Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622+3749 Observed by LHAASO-KM2A

We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622+3749 with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of 8.2σ for E>25  TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) =(95.47°±0.11°,37.92°±0.09°), and the extension is 0.40°±0.07°. The energy spectrum can be described by a power-law spectrum with an index of -2.92±0.17_{stat}±0.02_{sys}. No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of ∼160  TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.

Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources

The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10¹⁵ electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays¹. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. ²). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane^3-6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.

[Correlation between serum CCL20 level and disease severity in patients with rheumatoid arthritis]

Objective: To investigate the correlation between serum CCL20 level and disease severity in patients with rheumatoid arthritis (RA). Methods: From July 2018 to July 2019, a cross-sectional study was conducted in the Department of Rheumatology and Immunology, the Third Affiliated Hospital of Southern Medical University. The observation group consisted of 105 outpatients and inpatients diagnosed with RA, while the control group was 90 healthy people with age and gender matched physical examination in the Third Affiliated Hospital of Southern Medical University. According to Steinbroker classification, RA patients were divided into Steinbroker grade 2 group (n=35), Steinbroker grade 3 group (n=38) and steinbroker grade 4 group (n=32); according to DAS28 score, RA patients were divided into remission group (DAS28<2.6)(n=39), mild active group (DAS28 2.6-3.2)(n=25), moderate active stage group (DAS28 3.2-5.1)(n=20) and severe active stage group (DAS28 ≥ 5.1)(n=21). The levels of chemokine ligand 20 (CCL20), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were detected by ELISA. The levels of CCL20 in each group were compared, and the correlation between CCL20 and other indicators was analyzed. The receiver operating characteristic (ROC) curve of CCL20 in diagnosis of RA was analyzed to explore the correlation between CCL20 and disease severity of RA patients. Results: Compared with the normal control group, the serum CCL20 level in RA patients was significantly increased [(48.1±16.7) pg/ml vs (17.6±5.9) pg/ml, t=19.39, P<0.001]. In addition, serum CCL20 in steinbroker grade 4 group was significantly higher than that in Steinbroker grade 3 group [(59.5±10.1) pg/ml vs (47.4±17.5) pg/ml, t=3.472, P<0.001], and the serum CCL20 level in steinbroker grade 3 group was significantly higher than that in steinbroker grade 2 group [(47.4±17.5) pg/ml vs (38.4±14.6) pg/ml, t=2.370, P<0.001], CCL20 level in steinbroker grade 2 group was significantly higher than that in normal control group [(38.4±14.6) pg/ml vs (17.6±5.9) pg/ml, t=7.738, P<0.001]. In addition, serum CCL20 level was significantly positively correlated with steinbroker score (r=0.505, P<0.001); CCL20 level in active RA patients was significantly higher than that in remission RA patients [(57.2±13.2) pg/ml vs (32.7±8.9) pg/ml, t=10.31, P<0.001]. The serum CCL20 level in severe activity group was significantly higher than that in moderate activity group [(60.6±10.9) pg/ml vs (51.7±16.2) pg/ml, t=0.212, P=0.040], and the serum CCL20 level in moderate activity group was significantly higher than that in mild activity group [(51.7±16.2) pg/ml vs (40.5±18.6) pg/ml, t=0.217, P=0.037]. In addition, there was a significant positive correlation between serum CCL20 level and DAS28 score (r=0.451, P<0.001). In addition, serum CCL20 level was positively correlated with serum CRP (r=0.332, P<0.001). According to the ROC curve, the specificity of steinbroker grade 2 group was 0.53, and the sensitivity was 0.74, AUC was 0.659; the sensitivity of steinbroker grade 3 group was 0.78, and the specificity was 0.69, AUC was 0.734; the sensitivity of mild vs medium stage was 0.64, and the specificity was 0.70, AUC was 0.699; the sensitivity of medium stage vs severe stage was 0.57, and the specificity was 0.68,AUC was 0.678. Conclusion: Serum CCL20 level in RA patients is significantly increased and positively correlated with disease severity, which may be used as a marker to observe and evaluate the progression of RA.

Propofol suppresses proliferation and metastasis of colorectal cancer cells by regulating miR-124-3p.1/AKT3

BACKGROUND

Propofol, an extensively used intravenous anesthetic agents during cancer resection surgery, has been confirmed to execute anti-tumor effect on multiple cancers, including colorectal cancer (CRC). Although the role of propofol in CRC has been previously reported, its action mechanism remains poorly understood. This study further explored the biological function and underlying mechanism of propofol in CRC cells.

