PD-1 antibody in combination with chemotherapy for the treatment of SMARCA4-deficient advanced undifferentiated carcinoma of the duodenum: Two case reports.

BACKGROUND: SMARCA4 is a component of chromatin remodeling of SWItch/sucrose-nonfermenting (SWI/SNF) complexes and plays an essential role in oncogenesis. SMARCA4-deficient malignancies arising from the gastrointestinal tract are rare and have a poor prognosis. There is no standard treatment for advanced and undifferentiated SMARCA4-deficient duodenal malignancies. Programmed death 1 (PD-1) antibodies, known as immune checkpoint inhibitor antibodies, potentially play a role in treating gastrointestinal tract malignancies. CASE SUMMARY: We present two patients with SMARCA4 deficiency and TP53 gene mutation in advanced undifferentiated carcinomas of the duodenum. For both patients, SMARCA4 deficiency was confirmed by immunohistochemical staining for the BRG1 protein, while TP53 gene mutations were observed via next-generation sequencing. Both patients were administered chemotherapy in combination with an anti-PD-1 antibody. The two patients exhibited completely different responses to treatment and had different prognoses. Case 1 experienced rapid progression after PD-1 infusion and chemotherapy, case 2 experienced a remarkable response after treatment, and the progression-free survival was more than 6 months. CONCLUSION: This study described our clinical and pathological observations of SMARCA4-deficient advanced undifferentiated carcinoma of the duodenum. PD-1 combined with chemotherapy showed a certain efficacy in select patients, providing options for treating these highly malignant tumors. Patients with liver metastases had a worse prognosis than did those with only lymph node metastasis.

Rapid development of double-hit mRNA antibody cocktail against orthopoxviruses.

The Orthopoxvirus genus, especially variola virus (VARV), monkeypox virus (MPXV), remains a significant public health threat worldwide. The development of therapeutic antibodies against orthopoxviruses is largely hampered by the high cost of antibody engineering and manufacturing processes. mRNA-encoded antibodies have emerged as a powerful and universal platform for rapid antibody production. Herein, by using the established lipid nanoparticle (LNP)-encapsulated mRNA platform, we constructed four mRNA combinations that encode monoclonal antibodies with broad neutralization activities against orthopoxviruses. In vivo characterization demonstrated that a single intravenous injection of each LNP-encapsulated mRNA antibody in mice resulted in the rapid production of neutralizing antibodies. More importantly, mRNA antibody treatments showed significant protection from weight loss and mortality in the vaccinia virus (VACV) lethal challenge mouse model, and a unique mRNA antibody cocktail, Mix2a, exhibited superior in vivo protection by targeting both intracellular mature virus (IMV)-form and extracellular enveloped virus (EEV)-form viruses. In summary, our results demonstrate the proof-of-concept production of orthopoxvirus antibodies via the LNP-mRNA platform, highlighting the great potential of tailored mRNA antibody combinations as a universal strategy to combat orthopoxvirus as well as other emerging viruses.

Photoredox and Copper Dual-Catalyzed Cyclization of Alkyne-tethered α-Bromocarbonyls.

The synergistic systems of photoredox and copper catalyst have already appeared as a novel formation of green synthetic chemistry, which open new avenues for chemical synthesis applications. We describe a novel strategy for the cyclization of alkyne-tethered α-bromocarbonyls initiated by the cleavage of C(sp3 )-Br bond via the collaboration of photoredox and copper catalyst. The present protocol exhibits mildness using economical copper catalyst and visible-light at room temperature. The gram-scale and sunlight irradiation experiments proceeded smoothly to show the practicality of the methodology. It is notable that the newly generated oxygen in the product originates from H2 O.

Chemodivergent Tandem Radical Cyclization of Alkene-Substituted Quinazolinones: Rapid Access to Mono- and Di-Alkylated Ring-Fused Quinazolinones.

