Serum starvation induces abnormal spindle location, RhoA delocalization, and extension of intercellular bridge with the midbody

Polyploid cell dynamics and death before and after PEG-treatment of a NIH/3T3 derived culture: vinblastine effects on the regulation of cell subpopulations heterogeneity

BACKGROUND

Neoplastic subpopulations can include polyploid cells that can be involved in tumor evolution and recurrence. Their origin can be traced back to the tumor microenvironment or chemotherapeutic treatment, which can alter cell division or favor cell fusion, generating multinucleated cells. Their progeny, frequently genetically unstable, can result in new aggressive and more resistant to chemotherapy subpopulations. In our work, we used NIHs cells, previously derived from the NIH/3T3 line after serum deprivation, that induced a polyploidization increase with the appearance of cells with DNA content ranging from 4 to 24c. This study aimed to analyze the cellular dynamics of NIHs culture subpopulations before and after treatment with the fusogenic agent polyethylene glycol (PEG), which allowed us to obtain new giant polyploid cells. Successively, PEG-untreated and PEG-treated cultures were incubated with the antimicrotubular poison vinblastine. The dynamics of appearance, decrease and loss of cell subpopulations were evaluated by correlating cell DNA content to mono-multinuclearity resulting from cell fusion and division process alteration and to the peculiarities of cell death events.

RESULTS

DNA microfluorimetry and morphological techniques (phase contrast, fluorescence and TEM microscopies) indicated that PEG treatment induced a 4-24c cell increase and the appearance of new giant elements (64-140c DNA content). Ultrastructural analysis and autophagosomal-lysosomal compartment fluorochromization, which allowed us to correlate cytoplasmic changes to death events, indicated that cell depletion occurred through distinct mechanisms: apoptotic death involved 2c, 4c and 8c cells, while autophagic-like death involved intermediate 12-24c cells, showing nuclear (lobulation/micronucleation) and autophagic cytoplasm alterations. Death, spontaneously occurring, especially in intermediate-sized cells, was increased after vinblastine treatment. No evident cell loss by death events was detected in the 64-140c range.

CONCLUSIONS

PEG-treated NIHs cultures can represent a model of heterogeneous subpopulations originating from cell fusion and division process anomalies. Altogether, our results suggest that the different cell dynamics of NIHs subpopulations can affect the variability of responses to stimuli able to induce cell degeneration and death. Apoptptic, autophagic or hybrid forms of cell death can also depend on the DNA content and ability to progress through the cell cycle, which may influence the persistence and fate of polyploid cell descendants, also concerning chemotherapeutic agent action.

Differential migration-related gene expression and altered cytokine secretion in response to serum starvation in cultured MDA-MB-231 cells

Background

Serum starvation is mostly considered as a standard preparatory method in many cellular and molecular experiments. However, recent studies give some evidence that serum starvation is a major event that triggers various cell responses and has therefore great potential to change and interfere with the experimental results. In this study, the behavior of breast cancer cells in serum-starved condition was examined.

Objective

To focus on the role of serum starvation on cell migration and also the possible changes in the expression and secretion of genes and cytokines mostly involved in migration and chemotaxis of breast cancer cells.

Methods

MDA-MB-231 cells were cultured under serum-starved condition. Transwell migration assay was performed to evaluate the effect of serum starvation on cell migration after 24, 48, and 72 h. The transcriptional expression of migration-related genes was evaluated using real-time polymerase chain reaction. The cytokine secretion was also analyzed using enzyme-linked immunosorbent assay.

Results

Serum starvation suppressed cell migration in breast cancer cells. Additionally, the gene expression of markers involved in migration including β-catenin, twist, zinc finger E-box binding homeobox 1, vimentin, fibronectin, intercellular adhesion molecule 1, and vascular endothelial growth factor were downregulated. Moreover, cytokines of transforming growth factor, beta 1, matrix metallopeptidase 9, interleukin 8, and nitric oxide were differentially secreted.

Conclusions

Serum deprivation causes significant changes in cancer cell migration and also the expression of migration-related genes and cytokines, special care needs to be taken when this practice is used as preparatory method especially in migration and chemotaxis experiments on cancer cells.