November 6, 2020
Supplementary Materialsmolecules-25-00537-s001. demonstrated for the first time increased selectivity of SAL-based dual therapy with 5-fluorouracil or gemcitabine, especially towards A2780 cell line. Looking closer at the results, SAL acted synergistically with 5-fluorouracil towards the drug-resistant A2780 cell line. Our results suggest that combinations of SAL with other antineoplastics may become a new therapeutic option for patients with ovarian cancer. (strain no. 80614) . SAL was identified in 2009 2009 as the most active agent among 16,000 compounds tested towards breast CSCs . Since then, SAL has been found effective against many other types of cancer cells and CSCs, including those displaying multidrug resistance (MDR) and has been used in a small group of patients with advanced carcinoma of the head, neck, breast, and ovary . SAL acts as a sensitizer of malignant cells to radiotherapy or chemotherapy, i.e., colchicine, doxorubicin, and etoposide [14,15,16,17]. 2. Results 2.1. Derivation of Cisplatin-Resistant Cell Lines To test the usefulness of SAL and its derivatives in overcoming cisplatin-resistance, chemoresistant OvCa sub-cell lines were established. MTT and RT-qPCR followed the cell exposure to cisplatin to confirm derivation of stable phenotype of the resistant cell lines. A2780 CDDP and SK-OV-3 CDDP lines responded with morphological changes and increased IC50 against cisplatin as compared with their parental population (Physique 2A,B). Both resistant cell lines showed also enhanced expression of ABCB1, ABCG2, and ABCC2 versus control (Physique 2C,D). ABCB4 expression boosted significantly in SK-OV-3 CDDP cell line but only slightly in A2780 CDDP cell line. Open in a separate window Physique 2 Overview of cisplatin-resistant ovarian cancer cell lines (A2780, SK-OV-3). (A,B) Morphological MC-Val-Cit-PAB-clindamycin changes of both drug-resistant cancer sub-lines represent enlargement and slight spindle-like shape. Survival curves indicate increased IC50 for both resistant variants (RI = 18.08 for A2780; RI = 1.56 for SK-OV-3). The pictures were taken under 200 magnification. (C,D) RT-qPCR analysis of A2780 and SK-OV-3 revealed significantly increased expression of ABC drug transporters in derived resistant variants. 2.2. In Vitro Activity of Cytotoxic Drugs, Salinomycin, and Its Derivatives Against OvCa Cells It was clearly confirmed that chemical modification of SAL and other polyether ionophores may not only increase the biological activity of resulting derivatives but also reduce their general toxicity [18,19,20,21]. Furthermore, SAL with a modified C1 carboxyl group (amides or esters) transports cations by a biomimetic mechanism, while chemically unmodified SAL transports cations through biological membranes via an electroneutral mechanism [22,23]. This change in ionophoretic properties may result in better biological properties of SAL analogs than of those with a native structure. We devised a library of SAL derivatives based on the most active SAL IL-15 amides and MC-Val-Cit-PAB-clindamycin esters obtained in our previous studies by a chemical modification of C1 carboxyl group, i.e., amides 2 and 3, as well as esters 5 and 6, respectively (Physique 1) [18,19,20]. To expand structural diversity at C1 position and to better determine the structure-activity relationship (SAR), we additionally analyzed propargyl amide 4 and propargyl ester 7 (Physique 1), as these structures had shown promising bioactivity . Data gathered in Table 1 indicate that all tested compounds exhibited biological activity against malignant cells. The result towards ovarian A2780 cell line was much better than that against metastatic ovarian SK-OV-3 cell line distinctly. Briefly, the very best was unmodified SAL chemically, the game which was higher against A2780 cell range and equivalent against SK-OV-3 cell range than that of guide anticancer drugcisplatin (CDDP) (Desk 1). In OvCa cell lines A2780, SK-OV-3 aswell as their platinum-resistant sub-lines, all semi-synthetic derivatives of SAL (both from amide and ester series) required considerably higher IC50 beliefs to induce equivalent natural results than SAL itself (Desk 1). One of the most energetic SAL analog was 4-fluorophenethyl amide 3 (Body 1) but nonetheless its activity was one purchase of magnitude less than that of unmodified SAL (Desk 1). Needlessly to say, cisplatin-resistant sub-lines had been even more resistant to CDDP than both cisplatin-sensitive variations; hence, the anticancer activity of substances 3 and 5 (Body 1) was greater than that exhibited by CDDP towards A2780 CDDP cell range (Desk 1). Desk 1 The IC50 beliefs approximated for ovarian tumor cell lines (A2780, SK-OV-3, both drug-sensitive and drug-resistant variations) and regular diploid individual MRC-5 cell range after 72 h contact with salinomycin (SAL, 1), its 1:1 molar mixtures with cytotoxic medications (5-fluorouracil 5FU, gemcitabine Jewel), and salinomycin amides and esters (analogs 2C7). < 0.05. All tests had been repeated at least 3 x. Abbreviations 5FU5-fluorouracilABCB1ATP-binding cassette subfamily B member 1ABCB4ATP-binding cassette MC-Val-Cit-PAB-clindamycin subfamily B member 4ABCC2ATP-binding cassette subfamily C member 2ABCG2ATP-binding cassette subfamily G.