Chemodivergent tandem radical cyclization offers exciting possibilities for the synthesis of structurally diverse cyclic compounds. Herein, we revealed a chemodivergent tandem cyclization of alkene-substituted quinazolinones under metal- and base-free conditions, this transformation is initiated by alkyl radicals produced from oxidant-induced α-C(sp3 )-H functionalization of alkyl nitriles or esters. The reaction resulted in the selective synthesis of a series of mono- and di-alkylated ring-fused quinazolinones by modulating the loading of oxidant, reaction temperature, and reaction time. Mechanistic investigations show that the mono-alkylated ring-fused quinazolinones is constructed by the key process of 1,2-hydrogen shift, whereas the di-alkylated ring-fused quinazolinones is mainly achieved through crucial steps of resonance and proton transfer. This protocol is the first example of remote second alkylation on the aromatic ring via α-C(sp3 )-H functionalization and difunctionalization achieved by association of two unsaturated bonds in radical cyclization.

Efficacy and safety of third-line or later-line targeted treatment for patients with metastatic colorectal cancer: a meta-analysis.

Targeted therapy has been standardized in front-line therapies for metastatic colorectal cancer (mCRC), while explicit recommendations for third- or later-line are still lacking. This study evaluated the efficacy and safety of combining targeted therapy with chemotherapy in the third- or later-line treatment for mCRC via meta-analysis, providing evidence-based guidance for clinical or research practice. Comprehensive retrieval of related studies was conducted according to the PRISMA guideline. Studies were stratified with patient characteristics and pharmacological classification of the drugs. For the data available for quantitative analysis, pooled overall response rate, disease control rate, hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS), and adverse events rate with respective 95% confidence intervals (CIs) were calculated. A total of 22 studies (1,866 patients) were included in this meta-analysis. Data from 17 studies (1,769 patients) involving targets of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) were extracted for meta-analyses. The overall response rates for monotherapy and combined therapy were 4% (95% CI: 3%, 5%) and 20% (95% CI: 11%, 29%). The pooled HRs (combined therapy vs. mono) for OS and PFS were 0.72 (95% CI: 0.53, 0.99) and 0.34 (95% CI: 0.26, 0.45). Another five studies were included in narrative depiction, involving targets of BRAF, HER-2, ROS1, and NTRK. The findings of this meta-analysis indicate that VEGF and EGFR inhibitors manifest promising clinical response rates and prolonged survival in the treatment of mCRC with acceptable adverse events.

Inhalable vaccine of bacterial culture supernatant extract mediates protection against fatal pulmonary anthrax.

Pulmonary anthrax is the most fatal clinical form of anthrax and currently available injectable vaccines do not provide adequate protection against it. Hence, next-generation vaccines that effectively induce immunity against pulmonary anthrax are urgently needed. In the present study, we prepared an attenuated and low protease activity Bacillus anthracis strain A16R-5.1 by deleting five of its extracellular protease activity-associated genes and its lef gene through the CRISPR-Cas9 genome editing system. This mutant strain was then used to formulate a lethal toxin (LeTx)-free culture supernatant extract (CSE) anthrax vaccine, of which half was protective antigen (PA). We generated liquid, powder, and powder reconstituted formulations that could be delivered by aerosolized intratracheal inoculation. All of them induced strong humoral, cellular, and mucosal immune responses. The vaccines also produced LeTx neutralizing antibodies and conferred full protection against the lethal aerosol challenges of B. anthracis Pasteur II spores in mice. Compared to the recombinant PA vaccine, the CSE anthrax vaccine with equal PA content provided superior immunoprotection against pulmonary anthrax. The preceding results suggest that the CSE anthrax vaccine developed herein is suitable and scalable for use in inhalational immunization against pulmonary anthrax.

H-NS Represses Biofilm Formation and c-di-GMP Synthesis in Vibrio parahaemolyticus.

Objective: This study aimed to investigate the regulation of histone-like nucleoid structuring protein (H-NS) on biofilm formation and cyclic diguanylate (c-di-GMP) synthesis in Vibrio parahaemolyticus RIMD2210633. Methods: Regulatory mechanisms were analyzed by the combined utilization of crystal violet staining, quantification of c-di-GMP, quantitative real-time polymerase chain reaction, LacZ fusion, and electrophoretic-mobility shift assay. Results: The deletion of hns enhanced the biofilm formation and intracellular c-di-GMP levels in V. parahaemolyticus RIMD2210633. H-NS can bind the upstream promoter-proximal DNA regions of scrA, scrG, VP0117, VPA0198, VPA1176, VP0699, and VP2979 to repress their transcription. These genes encode a group of proteins with GGDEF and/or EAL domains associated with c-di-GMP metabolism. Conclusion: One of the mechanisms by which H-NS represses the biofilm formation by V. parahaemolyticus RIMD2210633 may be via repression of the production of intracellular c-di-GMP.

