One of the crucial challenges in the clinical management of cancer is the resistance to chemotherapeutics. We recently demonstrated that the Hedgehog receptor Patched, which is overexpressed in many recurrent and metastatic cancers, is a multidrug transporter for chemotherapeutic agents such as doxorubicin. The present work provides evidences that Patched is expressed in adrenocortical carcinoma (ACC) patients, and is a major player of the doxorubicin efflux and the doxorubicin resistance in the human ACC cell line H295R. We discovered that methiothepin inhibits the doxorubicin efflux activity of Patched. This drug-like molecule enhances the cytotoxic, pro-apoptotic, antiproliferative and anticlonogenic effects of doxorubicin on ACC cells which endogenously overexpress Patched, and thereby mitigates the resistance of these cancer cells to doxorubicin. Moreover, we report that in mice the combination of methiothepin with doxorubicin prevents the development of xenografted ACC tumors more efficiently than doxorubicin alone by enhancing the accumulation of doxorubicin specifically in tumors without obvious undesirable side effects. Our results suggest that the use of an inhibitor of Patched drug efflux such as methiothepin in combination with doxorubicin could be a promising therapeutic option for adrenocortical carcinoma, and most likely also for other Patched-expressing cancers.

Melanoma patients harboring the BRAFV600E mutation are treated with vemurafenib. Almost all of them ultimately acquire resistance, leading to disease progression. Here, we find that a small molecule from a marine sponge, panicein A hydroquinone (PAH), overcomes resistance of BRAFV600E melanoma cells to vemurafenib, leading to tumor elimination in corresponding human xenograft models in mice. We report the synthesis of PAH and demonstrate that this compound inhibits the drug efflux activity of the Hedgehog receptor, Patched. Our SAR study allowed identifying a key pharmacophore responsible for this activity. We showed that Patched is strongly expressed in metastatic samples from a cohort of melanoma patients and is correlated with decreased overall survival. Patched is a multidrug transporter that uses the proton motive force to efflux drugs. This makes its function specific to cancer cells, thereby avoiding toxicity issues that are commonly observed with inhibitors of ABC multidrug transporters. Our data provide strong evidence that PAH is a highly promising lead for the treatment of vemurafenib resistant BRAFV600E melanoma.

Extracellular vesicles (EVs) have been shown to play an important role in intercellular communication as carriers of DNA, RNA and proteins. While the intercellular transfer of miRNA through EVs has been extensively studied, the stability of extracellular miRNA (ex-miRNA) once engulfed by a recipient cell remains to be determined. Here, we identify the ex-miRNA-directed phenotype to be transient due to the rapid decay of ex-miRNA. We demonstrate that the ex-miR-223-3p transferred from polymorphonuclear leukocytes to cancer cells were functional, as demonstrated by the decreased expression of its target FOXO1 and the occurrence of epithelial-mesenchymal transition reprogramming. We showed that the engulfed ex-miRNA, unlike endogenous miRNA, was unstable, enabling dynamic regulation and a return to a non-invasive phenotype within 8 h. This transient phenotype could be modulated by targeting XRN1/PACMAN exonuclease. Indeed, its silencing was associated with slower decay of ex-miR-223-3p and subsequently prolonged the invasive properties. In conclusion, we showed that the ‘steady step’ level of engulfed miRNA and its subsequent activity was dependent on the presence of a donor cell in the surroundings to constantly fuel the recipient cell with ex-miRNAs and of XRN1 exonuclease, which is involved in the decay of these imported miRNA.

Perturbation of thyroid iodide uptake is a well-documented side effect of the use of iodinated contrast media (ICM) administered intravenously. This side effect is thought to be mediated by free iodide in ICM formulations, but this hypothesis has never been formally proven. The aim of the present study was to assess the validity of this hypothesis. We used mass spectrometry analysis to quantify free-iodide contamination in ICM. Established cell lines expressing the Na/I symporter (NIS) were used to quantify the effect of ICM on iodide uptake. SPECT/CT was used to measure the in vivo uptake ofTc-pertechnetate and I in 2 NIS-expressing mouse tissues, thyroid and salivary glands. Scintiscans of ICM-naïve and ICM-administered patients were compared. Immunohistologic and Western blot analyses were performed to evaluate NIS protein expression in these organs. Although free iodide was present in ICM formulations, in vitro uptake of iodide by NIS-expressing cells was not significantly affected by ICM. In mice, intravenous or sublingual administration of ICM led to a reduction in radiotracer uptake by the thyroid, accompanied by a dramatic reduction in NIS protein expression in this tissue. In the salivary glands, neither radiotracer uptake nor NIS protein expression was affected by ICM. The thyroid-selective effect of ICM was also observed in humans. Administration of potassium iodide as a source of free iodide led to a diminution of Tc-pertechnetate uptake in both mouse thyroid and mouse salivary glands. Altogether, these data rule out a direct intervention of free iodide in the perturbation of thyroid uptake and suggest a direct and selective effect of ICM on the thyroid. We demonstrated that ICM reduce thyroid uptake of iodide independently of free iodide. This effect is due to a specific and dramatic decrease in NIS expression in thyrocytes. These data cast serious doubt on the relevance of measuring urinary iodide concentration to evaluate the delay between ICM administration and radioiodine therapy in patients with differentiated thyroid carcinoma. Finally, the ability of ICM to perturb iodide uptake in the thyroid may be used in radioprotection.

