BACKGROUND: Triple-negative breast cancer (TNBC) remains one of the most challenging breast cancer subtypes to treat due to the lack of effective therapeutic options. Ribosome biogenesis has recently emerged as a promising therapeutic target across various cancers. Despite the current targeting of ribosome biogenesis through RNA polymerase I (RNA Pol I) inhibition, we speculated that other factors essential for ribosome assembly, such as ribosomal RNA (rRNA) maturation factors, may also represent therapeutic targets in TNBC. METHODS: Ribosome biogenesis was evaluated in each breast cancer subtype using expression level of ribosome biogenesis factors from the UCSC XENA database. The sensitivity of TNBC cell to inhibition of ribosome biogenesis was evaluated on the TNBC cell lines MDA-MB-231 and BT-20, either using RNA Pol I inhibitors CX-5461 or BMH-21 or by knocking-down Fibrillarin (FBL) gene using an shRNA approach. Tumor cell growth and survival was monitored both in vitro and as xenografted tumors. RESULTS: We demonstrate that ribosome biogenesis-related genes are significantly overexpressed in TNBC compared to other breast cancer subtypes, highlighting its potential role in TNBC progression. Accordingly, we show that RNA Pol I inhibition exerts potent anti-proliferative effects in pre-clinical models of TNBC, both in vitro and in vivo. However, the DNA-damaging activity of RNA Pol I inhibitors raises safety concerns, highlighting the need for alternative strategies to inhibit ribosome biogenesis. To this end, we show that targeting a downstream rRNA maturation step, specifically pre-rRNA cleavage, by inhibiting the maturation factor Fibrillarin, also inhibits tumor growth in TNBC models. Notably, ribosome biogenesis inhibition, through either RNA Pol I or Fibrillarin targeting, induces cell cycle arrest without triggering significant cell death. CONCLUSION: These findings establish ribosome biogenesis as a therapeutic vulnerability in TNBC and identify rRNA maturation, and Fibrillarin in particular, as novel targets for potential therapeutic intervention.

Cancer cells are highly dependent on bioenergetic processes to support their growth and survival. Disruption of metabolic pathways, particularly by targeting the mitochondrial electron transport chain complexes (ETC-I to V) has become an attractive therapeutic strategy. As a result, the search for clinically effective new respiratory chain inhibitors with minimized adverse effects is a major goal. Here, we characterize a new OXPHOS inhibitor compound called MS-L6, which behaves as an inhibitor of ETC-I, combining inhibition of NADH oxidation and uncoupling effect. MS-L6 is effective on both intact and sub-mitochondrial particles, indicating that its efficacy does not depend on its accumulation within the mitochondria. MS-L6 reduces ATP synthesis and induces a metabolic shift with increased glucose consumption and lactate production in cancer cell lines. MS-L6 either dose-dependently inhibits cell proliferation or induces cell death in a variety of cancer cell lines, including B-cell and T-cell lymphomas as well as pediatric sarcoma. Ectopic expression of Saccharomyces cerevisiae NADH dehydrogenase (NDI-1) partially restores the viability of B-lymphoma cells treated with MS-L6, demonstrating that the inhibition of NADH oxidation is functionally linked to its cytotoxic effect. Furthermore, MS-L6 administration induces robust inhibition of lymphoma tumor growth in two murine xenograft models without toxicity. Thus, our data present MS-L6 as an inhibitor of OXPHOS, with a dual mechanism of action on the respiratory chain and with potent antitumor properties in preclinical models, positioning it as the pioneering member of a promising drug class to be evaluated for cancer therapy. MS-L6 exerts dual mitochondrial effects: ETC-I inhibition and uncoupling of OXPHOS. In cancer cells, MS-L6 inhibited ETC-I at least 5 times more than in isolated rat hepatocytes. These mitochondrial effects lead to energy collapse in cancer cells, resulting in proliferation arrest and cell death. In contrast, hepatocytes which completely and rapidly inactivated this molecule, restored their energy status and survived exposure to MS-L6 without apparent toxicity.