Aerosolized Zika virus infection in Guinea pigs.

Zika virus (ZIKV) is primarily transmitted through mosquito bites and sexual contact, and vertical transmission of ZIKV has also been observed in humans. In addition, ZIKV infection via unknown transmission routes has been frequently reported in clinical settings. However, whether ZIKV can be transmitted via aerosol routes remains unknown. In this study, we demonstrated that aerosolized ZIKV is fully infectious in vitro and in vivo. Remarkably, intratracheal (i.t.) inoculation with aerosolized ZIKV led to rapid viremia and viral secretion in saliva, as well as robust humoral and innate immune responses in guinea pigs. Transcriptome analysis further revealed that the expression of genes related to viral processes, biological regulation and the immune response was significantly changed. Together, our results confirm that aerosolized ZIKV can result in systemic infection and induce both innate and adaptive immune responses in guinea pigs, highlighting the possibility of ZIKV transmission via aerosols.

Occupational burnout analysis of border guards in the background of COVID-19 / 中国职业医学

@#Objective To analyze the occupational burnout status and its influencing factors of border guards in the prevention （ - ）Methods and control of coronavirus disease COVID 19 . A total of 1 313 border guards who participate in the prevention and control of epidemic diseases were selected as research subjects using the random cluster sampling method. Military Occupational Burnout Scale and Military Occupational Stress Scale were used to investigate the occupational burnout status and Results occupational stress in the research subjects. The median and 25th and 75th percentiles of military occupational （ ， ） （ ， ）， burnout and occupational stress total scores were 9.0 3.0 15.0 and 76.0 70.0 86.0 respectively. About 73.1% of the subjects were suffered from high occupational stress. The results of multiple linear regression analysis indicated that the higher the scores of interpersonal relationship, military special life, work pressure, unclear role and leadership ability factor in P occupational stress, and the lower the score of personal development, the more serious the occupational burnout (all <0.05 ) ， after excluding the influence of confounding factors; subjects with panic psychology inconvenience caused by closed ， management fear on accountability for poor prevention and no personal hobbies had more serious occupational burnout than （ P ） Conclusion - ， subjects without those factors all <0.05 . In the period of COVID 19 prevention the level of occupational burnout and occupational stress of border guards were generally low. The occupational burnout was mainly affected by occupational stress and fear of the epidemic.

[Value of Neutrophil/Lymphocyte Ratio and Monocyte/Lymphocyte Ratio in the Prognosis of Patients with Multiple Myeloma].

OBJECTIVE: To investigate the effect of neutrophil/lymphocyte ratio (NLR) and monocyte/lymphocyte ratio (MLR) in the valuation prognosis of patients with multiple myeloma (MM). METHODS: The clinical data of 82 patients with initially diagnosed MM admitted to Gansu Provincial People's Hospital was analyzed retrospectively. NLR and MLR were calculated based on blood routine results respectively. The optimal cut-off point of NLR and MLR was determined according to the ROC curve, and the patients were divided into the high NLR/MLR group and the low NLR/MLR group. The general data, biochemical indicators and prognosis of the patients in each groups were compared respectively. The prognostic significance of the high NLR/MLR group and the low NLR/MLR group in patients between different treatment regimens and different clinical characteristics were analyzed. Risk stratification was designed based on NLR and high MLR as two risk factors, and the effect of risk factors, on the prognosis of MM patients were compared. RESULTS: ROC curve analysis determined that the optimal cut-off point of NLR was 3.1 (sensitivity 75%, specificity 70.7%) and the optimal cut-off point of MLR was 0.34 (sensitivity 83.3%, specificity 53.4%). The lactate dehydrogenase (LDH) and mean platelet volume (MPV) were correlated to NLR and MLR (P<0.05). There were no significant difference in age, sex, serum calcium (Ca), ß 2-microglobulin (ß 2-MG), albumin (Alb), hemoglobin (Hb), platelet (PLT), serum creatinine (Cr), bone marrow plasma cell ratio and ISS stage between the two groups (P>0.05). The OS rate of patients with higher NLR and MLR was lower than those with low NLR and MLR and showed poor prognosis; Further analysis showed that there were statistically significant differences in OS time among patients with different MLR and NLR in the new drug treatment group and the traditional chemotherapy group, as well as patients in different age stratification groups, different ß 2-MG stratification groups and different serum creatinine stratification groups. Patients with 2 risk factors showed a poorer prognosis than those with 0-1 risk factor. CONCLUSION: Elevated NLR and MLR are associated with poor prognosis in MM patients and may serve as the cost-effective and readily available prognostic biomarkers.

