Rare Case of Recurrent Adamantinoma of the Tibia: Limited Efficacy of Pazopanib as a Standalone Treatment.

BACKGROUND Adamantinoma is a rare low-grade malignant bone tumor, usually found in the tibial diaphysis and metaphysis, with histological similarities to mandibular ameloblastoma. The most effective treatment of recurrent adamantinoma is not yet clear. This report is of a 22-year-old woman with recurrent tibial adamantinoma treated with the tyrosine kinase inhibitor pazopanib. CASE REPORT We report the case of a 22-year-old woman who was referred to our center for a suspicious bone lesion in the right tibia. Bone biopsy findings were consistent with an adamantinoma. En bloc resection was completed successfully, with no postoperative complications. Five years later, a positive emission tomography scan revealed mildly increased tracer uptake near the area of the previous lesion and in the right inguinal lymph node. Biopsies of the lesion and inguinal lymph node confirmed recurrence of the adamantinoma. Due to abdominal and pelvic metastasis, the patient underwent surgical debulking, along with an appendectomy, right salpingo-oophorectomy, intraoperative radiation therapy, and hyperthermic intraperitoneal chemotherapy. Subsequently, the patient was placed on pazopanib for 4 months; however, her tumor continued to worsen after 4 months of chemotherapy. Currently, the patient is receiving gemcitabine and docetaxel as second-line medical therapy. CONCLUSIONS This report showed that pazopanib as standalone treatment does not appear to have promising role on patient outcomes. To the best of our knowledge, this is the second report of pazopanib in the treatment of adamantinoma.

Suspected NUT carcinoma progressing on pembrolizumab, carboplatin, and paclitaxel as first-line treatment: a case report.

Introduction and importance: NUT carcinoma of the thorax is an extremely rare neoplasm characterized by a translocation between the NUT M1 gene and members of the bromodomain genetic family. Due to the rarity of the neoplasm, standardized treatment guidelines have not yet been established. Several chemotherapeutic agents have been used with limited success, due to the rapid development of resistance to treatment. Pembrolizumab, an anti-programmed-death-1 antibody, has become increasingly used in non-small-cell lung carcinomas. Consequently, pembrolizumab may be beneficial in the treatment of NUT carcinoma. Case presentation: In this article, we discuss the case of a 24-year-old man who was referred to our centre due to an incidental mass finding on an unrelated computed tomography scan. Morphological and immunohistochemical characteristics are highly suspicious of NUT carcinoma with bone metastasis. The patient was placed on carboplatin, paclitaxel, and pembrolizumab as first-line therapy. The patient later progressed and began receiving second-line treatment according to Ewing's protocol. 20 months later, the mass continued to grow, and the patient was started on docetaxel and gemcitabine, which was unsuccessful. After discussing with the patient, he decided to stop chemotherapy and begin palliative care. Clinical discussion: NUT carcinoma is an aggressive tumour with poor prognosis. Treatment options are limited and pembrolizumab does not seem to influence the clinical outcome of the neoplasm. Conclusion: Overall, pembrolizumab does not seem to improve the outcomes of NUT carcinoma patients. To the authors' knowledge, this is the second article reporting the effects of pembrolizumab on the progression of NUT carcinoma.

Intralesional injection of bleomycin in the management of low flow vascular malformations: Results and factors affecting the outcome.

