Abstract
AbstractIn the present study an important phenomenon of cells was discovered: the change of intracellular density in cell's response to drug and environmental factors. For convenience, this phenomenon is named as "density alteration in non-physiological cells" ( DANCE). DANCE was determined by discontinuous sucrose gradient centrifugation (DSGC), in which cells were separated into several bands. The number and position of the bands in DSGC varied with the change of cell culture conditions, drugs, and physical process, indicating that cell's response to these factors was associated with alteration of intracellular density. Our results showed that the bands of cells were molecularly different from each other, such as the expression of some mRNAs. For most cells tested, intracellular density usually decreased when the cells were in bad conditions, in presence of drugs, or undergoing pathological changes. However, unlike other tissue cells, brain cells showed increased intracellular density in 24 hrs after the animal death. In addition, DANCE was found to be related to drug resistance, with higher drug-resistance in cells of lower intracellular density. Further study found that DANCE also occurred in microorganisms including bacteria and fungus, suggesting that DANCE might be a sensitive and general response of cells to drugs and environmental change. The mechanisms for DANCE are not clear. Based on our study the following causes were hypothesized: change of metabolism mode, change of cell membrane function, and pathological change. DANCE could be important in medical and biological sciences. Study of DANCE might be helpful to the understanding of drug resistance, development of new drugs, separation of new subtypes from a cell population, forensic analysis, and importantly, discovery of new physiological or pathological properties of cells.
Highlights
In a previous study we found that RT-PCR results varied in a significantly great range
When the seeding concentrations of K562 cells were 2.5×105/ml, 5×105/ml and 106/ml, cultured for two days, we found that intracellular density decreased (“DANCE up”) with increase of seeding concentration of the cells, i.e. only band S60 was found for 2.5×105/ml, both bands S50 and S60 were found for 5×105/ml, but only band S50 for 106/ml (Fig 1, C1-3)
Our results showed that cells of band S60 in both K562 and LOVO cell lines were more sensitive to drugs than that of S50 (Fig 2, A, B), and the most resistant K562 cells against retinoic acid were found to be those of S30 (Fig 2, A4)
Summary
Nature Precedings : hdl:10101/npre.2011.6541.1 : Posted 17 Oct 2011 Cell number change (normalized to day 1). A1-2: Normally cultured K562 cells (A1) and K562 cells in bad conditions with visible dead cells (A2). B1-3: K562 cells were continuously cultured for 2, 4, 6 days respectively. E1-4: Flowcytometric analysis of DNA contents for K562 cells of band S30, S40, S50 and S60 (A2), respectively. F1-4: Flowcytometric analysis of apoptosis for K562 cells of band S30, S40, S50 and S60 (A2), respectively. G: Growth curves (n=3) of K562 cells from the four bands ofA2. Nature Precedings : hdl:10101/npre.2011.6541.1 : Posted 17 Oct 2011 Cell number change (normalized to day 1) OD at 570nm Cell number change (normalized to day 1)
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