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Cancer-associated fibroblasts (CAFs) in the tumor microenvironment are often linked to drug resistance. Here, we found that coculture with CAFs or culture in CAF-conditioned medium unexpectedly induced drug sensitivity in certain lung cancer cell lines. Gene expression and secretome analyses of CAFs and normal lung–associated fibroblasts (NAFs) revealed differential abundance of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs), which promoted or inhibited, respectively, signaling by the receptor IGF1R and the kinase FAK. Similar drug sensitization was seen in gefitinib-resistant, EGFR-mutant PC9GR lung cancer cells treated with recombinant IGFBPs. Conversely, drug sensitivity was decreased by recombinant IGFs or conditioned medium from CAFs in which IGFBP5 or IGFBP6 was silenced. Phosphoproteomics and receptor tyrosine kinase (RTK) array analyses indicated that exposure of PC9GR cells to CAF-conditioned medium also inhibited compensatory IGF1R and FAK signaling induced by the EGFR inhibitor osimertinib. Combined small-molecule inhibition of IGF1R and FAK phenocopied the CAF-mediated effects in culture and increased the antitumor effect of osimertinib in mice. Cells that were osimertinib resistant and had MET amplification or showed epithelial-to-mesenchymal transition also displayed residual sensitivity to IGFBPs. Thus, CAFs promote or reduce drug resistance in a context-dependent manner, and deciphering the relationship between the differential content of CAF secretomes and the signaling dependencies of the tumor may reveal effective combination treatment strategies. Contextually complicated CAFs: Cancer-associated fibroblasts (CAFs) are often implicated in drug resistance and tumor progression. However, CAFs are phenotypically and functionally heterogeneous, and those with a specific proteomic profile are associated with tumor suppression. Remsing Rix et al. found another twist in the role of CAFs in drug efficacy. They found that the same CAFs that induced drug resistance in some lung cancer cell lines promoted drug sensitivity in others. In EGFR-mutant tumors, drug-induced compensatory signaling was attenuated by IGF-binding proteins (IGFBPs) secreted by CAFs, thus enhancing or restoring drug efficacy in treatment-naïve and drug-resistant cells. Thus, rather than being binary, the function of CAFs in drug resistance depends on the signaling context of the cancer cells with which they interact. [ABSTRACT FROM AUTHOR]

The intramolecular reaction of furans with alkynes catalyzed by PtCl2 is mechanistically related to that of enynes in polar solvents. The reactivity of intermediate platinum carbenes formed in the PtCl2-catalyzed reactions of alkynes with alkenes or furans.

A post-polyketide tailoring step of Mithramycin biosynthesis by Streptomyces argillaceus ATCC 12956, was proposed to be catalyzed by ketroreductase (KR) MtmW. The major product, Mithramycin SK, was tested in vitro against a variety of human cancer cell lines and in a vitro toxicity assay, and showed an improved therapeutic index, in comparison to the parent drug, Mithramycin.

The corresponding enzymes MtmC and MtmTIII are responsible for the 3-methyltransfer and 4-ketoreduction respectively. The results also provide information regarding substrate specificity of several post- polyketide synthase (PKS) enzymes involved in mithramycin biosynthesis.

Theoretically, small molecule CDK4/6 inhibitors (CDK4/6is) represent a logical therapeutic option in non-small cell lung cancers since most of these malignancies have wildtype RB, the key target of CDKs and master regulator of the cell cycle. Unfortunately, CDK4/6is are found to have limited clinical activity as single agents in non-small cell lung cancer. To address this problem and to identify effective CDK4/6i combinations, we screened a library of targeted agents for efficacy in four non-small cell lung cancer lines treated with CDK4/6 inhibitors Palbociclib or Abemaciclib. The pan-PAK (p21-activated kinase) inhibitor PF03758309 emerged as a promising candidate with viability ratios indicating synergy in all 4 cell lines and for both CDK4/6is. It is noteworthy that the PAKs are downstream effectors of small GTPases Rac1 and Cdc42 and are overexpressed in a wide variety of cancers. Individually the compounds primarily induced cell cycle arrest; however, the synergistic combination induced apoptosis, accounting for the synergy. Surprisingly, while the pan-PAK inhibitor PF03758309 synergizes with CDK4/6is, no synergy occurs with group I PAK inhibitors FRAX486 or FRAX597. Cell lines treated only with Ribociclib, FRAX486 or FRAX597 underwent G1/G0 arrest, whereas combination treatment with these compounds predominantly resulted in autophagy. Combining high concentrations of FRAX486, which weakly inhibits PAK4, and Ribociclib, mimics the autophagy and apoptotic effect of PF03758309 combined with Ribociclib. FRAX597, a PAKi that does not inhibit PAK4 did not reduce autophagy in combination with Ribociclib. Our results suggest that a unique combination of PAKs plays a crucial role in the synergy of PAK inhibitors with CDK4/6i. Targeting this unique PAK combination, could greatly improve the efficacy of CDK4/6i and broaden the spectrum of cancer treatment. [ABSTRACT FROM AUTHOR]

The intramolecular conjugate addition of sulfoximine carbanions to alpha-beta-unsaturated esters is a powerful method for establishing a stereogenic center at a benzylic position. The methodology has the potential for application to natural product synthesis, especially because a procedure for the reductive removal of the sulfur functionality is known.

