Signaling, cancer cell plasticity, and intratumor heterogeneity.

Cancer's complexity is in part due to the presence of intratumor heterogeneity and the dynamic nature of cancer cell plasticity, which create substantial obstacles in effective cancer management. Variability within a tumor arises from the existence of diverse populations of cancer cells, impacting the progression, spread, and resistance to treatments. At the core of this variability is the concept of cellular plasticity - the intrinsic ability of cancer cells to alter their molecular and cellular identity in reaction to environmental and genetic changes. This adaptability is a cornerstone of cancer's persistence and progression, making it a formidable target for treatments. Emerging studies have emphasized the critical role of such plasticity in fostering tumor diversity, which in turn influences the course of the disease and the effectiveness of therapeutic strategies. The transformative nature of cancer involves a network of signal transduction pathways, notably those that drive the epithelial-to-mesenchymal transition and metabolic remodeling, shaping the evolutionary path of cancer cells. Despite advancements, our understanding of the precise molecular machinations and signaling networks driving these changes is still evolving, underscoring the necessity for further research. This editorial presents a series entitled "Signaling Cancer Cell Plasticity and Intratumor Heterogeneity" in Cell Communication and Signaling, dedicated to unraveling these complex processes and proposing new avenues for therapeutic intervention.

Transcending frontiers in prostate cancer: the role of oncometabolites on epigenetic regulation, CSCs, and tumor microenvironment to identify new therapeutic strategies.

Prostate cancer, as one of the most prevalent malignancies in males, exhibits an approximate 5-year survival rate of 95% in advanced stages. A myriad of molecular events and mutations, including the accumulation of oncometabolites, underpin the genesis and progression of this cancer type. Despite growing research demonstrating the pivotal role of oncometabolites in supporting various cancers, including prostate cancer, the root causes of their accumulation, especially in the absence of enzymatic mutations, remain elusive. Consequently, identifying a tangible therapeutic target poses a formidable challenge. In this review, we aim to delve deeper into the implications of oncometabolite accumulation in prostate cancer. We center our focus on the consequential epigenetic alterations and impacts on cancer stem cells, with the ultimate goal of outlining novel therapeutic strategies.

Extracellular Matrix Composition Modulates the Responsiveness of Differentiated and Stem Pancreatic Cancer Cells to Lipophilic Derivate of Gemcitabine.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease. Gemcitabine (GEM) is used as the gold standard drug in PDAC treatment. However, due to its poor efficacy, it remains urgent to identify novel strategies to overcome resistance issues. In this context, an intense stroma reaction and the presence of cancer stem cells (CSCs) have been shown to influence PDAC aggressiveness, metastatic potential, and chemoresistance. METHODS: We used three-dimensional (3D) organotypic cultures grown on an extracellular matrix composed of Matrigel or collagen I to test the effect of the new potential therapeutic prodrug 4-(N)-stearoyl-GEM, called C18GEM. We analyzed C18GEM cytotoxic activity, intracellular uptake, apoptosis, necrosis, and autophagy induction in both Panc1 cell line (P) and their derived CSCs. RESULTS: PDAC CSCs show higher sensitivity to C18GEM treatment when cultured in both two-dimensional (2D) and 3D conditions, especially on collagen I, in comparison to GEM. The intracellular uptake mechanisms of C18GEM are mainly due to membrane nucleoside transporters' expression and fatty acid translocase CD36 in Panc1 P cells and to clathrin-mediated endocytosis and CD36 in Panc1 CSCs. Furthermore, C18GEM induces an increase in cell death compared to GEM in both cell lines grown on 2D and 3D cultures. Finally, C18GEM stimulated protective autophagy in Panc1 P and CSCs cultured on 3D conditions. CONCLUSION: We propose C18GEM together with autophagy inhibitors as a valid alternative therapeutic approach in PDAC treatment.

Mitochondrial Dynamics as Potential Modulators of Hormonal Therapy Effectiveness in Males.