OBJECTIVE: Ethanol has been a commonly used sclerosant for low-flow vascular malformations, but it carries a high risk of complications. Bleomycin has been recently introduced as a potentially effective treatment. The aim of this study was to evaluate the safety and efficacy of bleomycin intralesional injection for the treatment of low-flow vascular malformations and determine the different factors affecting the outcome. PATIENTS AND METHODS: A total of fifty patients with low-flow vascular malformations were enrolled in the study between April 2020 and March 2022. All patients underwent preoperative duplex ultrasound and magnetic resonance angiography. The procedure was performed under ultrasound and fluoroscopic guidance. All patients were assessed for the objective improvement, ultrasound assessment, and patient-reported outcome. RESULTS: The overall rate of objective improvement was 79.53% (78.05% in venous and 87.5% in lymphatic malformations), whereas 81.25% of the patients showed a degree of size reduction or complete obliteration on postoperative ultrasound. The patient-reported outcome analysis showed a statistically significant improvement in the mean score for the pain, overall symptoms, and self-confidence. On regression analysis, the only factor associated with poor objective outcome was diffuse lesions (ill-defined or extending in more than one body region or one compartment). No major complications were recorded. CONCLUSIONS: Bleomycin intralesional injection is a safe and effective treatment for low-flow vascular malformations.

Successful Recovery of COVID-19 Associated With Cardiomyopathy in Advanced Breast Cancer Patient With Pulmonary Lymphangitis Carcinomatosis.

SARS-CoV-2 infection induces myocardiopathy in 19% of severe cases, with a mortality rate of up to 51%. The mainstay of treatment is supportive care, steroids, and tocilizumab (anti-IL-6). This is a case of a 43-year-old woman diagnosed with hormone-positive breast cancer with lung metastasis and pulmonary lymphangitis carcinomatosis (PLC). Her baseline cardiac function was within normal limits. She presented to the emergency department with respiratory distress. Chest CT showed multiple bilateral ground-glass opacities consistent with COVID-19 pneumonia and confirmed by COVID-19-PCR nasal swab. Her condition deteriorated, and she was urgently admitted to the intensive care unit with evidence of a cytokine storm. She was started on tocilizumab, dexamethasone, and meropenem. Echocardiogram (echo) showed a severely reduced ejection fraction with severe global hypokinesis. A second dose of tocilizumab was given, and the dexamethasone dose was increased. Fortunately, the patient had significant clinical and biochemical improvement and regained her normal cardiac function. In conclusion, dexamethasone and tocilizumab could be promising aids in treating cardiomyopathy secondary to SARS-CoV-2 infection.

The Use of Crizotinib in Sclerosing Epithelioid Fibrosarcoma with ALK Mutation: A Case Report.

Sclerosing epithelioid fibrosarcoma is an ultra-rare and aggressive high-grade fibrosarcoma that was originally described in 1995. More than 100 cases are documented worldwide, with the most extensive case series reporting a high rate of recurrence and metastasis. ALK mutations are commonly seen in soft-tissue sarcomas; however, this is the first known case of an ALK V757M mutation. Here, we present a case using crizotinib in treating an ALK-positive sclerosing epithelioid fibrosarcoma refractory to all traditional treatment options.

GCC Countries Strategic Options in a Global Transition to Zero-Net Emissions.

Using a multi-level perspective approach combined with top-down macroeconomic models, we analyze the situation of the GCC countries in the perspective of a global transition to zero-net emissions before the end of the century. Based on these analyses, we propose strategic and political options for these oil and gas exporting countries. We show that it would be unwise for GCC member states to adopt an obstructionist strategy in international climate negotiations. On the contrary, these countries could be proactive in developing international emissions trading market and exploiting negative emissions obtained from CO2 direct reduction technologies, in particular direct air capture with CO2 sequestration, and thus contribute to a global net-zero-emissions regime in which clean fossil fuels are still used.

Increased Rates of Hospitalized Children with Type 1 and Type 2 Diabetes Mellitus in Central Brooklyn during the COVID-19 Pandemic.