The quest for targeted therapies is critical in the battle against cancer. The RAS/MAP kinase pathway is frequently implicated in neoplasia, with ERK playing a crucial role as the most distal kinase in the RAS signaling cascade. Our previous research demonstrated that the interaction between ERK and MYD88, an adaptor protein in innate immunity, is crucial for RAS-dependent transformation and cancer cell survival. In this study, we examine the biological consequences of disrupting the ERK-MYD88 interaction through the ERK D-recruitment site (DRS), while preserving ERK’s kinase activity. Our results indicate that EI-52, a small-molecule benzimidazole targeting ERK-MYD88 interaction induces an HRI-mediated integrated stress response (ISR), resulting in immunogenic apoptosis specific to cancer cells. Additionally, EI-52 exhibits anti-tumor efficacy in patient-derived tumors and induces an anti-tumor T cell response in mice in vivo. These findings suggest that inhibiting the ERK-MYD88 interaction may be a promising therapeutic approach in cancer treatment. The interaction between MyD88 and ERK is necessary for RAS-dependent transformation and cancer cell survival. Here, the authors identify benzimidazole compound EI-52 as a disrupter of this interaction and demonstrate its therapeutic efficacy in tumours via ERK dysregulation and the induction of immunogenic cell death.

Background High-grade adult-type diffuse gliomas (HGGs) constitute a heterogeneous group of aggressive tumors that are mostly incurable. Recent advances highlighting the contribution of ribosomes to cancer development have offered new clinical perspectives. Here, we uncovered that isocitrate dehydrogenase (IDH)wt and IDHmut HGGs display distinct alterations of ribosome biology, in terms of rRNA epitranscriptomics and ribosome biogenesis, which could constitute novel hallmarks that can be exploited for the management of these pathologies. Methods We analyzed (1) the ribosomal RNA 2’O-ribose methylation (rRNA 2’Ome) using RiboMethSeq and in-house developed bioinformatics tools (https://github.com/RibosomeCRCL/ribomethseq-nfandrRMSAnalyzer) on 3 independent cohorts compiling 71 HGGs (IDHwt n = 30, IDHmut n = 41) and 9 non-neoplastic samples, (2) the expression of ribosome biogenesis factors using medium throughput RT-qPCR as a readout of ribosome biogenesis, and (3) the sensitivity of 5 HGG cell lines to RNA Pol I inhibitors (CX5461, BMH-21). Results Unsupervised analysis demonstrated that HGGs could be distinguished based on their rRNA 2’Ome epitranscriptomic profile, with IDHwt glioblastomas displaying the most significant alterations of rRNA 2’Ome at specific sites. In contrast, IDHmut HGGs are largely characterized by an overexpression of ribosome biogenesis factors compared to non-neoplastic tissues or IDHwt glioblastomas. Finally, IDHmut HGG-derived spheroids display higher cytotoxicity to CX5461 than IDHwt glioblastoma, while all HGG spheroids display a similar cytotoxicity to BMH-21. Conclusions In HGGs, IDH mutational status is associated with specific alterations of the ribosome biology and with distinct sensitivities to RNA Pol I inhibitors.