[Analysis on Related Factors of Pulmonary Infection in Patients with Multiple Myeloma Treated with Bortezomib].

OBJECTIVE: To analyze the risk factors, distribution of pathogenic strains and tolerance of pulmonary infection in patients with multiple myeloma(MM) during bortezomib chemotherapy. METHODS: The clinical data of 85 patients with multiple myeloma treated by bortezomib in our hospital from January 2015 to January 2019 was analyzed. The patients were divided into infection group and control group according to whether they were infected. The tolerance, pathogen distribution, and related risk factors were retrospectively analyzed. RESULTS: Pulmonary infection rate was 55.29% in 85 MM patients. The proportions of the patients with anemia, neutropenia, and ECOG score ≥2 points in the infection group were significantly higher than those in the control group (P<0.05). In this study, 30 strains of pathogenic bacteria were detected, with gram-negative bacteria accounting for 60%, gram-positive bacteria for 33.33%, fungi for 3.3% and tuberculosis bacteria for 3.3%. Pseudomonas aeruginosa, klebsiella pneumoniae, streptococcus pneumoniae, staphylococcus aureus accounted showed the highest proportion. Most of MM patients with pulmonary infection showed a heterprognosis after two weeks antibiotic treatment, while 3 patients died. About 30 percent of early deaths were due to pulmonary infections. CONCLUSION: Anemia, neutropenia, ECOG score ≥2 points are the major clinical characteristics of the multiple myeloma patients with pulmonary infections. Pulmonary infection is an important cause of early death in patients with multiple myeloma. Pathogenic bacteria are mainly composed of gram-negative bacteria. Beta-lacta/ beta-lactamase inhibitor combinations or Carbapenems are effective empiric treatment for controlling the progression of pulmonary infection.

Application of Electromagnetic Navigation Bronchoscopy in the early diagnosis and treatment of lung cancer: a narrative review.

The diagnosis of lung cancer has long been a problem facing clinicians worldwide, and the emergence of electromagnetic navigation bronchoscopy (ENB) has played a critical role in the early diagnosis of lung cancer. Compared with other types of biopsy techniques (e.g., transthoracic needle biopsy, bronchoscopy, thoracoscopic biopsy, and thoracotomy), ENB guarantees high diagnostic accuracy and safety. In recent years, with the continuous development of ENB technology, the scope of its epitaxy has also expanded. This technology is no longer a simple auxiliary diagnosis test but an innovative technology that simultaneously assists in surgical treatment, opening new avenues of research for the treatment of early-stage lung cancer. However, ENB, as a human-mediated operating system, has some limitations and uncertainties in its actual clinical application and promotion, which need to be addressed as we continue to develop ENB technology. In response to the bottleneck in developing ENB technology in current clinical diagnosis and treatment, relevant scientific research and development personnel and clinicians have also performed continuing exploration and improvement of methods. However, to completely overcome the limitations of ENB, more technological innovations are needed. In this review, we describe the current major clinical application directions, application advantages, and limitations of ENB.

Histology transformation-mediated pathological atypism in small-cell lung cancer within the presence of chemotherapy: A case report.

BACKGROUND: The treatment of small-cell lung cancer (SCLC) has progressed little in recent years because of its unique biological activities and complex genomic alterations. Chemotherapy combined with radiotherapy has been widely accepted as the first-line treatment for SCLC. CASE SUMMARY: Here, we present a 68-year-old male smoker who was diagnosed with SCLC of the right lung. After several cycles of concurrent chemoradiotherapy, the tumor progressed with broad metastasis to liver and bone. Histopathological examination showed an obvious transformation to adenocarcinoma, probably a partial recurrence mediated by the chemotherapy-based regimen. A mixed tumor as the primary lesion and transformation from SCLC or/and tumor stem cells may have accounted for the pathology conversion. We adjusted the treatment schedule in accord with the change in phenotype. CONCLUSION: Although diffuse skeletal and hepatic metastases were seen on a recent computed tomography scan, the patient is alive, with intervals of progression and shrinkage of his cancer.

