• anticancer agents
• glucose transporters
• glucose uptake
• inhibitors
• oximes
• tumor metabolism
• Warburg effect

The family of glucose transporters (GLUTs) comprises 12 isoforms of trans-membrane channel-proteins, which allows the entrance of D-glucose into the cells. These isoforms possess different affinities for glucose and other hexoses and each isoform has a tissue-specific distribution. Isoform GLUT-1 was the object of this thesis, since it was found to be overexpressed in most carcinoma cell types. The over-expression of this protein on the tumor cell membranes allows this type of cells to accumulate and use a large amount of D-glucose and, consequently, to produce enough energy for their rapid growth and survival. In fact, tumor cells predominantly produce energy by a high rate of glycolysis, followed by lactic acid fermentation in the cytosol, rather than by a comparatively low rate of glycolysis followed by oxidation of pyruvate in mitochondria, such as that occurring in most normal cells. This metabolic switch is known as the Warburg Effect. Therefore, GLUT-1 inhibition may represent a very attractive way to attack cancer by blocking its main nutrient uptake, thus leading to a decrease in glycolytic flux and to cell death by starvation.
So far, several molecules have been reported to be able to block glucose uptake. Most of them are natural molecules such as flavonoids, flavones, chalcones, but there are also examples of synthetic molecules, such as tamoxifen, fulvestrant, 17β-estradiol. The interesting thing is that the many of these molecules are also active on estrogen receptor beta (ER). Based on this concept, some salycilaldoxime and salicylketoxime derivatives, that had been previously designed and synthetized as potential ER-ligands in the research group where I have carried out my thesis project, were also tested in cellular assays on GLUT-1, and some of them displayed good inhibitory activities on glucose uptake.
The recent crystallization (resolution 2.9 Å) of the xylose transporter of E. Coli, XyLE, coordinated with D-glucose provided a valid starting point for a more accurate analysis of human GLUT-1 and to study the putative interaction modes of the most active salicylketoxime molecules and flavonoids. This transporter is formed by 492 amino acids; there are 12 transmembranes and 4 intracellular helices and both the N-terminus and C-terminus are located in the intracellular part of the protein. The aqueous channel seems to be divided into two parts by two residues that form a gate in the middle of the channel: Trp388 and His154.
The project of my thesis was dedicated to study the introduction of various substituents in the phenyl ring of the scaffold required to have a good inhibitory activity on GLUT-1. The starting material for the synthesis of these compounds was the commercial 3-bromophenol, which was carbamoylated on the hydroxyl group. Then, an ortho-lithiation, followed by a quenching with hexachloroethane, produced the regioselective insertion of a chlorine atom in position 2 of the aromatic ring. The corresponding 2-chloro-3-bromo-carbamoylphenol was hydrolysed under basic conditions, to deprotect the phenolic hydroxyl and to obtain 3-bromo-2-chloro-phenol. This molecule was acetylated and then the acetyl group was transposed by a Fries rearrangement reaction to afford 3-bromo-2-chloro-6-acetylphenol.
This compound was the key-intermediate which was submitted to various cross-coupling reactions under Suzuki conditions using different boronic-acids to obtain variously substituted ketone intermediates. The ketone group was finally transformed into the desired ketoxime.
The final products are currently being evaluated for glucose uptake inhibition and antiproliferative activity against cancer cells.