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We have studied how the macrolide antibiotic Clarithromycin (Cla) regulates autophagy, which sustains cell survival and resistance to chemotherapy in cancer. We found Cla to inhibit the growth of human colorectal cancer (CRC) cells, by modulating the autophagic flux and triggering apoptosis. The accumulation of cytosolic autophagosomes accompanied by the modulation of autophagic markers LC3-II and p62/SQSTM1, points to autophagy exhaustion. Because Cla is known to bind human Ether-à-go-go Related Gene 1 (hERG1) K + channels, we studied if its effects depended on hERG1 and its conformational states. By availing of hERG1 mutants with different gating properties, we found that fluorescently labelled Cla preferentially bound to the closed channels. Furthermore, by sequestering the channel in the closed conformation, Cla inhibited the formation of a macromolecular complex between hERG1 and the p85 subunit of PI3K. This strongly reduced Akt phosphorylation, and stimulated the p53-dependent cell apoptosis, as witnessed by late caspase activation. Finally, Cla enhanced the cytotoxic effect of 5-fluorouracil (5-FU), the main chemotherapeutic agent in CRC, in vitro and in a xenograft CRC model. We conclude that Cla affects the autophagic flux by impairing the signaling pathway linking hERG1 and PI3K. Combining Cla with 5-FU might be a novel therapeutic option in CRC.

Monoclonal antibodies (mAbs), either mono-or bispecific (bsAb), represent one of the most successful approaches to treat many types of malignancies. However, there are certain limitations to the use of full length mAbs for clinical applications, which can be overcome by engineered antibody fragments. The aim of the present study was to develop a small bsAb, in the format of a single-chain diabody (scDb), to efficiently target two proteins, the hERG1 potassium channel and the 1 subunit of integrin receptors, which specifically form a macromolecular complex in cancer cells.We provide evidence that the scDb we produced binds to the hERG1/1 complex in cancer cells and tissues, whereas does not bind to the hERG1 channel in non-pathological tissues, in particular the heart. The scDb-hERG1-1 (1) downregulates the formation of the hERG1/1 complex, (2) inhibits Akt phosphorylation and HIF-1 expression and (3) decreases cell survival, proliferation and migration in vitro. These effects only occur in cancer cells (either colon, pancreatic or breast), but not in normal cells. In vivo, the scDb-hERG1-1 shows a good pharmacokinetic profile, with a half-life of 13.5 hours and no general, cardiac or renal toxicity when injected intravenously up to the dose of 8 mg/Kg. The scDb-hERG1-1 accumulates into subcutaneous xenografted tumors, arising from either colon or pancreatic human cancer cells, and induces a reduction of tumor growth and vascularization.Overall, the scDb-hERG1-1 represents an innovative single-chain bispecific antibody for therapeutic applications in solid cancers which over express the hERG1/1 integrin signaling complex.

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Electrochemical techniques were used to study the interaction between a panel of antiproliferative metallo-drugs and double-stranded DNA immobilized on screen-printed electrodes as a model of the analogous interaction occurring in solution. The propensity of a given metal drug to interact with DNA was measured as a function of the decrease of guanine oxidation signal, which was detected by square wave voltammetry. Estimates of variations in experimental parameters, such as the concentration of complexes, time following dissolution (ageing time) and the presence of chloride, are provided.