Insulin and novel thioglycosides exert suppressive effect on human breast and colon carcinoma cells

New syntheses of thiosaccharides utilizing substitution reactions

Novel synthetic methods published since 2005 affording carbohydrates containing sulfur atom(s) are reviewed. The review is divided to subchapters based on the position of sulfur atom(s) in the sugar molecule. Only those methods that take advantage of substitution are discussed.

Novel triple mutant of an extremophilic glycosyl hydrolase enables the rapid synthesis of thioglycosides

In order to expand the toolbox of enzymes available for thioglycoside synthesis, we describe here the first example of an extremophilic glycosyl hydrolase from Halothermothrix orenii (HorGH1) engineered towards thioglycosynthase activity with a novel combination of mutations. Using the triple mutant, HorGH1 M299R/E166A/E354G, a range of thioglycosides from glycosyl fluoride donors and aromatic thiols could be synthesised with exquisite stereoselectivity and good to excellent conversions (61-93%).

Insulin reverses choriocarcinoma 5- fluorouracil resistance

Choriocarcinoma (CC) is a gestational trophoblastic tumor secondary to a gravid or non-gravid pregnancy. It is characterized by rapid growth, high invasion, and high metastatic potential and chemotherapy resistance that significantly affect survival rate of CC patients. Insulin is implicated in alleviation of chemotherapy resistance in CC. However, the mechanism of reversing resistance in CC has not been explored. Our purpose was to explore insulin effect on 5-fluorouracil (5-FU) resistance in CC and elucidate its potential mechanism in vitro and in vivo. CKK-8, colony formation, Transwell, and flow cytometry were used to detect the effect of insulin on 5-FU resistance in CC cells JEG-3 and JARS. Xenograft mice were used to evaluate the effect of insulin on 5-FU resistance. Results showed that insulin combined with 5-FU suppressed cell viability by 30% in JEG-3 and 43% in JAR compared with 5-FU alone in 72 h. What’s more, insulin combined with 5-FU promoted cell apoptosis, inhibited cell proliferation, migration, and phosphorylation of survivin at residue threonine 34 (Thr34) and drug resistance-related proteins, P-GP and MRP1 levels (p < 0.05). In vivo experiment showed Insulin combined with 5-FU suppressed tumor volume by 35% compared with 5-FU alone and 73% compared with control in CC xenograft mice. In summary, the findings of this study show that insulin reversed chemoresistance of CC cells to 5-FU by inhibiting phosphorylation of survivin. Development of a therapeutic strategy that combines insulin with the chemotherapeutic agent 5-FU has a great potential in improving survival of CC patients.

In Vitro and In Vivo Efficacy of a Novel Glucose-Methotrexate Conjugate in Targeted Cancer Treatment

Methotrexate (MTX) is a commonly used antimetabolite, which inhibits folate and DNA synthesis to be effective in the treatment of various malignancies. However, MTX therapy is hindered by the lack of target tumor selectivity. We have designed, synthesized and evaluated a novel glucose–methotrexate conjugate (GLU–MTX) both in vitro and in vivo, in which a cleavable linkage allows intracellular MTX release after selective uptake through glucose transporter−1 (GLUT1). GLU–MTX inhibited the growth of colorectal (DLD-1), breast (MCF-7) and lung (A427) adenocarcinomas, squamous cell carcinoma (SCC-25), osteosarcoma (MG63) cell lines, but not in WI-38 healthy fibroblasts. In tumor cells, GLU–MTX uptake increased 17-fold compared to unconjugated MTX. 4,6-O-ethylidene-α-D-glucose (EDG), a GLUT1 inhibitor, significantly interfered with GLU–MTX induced growth inhibition, suggesting a glucose-mediated drug uptake. Glu-MTX also caused significant tumor growth delay in vivo in breast cancer-bearing mice. These results show that our GLUT-MTX conjugate can be selectively uptake by a range of tumor cells to cause their significant growth inhibition in vitro, which was also confirmed in a breast cancer model in vivo. GLUT1 inhibitor EDG interfered with these effects verifying the selective drug uptake. Accordingly, GLU–MTX offers a considerable tumor selectivity and may offer cancer growth inhibition at reduced toxicity.

Insulin enhancement of the antitumor activity of chemotherapeutic agents in colorectal cancer is linked with downregulating PIK3CA and GRB2

The present state of cancer chemotherapy is unsatisfactory. New anticancer drugs that marginally improve the survival of patients continue to be developed at an unsustainably high cost. The study aimed to elucidate the effects of insulin (INS), an inexpensive drug with a convincing safety profile, on the susceptibility of colon cancer to chemotherapeutic agents: 5-fluorouracil (FU), oxaliplatin (OXA), irinotecan (IRI), cyclophosphamide (CPA) and docetaxel (DOC). To examine the effects of insulin on cell viability and apoptosis, we performed an in vitro analysis on colon cancer cell lines Caco-2 and SW480. To verify the results, we performed in vivo analysis on mice bearing MC38 colon tumors. To assess the underlying mechanism of the therapy, we examined the mRNA expression of pathways related to the signaling downstream of insulin receptors (INSR). Moreover, we performed Western blotting to confirm expression patterns derived from the genetic analysis. For the quantification of circulating tumor cells in the peripheral blood, we used the maintrac method. The results of our study show that insulin-pretreated colon cancer cells are significantly more susceptible to commonly used chemotherapeutics. The apoptosis ratio was also enhanced when INS was administered complementary to the examined drugs. The in vivo study showed that the combination of INS and FU resulted in significant inhibition of tumor growth and reduction of the number of circulating tumor cells. This combination caused a significant downregulation of the key signaling substrates downstream of INSR. The results indicate that the downregulation of PIK3CA (phosphatidylinositol 3-kinase catalytic subunit alpha), which plays a critical role in cell signaling and GRB2 (growth factor receptor-bound protein 2), a regulator of cell proliferation and differentiation may be responsible for the sensitizing effect of INS. These findings were confirmed at protein levels by Western blotting. In conclusion, these results suggest that INS might be potentially applied to clinical use to enhance the therapeutic effectiveness of chemotherapeutic drugs. The findings may become a platform for the future development of new and inexpensive strategies for the clinical chemotherapy of tumors.

Crystal structure of racemic 2-[(β-arabino-pyran-osyl)-sulfanyl]-4,6-diphenylpyridine-3-carbo-nitrile

In the racemic title compound, C23H20N2O4S, the sulfur atom is attached equatorially to the sugar ring with unequal S-C bonds, viz.: S-Cs = 1.808 (2) and S-Cp = 1.770 (2) Å (s = sugar, p = pyrid-yl). The dihedral angles between the pyridine ring and its attached phenyl groups are 42.24 (8) and 6.37 (14)°. In the crystal, a system of classical O-H⋯O and O-H⋯(O,O) hydrogen bonds links the mol-ecules to form tube-like assemblies propagating parallel to the c-axis direction. Weak C-H⋯N inter-actions are also observed.