[Analysis of Risk Factors of Herpes Zoster in Patients with Multiple Myeloma Treated with Bortezomib].

OBJECTIVE: To explore and analyze the risk factors of herpes zoster in patients with multiple myeloma (MM) during the chemotherapy with bortezomib. METHODS: Clinical data of 85 MM patients treated with bontizomib from January 2015 to January 2019 were selected and divided into case group and control group accroding to the occurred of herpes zoster. The clinical characteristic, treatment outcome and related factor of herpes zoster were retrospective analyzed. RESULTS: Twenty of the 85 patients with MM treated with bortezomib developed herpes zoster occurred (23.5%). Single-factor analysis showed that age≥65 years, lymphocytopenia occurred before treatment, neutropenia occurred before treatment, ECOG score≥2, application of cyclophosphamide, absence of preventive antiviral therapy were associated with the genesis of herpes zoster (P＜0.05). Multivariate logistic regression analysis showed that lymphocytopenia occurred before treatment, the application of cyclophosphamide and the absence of preventive antiviral therapy were the independent risk factors for herpes zoster (P＜0.05). CONCLUSION: The incidence of herpes zoster is high in the multiple myeloma patients treated with bortezomib. Lymphocytopenia occurred before treatment, the application of cyclophosphamide, and the absence of prophylactic antiviral therapy are the important risk factors for herpes zoster, for which the clinicians should attach great importance.

Circular RNA in gastric cancer.

Gastric cancer (GC) is a common malignancy and is the third leading cause of cancer-related death. At present, there is no simple and effective screening method for early-stage GC, and the treatment results and prognosis are poor. With the continuous improvement of molecular biology techniques, research on circular RNA (circRNA) has gradually expanded over time. Much data supports the role of circRNA in tumorigenesis. Moreover, due to its structural specificity and biological stability, circRNA is anticipated to be a potential biomarker for tumor diagnosis. Studies have confirmed that circRNA can participate in the proliferation, invasion, metastasis, and apoptosis of GC. These findings will lead to novel directions for the diagnosis and treatment of GC. This article reviews the structure and function of circRNA, summarizes the current studies on circRNA, and discusses the potential diagnostic value of circRNA in GC.

Radiofrequency deep hyperthermia combined with chemotherapy in the treatment of advanced non-small cell lung cancer.

BACKGROUND: In the era of precision medicine, chemotherapy is still considered the cornerstone of treatment for lung cancer patients without gene mutations. How to reduce the toxicity and increase the efficiency of chemotherapy is worth exploring. This study aimed to investigate the curative effects and safety of hyperthermia combined with chemotherapy (HCT) for advanced patients with non-small cell lung cancer (NSCLC), especially those with malignant pleural effusion. METHODS: We retrospectively evaluated medical records of 93 patients with advanced NSCLC (stage IIIB-IV) from March 2011 to January 2014. The patients were divided into HCT and chemotherapy (CT) groups. The HCT group was treated with gemcitabine and cisplatin (GP) regimen combined with regional radiofrequency deep hyperthermia, while the CT group was treated with GP regimen only. Those with malignant pleural effusion extra underwent thoracentesis and intrapleural injection chemotherapy combined with hyperthermic or not. Clinical treatment results and adverse reactions were compared and analyzed after treatment. SPSS 19.0 software (SPSS Inc., USA) was used for statistical data processing. P values less than 0.05 were accepted to be statistically significant. RESULTS: Among the 93 patients, HCT group included 48 patients (16 patients with malignant pleural effusion), CT group included 45 patients (10 patients with malignant pleural effusion). There was no significant difference between the two groups in patient characteristics. The overall response rate (ORR) of pleural effusions was much better in HCT group than that in CT group (81.2% vs. 40.0%, P = 0.046). The patients in HCT group had lower incidence rate of weakness (12.5% vs. 46.7%, χ = 13.16, P < 0.001) and gastrointestinal (25.0% vs. 77.8%, χ = 25.88, P < 0.001) adverse reactions than that in CT group. The objective tumor response and survival showed no significant differences. CONCLUSIONS: Hyperthermia combined with chemotherapy might lead to the development of better therapeutic strategy for advanced NSCLC with malignant pleural effusion patients. Also, it could greatly reduce the chemotherapy toxic effects in the incidence of weakness and gastrointestinal adverse reactions in advanced NSCLC patients.