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We previously reported that methiothepin, a small molecule known as a nonselective serotonin 5-HT receptor antagonist, inhibited the doxorubicin efflux activity of the Hedgehog receptor Ptch1 and enhanced the cytotoxic, pro-apoptotic, anti-proliferative, and anti-clonogenic effects of doxorubicin on adrenocortical carcinoma cells. Here, we show that methiothepin also inhibits doxorubicin efflux and increases doxorubicin cytotoxicity in melanoma cells which endogenously overexpress Ptch1. Melanoma patients having the BRAFV600E mutation are treated with vemurafenib, an inhibitor of BRAFV600E, often in combination with trametinib, an inhibitor of MEK. Almost all patients ultimately acquire resistance to the treatment leading to disease progression. Here, we report that methiothepin overcomes the resistance of BRAFV600E melanoma cells by enhancing the cytotoxicity of vemurafenib and trametinib on these cells leading to melanoma cells death. We observe that the addition of methiothepin to vemurafenib prevents migration of resistant melanoma cells more efficiently than vemurafenib alone. Our results provide an additional proof that Ptch1 drug efflux inhibition increases the effectiveness of anti-cancer treatments and overcomes resistance of melanoma cells expressing Ptch1.

Clinical responses to immune checkpoint blockade by anti-PD-1/PD-L1 monoclonal antibodies in non-small-cell lung cancer (NSCLC) may be associated with PD-L1 expression. This study was undertaken to determine the expression profile of PD-L1 in patients with Kras-mutant lung adenocarcinoma (LUAD) and to investigate the activation of Kras codon subtypes as a mechanism of PD-L1 regulation. Immunohistochemistry analysis of PD-L1 expression (SP142 clone) on 117 LUAD (KrasWT, n = 51; KrasG12D, n = 25; KrasG12V, n = 14; KrasG12C, n = 27), showed significantly greater expression of PD-L1 in both tumor and immune cells compartments in Kras mutant LUAD compared with KrasWT wild-type tumors (37% vs. 18%; P = 0.005). PD-L1+ tumors had greater CD66b+ neutrophil infiltrate and lower CD8+ T-cell infiltrate than PD-L1− tumors, notably in KrasG12D tumors. To determine the effect of Kras codon subtypes on PD-L1 expression, stable cell lines were generated by transfection of KrasG12D, KrasG12V, KrasG12C and KrasWT plasmids into Beas2B bronchial cells. At basal level, mutant Kras led to significantly higher cell-surface PD-L1 expression and PD-L1 transcripts, notably in KrasG12C and KrasG12V cells, suggesting transcriptional regulation. Moreover, there was differential activation of NF-kB, ERK and Pi3k/Akt pathways between Kras mutant subtypes. In addition, PD-L1 was upregulated 3-fold by stimulation with IFNγ, independently of the Kras codon subtypes. Instead, hypoxia significantly increased PD-L1 expression in KrasG12C and KrasG12D cells. Co-culture experiments with human PBMCs from healthy patients were performed to determine the functional effect of altered PD-L1 expression. Increased PD-L1 expression by tumor cells induced by Kras mutations led to decreased PBMCs proliferation and increased apoptosis. PD-L1 is expressed in 37% of Kras mutant LUAD, suggesting PD-L1 as a therapeutic target in this subset. According to the Kras mutation subtype, potential drugs targeting the NF-kB, ERK or Pi3k/Akt pathways may increase the antitumor adaptive immune responses. Citation Format: Marius Ilie, Laetitia Fazzalari, Nicolas Guibert, Nathalie Yazbeck, Laurie Signetti, Véronique Hofman, Elodie Long, Katia Zahaf, Julien Fayada, Virginie Lespinet, Olivier Bordone, Virginie Tanga, Kevin Washetine, Nicolas Vénissac, Jérôme Mouroux, Charles Hugo Marquette, Patrick Brest, Paul Hofman. Impact of Kras mutant subtypes on PD-L1 expression in lung adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4025.

Phosphorylation of Ser/Thr residues is a well-established modulating mechanism of the pro-apoptotic function of the BH3-only protein Bim. However, nothing is known about the putative tyrosine phosphorylation of this Bcl-2 family member and its potential impact on Bim function and subsequent Bax/Bak-mediated cytochrome c release and apoptosis. As we have previously shown that the tyrosine kinase Lyn could behave as an anti-apoptotic molecule, we investigated whether this Src family member could directly regulate the pro-apoptotic function of Bim. In the present study, we show that Bim is phosphorylated onto tyrosine residues 92 and 161 by Lyn, which results in an inhibition of its pro-apoptotic function. Mechanistically, we show that Lyn-dependent tyrosine phosphorylation of Bim increases its interaction with anti-apoptotic members such as Bcl-xL, therefore limiting mitochondrial outer membrane permeabilization and subsequent apoptosis. Collectively, our data uncover one molecular mechanism through which the oncogenic tyrosine kinase Lyn negatively regulates the mitochondrial apoptotic pathway, which may contribute to the transformation and/or the chemotherapeutic resistance of cancer cells.