Black representation in those studies is suboptimal. METHODS: A multi-institutional, retrospective analysis of Black men with mHSPC was conducted, focusing on baseline demographics, treatment patterns, genomic profiles, clinical outcomes including prostate-specific antigen response, time to castrate-resistant prostate cancer (CRPC), and subsequent treatments. RESULTS: A total of 107 patients, median age 64 years, 62% with de novo metastases at diagnosis and 64% with high-volume disease, were included. Twenty-nine patients (27%) were treated with androgen deprivation therapy (ADT) with and without first generation anti-androgens, while 20%, 38% and 5% received chemotherapy, abiraterone, and enzalutamide, respectively. At time of data cut-off, 57 (54%) patients had developed CRPC, with a median time to CRPC of 25.4 months (95% CI 20.3-30.4). The median time to CRPC was 46.3 months (18.9-73.7) and 23.4 months (18.6-28.2) for patients who received ADT with or without first-generation anti-androgens and treatment intensification, respectively. The 2-year survival rate was 93.3%, and estimated median overall survival of was 74.9 months (95% CI, 68.7-81.0). Most patients (90%) underwent germline testing; the most frequent known alterations were found within the DNA repair group of genes. Somatic testing revealed pathogenic alterations of interest, notably TP53 (24%) and CDK12 (12%). CONCLUSION: In our cohort, Black men with mHSPC presented with a high proportion of de novo metastases and high-volume disease. Treatment outcomes were very favorable with ADT-based regimens. The genomic landscape suggests different molecular profile relative to White patients with potential therapeutic implications.

Efficacy of enfortumab vedotin in advanced urothelial cancer: Analysis from the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) study.

BACKGROUND: Enfortumab vedotin (EV) is a novel antibody-drug conjugate approved for advanced urothelial cancer (aUC) refractory to prior therapy. In the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) study, the authors looked at the experience with EV in patient subsets of interest for which activity had not been well defined in clinical trials. METHODS: UNITE was a retrospective study of patients with aUC treated with recently approved agents. This initial analysis focused on patients treated with EV. Patient data were abstracted from chart reviews by investigators at each site. The observed response rate (ORR) was investigator-assessed for patients with at least 1 post-baseline scan or clear evidence of clinical progression. ORRs were compared across subsets of interest for patients treated with EV monotherapy. RESULTS: The initial UNITE analysis included 304 patients from 16 institutions; 260 of these patients were treated with EV monotherapy and included in the analyses. In the monotherapy cohort, the ORR was 52%, and it was >40% in all reported subsets of interest, including patients with comorbidities previously excluded from clinical trials (baseline renal impairment, diabetes, and neuropathy) and patients with fibroblast growth factor receptor 3 (FGFR3) alterations. Progression-free survival and overall survival were 6.8 and 14.4 months, respectively. Patients with a pure urothelial histology had a higher ORR than patients with a variant histology component (58% vs 42%; P = .06). CONCLUSIONS: In a large retrospective cohort, responses to EV monotherapy were consistent with data previously reported in clinical trials and were also observed in various patient subsets, including patients with variant histology, patients with FGFR3 alterations, and patients previously excluded from clinical trials with an estimated glomerular filtration rate < 30 mL/min and significant comorbidities. LAY SUMMARY: Enfortumab vedotin, approved by the Food and Drug Administration in 2019, is an important new drug for the treatment of patients with advanced bladder cancer. This study looks at the effectiveness of enfortumab vedotin as it has been used at multiple centers since approval, and focuses on important patient populations previously excluded from clinical trials. These populations include patients with decreased kidney function, diabetes, and important mutations. Enfortumab vedotin is effective for treating these patients. Previously reported clinical trial data have been replicated in this real-world setting, and support the use of this drug in broader patient populations.

Outcomes With First-Line PD-1/PD-L1 Inhibitor Monotherapy for Metastatic Renal Cell Carcinoma (mRCC): A Multi-Institutional Cohort.

