After lung cancer, breast cancer (BC) is the most frequent cause of cancer death among women, worldwide. Although advances in screening approaches and targeted therapeutic agents have decreased BC incidence and mortality, over the past five years, triple-negative breast cancer (TNBC) remains the breast cancer subtype that displays the worst prognosis, mainly due to the lack of clinically actionable targets. Genetic and molecular profiling has unveiled the high intrinsic heterogeneity of TNBC, with the basal-like molecular subtypes representing the most diffuse TNBC subtypes, characterized by the expression of basal epithelial markers, such as the transcription factor p63. In this review, we will provide a broad picture on the physiological role of p63, in maintaining the basal epithelial identity, as well as its involvement in breast cancer progression, emphasizing its relevance in tumor cell invasion and stemness.

The ubiquitin system is a dynamic regulatory pathway controlling the activity, subcellular localization and stability of a myriad of cellular proteins, which in turn affects cellular homeostasis through the regulation of a variety of signaling cascades. Aberrant activity of key components of the ubiquitin system has been functionally linked with numerous human diseases including the initiation and progression of human tumors. In this review, we will contextualize the importance of the two main components of the ubiquitin system, the E3 ubiquitin ligases (E3s) and deubiquitinating enzymes (DUBs), in the etiology of squamous cell carcinomas (SCCs). We will discuss the signaling pathways regulated by these enzymes, emphasizing the genetic and molecular determinants underlying their deregulation in SCCs.

Background. Malignant pleural mesothelioma (MPM) is still a rather incurable disease. Many classes of compounds with various mechanisms of action have been tested in vivo and ex-vivo, with rather disappointing results. This is partly due to preclinical studies mostly performed in models that fail to recapitulate MPM complexity and do not retain the intra-tumor heterogeneity, a propelling force for tumor progression. Additionally, we and others have shown that, under stress-induced chemotherapy, profound rearrangements take place in MPM cultures to fuel the emergence of chemoresistant cell subpopulations. Thus, finding clinically actionable modulators of MPM resistance is still a very urgent need. Methods. Setup and propagation of patient-derived organoid cultures from MPM pleural effusions; flow cytometry-based validation of organoid cultures, isola-tion and propagation of mesothelioma-associated fibroblasts; co-cultures, Lu-minex-based Cytokine array, ELISA assay to quantitate IL-6 in the conditioned media, qRT-PCR to assess mRNA expression of cancer stem cell markers and fibroblast markers. Results. Organoid cultures were obtained from eight MPM patients by using specific growth media and conditions to propagate pleural effusion-derived cells. We proved that primary MPM specimens and serially passaged (mesothelio-ma-Patient-Derived-Organoids) mPDOs were cytologically similar, with the obtained mPDOs expressing mesothelial markers similarly to the originating specimen. As expected from a clinically relevant model, the size and number of mPDOs were altered, in a patient-specific way, when pharmacologically relevant doses of chemotherapy drugs were added. We derived Mesothelio-ma-Associated-Fibroblasts (MAFs) and the addition of MAFs, to various ratios, altered the response of the mPDOs to pemetrexed + cisplatin, toward a reduced sensitivity to the latter anticancer agents. Additionally, organoid formation and size were altered by MAF-conditioned media, and this correlated with increased expression of cancer stem cell markers. We showed increased levels of IL-6 in the media of the treated cocultures and showed that this latter was derived from the MAFs. Conclusions. Increased secretion of IL-6 by mesothelioma-associated fibroblasts (MAFs) contributes to the resistance of the MPM to therapy.