This study explored the design of supersaturable self-microemulsifying drug delivery systems (S-SMEDDS) to address poor solubility and oral bioavailability of a novel benzimidazole derivative anticancer drug (BI). Firstly, self-microemulsifying drug delivery systems SMEDDS made of Miglyol® 812, Kolliphor® RH40, Transcutol® HP, and ethanol were prepared and loaded with the BI drug. Upon dispersion, the systems formed neutrally charged droplets of around 20 nm. However, drug precipitation was observed following incubation with simulated gastric fluid (pH 1.2). Aiming at reducing this precipitation and enhancing drug payload, supersaturable systems were then prepared by adding 1% hydroxypropyl cellulose as precipitation inhibitor. Supersaturable systems maintained a higher amount of drug in a supersaturated state in gastric medium compared with conventional formulations and were stable in simulated intestinal medium (pH 6.8). In vitro cell studies using Caco-2 cell line showed that these formulations reduced in a transient manner the transepithelial electrical resistance of the monolayers without toxicity. Accordingly, confocal images revealed that the systems accumulated at tight junctions after a 2 h exposure. In vivo pharmacokinetic studies carried out following oral administration of BI-loaded S-SMEDDS, SMEDDS, and free drug to healthy mice showed that supersaturable systems promoted drug absorption compared with the other formulations. Overall, these data highlight the potential of using the supersaturable approach as an alternative to conventional SMEDDS for improving oral systemic absorption of lipophilic drugs.

Targeted therapies have improved the outcome of cancer, but their efficacy is intrinsically limited by the emergence of subclones with a mutation in the gene encoding the target protein. A few examples of collateral sensitivity have demonstrated that the conformational changes induced by these mutations can create unexpected sensitivity to other kinase inhibitors, but whether this concept can be generalized is unknown. Here is described the development of a model to screen a library of kinase inhibitors for collateral sensitivity drugs active on the Bruton Tyrosine Kinase (BTK) protein with the ibrutinib resistance mutation C481S. First, we demonstrate that overexpression of the constitutively active mutant of BTK harboring the E41K mutation in Ba/F3 cells creates an oncogenic addiction to BTK. Then, we have exploited this phenotype to perform a screen of a kinase inhibitor library on cells with or without the ibrutinib resistance mutation. The BTK inhibitors showed the expected sensitivity profile, but none of the drugs tested had a specific activity against the C481S mutant of BTK, suggesting that extending the collateral sensitivity paradigm to all kinases targeted by cancer therapy might not be trivial.

The above article from Proteomics, published online on 19 September 2007 in Wiley Online Library (http://onlinelibrary.wiley.com/doi/10.1002/pmic.200700148/pdf) and in Volume 7, No. 20, pp. 3735–3742, has been retracted by agreement between some of the authors (S. Giraud, W. V. Bienvenut, J. J. Diaz), the Editor‐in‐Chief and Wiley‐VCH GmbH & Co. KGaA. The retraction has been agreed due to concerns in relation to Figure 2C. Multiple HMGA1‐pulldown bands in the immunoblot images (upper panel) appear to have been duplicated. In addition, the Coomassie gel bands of Figure 2C (lower panel) appear to have also been duplicated. The authors are unable to provide the original source files that were used to generate these data. While the authors maintain that these findings were confirmed in replicate experiments, the Editorial Board of Proteomics has decided to retract the paper. No issues have been raised with regard to any of the other data in this manuscript. The remaining authors (G. M. Pierantoni, F. Esposito, A. Fusco) have not agreed to the retraction.

ABSTRACT Homeodomain-interacting protein kinase 2 (HIPK2) is a nuclear serine/threonine kinase of the subfamily of dual-specificity Yak1-related kinase proteins. HIPK2 was first described as a homeodomain-interacting protein kinase acting as a corepressor for homeodomain transcription factors. More recently, it was reported that HIPK2 plays a role in p53-mediated cellular apoptosis and could also participate in the regulation of the cell cycle. US11 protein of herpes simplex virus type 1 is a multifunctional protein involved in the regulation of several processes related to the survival of cells submitted to environmental stresses by mechanisms that are not fully elucidated. In an attempt to better understand the multiple functions of US11, we identified cellular binding partners of this protein by using the yeast two-hybrid system. We report that US11 interacts with HIPK2 through the PEST domain of HIPK2 and that this interaction occurs also in human cells. This interaction modifies the subcellular distribution of HIPK2 and protects the cell against the HIPK2-induced cell growth arrest.