The landomycins, an angucycline family of antibiotics processing potent anticancer activities is studied widely since its first discovery in 1990 as products of Streptomyces cyanagenus S136. The two genes clusters encoding landomycin biosyntheses was cloned and sequenced. The study revealed that the clusters display an extraordinarily high degree of identity with regard to both the gene cluster organization and the DNA sequence of the respective genes.

A study was conducted, with nuclear magnetic resonance (NMR) analysis data, to investigate the structure of jadomycin B and the production of profile of S. venezuelae ISP5230. The result revealed that the jadomycin B appears as an inseparable diastereomeric mixture with 67% 3a-S and 33% 3a-R configuration.

Lung cancer patients with mutations in epidermal growth factor receptor (EGFR) benefit from treatments targeting tyrosine kinase inhibitors (TKIs). However, both intrinsic and acquired resistance of tumors to TKIs are common, and EGFR variants have been identified that are resistant to multiple TKIs. In the present study, we characterized selected EGFR variants previously observed in lung cancer patients and expressed in a murine bone marrow pro‐B Ba/F3 cell model. Among these EGFR variants, we report that an exon 20 deletion/insertion mutation S768insVGH is resistant to erlotinib (a first‐generation TKI), but sensitive to osimertinib (a third‐generation TKI). We also characterized a rare exon 21 germline variant, EGFR P848L, which transformed Ba/F3 cells and conferred resistance to multiple EGFR‐targeting TKIs. Our analysis revealed that P848L (a) does not bind erlotinib; (b) is turned over less rapidly than L858R (a common tumor‐derived EGFR mutation); (c) is not autophosphorylated at Tyr 1045 [the major docking site for Cbl proto‐oncogene (c‐Cbl) binding]; and (d) does not bind c‐Cbl. Using viability assays including 300 clinically relevant targeted compounds, we observed that Ba/F3 cells transduced with EGFR P848L, S768insVGH, or L858R have very different drug‐sensitivity profiles. In particular, EGFR P848L, but not L858R or S768insVGH, was sensitive to multiple Janus kinase 1/2 inhibitors. In contrast, cells driven by L858R, but not by P848L, were sensitive to multikinase MAPK/extracellular‐signal‐regulated kinase (ERK) kinase and ERK inhibitors including EGFR‐specific TKIs. These observations suggest that continued investigation of rare TKI‐resistant EGFR variants is warranted to identify optimal treatments for cancer. [ABSTRACT FROM AUTHOR]

Rational design of novel glycosylated derivatives from two nonglycosylated tetracyclic premithramycin-type molecules is described by expressing a glycosyltransferase gene from the urdamycin A pathway of Streptomyces fradiae into mithramycin nonproducing mutants of S. argillaceus. The results prove the unique substrate flexibility of the C-glycosyltransferase UrdGT2, which tolerates variety of sugar-donor substrates and various acceptor substrates.

TANK-binding kinase 1 (TBK1) has emerged as a novel therapeutic target for unspecified subset of lung cancers. TBK1 reportedly mediates prosurvival signaling by activating NF-κB and AKT. However, we observed that TBK1 knockdown also decreased viability of cells expressing constitutively active NF-κB and interferon regulatory factor 3. Basal phospho-AKT level was not reduced after TBK1 knockdown in TBK1-sensitive lung cancer cells, implicating that TBK1 mediates unknown survival mechanisms. To gain better insight into TBK1 survival signaling, we searched for altered phos-phoproteins using mass spectrometry following RNAi-mediated TBK1 knockdown. In total, we identified 2,080 phosphoproteins (4,621 peptides), of which 385 proteins (477 peptides) were affected after TBK1 knockdown. A view of the altered network identified a central role of Polo-like kinase 1 (PLK1) and known PLK1 targets. We found that TBK1 directly phosphorylated PLK1 in vitro. TBK1 phosphorylation was induced at mitosis, and loss of TBK1 impaired mitotic phosphorylation of PLK1 in TBK1 -sensitive lung cancer cells. Furthermore, lung cancer cell sensitivity to TBK1 was highly correlated with sensitivity to pharmacological PLK inhibition. We additionally found that TBK1 knockdown decreased metadherin phosphorylation at Ser-568. Metadherin was associated with poor outcome in lung cancer, and loss of metadherin caused growth inhibition and apoptosis in TBK1-sensitive lung cancer cells. These results collectively revealed TBK1 as a mitosis regulator through activation of PLK1 and also suggested metadherin as a putative TBK1 downstream effector involved in lung cancer cell survival. [ABSTRACT FROM AUTHOR]

