Oxygen or nutrient deprivation of early stage tumoral spheroids can be used to reliably mimic the initial growth of primary and metastatic cancer cells. However, cancer cell growth during the initial stages has not been fully explored using a genome-wide approach. Thus, in the present study, we investigated the transcriptome of breast cancer cells during the initial stages of tumoral growth using RNAseq in a model of Multicellular Tumor Spheroids (MTS). Network analyses showed that a metastatic signature was enriched as several adhesion molecules were deregulated, including EPCAM, E-cadherin, integrins and syndecans, which were further supported by an increase in cell migration. Interestingly, we also found that the cancer cells at this stage of growth exhibited a paradoxical hyperactivation of oxidative mitochondrial metabolism. In addition, we found a large number of regulated (long non coding RNA) lncRNAs, several of which were co-regulated with neighboring genes. The regulatory role of some of these lncRNAs on mRNA expression was demonstrated with gain of function assays. This is the first report of an early-stage MTS transcriptome, which not only reveals a complex expression landscape, but points toward an important contribution of long non-coding RNAs in the final phenotype of three-dimensional cellular models.

Collagen-polyvinylpyrrolidone (C-PVP) is a copolymer that is generated from the γ irradiation of a mixture of type I collagen and low-molecular-weight PVP. It is characterized by immunomodulatory, fibrolytic, and antifibrotic properties. Here, we used various physicochemical and biological strategies to characterize the structure, biochemical susceptibility, as well as its effects on metabolic activity in fibroblasts. C-PVP contained 16 times more PVP than collagen, but only 55.8% of PVP was bonded. Nevertheless, the remaining PVP exerted strong structural activity due to the existence of weak bonds that provided shielding in the NMR spectra. On SEM and AFM, freeze-dried C-PVP appeared as a film that uniformly covered the collagen fibers. Size analysis revealed the presence of abundant PVP molecules in the solution of the copolymer with a unique dimension related to macromolecular combinations. Calorimetric analysis showed that the copolymer in solution exhibited structural changes at 110 °C, whereas the lyophilized form showed such changes at temperatures below 50 °C. The copolymer presented a rheopectic behavior, with a predominant effect of the collagen. C-PVP had biological effects on the expression of integrin α2 and prolyl-hydroxylase but did not interact with cells through the collagen receptors because it did not inhibit or slow contraction.