C-S-Selective Stille-Coupling Enables Stereodefined Alkene Synthesis.

A palladium-catalyzed highly C‒S-selective Stille cross-coupling between aryl thianthrenium salts and tri- or tetrasubstituted alkenyl stannanes is described. Herein, critical challenges including site- and chemoselectivity control are well addressed through C‒H thianthrenation and C‒S alkenylation, thereby providing an expedient access to stereodefined tri- and tetrasubstituted alkenes in a stereoretentive fashion. Indeed, the palladium-catalyzed Stille-alkenylation of poly(pseudo)halogenated arenes displays privileged capability to differentiate C‒S over C‒I, C‒Br, C‒Cl bonds, as well as oxygen-based triflates (C‒OTf), tosylates (C‒OTs), carbamates and sulfamates under mild reaction conditions. Sequential and multiple cross-couplings via selective C‒X functionalization should be widely applicable for increasing functional molecular complexity. Modular installation of stereospecific alkene motifs into pharmaceuticals illustrated the synthetic application of the present protocol in drug discovery.

Bmi-1-induced miR-27a and miR-155 promote tumor metastasis and chemoresistance by targeting RKIP in gastric cancer.

BACKGROUND: We previously reported an inverse relationship between B cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) and Raf kinase inhibitory protein (RKIP), which is associated with the prognosis of gastric cancer (GC). In this study, we further explored the microRNA (miRNA) regulatory mechanism between Bmi-1 and RKIP. METHODS: Microarray analysis was first carried out to identify miRNA profiles that were differentially expressed in cells overexpressing Bmi-1. Then, miRNAs that could regulate RKIP were identified. Quantitative real-time PCR (qRT-PCR) and Western blotting were performed to measure the expression of Bmi-1, miR-155, miR-27a and RKIP. RKIP was confirmed as a target of miR-27a and miR-155 through luciferase reporter assays, qRT-PCR and Western blotting. The effects of the Bmi-1/miR-27a/RKIP and Bmi-1/miR-155/RKIP axes on tumor growth, proliferation, migration, invasion, colony-formation ability, metastasis and chemoresistance were investigated both in vitro and in vivo. RESULTS: The downregulation of RKIP by Bmi-1 occurred at the protein but not mRNA level. This indicates probable posttranscriptional regulation. miRNA expression profiles of cells with ectopic expression of Bmi-1 were analyzed and compared to those of control cells by microarray analysis. A total of 51 upregulated and 72 downregulated miRNAs were identified. Based on publicly available algorithms, miR-27a and miR-155 were predicted, selected and demonstrated to target RKIP. Bmi-1, miR-27a and miR-155 are elevated in human GC and associated with poor prognosis of GC, while RKIP is expressed at lower levels in GC and correlated with good prognosis. Then, in vitro tests shown that in addition to regulating RKIP expression via miR-27a and miR-155, Bmi-1 was also able to regulate the migration, invasion, proliferation, colony-formation ability and chemosensitivity of GC cells through the same pathway. Finally, the in vivo test showed similar results, whereby the knockdown of the Bmi-1 gene led to the inhibition of tumor growth, metastasis and chemoresistance through miR-27a and miR-155. CONCLUSIONS: Bmi-1 was proven to induce the expression of miR-27a and miR-155 and thus promote tumor metastasis and chemoresistance by targeting RKIP in GC. Overall, miR-27a and miR-155 might be promising targets for the screening, diagnosis, prognosis, treatment and disease monitoring of GC.

Identification of gemcitabine resistance-related AHNAK2 gene associated with prognosis and immune infiltration in pancreatic cancer.

