Transcriptional frameshifts contribute to protein allergenicity

Transcription infidelity (TI) is a mechanism that increases RNA and protein diversity. We found that single-base omissions (i.e., gaps) occurred at significantly higher rates in the RNA of highly allergenic legumes. Transcripts from peanut, soybean, sesame, and mite allergens contained a higher density of gaps than those of nonallergens. Allergen transcripts translate into proteins with a cationic carboxy terminus depleted in hydrophobic residues. In mice, recombinant TI variants of the peanut allergen Ara h 2, but not the canonical allergen itself, induced, without adjuvant, the production of anaphylactogenic specific IgE (sIgE), binding to linear epitopes on both canonical and TI segments of the TI variants. The removal of cationic proteins from bovine lactoserum markedly reduced its capacity to induce sIgE. In peanut-allergic children, the sIgE reactivity was directed toward both canonical and TI segments of Ara h 2 variants. We discovered 2 peanut allergens, which we believe to be previously unreported, because of their RNA-DNA divergence gap patterns and TI peptide amino acid composition. Finally, we showed that the sIgE of children with IgE-negative milk allergy targeted cationic proteins in lactoserum. We propose that it is not the canonical allergens, but their TI variants, that initiate sIgE isotype switching, while both canonical and TI variants elicit clinical allergic reactions.

Abstract 5287: RNA DNA divergences: An unsuspected marker of cancer genomic instability accurately predicts triple-negative breast cancer severity

Next generation sequencing provides 3 measures of cancer genomic instability i.e. somatic DNA variations, differential gene expression and RNA DNA divergences (RDD). The latter reflects changes in RNA sequences that are not present at the DNA level. Triple negative breast cancers (TNBC) represent the most severe form of the disease and are currently not amenable to targeted therapies nor to prognosis testing. We used the 3 measures of genomic instability to construct specific optimal algorithms that effectively separated 20 TNBC patients with poor or good clinical outcomes: 11 patients died from the disease within 1000 days following diagnosis of non metastatic TNBC while 9 were alive after 2500 days of follow up. All 3 models efficiently separated these 2 clinically polarized groups. However, only RDD based algorithms and not those relying on somatic mutations and expression profiles retains performances in excess of 90% accuracy after statistical cross validation. The 3 models were then applied in blind to 45 unknown patients with the same inclusion criteria i.e. non metastatic TNBC diagnosed before the age of 65 irrespective of menopausal, lymph node, tumor size and ethnic origin or recruitment centers. Kaplan-Meier analysis showed that the RDD based algorithm was highly predictive of clinical outcome i.e. 100% of patients predicted with good outcome were alive while 80% of patients predicted with poor outcome died in the same time interval (p<10-5). Algorithm based on somatic mutations and expression failed to predict clinical outcome in Kaplan-Meier analysis of validation set (p = NS). We then applied RDD predictive algorithm to TNBC cell lines and found that cells with RDD rate leading to poor clinical outcome prediction were statistically significantly associated with higher invasion and migration capacity (p<0.001). Inactivation of the expression of the most important transcript contributing to the RDD model reversed the in vitro phenotype. Comparison of RDD events occurring in good an poor outcome patients showed statistically significant differences in affected and replacement bases between the 2 groups. Therefore, RDD originate in non-random defects in the transfer of information between DNA and RNA that strongly contribute to tumor severity, further identification of specific transcripts differentially affected by RDD rate between poor and good clinical outcome allows development of novel strategies for selective therapeutic intervention.

Citation Format: Bernard E. Bihain, Stéphane Verdun, Julie Tomasina, Benoit Hilselberger, Marie Brulliard, Lionel Bonnard, Marina Trarbach, Olivier Roitel, Sandrine Jacquenet, Virginie Ogier, Jean-Pierre Armand, Benoit Thouvenot. RNA DNA divergences: An unsuspected marker of cancer genomic instability accurately predicts triple-negative breast cancer severity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5287. doi:10.1158/1538-7445.AM2015-5287

Rapid and soft formulation of folate-functionalized nanoparticles for the targeted delivery of tripentone in ovarian carcinoma

We report the development of folate-functionalized nanoparticles able to target folate receptors, and to deliver a poorly water soluble cytotoxic agent, a tripentone, in ovarian carcinoma. The stability under incubation of lipid nanoparticles formulated by a low-energy phase inversion temperature method was investigated. Thanks to the presence of Labrasol(®), a macrogolglyceride into the composition of the nanocarriers, the conjugation of different quantities of a folate derivate (folic acid-polyethylene glycol2000-distearylphosphatidylethanolamine) to nanoparticles was possible by a rapid, soft, very simple post-insertion process. As determined by dynamic light scattering, nanoparticles present a monodisperse diameter of about 100 nm, a spherical shape as attested by transmission electron micrographs, a weakly negative surface zeta potential, and are able to encapsulate the tripentone MR22388. The presence of folate receptors on SKOV3 human ovarian cancer cells was identified by fluorescent immunocytochemistry. Cellular uptake studies assessed by flow cytometry indicated that these nanoparticles reached the SKOV3 cells rapidly, and were internalized by a folate-receptor mediated endocytosis pathway. Moreover, nanoparticles allowed the rapid delivery of the antitumor agent tripentone into cells as shown in vitro by real-time cellular activity assay. Such folate-lipid nanoparticles are a potential carrier for targeted delivery of poorly water soluble compounds into ovarian carcinoma.

Sensitization of ovarian carcinoma cells to Bcl-xL-targeting strategies through indirect modulation of Mcl-1 activity by MR22388, a molecule of the tripentone family

Background

Our work has been carried out in the context of the therapeutic failure in ovarian carcinoma, which remains the leading cause of death by gynecologic malignancy. In these tumours, recurrence and subsequent acquired chemoresistance constitute major hurdles to successful therapy. Here we studied the interest of a member of the tripentone chemical family, MR22388, for the treatment of chemoresistant ovarian cancer cells.

Findings

MR22388 activity has been assessed in vitro on cisplatin-resistant (SKOV3 and IGROV1-R10) ovarian cancer cell lines by conventional analysis, alone or combined to a BH3-mimetic molecule, ABT-737. MR22388 exerts its activity on cisplatin resistant cells, and we showed that it induces a decrease of the Mcl-1 anti-apoptotic protein expression. Considering our previous work demonstrating that the efficiency of Bcl-x_L targeting strategies is conditioned to the concomitant inhibition of Mcl-1 we studied the interest of the association of this MR22388 with ABT-737, and showed that this combination was highly cytotoxic in chemoresistant cells.

Conclusions

This work thus opens new perspectives for the use of this promising molecule for the treatment of highly chemoresistant ovarian cancer cells and for sensitization of emerging Bcl-x_L targeting strategies such as the use of BH3-mimetic molecules.