METHODS

The cell proliferation, migration and invasion were assessed by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, wound healing assay and transwell assay, respectively. The expression levels microRNA-124-3p.1 (miR-124-3p.1) and AKT serine/threonine kinase 3 (AKT3) was analyzed by quantitative real-time polymerase chain reaction. Western blot assay was employed to measure the protein expression of MMP-9, Vimentin and Cyclin D1. The interaction between miR-124-3p.1 and AKT3 was predicted by TargetScan and confirmed by dual-luciferase reporter assay.

RESULTS

Propofol inhibited CRC cell proliferation, migration and invasion. Knockdown of miR-124-3p.1 or AKT3 upregulation reversed the inhibitory effects of propofol on CRC cell proliferation and metastasis. Besides, AKT3 was a direct target of miR-124-3p.1 and its overexpression abated the anti-tumor effect of miR-124-3p.1 on CRC cell proliferation and metastasis.

CONCLUSION

Propofol inhibited CRC cell proliferation, migration and invasion by upregulating miR-124-3p.1 and downregulating AKT3, providing a new sight for propofol treatment of CRC.

[Risk factors for low anterior resection syndrome]

Objective: While low anterior resection avoided a permanent stoma, it might also cause bowel dysfunction which can significantly impact patients' quality of life. The objective of this study was to identify the incidence and risk factors for the development of bowel dysfunction following rectal surgery. Methods: Patients undergoing anterior resection for rectal neoplasm between January 2010 and December 2015 were identified from a rectal cancer database at the Department of Gastrointestinal Surgery, Beijing Hospital. All patients were asked to fill in a low anterior resection syndrome (LARS) questionnaire. Clinical factors were compared between patients with major LARS and those with minor or no LARS using conditional logistic regression. Results: There was 254 patients enrolled in the study. One hundred and eleven (44.1%) had major LARS symptoms. Neoadjuvant radiotherapy (OR=2.814, 95%CI: 1.097-5.561, P<0.001), low tumor location (OR=3.568, 95%CI: 1.159-6.546, P<0.001) and anastomotic leakage (OR=6.574, 95%CI: 1.689-15.367, P<0.001) were independent risk factors for development of major LARS symptoms. Conclusions: For patients with high risk of low anterior resection syndrome, the potential for long-term poor functional results should be discussed with patients and form a part of the decision-making in individual treatment plans. Sphincter-preserving surgery should be performed in highly selected patients to avoid major bowel dysfunction.

Donor-Derived Metastatic Melanoma and Checkpoint Inhibition

Donor-derived malignancy, particularly melanoma, is a rare but known complication of organ transplantation. Here we describe a case of metastatic melanoma in a deceased-donor kidney transplant recipient. After diagnosis, the patient was successfully treated with cessation of immunosuppression, explantation of the renal allograft, and novel melanoma therapies, including the mutation-targeted agents dabrafenib and trametinib and the immune checkpoint inhibitor nivolumab. These 2 new classes of melanoma therapy have revolutionized the course of metastatic melanoma, altering it from one of nearly certain mortality to one of potential cure. This case reviews the mechanisms of action of these therapies and reports our experience with them in the rare setting of donor-derived melanoma in a dialysis-dependent patient.

Opinion diversity and community formation in adaptive networks

It is interesting and of significant importance to investigate how network structures co-evolve with opinions. In this article, we show that, a simple model integrating consensus formation, link rewiring, and opinion change allows complex system dynamics to emerge, driving the system into a dynamic equilibrium with the co-existence of diversified opinions. Specifically, similar opinion holders may form into communities yet with no strict community consensus; and rather than being separated into disconnected communities, different communities are connected by a non-trivial proportion of inter-community links. More importantly, we show that the complex dynamics may lead to different numbers of communities at the steady state with a given tolerance between different opinion holders. We construct a framework for theoretically analyzing the co-evolution process. Theoretical analysis and extensive simulation results reveal some useful insights into the complex co-evolution process, including the formation of dynamic equilibrium, the transition between different steady states with different numbers of communities, and the dynamics between opinion distribution and network modularity.

Matrix replenishing by BMSCs is beneficial for osteoarthritic temporomandibular joint cartilage

OBJECTIVES

The present goal was to explore whether matrix replenishment is the primary requirement for osteoarthritic (OA) cartilage.

