Cancer still poses a global threat, since a lot of tumors remain untreatable despite all the available chemotherapeutic drugs, whose side effects, it must also be noted, still raise concerns. The antitumoral properties of marine seaweeds make them a potential source of new, less toxic, and more active antitumoral agents. Furthermore, these natural extracts can be combined with nanotechnology to increase their efficacy and improve targeting. In this work, a Codium tomentosum (CT) aqueous extract was employed for the green synthesis of gold nanoparticles (Au@CT). The complete characterization of Au@CT was performed by UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Zeta potential, electron microscopy, X-ray powder diffraction (XRD), high-performance steric exclusion chromatography (HPSEC), and by the determination of their antioxidant capacity. The antiproliferative activity of Au@CT was then tested in hepatic (HEPG-2) and pancreatic (BxPC-3) cell lines. Their potential capacity as enhancers of gemcitabine, a drug frequently used to treat both types of tumors, was also tested. The activity of Au@CT was compared to the activity of the CT extract alone. A synergistic effect with gemcitabine was proven for HEPG-2. Our results showed that gold nanoparticles synthesized from seaweed extracts with antitumoral activity could be a good gemcitabine enhancer.

Epigenetic modifications could drive some of the molecular events implicated in proliferation, drug resistance and metastasis of pancreatic ductal adenocarcinoma (PDAC). Thus, epigenetic enzyme inhibitors could be the key to revert those events and transform PDAC into a drug-sensitive tumor. We performed a systematic study with five different epigenetic enzyme inhibitors (1, UVI5008, MS275, psammaplin A, and BIX01294) targeting either Histone Deacetylase (HDAC) 1 or 1/4, DNA methyltransferase 3a (DNMT3a), Euchromatic histone lysine methyltransferase 2 (EHMT2), or Sirtuin 1 (SIRT1), as well as one drug that restores the p53 function (P53R3), in three different human PDAC cell lines (SKPC-1, MIA PaCa-2, and BxPC-3) using 2D and 3D cell cultures. The synergistic effect of these antitumoral drugs with gemcitabine was tested and the most efficient combinations were characterized by RNA-seq. The inhibition of HDAC1/4 (MS275), HDAC1/4/SIRT1/DNMT3a (UVI5008) or EHMT2 (BIX01294) induced a significant reduction on the cell viability, even in gemcitabine-resistance cells. The combination of UVI5008 or MS275 with gemcitabine induced a synergistic effect at low concentration and the RNA-Seq analysis revealed some synergy candidate genes as potential biomarkers. Reverting aberrant epigenetic modifications in combination with gemcitabine offers an alternative treatment for PDAC patients, with an important reduction of the therapeutic dose.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and often fatal form of malignancy frequently diagnosed at an advanced stage, posing significant challenges for treatment. The complex and intricate microenvironment of PDAC, characterized by heterogenous tumoral cells harbouring diverse mutations and epigenetic alterations, immune cells (primarily in an immunosuppressive state), cancer-associated fibroblasts (CAFs), low vascularization and extracellular matrix components supporting tumor growth, creates a physical barrier that impedes drug delivery and anti-tumoral immune cell responses, leading to therapy resistance. Despite advancements in early detection methods, and available treatments for PDAC-including surgery, radiotherapy, chemotherapy, and immunotherapy, all have shown limited efficacy. Recently, liposomal drugs in combination therapy, PDAC-targeted CAR-T cells and anti-tumor RNA vaccines have emerged as promising therapeutic approaches. However, significant challenges remain, including the presence of a dense stroma, resistance to chemotherapy, and robust immune suppression, all of which pose substantial barriers to effective treatments. In this context, epigenetic therapy aims to modify gene expression patterns in PDAC cells, potentially curtailing their resistance. This review provides an overview of the current landscape of PDAC research and the role of epigenetic inhibitors in the treatment of this lethal disease, emphasizing the potential of combining these novel drugs with conventional chemotherapy or immunotherapy, new drug delivery approaches and future directions in the field. A multi-approach therapy, switch to simultaneously targeting various facets of the PDAC characteristics, could enhance the anti-tumoral efficacy by overcoming its resistance mechanisms, improving patient prognosis.