Following reports of increased new-onset diabetes and worse severity of DKA for children with diabetes following SARS-CoV-2 infection, we studied hospitalization rates for children with type 1 diabetes (T1DM) and type 2 diabetes (T2DM) in our center during the citywide shutdown. Methods. We conducted a retrospective chart review of children admitted to our two hospitals from January 1, 2018, to December 31, 2020. We included ICD-10 codes for diabetic ketoacidosis (DKA), hyperglycemic hyperosmolar syndrome (HHS), and hyperglycemia only. Results. We included 132 patients with 214 hospitalizations: 157 T1DM, 41 T2DM, and 16 others (14 steroid induced, 2 MODY). Overall admissions rates for patients with all types of diabetes were 3.08% in 2018 to 3.54% in 2019 (p = 0.0120) and 4.73% in 2020 (p = 0.0772). Although there was no increase of T1DM admissions across all 3 years, T2DM admission rates increased from 0.29% to 1.47% (p = 0.0056). Newly diagnosed T1DM rates increased from 0.34% in 2018 to 1.28% (p = 0.002) in 2020, and new-onset T2DM rates also increased from 0.14% in 2018 to 0.9% in 2020 (p = 0.0012). Rates of new-onset diabetes presenting with DKA increased from 0.24% in 2018 to 0.96% in 2020 (p = 0.0014). HHS increased from 0.1% in 2018 to 0.45% in 2020 (p = 0.044). The severity of DKA in newly diagnosed was unaffected (p = 0.1582). Only 3 patients tested positive for SARS-CoV-2 infection by PCR. Conclusion. Our urban medical center is located in Central Brooklyn and serves a majority who are Black. This is the first study investigating pediatric diabetes cases admitted to Brooklyn during the first wave of the pandemic. Despite the overall pediatric admissions declining in 2020 due to the citywide shutdown, overall hospitalization rates in children with T2DM and in new-onset T1DM and T2DM increased, which is not directly associated with active SARS-CoV-2 infection. More studies are needed to elucidate the reason for this observed increase in hospitalization rates.

Gemcitabine-Induced Myositis in a Luminal B Breast Cancer patient: A Case Report.

Human epidermal growth factor receptor-positive breast cancer is an aggressive cancer which represents approximately a quarter of all breast cancers worldwide. Recent advances have led to the development of targeted therapies, such as trastuzumab (H), which have significantly improved prognosis. Such therapies are currently used alongside other chemotherapeutic agents, such as paclitaxel (P) and gemcitabine (G). The most common side effects of PGH combination therapy include thrombocytopenia and anemias. However, there have been no previous reports of myositis resulting from this combination. We report the case of a 54-year-old metastatic breast cancer patient on PGH therapy who developed muscle weakness. The patient was initially treated with trastuzumab, pertuzumab, and paclitaxel. However, pertuzumab was changed to gemcitabine due to severe diarrhea. After the fourth cycle of PGH, the patient presented with muscle weakness and creatine kinase levels of up to 6755 U/L. Magnetic resonance imaging of the femur and pelvis revealed diffuse bilateral myositis, suggesting a diagnosis of gemcitabine-induced myositis. The patient was placed on intravenous fluids and corticosteroids, which resolved her condition. To our knowledge, this is the first report of gemcitabine-induced myositis in a breast cancer patient. Further studies are needed to determine the underlying mechanisms of gemcitabine-induced myositis and develop preventative measures.

Characteristics and outcomes of small bowel adenocarcinoma: 14 years of experience at a single tertiary hospital in Saudi Arabia.

Small bowel adenocarcinoma (SBA) is an extremely rare cancer type. In the present study, the patient characteristics and clinical outcomes of patients diagnosed and treated for SBA at a single tertiary hospital were reported. All patients diagnosed and managed between 2007 and 2020 were reviewed. Regression analysis was used to assess variables associated with the metastatic stage at diagnosis. The Kaplan-Meier method was used to estimate survival and the log-rank test was used to determine factors associated with survival outcomes. Out of 137 cases of small bowel primary tumor, 43 consecutive patients with SBA were diagnosed with a median age of 53 years and the majority (76.7%) were males. The common initial presenting symptoms were abdominal pain (58.8%) and bowel obstruction (30.2%). The most common primary site was the duodenum (60.5%) and the majority (65.1%) were diagnosed with stage III/IV disease. Patients with a high neutrophil-lymphocyte ratio (NLR) (≥0.85) were more likely to be in the metastatic stage at diagnosis (P=0.01). The 3-year overall survival (OS) rates based on stage were 100% (I), 85% (II), 53% (III) and 33.9% (IV) (P=0.001). In addition to the stage, the Eastern Cooperative Oncology Group Performance Status (P<0.001), NLR (P<0.001), hypoalbuminemia (P=0.02) and chemotherapy in a metastatic setting (P=0.02) were prognostic factors for OS. In conclusion, NLR is a potential prognostic biomarker for a metastatic stage at diagnosis. Advanced stage, lower performance status score, low albumin level and high NLR are associated with short OS.