METHODS

Cells isolated from the superficial and deep zone cartilage of a pig temporomandibular joint (TMJ) were exposed to fluid flow shear stress (FFSS). Differences in matrix production and cellular differentiation were detected. Unilateral anterior crossbite (UAC) was applied to C57BL/6J female mice. Green fluorescent protein-labeled exogenous bone marrow stromal cells (GFP-BMSCs) were injected weekly into TMJs, starting from 3 weeks of UAC stimulation and continuing for 4-, 8- and 12-weeks. Another GFP-BMSCs injection UAC group stopped receiving injections for 4-weeks after 8-weeks of injections. Assessments were focused on morphological alterations in UAC mouse TMJ cartilage, the expression levels of DAP3, an anoikis marker, CD163, a scavenger receptor family member, and ki67, a proliferation indicator.

RESULTS

FFSS down-regulated type-II collagen expression but stimulated terminal differentiation in cells isolated from deep zone cartilage. It down-regulated aggrecan expression but up-regulated type I collagen in cells isolated from both superficial and deep zones. UAC caused matrix loss and anoikis and enhanced scavenging activity in deep zone chondrocytes without affecting cell proliferation. Superficial fibrillation was obvious in the late stage. Weekly injections of BMSCs largely restored these changes. The implanted BMSCs expressed a high level of CD163 protein but did not show remarkable cell proliferation. Terminating the supply of exogenous BMSCs reversed the restorative effects.

CONCLUSIONS

Scavenging the degraded matrix and replenishing the fibrosis-developmental matrix are the primary requirements for the repair of OA cartilage.

Effect of Retrievable Stent Size on Endovascular Treatment of Acute Ischemic Stroke: A Multicenter Study

BACKGROUND AND PURPOSE

In clinical practice, stent diameter is one of the variable properties important for endovascular treatment. A consensus guideline for stent retriever size selection has yet to be established. The aim of this study was to investigate the effects of different diameters of Solitaire retrievers on outcomes.

MATERIALS AND METHODS

Of 628 patients enrolled from the Endovascular Treatment for Acute Anterior Circulation Ischemic Stroke Registry, 256 were treated with the Solitaire 4-mm device and 372, with the 6-mm device. We matched patients treated with the 2 stent sizes using propensity score analysis. The successful outcome was reperfusion as measured by the modified Thrombolysis in Cerebral Infarction score immediately postprocedure and the dichotomized modified Rankin Scale score at 90 days. Symptomatic intracerebral hemorrhage and in-hospital mortality were also recorded.

RESULTS

After propensity score analysis, group outcomes did not differ. In addition, in patients with atherosclerosis-related occlusion, a higher reperfusion rate (P = .021) was observed in the Solitaire 4 group, as well as a shorter time interval (P = .002) and fewer passes (P = .025). Independent predictors of successful reperfusion in patients with atherosclerotic disease on logistic analysis were the small stent (OR, 3.217; 95% CI, 1.129-9.162; P = .029) and the propensity score acting as a covariate (OR, 52.84; 95% CI, 3.468-805.018; P = .004).

CONCLUSIONS

We found no evidence of a differential effect of intra-arterial therapy based on the size of Solitaire retrievers. In patients with atherosclerotic disease, favorable reperfusion was associated with deployment of a small stent.

Comprehensive evaluation of published gene expression prognostic signatures for biomarker-based lung cancer clinical studies

Background

A more accurate prognosis for non-small-cell lung cancer (NSCLC) patients could aid in the identification of patients at high risk for recurrence. Many NSCLC mRNA expression signatures claiming to be prognostic have been reported in the literature. The goal of this study was to identify the most promising mRNA prognostic signatures in NSCLC for further prospective clinical validation.

Experimental design

We carried out a systematic review and meta-analysis of published mRNA prognostic signatures for resected NSCLC. The prognostic performance of each signature was evaluated via a meta-analysis of 1927 early stage NSCLC patients collected from 15 studies using three evaluation metrics (hazard ratios, concordance scores, and time-dependent receiver-operating characteristic curves). The performance of each signature was then evaluated against 100 random signatures. The prognostic power independent of clinical risk factors was assessed by multivariate Cox models.

Results

Through a literature search, we identified 42 lung cancer prognostic signatures derived from genome-wide expression profiling analysis. Based on meta-analysis, 25 signatures were prognostic for survival after adjusting for clinical risk factors and 18 signatures carried out significantly better than random signatures. When analyzing histology types separately, 17 signatures and 8 signatures are prognostic for adenocarcinoma and squamous cell lung cancer, respectively. Despite little overlap among published gene signatures, the top-performing signatures are highly concordant in predicted patient outcomes.

Conclusions

Based on this large-scale meta-analysis, we identified a set of mRNA expression prognostic signatures appropriate for further validation in prospective clinical studies.