Purpose: Gemcitabine is a basic chemotherapy drug for pancreatic cancer (PC), but resistance is common and causes tumor recurrence and metastasis. Therefore, it is significant to explore gemcitabine resistance-related molecules for individualized treatment and prognosis assessment of PC. Methods: In this study, transcriptome sequencing and TCGA database analysis were performed, and a differentiated gene AHNAK2 was screened. MEXPRESS database, tissue microarray analysis, and CIBERSORT and TIMER databases were used to correlate AHNAK2 expression with clinicopathological features and prognosis and immune infiltration of PC. Enrichment analysis was used to investigate the significant biological processes associated with AHNAK2. Results: AHNAK2 was highly expressed in gemcitabine-resistant cells. High expression of AHNAK2 increased the risk of poor overall survival (OS) and progression-free survival (PFS) in PC. Clinicopathologic analysis revealed that AHNAK2 correlated with KRAS, TP53 mutations, histologic type, short OS, N stage, and elevated CA199 levels in PC. Knockdown of AHNAK2 inhibited the ability of cell proliferation and colony formation and enhanced the toxic effect of gemcitabine in PC. Meanwhile, the knockdown of AHNAK2 expression enhanced cell-ECM adhesion, inhibited cell-cell adhesion, and downregulated the KRAS/p53 signaling pathway in PC. Furthermore, AHNAK2 was correlated with immune infiltration, especially B cells and macrophages. Conclusions: Our study unveils for the first time the pivotal role of AHNAK2 in PC, particularly its association with gemcitabine resistance, clinical prognosis, and immune infiltration. AHNAK2 not only drives the proliferation and drug resistance of PC cells by potentially activating the KRAS/p53 pathway but also significantly impacts cell-cell and cell- ECM adhesion. Additionally, AHNAK2 plays a crucial role in modulating the tumor immune microenvironment. These insights underscore AHNAK2's unique potential as a novel therapeutic target for overcoming gemcitabine resistance, offering new perspectives for PC treatment strategies.

Prognostic value of RRM1 and its effect on chemoresistance in pancreatic cancer.

PURPOSE: Pancreatic cancer (PC) remains a lethal disease, and gemcitabine resistance is prevalent. However, the biomarkers suggestive of gemcitabine resistance remain unclear. METHODS: Bioinformatic tools identified ribonucleotide reductase catalytic subunit M1 (RRM1) in gemcitabine-related datasets. A cox regression model revealed the predictive value of RRM1 with clinical features. An external clinical cohort confirmed the prognostic value of RRM1. RRM1 expression was validated in gemcitabine-resistant cells in vitro and in orthotopic PC model. CCK8, flow cytometry, transwell migration, and invasion assays were used to explore the effect of RRM1 on gemcitabine-resistant cells. The CIBERSORT algorithm investigated the impact of RRM1 on immune infiltration. RESULTS: The constructed nomogram based on RRM1 effectively predicted prognosis and was further validated. Moreover, patients with higher RRM1 had shorter overall survival. RRM1 expression was significantly higher in PC tissue and gemcitabine-resistant cells in vitro and in vivo. RRM1 knockdown reversed gemcitabine resistance, inhibited migration and invasion. The infiltration levels of CD4 + T cells, CD8 + T cells, neutrophils, and plasma cells correlated markedly with RRM1 expression, and communication between tumor and immune cells probably depends on NF-κB/mTOR signaling. CONCLUSION: RRM1 may be a potential marker for prognosis and a target marker for gemcitabine resistance in PC.

Arsenic trioxide sensitizes pancreatic cancer cells to gemcitabine through downregulation of the TIMP1/PI3K/AKT/mTOR axis.

Gemcitabine (GEM) is the first-line medication for pancreatic ductal adenocarcinoma (PDAC). However, over some treatment cycles, GEM sensitivity declines and chemotherapeutic resistance develops, resulting in tumor recurrence and metastasis. Therefore, it is critical to elucidate the mechanism of GEM chemoresistance. And a specific drug that is closely related to the mechanism is urgently required to sensitize GEM. Here, tissue inhibitor of matrix metalloproteinases 1 (TIMP1) and phosphorylated mammalian target of rapamycin (p-mTOR) were found to be substantially elevated in PDAC patients and were associated with worse overall survival. The TIMP1/PI3K/AKT/mTOR pathway was found in GEM-resistant PDAC cells and was revealed to be involved in epithelial-mesenchymal transition (EMT) and apoptosis. Furthermore, arsenic trioxide (ATO), a basic therapeutic drug for acute promyelocytic leukemia, mediated TIMP1 reduction by inducing reactive oxygen species generation and hampered the subsequent PI3K/AKT/mTOR axis. Moreover, the combination of ATO and GEM cooperatively suppressed the TIMP1/PI3K/AKT/mTOR pathway, synergistically inhibited EMT and promoted apoptosis. In vitro and in vivo, ATO combined with GEM has a collaborative anticancer effect, inhibiting cancer cell proliferation, migration, invasion, and suppressing tumor growth both in PDAC parental and GEM-resistant cells. Overall, the TIMP1/PI3K/AKT/mTOR pathway is present in PDAC and linked to GEM resistance. ATO suppresses the axis to sensitize GEM and reverse GEM resistance, suggesting a promising treatment for the disease.