Analysis of Differential Expressions of Long Non-coding RNAs in Nasopharyngeal Carcinoma Using Next-generation Deep Sequencing.

Background: Little knowledge about long non-coding RNAs(lncRNAs) in nasopharyngeal carcinoma (NPC) has been acquired. Methods: Next-generation sequencing was applied in 7 cases of NPC tissues and 7 cases of normal tissues in nasopharynx. PLEX, CNCI and CPAT soft-wares were used to predict novel lncRNAs. Real-time Quantitative PCR (qPCR) further validated the data in 20 cases of NPC tissues and 14 cases of normal tissues. Then the cis-regulators and trans-regulators and potential biological functions together with pathways were predicted by Bioinformatics. Results: Totally, 4248 novel lncRNAs were found to be expressed in our samples. And 2192 lncRNAs and 23342 mRNAs were considered to be differentially expressed in NPC. Among the results, 306 lncRNAs and 4599 mRNAs were significantly up-regulated, whereas 204 lncRNAs and 2059 mRNAs were significantly down-regulated, respectively. Moreover, 62 lncRNAs trans-regulated genes were involved in Epstein-Barr virus (EBV) infection pathway in our study. Jun proto-oncogene (JUN), which was related to a cis-regulator lncRNA RP4-794H19.1, was enriched in cancers and involved in Tumor Necrosis Factor (TNF) signaling pathway, might play a key role in NPC. Conclusion: These findings broadened the lncRNAs landscape of NPC tissues and shed light on the roles of these lncRNAs, which might be conducive to the comprehensive management of NPC.

Revision of the concept of anti-angiogenesis and its applications in tumor treatment.

Anti-angiogenesis therapy, by blocking formation of new blood vessels in tumors, is the standard-of-care therapy for various cancer types. The classic concept of anti-angiogenesis is expected to turn a tumor into a "dormant" disease. However, the combination of anti-angiogenesis agents with conventional therapeutics has generally produced only modest survival benefits for cancer patients in clinical trials. Therefore, the concept and applications of anti-angiogenesis have evolved dramatically along with lessons learned from recent clinical experience. In this article, we will discuss the revised concept of anti-angiogenesis therapy and the applications of anti-angiogenesis drugs, and focus particularly on how to utilize current anti-angiogenesis agents and develop new approaches to provide more benefits to patients with cancer.

Changes in TL1A levels and associated cytokines during pathogenesis of diabetic retinopathy.

Tumor necrosis factor (TNF) ligand related molecule 1A (TL1A), also termed TNF superfamily member 15 and vascular endothelial growth inhibitor is important for tumorigenicity and autoimmunity. However, the function of TL1A in diabetic retinopathy (DR) remains to be elucidated. The present study established a diabetes mellitus (DM) rat model to investigate TL1A, vascular endothelial growth factor (VEGF), tumor necrosis factor­α (TNF­α) and interleukin­1ß (IL­1ß) expression levels in the retina, vitreous and serum of rats with DM at different stages (1 month group, 3 month group and 6 month group). The present study determined that TL1A expression levels in the retina and vitreous from the DM 1 month group were significantly lower compared with the control group. However, TL1A levels in the retina and vitreous were significantly increased in advanced stages of DM compared with the control group. Furthermore, the levels of VEGF in the retina and vitreous were significantly higher in the DM groups compared with the control group. The expression levels of TNF­α and IL­1ß in the retina and vitreous were significantly higher in DM 3 month and 6 month groups compared with the control group. It is of note that the expression levels of TL1A were significantly lower in the DM 1 and 3 month groups compared with the control group; however, they were significantly increased in the DM 6 month group compared with the DM 3 month group. The expression levels of VEGF, TNF­α and IL­1ß in blood serum have been observed to exhibit similar expression change dynamics as those of the retina and vitreous. Therefore, these findings suggest that TL1A may be a protective factor of DR, and may provide a rationale for the development of novel therapeutic strategies to treat DR.