Abstract P5-07-10: MiR-146a functions as suppressive non-coding gene via indirect upregulation of Let-7 to promote asymmetric division and inhibit the self-renewal ability of breast cancer stem-like cells

MiR-146a plays as diverse roles in systemic malignancies, stimulating the tumor growth or blocking the tumor proliferation. However, its roles in breast cancer stem-like cells are barely known. We first identified the suppressive role of miR-146a in stem cells' renewal, promoting the asymmetric division of stem-like cells, and the expression of miR-146a was positively related with Let-7b level in vitro and in clinical specimens. Previous studies of Let-7 revealed its suppressive functions in stem-like cells expansion, and miR-146 was predicated to target and bind to the 3'UTR of LIN28, a negative regulator of Let-7 maturation. By using luc-assay and western, results showed that miR-146a increased the Let-7b level through degrading Lin28, and Lin28 is required for miR-146a induction of stem cells arresting and more asymmetric stem cells division. Moreover, Let-7 controlled Wnt signaling pathway activity is governed and strengthened by miR-146a, contributing to decrease the ratio of stem-like cells, forcing stem cells dividing asymmetrically. MiR-146a in turn formed negative feedback loop with Let-7 via the repression of NF-kB and Snai1 caused by Let-7b. Our results suggested the possible miR-146a/LIN28/Let-7/Snai1 signaling pathway in restraining the symmetric cells division, which was referred to the self-renewal capacity of breast cancer-stem like cells, and this axis helps to prohibit long–term tumor resistance and recurrence.MiR-146a plays as diverse roles in systemic malignancies, stimulating the tumor growth or blocking the tumor proliferation. However, its roles in breast cancer stem-like cells are barely known. We first identified the suppressive role of miR-146a in stem cells' renewal, promoting the asymmetric division of stem-like cells, and the expression of miR-146a was positively related with Let-7b level in vitro and in clinical specimens. Previous studies of Let-7 revealed its suppressive functions in stem-like cells expansion, and miR-146 was predicated to target and bind to the 3'UTR of LIN28, a negative regulator of Let-7 maturation. By using luc-assay and western, results showed that miR-146a increased the Let-7b level through degrading Lin28, and Lin28 is required for miR-146a induction of stem cells arresting and more asymmetric stem cells division. Moreover, Let-7 controlled Wnt signaling pathway activity is governed and strengthened by miR-146a, contributing to decrease the ratio of stem-like cells, forcing stem cells dividing asymmetrically. MiR-146a in turn formed negative feedback loop with Let-7 via the repression of NF-kB and Snai1 caused by Let-7b. Our results suggested the possible miR-146a/LIN28/Let-7/Snai1 signaling pathway in restraining the symmetric cells division, which was referred to the self-renewal capacity of breast cancer-stem like cells, and this axis helps to prohibit long–term tumor resistance and recurrence.

Citation Format: Sun X, Du N, Li G, Zhang J, Zhang J, Xiao G, Wang J, Tang S-C, Ren H. MiR-146a functions as suppressive non-coding gene via indirect upregulation of Let-7 to promote asymmetric division and inhibit the self-renewal ability of breast cancer stem-like cells [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-07-10.

Abstract P4-07-11: MicroRNA-367a promotes tumor growth and stemness potential by targeting FBXW7 in breast cancer

Increasing studies showed that MicroRNAs (miRNAs)participate in the carcinogenesis and progression of breast cancer, but the specific mechanism of miRNAs in breast cancer needs to be furtherexplored. in this study, wefound that miR-367a was significantly up-regulated in breast cancer tissue samples and cell lines, compared to paired normal tumor-adjacent samples and MCF-10A. meanwhile, Kaplan–Meier analysis demonstrated high miR-367a expression was evidently correlated with poor prognostic features of breast cancer. overexpression of miR-367a remarkably promoted proliferation, cell cycle,inhibited apoptosis ratios and stem-like capacity of breast cancer cells in vitro, whilesilencing the expression of miR-367a dramaticallyreversed these cellular events .in addition,In vivo studies showed that knockdown of miR-367a inhibited tumor growth of breast cancer ,moreover, F-box and WD repeat domain-containing 7 (FBXW7) was identified as a direct target genes of miR-367a, as miR-367a directly bound to the 3'untranslated region of FBXW7 . Notably, alterations of FBXW7 levels abrogated the effects of miR-367a on breast cancer cell proliferation, cell cycle, apoptosis and stemness potential. In conclusion,evidence from this study demonstrated that miR-367amay serve as a novel prognostic indicator for breast cancer patients andexerts tumor promotion,at least in part, by inhibiting FBXW7.