Worldwide the incidence of andrological diseases is rising every year and, together with it, also the interest in them is increasing due to their strict association with disorders of the reproductive system, including impairment of male fertility, alterations of male hormones production, and/or sexual function. Prevention and early diagnosis of andrological dysfunctions have long been neglected, with the consequent increase in the incidence and prevalence of diseases otherwise easy to prevent and treat if diagnosed early. In this review, we report the latest evidence of the effect of andrological alterations on fertility potential in both young and adult patients, with a focus on the link between gonadotropins' mechanism of action and mitochondria. Indeed, mitochondria are highly dynamic cellular organelles that undergo rapid morphological adaptations, conditioning a multitude of aspects, including their size, shape, number, transport, cellular distribution, and, consequently, their function. Since the first step of steroidogenesis takes place in these organelles, we consider that mitochondria dynamics might have a possible role in a plethora of signaling cascades, including testosterone production. In addition, we also hypothesize a central role of mitochondria fission boost on the decreased response to the commonly administrated hormonal therapy used to treat urological disease in pediatric and adolescent patients as well as infertile adults.

Divergent Roles of Mitochondria Dynamics in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive tumors; it is often diagnosed at an advanced stage and is hardly treatable. These issues are strictly linked to the absence of early diagnostic markers and the low efficacy of treatment approaches. Recently, the study of the metabolic alterations in cancer cells has opened the way to important findings that can be exploited to generate new potential therapies. Within this scenario, mitochondria represent important organelles within which many essential functions are necessary for cell survival, including some key reactions involved in energy metabolism. These organelles remodel their shape by dividing or fusing themselves in response to cellular needs or stimuli. Interestingly, many authors have shown that mitochondrial dynamic equilibrium is altered in many different tumor types. However, up to now, it is not clear whether PDAC cells preferentially take advantage of fusion or fission processes since some studies reported a wide range of different results. This review described the role of both mitochondria arrangement processes, i.e., fusion and fission events, in PDAC, showing that a preference for mitochondria fragmentation could sustain tumor needs. In addition, we also highlight the importance of considering the metabolic arrangement and mitochondria assessment of cancer stem cells, which represent the most aggressive tumor cell type that has been shown to have distinctive metabolic features to that of differentiated tumor cells.

CRISPR/Cas9-mediated knock-out of AGXT1 in HepG2 cells as a new in vitro model of Primary Hyperoxaluria Type 1.

AGXT1 encodes alanine:glyoxylate aminotransferase 1 (AGT1), a liver peroxisomal pyridoxal 5'-phosphate dependent-enzyme whose deficit causes Primary Hyperoxaluria Type 1 (PH1). PH1 is a rare disease characterized by overproduction of oxalate, first leading to kidney stones formation, and possibly evolving to life-threatening systemic oxalosis. A minority of PH1 patients is responsive to pyridoxine, while the option for non-responders is liver-kidney transplantation. Therefore, huge efforts are currently focused on the identification of new therapies, including the promising approaches based on RNA silencing recently approved. Many PH1-associated mutations are missense and lead to a variety of kinetic and/or folding defects on AGT1. In this context, the availability of a reliable in vitro disease model would be essential to better understand the phenotype of known or newly-identified pathogenic variants as well as to test novel drug candidates. Here, we took advantage of the CRISPR/Cas9 technology to specifically knock-out AGXT1 in HepG2 cells, a hepatoma-derived cell model exhibiting a conserved glyoxylate metabolism. AGXT1-KO HepG2 displayed null AGT1 expression and significantly reduced transaminase activity leading to an enhanced secretion of oxalate upon glycolate challenge. Known pathogenic AGT1 variants expressed in AGXT1-KO HepG2 cells showed alteration in both protein levels and specific transaminase activity, as well as a partial mitochondrial mistargeting when associated with a common polymorphism. Notably, pyridoxine treatment was able to partially rescue activity and localization of clinically-responsive variants. Overall, our data validate AGXT1-KO HepG2 cells as a novel cellular model to investigate PH1 pathophysiology, and as a platform for drug discovery and development.

Mitochondrial Elongation and OPA1 Play Crucial Roles during the Stemness Acquisition Process in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer with an overall 5-year survival rate of less than 9%. The high aggressiveness of PDAC is linked to the presence of a subpopulation of cancer cells with a greater tumorigenic capacity, generically called cancer stem cells (CSCs). CSCs present a heterogeneous metabolic profile that might be supported by an adaptation of mitochondrial function; however, the role of this organelle in the development and maintenance of CSCs remains controversial. To determine the role of mitochondria in CSCs over longer periods, which may reflect more accurately their quiescent state, we studied the mitochondrial physiology in CSCs at short-, medium-, and long-term culture periods. We found that CSCs show a significant increase in mitochondrial mass, more mitochondrial fusion, and higher mRNA expression of genes involved in mitochondrial biogenesis than parental cells. These changes are accompanied by a regulation of the activities of OXPHOS complexes II and IV. Furthermore, the protein OPA1, which is involved in mitochondrial dynamics, is overexpressed in CSCs and modulates the tumorsphere formation. Our findings indicate that CSCs undergo mitochondrial remodeling during the stemness acquisition process, which could be exploited as a promising therapeutic target against pancreatic CSCs.

