Solute carrier (SLC) transporters regulate the cellular influx and disposition of endogenous and xenobiotic compounds, including anticancer agents such as the multikinase inhibitors (MKIs). Recent evidence suggests that MKIs may also inhibit SLC-dependent transport of coadministered drugs, although present information on the relative susceptibilities of multiple SLC transporters is limited. This study evaluated 18 MKI drugs and metabolites as inhibitors of prototypic substrate uptake by 13 SLC transporters that were overexpressed in human embryonic kidney cells. Organic anion transporting polypeptides (OATPs) 1A2, 1B3, and 2B1, organic anion transporter 3 (OAT3), and organic cation transporter 1 (OCT1) were inhibited by most MKIs, whereas substrate uptake by OATP1B1, OAT1, 2, and 4, OCT2 and 3, and organic zwitterion/cation transporter 1 (OCTN1) was less susceptible to inhibition; OCTN2 was also inhibited by cediranib. In further studies, IC₅₀ values were determined for the most effective MKIs, and erlotinib and cediranib were found to be potent competitive inhibitors of OATP2B1 (K_i = 41 nM) and OATP1A2 (K_i = 33 nM), respectively. From predictive approaches, several MKI-SLC interactions were found to be of potential in vivo significance.

Cytochrome P450 2J2 (CYP2J2) expression is elevated in breast and other tumours, and is known to be protective against cytotoxic agents that may be used in cancer chemotherapy. This study evaluated the mechanisms by which MDA-MB-468 breast cancer cells that stably expressed CYP2J2 (MDA-2J2 cells) were protected against killing by the anti-cancer agent paclitaxel. Compared to control cells caspase-3/7 activation by paclitaxel was lower in MDA-2J2 cells, while cell proliferation and colony formation following paclitaxel treatment were increased. Basal lipid peroxidation was lower in MDA-2J2 cells than in control cells, and the paclitaxel-mediated increase in peroxidation was attenuated. The mitochondrial complex III inhibitor antimycin A modulated basal and paclitaxel-activated reactive oxygen species (ROS) formation in control cells; paclitaxel-activated ROS production was also modulated by the NADPH oxidase inhibitor diphenyleneiodonium. Paclitaxel increased the formation of protein adducts by the reactive aldehyde 4-hydroxynonenal that is produced by lipid peroxidation; adduct formation was attenuated in MDA-2J2 cells. ALDH1A1 expression and activity was strongly upregulated in MDA-2J2 cells that was attributed to CYP2J2-derived 14,15-epoxyeicosatrienoic acid (14,15-EET); the 8,9- and 11,12-EET regioisomers did not activate ALDH1A1 expression. Silencing of ALDH1A1 restored the sensitivity of MDA-2J2 cells to paclitaxel, as indicated by a more pronounced decrease in proliferation, and greater increases in caspase activity and formation of ROS to levels comparable with control cells. Similar findings were observed with doxorubicin, sorafenib and staurosporine, that also promoted ROS-mediated cell death that was attenuated in MDA-2J2 cells and reversed by ALDH1A1 gene silencing. These findings implicate ALDH1A1 as an important gene that is activated in MDA-MB-468-derived cells that contain high levels of CYP2J2. ALDH1A1 modulates the production of ROS by anti-cancer agents such as paclitaxel and diminishes their efficacy. Future approaches could adapt this information to facilitate the targeting of ALDH1A1 to promote the efficacy of ROS-generating cytotoxic agents and enhance the treatment of breast cancer.

Polyunsaturated fatty acids (PUFAs) undergo cytochrome P450 (CYP)-dependent oxidation to epoxides that modulate important physiological functions, including vasoactivity, inflammation, nociception, proliferation and viability. One of the most important human CYP epoxygenases is human CYP2J2 that is widely expressed in tissues, especially heart, vascular smooth muscle, salivary glands and placenta. Recent studies have shown that overexpression of CYP2J2 in vivo reverses several pathological processes in animals, including hypertension and other cardiovascular pathologies and insulin resistance. Information on the molecular regulation of CYP2J2 is sparse but supports roles for specificity protein-1 (Sp1) and activator protein-1 (AP-1) in transcription and the micro-RNA Let-7b in post-transcriptional regulation. Exposure to stress stimuli, including pro- and antioxidant factors and pro-inflammatory cytokines regulates CYP2J2, possibly in a cell-specific fashion. CYP2J2 is also subject to genetic variation and the promoter region SNP (CYP2J2-76G > T; *7 allele) reportedly decreases epoxygenase activity in vivo. Several studies have suggested that carriers of the *7 allele may be predisposed to adverse cardiovascular and related health outcomes, although other studies report different findings. Greater understanding of the mechanisms by which CYP2J2 is regulated could provide insights into important pathogenic processes in complex disease states. Such studies may also lead to the development of novel therapeutic strategies that seek to activate CYP2J2 expression in tissues. Additionally, the development of agents that promote fatty acid epoxide production, or stable analogs that retain the activities of the epoxides, offer promising new avenues for utilizing the beneficial actions of these molecules.

A saturated analog of the cytochrome P450–mediated ω‐3‐17,18‐epoxide of ω‐3‐eicosapentaenoic acid (C20E) activated apoptosis in human triple‐negative MDA‐MB‐231 breast cancer cells. This study evaluated the apoptotic mechanism of C20E. Increased cytosolic cytochrome c expression and altered expression of pro‐ and antiapoptotic B‐cell lymphoma‐2 proteins indicated activation of the mitochondrial pathway. Caspase‐3 activation by C20E was prevented by pharmacological inhibition and silencing of the JNK and p38 MAP kinases (MAPK), upstream MAPK kinases MKK4 and MKK7, and the upstream MAPK kinase kinase apoptosis signal‐regulating kinase 1 (ASK1). Silencing of the death receptor TNF receptor 1 (TNFR1), but not Fas, DR4, or DR5, and the adapters TRADD and TNF receptor–associated factor 2, but not Fas‐associated death domain, prevented C20E‐mediated apoptosis. B‐cell lymphoma‐2 homology 3–interacting domain death agonist (Bid) cleavage by JNK/p38 MAPK linked the extrinsic and mitochondrial pathways of apoptosis. In further studies, an antibody against the extracellular domain of TNFR1 prevented apoptosis by TNF‐α but not C20E. These findings suggest that C20E acts intracellularly at TNFR1 to activate ASK1‐MKK4/7‐JNK/p38 MAPK signaling and to promote Bid‐dependent mitochondrial disruption and apoptosis. In in vivo studies, tumors isolated from C20E‐treated nu/nu mice carrying MDA‐MB‐231 xenografts showed increased TUNEL staining and decreased Ki67 staining, reflecting increased apoptosis and decreased proliferation, respectively. ω‐3‐Epoxy fatty acids like C20E could be incorporated into treatments for triple‐negative breast cancers.—Dyari, H. R. E., Rawling, T., Chen, Y., Sudarmana, W., Bourget, K., Dwyer, J. M., Allison, S. E., Murray, M. A novel synthetic analogue of ω‐317,18‐epoxyeicosatetraenoic acid activates TNF receptor‐1/ASK1/JNK signaling to promote apoptosis in human breast cancer cells. FASEB J. 31, 5246−5257 (2017). www.fasebj.org