Key words: miR-367a, FBXW7, breast cancer, tumor growth, stem-like capacity.

Citation Format: Xiao G, Zhang J, Sun X, Qin S, Zhang B, Liu D, Liu J, Ren H. MicroRNA-367a promotes tumor growth and stemness potential by targeting FBXW7 in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-07-11.

Ontogeny of Hepatic Drug Transporters as Quantified by LC-MS/MS Proteomics

Protein expression of major hepatic uptake and efflux drug transporters in human pediatric (n = 69) and adult (n = 41) livers was quantified by liquid chromatography / tandem mass spectroscopy (LC-MS/MS). Transporter protein expression of OCT1, OATP1B3, P-gp, and MRP3 was age-dependent. Particularly, significant differences were observed in transporter expression (P < 0.05) between the following age groups: neonates vs. adults (OCT1, OATP1B3, P-gp), neonates or infants vs. adolescents and/or adults (OCT1, OATP1B3, and P-gp), infants vs. children (OATP1B3 and P-gp), and adolescents vs. adults (MRP3). OCT1 showed the largest increase, of almost 5-fold, in protein expression with age. Ontogenic expression of OATP1B1 was confounded by genotype and was revealed only in livers harboring SLCO1B1*1A/*1A. In livers >1 year, tissues harboring SLCO1B1*14/*1A showed 2.5-fold higher (P < 0.05) protein expression than SLCO1B1*15/*1A. Integration of these ontogeny data in physiologically based pharmacokinetic (PBPK) models will be a crucial step in predicting hepatic drug disposition in children.

[Analysis of clinical predictive factors of pathologic complete response after neoadjuvant chemoradiotherapy in rectal cancer]

OBJECTIVE

To evaluate the clinical predictive factors associated with pathologic complete response (pCR) after neoadjuvant chemoradiotherapy in rectal cancer.

METHODS

A retrospective analysis was performed on clinical data of 87 patients with rectal cancer, who underwent neoadjuvant chemoradiotherapy followed by radical surgery from April 2007 to May 2015. All patients received pelvic intensity-modulated radiotherapy (50 Gy/25 fractions) with concurrent fluorouracil- based chemotherapy and then underwent radical surgery 4-8 weeks later. The clinical factors associated with pCR or non-pCR were analyzed by Logistic regression.

RESULTS

Eighty-three patients had completed treatment, of which 15 patients (18.1%) achieved pCR after neoadjuvant chemoradiotherapy. Univariate analysis showed non-diabetes(P=0.033), pre-chemoradiotherapy plasma glucose(≤6.1 mmol/L)(P=0.033), pre-chemoradiotherapy CEA(≤5 μg/L)(P=0.026), pre- chemoradiotherapy plasma lymphocytes count(≤1.5×10(9)/L)(P=0.042), pre- chemoradiotherapy plasma platelet(≤240×10(12))(P=0.043), tumor pathological type(adenocarcinoma)(P=0.036)were significantly correlated with pCR after neoadjuvant chemoradiotherapy in rectal cancer. Logistic regression revealed that non-diabetes, pre-chemoradiotherapy plasma glucose, pre-chemoradiotherapy CEA(≤5 μg/L), pre-chemoradiotherapy plasma lymphocytes count(≤1.5×10(9)/L), tumor pathological type(adenocarcinoma) were independent predictive factors of pCR after neoadjuvant chemoradiotherapy in rectal cancer.

CONCLUSION

Patients with non-diabetes, normal plasma glucose, normal CEA, lower plasma lymphocytes count and adenocarcinoma were associated with pCR after neoadjuvant chemoradiotherapy for rectal cancer.

DIGRE: Drug-Induced Genomic Residual Effect Model for Successful Prediction of Multidrug Effects

Multidrug regimens are a promising strategy for improving therapeutic efficacy and reducing side effects, especially for complex disorders such as cancer. However, the use of multidrug therapies is very challenging, due to a lack of understanding of the mechanisms of drug interactions. We herein present a novel computational approach-Drug-Induced Genomic Residual Effect (DIGRE) Computational Model-to predict drug combination effects by explicitly modeling drug response curves and gene expression changes after drug treatments. The prediction performance of DIGRE was evaluated using two datasets: (i) OCI-LY3 B-lymphoma cells treated with 14 different drugs and (ii) MCF breast cancer cells treated with combinations of gefitinib and docetaxel at different doses. In both datasets, the predicted drug combination effects significantly correlated with the experimental results. The results indicated the model was useful in predicting drug combination effects, which may greatly facilitate the discovery of new, effective multidrug therapies.