In most human tumors, the MAPK pathway is constitutively activated. Since p90RSK is downstream of MAPK, it is often hyperactive and capable of phosphorylating oncogenic substrates. We have previously shown that p90RSK phosphorylates MDM2 at S166, promoting p53 degradation in follicular thyroid carcinomas. Thus, the inhibition of p90RSK restores p53 expression, which in turn inhibits cell proliferation and promotes apoptosis. In the present study, we demonstrated that the p90RSK/MDM2/p53 pathway proved to be an excellent target in the therapy of tumors with MAPK hyperactivation. For this purpose, we selected p53wt melanoma, lung and medullary thyroid carcinoma cell lines with high activation of p90RSK. In these cell lines, we demonstrated that the p90RSK/MDM2/p53 pathway is implicated in the regulation of the cell cycle and apoptosis through p53-dependent transcriptional control of p21 and Bcl-2. Furthermore, with an immunohistochemical evaluation of primary melanomas and lung tumors, which exhibit highly activated p90RSK compared to corresponding normal tissue, we demonstrated that MDM2 stabilization was associated with p90RSK phosphorylation. The results indicate that p90RSK is able to control the proliferative rate and induction of apoptosis through the regulation of p53wt levels by stabilizing MDM2 in selected tumors with constitutively activated MAPKs, making p90RSK a new attractive target for anticancer therapy.

The expression level of the tumor suppressor p53 is controlled by the E3 ubiquitin ligase MDM2 with a regulatory feedback loop, which allows p53 to upregulate its inhibitor MDM2. In this manuscript we demonstrated that p90RSK binds and phosphorylates MDM2 on serine 166 both in vitro and in vivo by kinase assay, immunoblot, and co-immunoprecipitation assay; this phosphorylation increases the stability of MDM2 which in turn binds p53, ubiquitinating it and promoting its degradation by proteasome. A pharmacological inhibitor of p90RSK, BI-D1870, decreases MDM2 phosphorylation, and restores p53 function, which in turn transcriptionally increases the expression of cell cycle inhibitor p21 and of pro-apoptotic protein Bax and downregulates the anti-apoptotic protein Bcl-2, causing a block of cell proliferation, measured by a BrdU assay and growth curve, and promoting apoptosis, measured by a TUNEL assay. Finally, an immunohistochemistry evaluation of primary thyroid tumors, in which p90RSK is very active, confirms MDM2 stabilization mediated by p90RSK phosphorylation.

Pancreatic ductal adenocarcinoma (PDAC) remains a highly aggressive malignancy with poor therapeutic outcomes due to its desmoplastic tumor microenvironment (TME), hindering drug and activated immune cell penetration. Cancer-associated fibroblasts (CAFs) are central in supporting tumor growth and forming a protective stroma. We propose a novel dual-therapy targeting the Hippo/MAPK pathways and histone deacetylation, both involved in tumor progression, resistance, and stromal interactions, to overcome PDAC therapeutic resistance. We developed liposomal siRNA complexes (lipoplexes) to deliver siRNA targeting YAP1 and FOSL1, key transcription factors involved in stromal remodeling and tumor progression. Our strategy involves a sequential approach with initial YAP1/FOSL1 silencing, followed by combination chemotherapy with entinostat (a histone deacetylation inhibitor) and gemcitabine. We evaluated this approach in PDAC xenograft mouse models and 3D organoids, demonstrating that sequential YAP1/FOSL1 silencing enhanced the efficacy of subsequent chemotherapy by reducing stromal components and improving drug penetration. These findings suggest that targeting the Hippo/MAPK pathways, combined with epigenetic modulation, holds significant promise for improving PDAC treatment.