Occurrence of the BCR-ABLT315I gatekeeper mutation is among the most pressing challenges in the therapy of chronic myeloid leukemia (CML). Several BCR-ABL inhibitors have multiple targets and pleiotropic effects that could be exploited for their synergistic potential. Testing combinations of such kinase inhibitors identified a strong synergy between danusertib and bosutinib that exclusively affected CML cells harboring BCR-ABLT315I. To elucidate the underlying mechanisms, we applied a systems-level approach comprising phosphoproteomics, transcriptomics and chemical proteomics. Data integration revealed that both compounds targeted Mapk pathways downstream of BCR-ABL, resulting in impaired activity of c-Myc. Using pharmacological validation, we assessed that the relative contributions of danusertib and bosutinib could be mimicked individually by Mapk inhibitors and collectively by downregulation of c-Myc through Brd4 inhibition. Thus, integration of genome- and proteome-wide technologies enabled the elucidation of the mechanism by which a new drug synergy targets the dependency of BCR-ABLT315I CML cells on c-Myc through nonobvious off targets. [ABSTRACT FROM AUTHOR]

Prediction of drug action in human cells is a major challenge in biomedical research. Additionally, there is strong interest in finding new applications for approved drugs and identifying potential side effects. We present a computational strategy to predict mechanisms, risks and potential new domains of drug treatment on the basis of target profiles acquired through chemical proteomics. Functional protein-protein interaction networks that share one biological function are constructed and their crosstalk with the drug is scored regarding function disruption. We apply this procedure to the target profile of the second-generation BCR-ABL inhibitor bafetinib which is in development for the treatment of imatinib-resistant chronic myeloid leukemia. Beside the well known effect on apoptosis, we propose potential treatment of lung cancer and IGF1R expressing blast crisis. [ABSTRACT FROM AUTHOR]

We describe a strategy for comprehending signaling pathways that are active in lung cancer cells and that are targeted by dasatinib using chemical proteomics to identify direct interacting proteins combined with immunoaffinity purification of tyrosine-phosphorylated peptides corresponding to activated tyrosine kinases. We identified nearly 40 different kinase targets of dasatinib. These include SRC-family kinase (SFK) members (LYN, SRC, FYN, LCK and YES), nonreceptor tyrosine kinases (FRK, BRK and ACK) and receptor tyrosine kinases (Ephrin receptors, DDR1 and EGFR). Using quantitative phosphoproteomics, we identified peptides corresponding to autophosphorylation sites of these tyrosine kinases that are inhibited in a concentration-dependent manner by dasatinib. Using drug-resistant gatekeeper mutants, we show that SFKs (particularly SRC and FYN), as well as EGFR, are relevant targets for dasatinib action. The combined mass spectrometry–based approach described here provides a system-level view of dasatinib action in cancer cells and suggests both functional targets and a rationale for combinatorial therapeutic strategies. [ABSTRACT FROM AUTHOR]

The medical and pharmaceutical communities are facing a dire need for new druggable targets, while, paradoxically, the targets of some drugs that are in clinical use or development remain elusive. Many compounds have been found to be more promiscuous than originally anticipated, which can potentially lead to side effects, but which may also open up additional medical uses. As we move toward systems biology and personalized medicine, comprehensively determining small molecule–target interaction profiles and mapping these on signaling and metabolic pathways will become increasingly necessary. Chemical proteomics is a powerful mass spectrometry–based affinity chromatography approach for identifying proteome-wide small molecule–protein interactions. Here we will provide a critical overview of the basic concepts and recent advances in chemical proteomics and review recent applications, with a particular emphasis on kinase inhibitors and natural products. [ABSTRACT FROM AUTHOR]

Following the initial success of imatinib as frontline therapy for chronic myeloid leukemia (CML), several second-generation therapeutics have been developed with increased potency and the ability to inhibit the majority of imatinib-resistant mutations. Here, we review the current knowledge about the target specificity of the two new inhibitors nilotinib and dasatinib in comparison to imatinib, including the recent large-scale chemical proteomics screens. [ABSTRACT FROM AUTHOR]

A 3 kb DNA fragment from the Streptomyces globisporus 1912 landomycin E (LaE) biosynthetic gene cluster (lnd) was completely sequenced. Three open reading frames were identified, lndGT4, lndZ4, and lndZ5, whose probable translation products resemble a glycosyltransferase, a reductase, and a hydroxylase, respectively. Studies of generated mutants from disruption and complementation experiments involving the lndGT4 gene allowed us to determine that LndGT4 controls the terminal L-rhodinose sugar attachment during LaE biosynthesis and that LndZ4/LndZ5 are responsible for the unique C11-hydroxylation of the landomycins. Generation of the novel landomycins F, G, and H in the course of these studies provided evidence for the flexibility of lnd glycosyltransferases toward their acceptor substrates and a basis for initial structure-activity relationships within the landomycin family of antibiotics. [Copyright &y& Elsevier]