Combining Sunitinib and Bevacizumab for the Management of Advanced Renal Cell Carcinoma: A Phase I/II Trial.

BACKGROUND: Tyrosine kinase inhibitors remain a cornerstone in managing metastatic clear cell renal cell carcinoma (RCC). The 4 weeks on/2 weeks off intermittent sunitinib schedule could result in rebound angiogenesis and tumor progression in the 2-week rest period. We propose using bevacizumab during this period for continuous antiangiogenic effects. METHOD: This was a phase I/II study of patients with advanced clear cell RCC. Sunitinib was given 50 mg daily on a 4-week on/2-week off schedule. Bevacizumab was given on day 29 of each sunitinib cycle. The bevacizumab starting dose was 5 mg/kg, and the dose was escalated to 10 mg if there was no dose-limiting toxicity. The primary endpoints were response rate and progression-free survival (PFS). RESULTS: Twenty-five patients were recruited. The study was closed prematurely because of poor accrual. No dose-limiting toxicity was observed with 5 mg bevacizumab. One patient achieved a complete response, and 12 achieved a partial response (52% response rate). At a median follow-up of 42.2 months (95%, confidence interval (CI) 32.9 to 51.4), the median PFS duration was 16.5 months (95% CI 4.1-28.8), and the median overall survival time was 33.3 months (95% CI 19.4-47.3). Twenty-two patients (88%) had at least one grade 3 or 4 toxicity; the most common were thrombocytopenia (32%), lymphopenia (32%), hypertension (28%), and fatigue (24%). CONCLUSION: Continuous angiogenesis blockade by adding bevacizumab to the sunitinib on/off regimen for advanced RCC yields significant antitumor activity with manageable increased toxicity.

Combined Prophylactic Hyperthermic Intraperitoneal Chemotherapy and Intraoperative Radiotherapy for Localized Gastroesophageal Junction and Gastric Cancer: A Comparative Nonrandomized Study.

BACKGROUND: The peritoneum frequently is the only recurrence site after radical resection of gastric cancer. Data suggest that hyperthermic intraperitoneal chemotherapy (HIPEC) and intraoperative radiotherapy (IORT) reduce peritoneal recurrence and possibly improve survival for patients with resected gastric and serosal involvement. This study aimed to evaluate the efficacy of combining prophylactic HIPEC and IORT after radical resection of localized gastric cancer. METHODS: In this retrospective study, the medical records of adult patients with histologically proven gastric/gastroesophageal adenocarcinoma who underwent radical resection with curative intent were evaluated for recurrence and survival according to whether they received prophylactic HIPEC and IORT. RESULTS: The eligibility criteria were met by 58 patients, 33 of whom underwent prophylactic HIPEC and IORT after radical surgery. Overall, 91% the HIPEC/IORT group and 72% of the surgery-only group had ≤pT3 disease. The median follow-up period was 26.6 months for the HIPEC/IORT group and 50.6 months for the surgery group. Locoregional recurrence occurred for six patients (18.1%) in the HIPEC/IORT group and five patients (20%) in the surgery-only group, with peritoneal metastasis (PM) occurring in respectively three (9%) and six (24%) patients. The median recurrence-free survival (RFS) duration was 23.2 months (95% confidence interval [CI] 6.5-39.9 months) for the HIPEC/IORT group versus 24.8 months (95% CI 0.0-51.1 months) for the surgery-only group (p = 0.88), and the corresponding 5-year overall survival (OS) estimates were 69% and 58%. CONCLUSION: Prophylactic HIPEC and IORT after radical surgery for localized gastric or gastroesophageal cancer did not improve RFS or OS for an unselected group of patients at risk for peritoneal recurrence.