Introduction: The treatment landscape of metastatic renal cell carcinoma has advanced significantly with the approval of combination regimens containing an immune checkpoint inhibitor (ICI) for patients with treatment-naïve disease. Little information is available regarding the activity of single-agent ICIs for patients with previously untreated mRCC not enrolled in clinical trials. Methods: This retrospective, multicenter cohort included consecutive treatment-naïve mRCC patients from six institutions in the United States who received ≥1 dose of an ICI outside a clinical trial, between June 2017 and October 2019. Descriptive statistics were used to analyze outcomes including objective best response rate (ORR), progression-free survival (PFS), and tolerability. Results: The final analysis included 27 patients, 70% men, median age 64 years (range 42-92), 67% Caucasian, and 33% with ECOG 2 or 3 at baseline. Most patients had intermediate risk (85%, IMDC) with clear cell (56%), papillary (26%), unclassified (11%), chromophobe (4%), and translocation (4%) RCC. All patients had evidence of metastatic disease involving the lungs (59%), lymph node (41%), CNS (19%), liver (11%), adrenal gland (11%), and bone (11%). The median time on ICI was 3.1 (0.1-26.8) months, and the median PFS was 6.3 (95% CI, 0-18.6) months. Among the 21 patients with an evaluable response, the best ORR was 33%, including two complete responses and five partial responses. The ORR was 29% (n = 1 complete response, n = 5 partial response) in clear cell and 5% (n = 1 complete response) in non-clear cell RCC. Adverse events (AEs) of any cause were reported in 37% and included fatigue (11%), dermatitis (11%), diarrhea (7%), and shortness of breath (7%). Significant AEs (30%) included shortness of breath (7%), acute kidney injury (4%), dermatitis (4%), Clostridium difficile infection (4%), cerebrovascular accident (4%), and fatigue (7%). Three patients discontinued therapy due to grade 4 AEs. Conclusions: In this multi-institutional case series, single-agent ICI demonstrated objective responses and was well tolerated in a heterogeneous treatment-naïve mRCC cohort. ICI monotherapy is not the standard of care for patients with mRCC, and further investigation is necessary to explore predictive biomarkers for optimal treatment selection in this setting.

The hibernating 100S complex is a target of ribosome-recycling factor and elongation factor G in Staphylococcus aureus.

The formation of translationally inactive 70S dimers (called 100S ribosomes) by hibernation-promoting factor is a widespread survival strategy among bacteria. Ribosome dimerization is thought to be reversible, with the dissociation of the 100S complexes enabling ribosome recycling for participation in new rounds of translation. The precise pathway of 100S ribosome recycling has been unclear. We previously found that the heat-shock GTPase HflX in the human pathogen Staphylococcus aureus is a minor disassembly factor. Cells lacking hflX do not accumulate 100S ribosomes unless they are subjected to heat exposure, suggesting the existence of an alternative pathway during nonstressed conditions. Here, we provide biochemical and genetic evidence that two essential translation factors, ribosome-recycling factor (RRF) and GTPase elongation factor G (EF-G), synergistically split 100S ribosomes in a GTP-dependent but tRNA translocation-independent manner. We found that although HflX and the RRF/EF-G pair are functionally interchangeable, HflX is expressed at low levels and is dispensable under normal growth conditions. The bacterial RRF/EF-G pair was previously known to target only the post-termination 70S complexes; our results reveal a new role in the reversal of ribosome hibernation that is intimately linked to bacterial pathogenesis, persister formation, stress responses, and ribosome integrity.

Neoadjuvant Therapies for Bladder Cancer in Cisplatin-ineligible Patients: What Options Do We Have?

Neoadjuvant chemotherapy has proven clinical benefit in muscle- invasive bladder cancer. Cisplatin is the likely driver of this benefit. Textbook definitions of cisplatin ineligibility may restrict almost 50% of patients from therapy. Checkpoint inhibitors (anti- PD-1 antibodies and anti- CTLA-4 antibodies) are currently in clinical trials for neoadjuvant use. Initial data from these studies appear promising.

Nivolumab-induced hypophysitis leading to hypopituitarism and secondary empty sella syndrome in a patient with non-small cell lung cancer.

We describe the clinical course of a 64-year-old woman with stage IVa lung adenocarcinoma who presented with over 1 month of fatigue, unintentional weight loss and emesis. She initiated treatment with nivolumab immunotherapy 1 year prior and had been tolerating the treatment well. A comprehensive workup revealed multiple endocrinological abnormalities consistent with hypophysitis leading to hypopituitarism in the form of central adrenal insufficiency and hypogonadism as well as a partially empty sella on imaging. This case demonstrates that while receiving novel forms of treatment such as immunotherapy, patients should be monitored closely for a wide range of adverse effects.

Association of PD-L1, PD-L2, and Immune Response Markers in Matched Renal Clear Cell Carcinoma Primary and Metastatic Tissue Specimens.

Objectives: Immune checkpoint therapy has been promising in renal cell carcinoma, but no validated clinically relevant biomarkers exist. Metastatic deposits may have discordant biomarker expression. Methods: Fifty matched pairs of primary and metastatic kidney tumors were evaluated via immunohistochemistry for immune checkpoint proteins PD-1, PD-L1, and PD-L2 and the T-cell and macrophage surface markers CD3, FOXP3, and CD163. Semiquantitative scores incorporating prevalence of both tumor and nontumor labeling were compared between metastatic and primary kidney tumor specimens. Results: A large minority of patients had discordant expression of PD-1 (31.2%), PD-L1 (22.5%), or PD-L2 (21.5%) between primary and metastatic sites. The expression of the novel marker PD-L2 correlated with both PD-1 (r = 0.47, P = .02) and PD-L1 (r = 0.67, P < .001) in metastatic deposits. Conclusions: This study demonstrates that renal clear cell carcinoma primary tumors and metastatic deposits have some discordance in the expression of PD-L1, PD-1, and PD-L2.