A novel approach for quantitative determination of cellulose content in tobacco via 2D HSQC NMR spectroscopy.

Cellulose is an important component of tobacco (Nicotiana tabacum L.) cell walls, which can be precursors for many harmful compounds in smoke. Traditional cellulose content analysis methods involve sequential extraction and separation steps, which are time-consuming and environmentally unfriendly. In this study, a novel method was first introduced to analyze cellulose content in tobacco via two-dimensional heteronuclear single quantum coherence (2D HSQC) NMR spectroscopy. The method was based on derivatization approach to allow the dissolution of insoluble polysaccharide fractions of tobacco cell walls in DMSO­d6/pyridine-d5 (4:1 v/v) for NMR analysis. The NMR results suggested that besides the main NMR signals of cellulose, partial signals of hemicellulose including mannopyranose, arabinofuranose, and galactopyranose units could also be identified. In addition, the utilization of relaxation reagents has proved to be an effective way to improve the sensitivity of 2D NMR spectroscopy, which was beneficial for quantification of biological samples with limited quantities. To overcome the limitations of quantification using 2D NMR, the calibration curve of cellulose with 1,3,5-trimethoxybenzene as internal reference was constructed and thus the accurate measurement of cellulose in tobacco was achieved. Compared with the chemical method, the interesting method was simple, reliable, and environmentally friendly, which provided a new insight for quantitative determination and structure analysis of plant macromolecules in complex samples.

Simultaneous Determination of Fifteen Polyphenols in Fruit Juice Using Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry Combining Dispersive Liquid-Liquid Microextraction.

Polyphenols are secondary metabolites of plants and used as effective antioxidants in dietary supplements, whose main sources are fruits, vegetables, and grains. To clarify the content and distribution of polyphenols in different fruit species samples accurately, a rapid and sensitive ultrahigh-pressure liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method combining dispersive liquid-liquid microextraction (DLLME) was developed for quantitative determination of fifteen polyphenol compounds in fruit juice. In this method, the targets were first extracted from 1 g of fruit juice sample using 10 mL of 80% ethanol solution by ultrasonic-assisted extraction (UAE). Then, 1.0 mL of UAE extracted solution, 60 µL of n-octanol and 2.0 mL of H2O were performed in the following DLLME procedure. A C18 reversed-phase column, ZORBAX SB (100 × 4.6 mm, 3.5 µm), was proposed under gradient elution with 0.1% formic acid aqueous solution and methanol mobile phases for the determination of 15 polyphenols, allowing us to obtain polyphenolic profiles in less than 23.0 min. Under the optimum conditions, the enrichment factors ranged from 162 to 194. The results showed that the 15 polyphenols had linear correlation coefficients (R 2) more than 0.99. The limits of detection (LODs) were between 18.3 and 103.5 ng/g, and the average recoveries were between 96.9 and 116.3% with interday relative standard deviations (RSDs) ranging from 4.4 to 8.2% in all cases. The method was successfully applied to the analysis of real fruit juice samples and presented itself as a simple, rapid, practical, and environment-friendly technique.

TIMP1 derived from pancreatic cancer cells stimulates Schwann cells and promotes the occurrence of perineural invasion.