Adult-Type Ovarian Granulosa Cell Tumour: Treatment Outcomes From a Single-Institution Experience.

OBJECTIVES:  Ovarian granulosa cell tumour is rare. This study aims to report the clinical characteristics and long-term outcomes of adult-type ovarian granulosa cell tumour (AOGCT) at King Faisal Specialist Hospital and Research Centre (KFSH&RC) and to determine the prognostic factors affecting relapse and survival. METHODS: We retrospectively reviewed patients with AOGCT, from 1988 to 2014, who were treated at our institution. Baseline characteristics, pathological findings, and outcomes were analysed and reported. RESULTS: Sixty-one patients with AOGCT were identified with a median age of 49 years. Median follow-up was 5.0 years (range 2.1-8.2 years). 74% of patients were FIGO (International Federation of Gynecology and Obstetrics) stage I, whereas 7% were stage II, 5% were stage III, and unknown in 14% of the cases. The most common presenting symptoms included abdominal pain (43%) and vaginal bleeding (43%). The majority of patients (38 patients, 62%) were treated with total abdominal hysterectomy and bilateral salpingo-oophorectomy. Five (8%) patients received adjuvant chemotherapy. Sixteen patients (26%) relapsed with a median time to relapse of 5.5 years (0.7-8.1 years). Half of the recurrences (eight patients, 50%) occurred after five years of diagnosis. Five-year overall survival and disease-free survival (DFS) were 93% and 84%, respectively. Factors associated with a high risk of recurrence were the presence of ascites (p=0.000) and elevated preoperative CA 125 level (p=0.048). The overall survival was significantly influenced by the menopausal status (premenopausal 100% vs. postmenopausal 84%; p=0.02), preoperative CA 125 (normal 100% vs. elevated 64%; p=0.005), ascites (present 33% vs. absent 100%; p=0.000), and age (<55 years 100% vs. ≥ 55 years 77%; p= 0.002). CONCLUSION:  This study confirms a good outcome for patients with AOGCT. They require long-term follow-up as late recurrences can occur many years post definitive therapy. The presence of ascites and elevated preoperative CA 125 levels were associated with a higher risk of recurrence and poor prognosis. Outcomes appear unaffected by fertility-sparing surgery or adjuvant chemotherapy.

Efficacy of Everolimus Combined with 177Lu-Dotatate in the Treatment of Neuroendocrine Tumors.

Background: Both everolimus and peptide receptor radionuclide therapy (PRRT) are approved as monotherapies for advanced neuroendocrine tumors (NETs). Research in animal models showed synergism between the two treatment modalities. This study aimed to evaluate the safety and efficacy of combining everolimus and PRRT in the treatment of unresectable NETs. Methods: Adult patients (≥18 years) with progressing and unresectable histologically confirmed grade 1-2 NETs of all origins were enrolled. Everolimus was started at a 5 mg daily dose and was increased after the initial three patients to 10 mg daily. Patients were treated concurrently with 177Lu-DOTATATE at an 8-week interval, with planned four cycles. Safety was the primary endpoint, with response rate and progression-free survival (PFS) being secondary. Results: Eleven patients were enrolled. The trial was terminated early for poor accrual. The median age was 51 years (18-64), and 4 were males. The median number of cycles of 177Lu-DOTATATE was 3, and the median cumulative dose was 300 mCi. The most frequent grade 1-2 toxicities were stomatitis (90.9%) and nausea (72.7%). Less frequent were fatigue (63.6%), anorexia, diarrhea, and skin changes (each at a 36.4% rate). Grade 3 toxicities occurred in 36% (fatigue, infection, pneumonitis, neutropenia, and stroke). No patient developed grade 4 toxicity. Treatment was stopped because of progression in three patients, and toxicity in another three patients, in addition, in four patients due to therapy interruption and in one patient who developed stroke. One patient achieved partial response, and nine had stable disease. One patient developed disease progression. At a median follow-up of 18.9 months, three died and one was lost to follow-up. The median PFS was 23.3 months. Conclusions: The combination of everolimus at a dose of 10 mg daily and 177Lu-DOTATATE appears not to be feasible. A larger trial at a lower dose of everolimus is warranted.