Post-treatment changes in hematological parameters predict response to nivolumab monotherapy in non-small cell lung cancer patients.

BACKGROUND: The absolute neutrophil count (ANC), absolute lymphocyte count (ALC), absolute monocyte count (AMC) and neutrophil to lymphocyte ratio (NLR) are known markers of inflammation. We evaluated whether ANC, ALC, AMC and NLR, both before and after treatment with nivolumab, are indicative markers of overall survival (OS) and evaluated change in NLR as a predictive marker of response in non -small cell lung cancer (NSCLC) patients treated with nivolumab. METHODS: A total of 109 patients with advanced NSCLC treated with nivolumab were included. ANC, ALC, AMC and NLR were examined at initiation of nivolumab therapy and after two cycles. The prognostic role of ANC, ALC, AMC and NLR with OS and changes in NLR ratio were examined with Kaplan-Meier curves and proportional hazard model. RESULT: Post-treatment NLR ≥5 after two cycles of nivolumab was associated with poor OS (median OS in NLR = <5 vs NLR = ≥5 was 29.1 (16.2-40.9) vs 24.2(16.1-36.2) months respectively, p<0.001). In addition NLR increased in non-responders after two cycles of nivolumab by 6.6±21.8 as compared to responders (p = 0.027). CONCLUSIONS: Post-treatment ANC, ALC and NLR are independent prognostic factors in NSCLC patients treated with nivolumab. Changes in NLR can be an early biomarker for response in NSCLC patients treated with nivolumab.

Thermal and Nutritional Regulation of Ribosome Hibernation in Staphylococcus aureus.

The translationally silent 100S ribosome is a poorly understood form of the dimeric 70S complex that is ubiquitously found in all bacterial phyla. The elimination of the hibernating 100S ribosome leads to translational derepression, ribosome instability, antibiotic sensitivity, and biofilm defects in some bacteria. In Firmicutes, such as the opportunistic pathogen Staphylococcus aureus, a 190-amino acid protein called hibernating-promoting factor (HPF) dimerizes and conjoins two 70S ribosomes through a direct interaction between the HPF homodimer, with each HPF monomer tethered on an individual 70S complex. While the formation of the 100S ribosome in gammaproteobacteria and cyanobacteria is exclusively induced during postexponential growth phase and darkness, respectively, the 100S ribosomes in Firmicutes are constitutively produced from the lag-logarithmic phase through the post-stationary phase. Very little is known about the regulatory pathways that control hpf expression and 100S ribosome abundance. Here, we show that a general stress response (GSR) sigma factor (SigB) and a GTP-sensing transcription factor (CodY) integrate nutrient and thermal signals to regulate hpf synthesis in S. aureus, resulting in an enhanced virulence of the pathogen in a mouse model of septicemic infection. CodY-dependent regulation of hpf is strain specific. An epistasis analysis further demonstrated that CodY functions upstream of the GSR pathway in a condition-dependent manner. The results reveal an important link between S. aureus stress physiology, ribosome metabolism, and infection biology.IMPORTANCE The dimerization of 70S ribosomes (100S complex) plays an important role in translational regulation and infectivity of the major human pathogen Staphylococcus aureus Although the dimerizing factor HPF has been characterized biochemically, the pathways that regulate 100S ribosome abundance remain elusive. We identified a metabolite- and nutrient-sensing transcription factor, CodY, that serves both as an activator and a repressor of hpf expression in nutrient- and temperature-dependent manners. Furthermore, CodY-mediated activation of hpf masks a secondary hpf transcript derived from a general stress response SigB promoter. CodY and SigB regulate a repertoire of virulence genes. The unexpected link between ribosome homeostasis and the two master virulence regulators provides new opportunities for alternative druggable sites.

Disassembly of the Staphylococcus aureus hibernating 100S ribosome by an evolutionarily conserved GTPase.

The bacterial hibernating 100S ribosome is a poorly understood form of the dimeric 70S particle that has been linked to pathogenesis, translational repression, starvation responses, and ribosome turnover. In the opportunistic pathogen Staphylococcus aureus and most other bacteria, hibernation-promoting factor (HPF) homodimerizes the 70S ribosomes to form a translationally silent 100S complex. Conversely, the 100S ribosomes dissociate into subunits and are presumably recycled for new rounds of translation. The regulation and disassembly of the 100S ribosome are largely unknown because the temporal abundance of the 100S ribosome varies considerably among different bacterial phyla. Here, we identify a universally conserved GTPase (HflX) as a bona fide dissociation factor of the S. aureus 100S ribosome. The expression levels hpf and hflX are coregulated by general stress and stringent responses in a temperature-dependent manner. While all tested guanosine analogs stimulate the splitting activity of HflX on the 70S ribosome, only GTP can completely dissociate the 100S ribosome. Our results reveal the antagonistic relationship of HPF and HflX and uncover the key regulators of 70S and 100S ribosome homeostasis that are intimately associated with bacterial survival.