## 4 Discussion  
Currently, there are no reports about the changes that MSCs undergo when exposed to a tumor environment. In this work, we specifically studied the changes in the morphology, cytoskeleton, and migration of exposed MSCs into the secretome of cancer cells verified by impedance. In the 24 h secretome, the results showed a morphological diversity, greater migration (Figures 5 and 6) development, and greater organization of the cytoskeleton (Figure 7) due to evident changes in the arrangement of actin fibers and the cell polarity of the exposed MSCs to the 24 h secretome. This was not observed in cultures that were exposed to the 48 h  
Figure 10: (**a**) Gel electrophoresis and (**b–d**) graphs showing the relative expression of associated molecules. (**b**) Relative expression of the molecular markers of MSCs. (**c**) Relative expression of NANOG/OCT4 as indicators of malignancy. (**d**) Relative expression of pro-inflammatory cytokines. (**a**) mRNA detection. Lane 1: MSCs incubated with DMEM F-12 at 10% FBS. Lane 2: MSCs stimulated with MC48 and evaluated after 24 h of incubation. Lane 3: MSCs stimulated with MC48 and evaluated after 72 h of incubation. GAPDH was used as a housekeeping gene. Asterisks (*) indicate significant differences (\(p<0.05\)) between the control and different conditions. secretome since the cells had a homogeneous morphology, a marked inhibition of migration, and a different disposition of the cytoskeleton. The MSCs had no alterations in their nucleus/cytoplasm ratio, and neither cell hyperchromatism nor aberrant mitoses induced by the tumor secretome were observed. Since cell morphology is not a determining criterion to establish a neoplastic phenotype, it cannot be concluded with determination that MSCs undergo malignant transformation. Although no morphological changes related to cellular dysplasia were observed, the homogeneity of cellular morphology with a singular triangular predominance in the experimental conditions could be appreciated. This triangular morphology can be observed when MSCs are cultivated in vitro and is generally seen after a short time in cultures [45]. To study the arrangement of actin filaments (responsible for cell morphology) upon the secretome stimulation of MSCs, fluorescence microscopy was chosen. MSCs were stained with a protein related to actin fibers (phalloidin coupled to Green 488 fluorophore), which are closely related to cell morphology, as actin fibers orchestrate the control of cell shape dynamics as well as cell polarity [46; 47]. In some cell systems, changes in MSCs, such as cell asymmetry, are a result of cell polarization, which is a fundamental step prior to cell migration [46]; therefore, the characteristics of fiber organization and cell polarity presented by MSCs exposed to a secretome are indicative that the secretome has components that could induce MSC migration, reflecting early changes in the morphological pattern. It has been reported that the secretome of MCF-7 contains molecules such as vascular endothelial growth factor (VEGF) and interleukin 8 [48; 49] which could explain this effect. [PERSON] [29] mentioned that migration processes are due to branched networks of actin arranged in filipodia and lamellipodia and that these processes are actin-dependent. According to our results, the MSCs exposed to secretomes presented a greater organization of the dorsal fibers in the lamellipodia compared to the control, which are indications of migration. It might be interesting to investigate whether molecules such as Rho A are involved in this migration process, as described in the stromal tissue of prostate and ovarian cancer [50]. Recently, some techniques from a bioengineering perspective have emerged to describe the cellular state; this is the case for electrical bioimpedance [51] which allows us to detect differences between benign cells and malignant cells due to the different lineages of physiological characteristics [40; 45; 46; 47; 48; 49; 50; 51; 52]. [PERSON] et al.