Morphometric measurements and the relationship with body weight in the Sudanese Dorcas Gazelle and Bohor Reedbuck.

The objectives were to describe the morphometric measurements and determine the best model for estimating the relationship between body weight and morphometric measurements of the two Sudanese antelopes, Dorcas Gazelle (Gazella dorcas) and Bohor Reedbuck (Redunca redunca). Twenty-four animals belonging to two Sudanese antelope species, six males and six females from each species were used. Data on body weight and body measurements were recorded from each species. Averages of body weight and morphometric traits of Bohor Reedbuck were larger than the corresponding values of Dorcas Gazelle, while the opposite was true in the case of horn thickness, which was larger in the later. Stepwise regression analysis indicated that, the best model for Dorcas Gazelle had the variables neck length, belly girth and chest height, while Bohor Reedbuck had body length, head length, neck length, tail length, chest girth and pelvic height. These variables explained 82% of the total variation in body weight of Dorcas Gazelle, and 92% of the variation of Bohor Reedbuck. These results are discussed in relation to morphometric measurements reported for antelopes elsewhere.

Natural and engineered precision antibiotics in the context of resistance.

Antibiotics are essential weapons in our fight against infectious disease, yet the consequences of broad-spectrum antibiotic use on microbiome stability and pathogen resistance are prompting investigations into more selective alternatives. Echoing the advent of precision medicine in oncology, precision antibiotics with focused activities are emerging as a means of addressing infections without damaging microbiomes or incentivizing resistance. Historically, antibiotic design principles have been gleaned from Nature, and reinvestigation of overlooked antibacterials is now providing scaffolds and targets for the design of pathogen-specific drugs. In this perspective, we summarize the biosynthetic and antibacterial mechanisms used to access these activities, and discuss how such strategies may be co-opted through engineering approaches to afford precision antibiotics.

Neoadjuvant concurrent chemoradiotherapy using infusional gemcitabine in locally advanced rectal cancer: A phase II trial.

INTRODUCTION: Gemcitabine is a well-known radiosensitizer. Herein, we tested the efficacy and toxicity of preoperative concurrent infusional gemcitabine and radiotherapy in locally advanced rectal cancer. PATIENTS AND METHODS: This was a phase II, single-arm trial. Eligible patients had a diagnosis of rectal adenocarcinoma with clinical stage T3-T4 and/or nodal involvement, age ≥18 years, and no prior chemotherapy or radiotherapy. Patients received preoperative radiation at a dose of 50.4-54 Gy over 28 days with concurrent infusional gemcitabine administered at a dose of 100 mg/m2 over the course of 24 h weekly for 6 weeks. The primary endpoint was pathological complete response (pCR). RESULTS: Forty patients were recruited. Only one patient did not complete therapy due to death. Eight patients did not undergo surgery, one died, two progressed to nonresectable disease, and five withdrew consent. Five patients progressed prior to surgery, with two having unresectable metastases and three having resectable liver metastases. One was found to have peritoneal metastasis during surgery. Out of the 32 patients who underwent surgery, seven achieved pCR at a rate of 20%. With a median follow-up of 30 months, four additional patients had a distant relapse (one had a subsequent local relapse). The 3-year event-free and overall survival rates were 70% and 85%, respectively. The commonest preoperative grade 3-4 toxicity included lymphopenia (50%), neutropenia (41%), anemia (15%), diarrhea (12%), abdominal pain (12%), and proctitis (8%). CONCLUSION: Concurrent preoperative chemoradiotherapy using infusional gemcitabine for locally advanced rectal cancer achieved an encouraging degree of local control with manageable toxicity.