Perineural invasion (PNI) occurs in most pancreatic ductal adenocarcinomas (PDACs). The relationship between cancer cells and peripheral nerves, however, is unknown. Therefore, we focused on the cooperation of PDAC cells and peripheral nerve astrocytes, Schwann cells (SCs), in PNI. The mutual tumor-supportive secretory cytokines between SCs (sNF96.2) and PDAC cells (PANC-1, BxPC-3) were screened by human cytokine arrays and verified. The prognostic value of selected cytokines and SC-associated markers was confirmed in PDAC patients. TIMP1 and CCL7 were found to form a paracrine feedback loop between PDAC cells and SCs. PDAC cell-derived TIMP1 promotes SCs proliferation and migration via CD63/PI3K/AKT signaling. CCL7 secreted from SCs enhances PDAC cell migration, invasion and expression of TIMP1 via CCR2/STAT3. PDAC cell-SC cooperation in PNI was blocked when TIMP1 knockdown in vitro and in vivo. Finally, TIMP1, CCL7 and SC-associated markers were correlated with PNI and prognosis in PDAC patients. In conclusion, SCs collaborate with PDAC cells through the TIMP1-CCL7 paracrine feedback loop to promote PNI. TIMP1 knockdown in PDAC cells suppresses PNI. Strategies to disrupt the TIMP1-CCL7 feedback loop might be developed to inhibit PNI in PDAC.

TIMP1 down-regulation enhances gemcitabine sensitivity and reverses chemoresistance in pancreatic cancer.

The therapeutic effect of gemcitabine (GEM) in pancreatic ductal adenocarcinoma (PDAC) is limited due to low drug sensitivity and high drug resistance. Tissue inhibitor of matrix metalloprotease 1 (TIMP1) is reportedly associated with GEM resistance in PDAC. However, the effect of TIMP1 down-regulation in combination with GEM treatment is unknown. We analyzed the expression of TIMP1 in human PDAC tissue using western blot, quantitative real-time polymerase chain reaction (qRT-PCR), and immunohistochemistry. TIMP1 was highly expressed in PDAC specimens. Kaplan-Meier survival analysis suggested that a higher level of TIMP1 was correlated with poorer overall survival in 103 PDAC patients. The mRNA and protein expression profiles of TIMP1 were explored in the HTERT-HPNE human pancreatic ductal epithelium cell line, five PDAC cell lines (MIA PaCa-2, PANC-1, BxPC-3, Capan2, and SW1990), and two GEM-resistant PDAC cell lines (MIA PaCa-2R and PANC-1R). Compared with HTERT-HPNE, TIMP1 was highly expressed in the PDAC cell lines. In addition, TIMP1 was upregulated in GEM-resistant PDAC cell lines compared with their parental cells. When TIMP1 was knocked-down using short hairpin RNA, GEM-induced cytotoxicity and apoptosis were increased, while colony formation was repressed in MIA PaCa-2, PANC-1, and their GEM-resistant cells. When Bax was activated by BAM7 or Bcl-2 was inhibited by venetoclax, CCK-8 assays demonstrated that GEM sensitivity was restored in GEM-resistant cells. When Bax was down-regulated by siRNA, CCK-8 assays verified that GEM sensitivity was decreased in PDAC cells. The observations that TIMP1 knockdown enhanced GEM sensitivity and reversed chemoresistance by inducing cells apoptosis indicated cooperative antitumor effects of shTIMP1 and GEM therapy on PDAC cells. The combination may be a potential strategy for PDAC therapy.

Development of a rapid method for the quantification of cellulose in tobacco by (13)C CP/MAS NMR.

A method was developed for rapid quantitative determination of cellulose in tobacco by utilizing (13)C cross polarization magic angle spinning NMR spectroscopy ((13)C CP/MAS NMR). Sample powder was loaded into NMR rotor, which was customized rotor containing a matched silicon tube as an intensity reference. (13)C CP/MAS NMR spectra of tobacco samples were processed with spectral deconvolution to obtain the area of the C-1 resonance at 105.5ppm and the internal standard at 0ppm. The ratio between the area of 105.5ppm and 0ppm of a set of standard cellulose samples was used to construct a calibration curve. The cellulose content of a tobacco sample was determined by comparison of the ratio between the area of 105.5ppm and 0ppm to the calibration curve. Results of this developed method showed good agreement with those obtained from chemical analysis. The proposed method has such advantages of accuracy, quickness and efficiency, and could be an alternative to chemical analyses of cellulose.