The dominant exported proteins and protective antigens of Mycobacterium tuberculosis are a triad of related gene products called the antigen 85 (Ag85) complex. Each has also been implicated in disease pathogenesis through its fibronectin-binding capacities. A carboxylesterase domain was found within the amino acid sequences of Ag85A, B, and C, and each protein acted as a mycolyltransferase involved in the final stages of mycobacterial cell wall assembly, as shown by direct enzyme assay and site-directed mutagenesis. Furthermore, the use of an antagonist (6-azido-6-deoxy-alpha, alpha'-trehalose) of this activity demonstrates that these proteins are essential and potential targets for new antimycobacterial drugs.

Mycobacterium tuberculosis is known to synthesize α-, methoxy-, and keto-mycolic acids. We propose a detailed pathway to the biosynthesis of all mycolic acids in M. tuberculosis. Fatty acid synthetase I provides C20-S-coenzyme A to the fatty acid synthetase II system (FAS-IIA). Modules of FAS-IIA and FAS-IIB introduce cis unsaturation at two locations on a growing meroacid chain to yield three different forms of cis,cis-diunsaturated fatty acids (intermediates to α-, methoxy-, and keto-meroacids). These are methylated, and the mature meroacids and carboxylated C26-S-acyl carrier protein enter into the final Claisen-type condensation with polyketide synthase-13 (Pks13) to yield mycolyl-S-Pks13. We list candidate genes in the genome encoding the proposed dehydrase and isomerase in the FAS-IIA and FAS-IIB modules. We propose that the processing of mycolic acids begins by transfer of mycolic acids from mycolyl-S-Pks13 to d-mannopyranosyl-1-phosphoheptaprenol to yield 6-O-mycolyl-β-d-mannopyranosyl-1-phosphoheptaprenol and then to trehalose 6-phosphate to yield phosphorylated trehalose monomycolate (TMM-P). Phosphatase releases the phosphate group to yield TMM, which is immediately transported outside the cell by the ABC transporter. Antigen 85 then catalyzes the transfer of a mycolyl group from TMM to the cell wall arabinogalactan and to other TMMs to produce arabinogalactan-mycolate and trehalose dimycolate, respectively. We list candidate genes in the genome that encode the proposed mycolyltransferases I and II, phosphatase, and ABC transporter. The enzymes within this total pathway are targets for new drug discovery

High expression of PD-L1 was associated with the presence of EGFR mutations in surgically resected NSCLC and was an independent negative prognostic factor for this disease.

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Purpose: Therapies targeted to the immune checkpoint mediated by PD-1 and PD-L1 show antitumor activity in a subset of patients with non-small cell lung cancer (NSCLC). We have now examined PD-L1 expression and its regulation in NSCLC positive for the EML4-ALK fusion gene.Experimental Design: The expression of PD-L1 at the protein and mRNA levels in NSCLC cell lines was examined by flow cytometry and by reverse transcription and real-time PCR analysis, respectively. The expression of PD-L1 in 134 surgically resected NSCLC specimens was evaluated by immunohistochemical analysis.Results: The PD-L1 expression level was higher in NSCLC cell lines positive for EML4-ALK than in those negative for the fusion gene. Forced expression of EML4-ALK in Ba/F3 cells markedly increased PD-L1 expression, whereas endogenous PD-L1 expression in EML4-ALK-positive NSCLC cells was attenuated by treatment with the specific ALK inhibitor alectinib or by RNAi with ALK siRNAs. Furthermore, expression of PD-L1 was downregulated by inhibitors of the MEK-ERK and PI3K-AKT signaling pathways in NSCLC cells positive for either EML4-ALK or activating mutations of the EGFR. Finally, the expression level of PD-L1 was positively associated with the presence of EML4-ALK in NSCLC specimens.Conclusions: Our findings that both EML4-ALK and mutant EGFR upregulate PD-L1 by activating PI3K-AKT and MEK-ERK signaling pathways in NSCLC reveal a direct link between oncogenic drivers and PD-L1 expression.

A novel EGFR-tyrosine kinase inhibitor (TKI), osimertinib, has marked efficacy in patients with EGFR-mutated lung cancer. However, some patients show intrinsic resistance and an insufficient response to osimertinib. This study showed that osimertinib stimulated AXL by inhibiting a negative feedback loop. Activated AXL was associated with EGFR and HER3 in maintaining cell survival and inducing the emergence of cells tolerant to osimertinib. AXL inhibition reduced the viability of EGFR-mutated lung cancer cells overexpressing AXL that were exposed to osimertinib. The addition of an AXL inhibitor during either the initial or tolerant phases reduced tumor size and delayed tumor re-growth compared to osimertinib alone. AXL was highly expressed in clinical specimens of EGFR-mutated lung cancers and its high expression was associated with a low response rate to EGFR-TKI. These results indicated pivotal roles for AXL and its inhibition in the intrinsic resistance to osimertinib and the emergence of osimertinib-tolerant cells.

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The purpose of this study was to assess the relative advantages and drawbacks of the nanoprecipitation-solvent displacement method for a range of drugs with respect to the particle size and drug encapsulation in polylactic-co-glycolic acid (PLGA) nanoparticles. The particle size analysis indicated a unimodal particle size distribution in all systems, with a mean diameter of 160-170 nm, except for insulin nanoparticles, which showed a smaller particle size. The results of the encapsulation efficiency analysis demonstrated that more lipophilic drugs, such as cyclosporin and indomethacin, do not suffer from the problems of drug leakage to the external medium, resulting in improved drug content in the nanoparticles. In spite of the fact that valproic acid is a liquid that is very sparingly soluble in water, very low encapsulation efficiency was obtained. Ketoprofen, a drug sparingly soluble in water, demonstrated intermediate values of encapsulation that were well correlated with its intermediate lipophilicity. More hydrophilic drugs, such as vancomycin and phenobarbital, were poorly encapsulated in PLGA nanoparticles. Insulin was preferentially surface bound on the PLGA nanoparticles. However, a strong hypoglycemic effect of the insulin was observed after administration of the suspension of PLGA nanoparticles with surface-bound insulin to the ileum loop of male Wistar rats.