Dimerization Drives Proper Folding of Human Alanine:Glyoxylate Aminotransferase But Is Dispensable for Peroxisomal Targeting.

Peroxisomal matrix proteins are transported into peroxisomes in a fully-folded state, but whether multimeric proteins are imported as monomers or oligomers is still disputed. Here, we used alanine:glyoxylate aminotransferase (AGT), a homodimeric pyridoxal 5'-phosphate (PLP)-dependent enzyme, whose deficit causes primary hyperoxaluria type I (PH1), as a model protein and compared the intracellular behavior and peroxisomal import of native dimeric and artificial monomeric forms. Monomerization strongly reduces AGT intracellular stability and increases its aggregation/degradation propensity. In addition, monomers are partly retained in the cytosol. To assess possible differences in import kinetics, we engineered AGT to allow binding of a membrane-permeable dye and followed its intracellular trafficking without interfering with its biochemical properties. By fluorescence recovery after photobleaching, we measured the import rate in live cells. Dimeric and monomeric AGT displayed a similar import rate, suggesting that the oligomeric state per se does not influence import kinetics. However, when dimerization is compromised, monomers are prone to misfolding events that can prevent peroxisomal import, a finding crucial to predicting the consequences of PH1-causing mutations that destabilize the dimer. Treatment with pyridoxine of cells expressing monomeric AGT promotes dimerization and folding, thus, demonstrating the chaperone role of PLP. Our data support a model in which dimerization represents a potential key checkpoint in the cytosol at the crossroad between misfolding and correct targeting, a possible general mechanism for other oligomeric peroxisomal proteins.

Progressively De-Differentiated Pancreatic Cancer Cells Shift from Glycolysis to Oxidative Metabolism and Gain a Quiescent Stem State.

Pancreatic ductal adenocarcinoma (PDAC) is typically characterized by high chemoresistance and metastatic spread, features mainly attributable to cancer stem cells (CSCs). It is of central interest the characterization of CSCs and, in particular, the study of their metabolic features in order to selectively identify their peculiarities for an efficient therapeutic approach. In this study, CSCs have been obtained by culturing different PDAC cell lines with a specific growth medium. Cells were characterized for the typical stem/mesenchymal properties at short-, medium-, and long-term culture. Metabolomics, proteomics, analysis of oxygen consumption rate in live cells, and the effect of the inhibition of lactate transporter on cell proliferation have been performed to delineate the metabolism of CSCs. We show that gradually de-differentiated pancreatic cancer cells progressively increase the expression of both stem and epithelial-to-mesenchymal transition markers, shift their metabolism from a glycolytic to an oxidative one, and lastly gain a quiescent state. These quiescent stem cells are characterized by high chemo-resistance, clonogenic ability, and metastatic potential. Re-differentiation reverts these features, re-activating their proliferative capacity and glycolytic metabolism, which generally correlates with high aggressiveness. These observations add an important piece of knowledge to the comprehension of the biology of CSCs, whose metabolic plasticity could be exploited for the generation of promising and selective therapeutic approaches for PDAC patients.

Oncometabolites in cancer aggressiveness and tumour repopulation.

Tumour repopulation is recognized as a crucial event in tumour relapse where therapy-sensitive dying cancer cells influence the tumour microenvironment to sustain therapy-resistant cancer cell growth. Recent studies highlight the role of the oncometabolites succinate, fumarate, and 2-hydroxyglutarate in the aggressiveness of cancer cells and in the worsening of the patient's clinical outcome. These oncometabolites can be produced and secreted by cancer and/or surrounding cells, modifying the tumour microenvironment and sustaining an invasive neoplastic phenotype. In this review, we report recent findings concerning the role in cancer development of succinate, fumarate, and 2-hydroxyglutarate and the regulation of their related enzymes succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase. We propose that oncometabolites are crucially involved in tumour repopulation. The study of the mechanisms underlying the relationship between oncometabolites and tumour repopulation is fundamental for identifying efficient anti-cancer therapeutic strategies and novel serum biomarkers in order to overcome cancer relapse.