The supramolecular organization of cancer metabolism: From macromolecular crowding to metabolic reprogramming underlying cancer metastasis and drug resistance

Abstract

Metastasis and drug resistance represent the two main causes of therapeutic failure in oncology. In the present dissertation, the interplay between them has been interrogated using metabolomics, systems biology and biophysical approaches, in an attempt to find common phenotypic adaptations and metabolic vulnerabilities of metastatic and resistant cancer cells, potentially exploitable in novel combination therapies. The obtained results unveil that highly metastatic e-CSC phenotypes of CRPC present particular metabolic vulnerabilities that can potentially lead to establishing putative biomarkers and metabolic targets that are specific for PCa subsets with high tumorigenic potential. Moreover, by generating isogenic cell models of multiplatinum resistance in CRPC and CRC we also identified that metastatic solid tumors with originally opposed metabolic profiles can lead to different metabolic adaptations as they acquire platinum resistance, but that a common metabolic signature of acquired platinum resistance arises, which also includes alterations in proline and one carbon metabolism, glutathione synthesis and ROS production. In addition to characterizing in deep the metabolic reprogramming associated to resistance to platinum compounds already used in the clinics, we also explored the possibility to design of novel platinum drugs able to counter platinum-resistant tumors. In this regard, we identified novel families of cyclometallated platinum (II) and platinum (IV) compounds exhibit strong antiproliferative effects in the low micromolar range against a wide variety of solid tumors. The leading compounds of each series also exhibit remarkable selectivity for cancer cells and the capacity to arrest the cell cycle at S and G2/M phases, induce apoptosis and increase intracellular ROS levels. The multiple combinations of equatorial and axial ligands explored in this work, allowed us to conclude that octahedral Pt (IV) compounds containing tridentate [C,N,N’] ligands are the optimal design to improve efficacy and selectivity against cancer cell lines. Remarkably, we have also identified that these novel cyclometallated Pt (IV) exhibit a complete absence of cross-resistance with the platinum-resistant CRC and CRPC models generated in this work. Indeed, platinum-based chemotherapy can severely affect internal cell architecture, causing fluctuations in the levels of macromolecular crowding inside cells and having an impact on the supramolecular organization of cell metabolism. In turn, this has been proved to have a profound impact on the kinetic behavior of metabolic enzymes that govern the rate of metabolic pathways that we have identified as important throughout this work. Thus, we have explored the kinetic behavior of lactate dehydrogenase (LDH), as a representative of aerobic glycolysis, under the presence of globular obstacles that do not introduce specific interactions with either LDH or its substrates, dextran polymers, obtaining that LDH kinetics is impaired in an obstacle size- and concentration-dependent manner. Additionally, we unveiled that LDH kinetic behavior shifts from activation control to diffusion control as crowding increases, implying that the behavior of LDH inside cells could be significantly different than previous dilute solution kinetic studies of this enzyme had predicted. On the other hand, the effect of macromolecular crowding on glutaminolysis had not been explored prior to this work. By studying the kinetic behavior of glutamate dehydrogenase (GLDH) in crowded media and characterizing its negative cooperativity, we have concluded that its kinetics is impaired by crowding in an obstacle size- and concentration-dependent manner, but that negative cooperativity is not significantly altered by macromolecular crowding. The actual impact of macromolecular crowding on cell metabolism has been scarcely explored and we are just scratching the surface of the understanding of the multiple implications that this phenomenon may entail for cell physiology and, in particular, for the metabolic alterations of cancer cells. Our observations throughout this work will hopefully have contributed to set grounds onto this enthralling enterprise, as long as meaningfully contributed to encounter valuable therapeutic tools against metastatic CRPC and CRC that can circumvent platinum resistance, both with new generations of platinum compounds and novel metabolic targets that selectively target metastatic solid tumors.