Multiplex suppression of four quadruplet codons via tRNA directed evolution.

Genetic code expansion technologies supplement the natural codon repertoire with assignable variants in vivo, but are often limited by heterologous translational components and low suppression efficiencies. Here, we explore engineered Escherichia coli tRNAs supporting quadruplet codon translation by first developing a library-cross-library selection to nominate quadruplet codon-anticodon pairs. We extend our findings using a phage-assisted continuous evolution strategy for quadruplet-decoding tRNA evolution (qtRNA-PACE) that improved quadruplet codon translation efficiencies up to 80-fold. Evolved qtRNAs appear to maintain codon-anticodon base pairing, are typically aminoacylated by their cognate tRNA synthetases, and enable processive translation of adjacent quadruplet codons. Using these components, we showcase the multiplexed decoding of up to four unique quadruplet codons by their corresponding qtRNAs in a single reporter. Cumulatively, our findings highlight how E. coli tRNAs can be engineered, evolved, and combined to decode quadruplet codons, portending future developments towards an exclusively quadruplet codon translation system.

Directed evolution of rRNA improves translation kinetics and recombinant protein yield.

In bacteria, ribosome kinetics are considered rate-limiting for protein synthesis and cell growth. Enhanced ribosome kinetics may augment bacterial growth and biomanufacturing through improvements to overall protein yield, but whether this can be achieved by ribosome-specific modifications remains unknown. Here, we evolve 16S ribosomal RNAs (rRNAs) from Escherichia coli, Pseudomonas aeruginosa, and Vibrio cholerae towards enhanced protein synthesis rates. We find that rRNA sequence origin significantly impacted evolutionary trajectory and generated rRNA mutants with augmented protein synthesis rates in both natural and engineered contexts, including the incorporation of noncanonical amino acids. Moreover, discovered consensus mutations can be ported onto phylogenetically divergent rRNAs, imparting improved translational activities. Finally, we show that increased translation rates in vivo coincide with only moderately reduced translational fidelity, but do not enhance bacterial population growth. Together, these findings provide a versatile platform for development of unnatural ribosomal functions in vivo.

Bacterial translation machinery for deliberate mistranslation of the genetic code.

Inaccurate expression of the genetic code, also known as mistranslation, is an emerging paradigm in microbial studies. Growing evidence suggests that many microbial pathogens can deliberately mistranslate their genetic code to help invade a host or evade host immune responses. However, discovering different capacities for deliberate mistranslation remains a challenge because each group of pathogens typically employs a unique mistranslation mechanism. In this study, we address this problem by studying duplicated genes of aminoacyl-transfer RNA (tRNA) synthetases. Using bacterial prolyl-tRNA synthetase (ProRS) genes as an example, we identify an anomalous ProRS isoform, ProRSx, and a corresponding tRNA, tRNAProA, that are predominately found in plant pathogens from Streptomyces species. We then show that tRNAProA has an unusual hybrid structure that allows this tRNA to mistranslate alanine codons as proline. Finally, we provide biochemical, genetic, and mass spectrometric evidence that cells which express ProRSx and tRNAProA can translate GCU alanine codons as both alanine and proline. This dual use of alanine codons creates a hidden proteome diversity due to stochastic Ala→Pro mutations in protein sequences. Thus, we show that important plant pathogens are equipped with a tool to alter the identity of their sense codons. This finding reveals the initial example of a natural tRNA synthetase/tRNA pair for dedicated mistranslation of sense codons.