MS9117

HL-60 cells are a human promyelocytic leukemia cell model that can be induced toward granulocytic/neutrophil-like differentiation by DMSO, ATRA, or combined ATRA+DMSO treatment; differentiation is evaluated by morphology, reduced proliferation, CD11b gain, CD71 loss, phagocytosis, oxidative burst/NBT reduction, ROS formation, and, where relevant, NET-related assays. A literature-supported default protocol is 5 days of combined 1 µM ATRA plus 1% DMSO, because this condition produced neutrophil-like morphology, cell-cycle arrest, high CD11b positivity, low CD71 positivity, and increased phagocytic capacity compared with ATRA or DMSO alone in the cited study.

Soft agar colony formation assay measures anchorage-independent growth, in which transformed or tumorigenic cells proliferate as colonies in a semisolid agar matrix while many non-transformed adherent cells fail to proliferate without attachment; classic studies showed that growth in semisolid medium correlates with tumorigenicity in nude mice, and later protocol papers describe the method as a stringent in vitro assay for malignant transformation. The readout is the number, size, morphology, or signal intensity of colonies formed within agar after incubation; published formats include manual colony counting after staining, 96-well or 384-well quantitative formats, DNA-binding dye detection, MTT/tetrazolium-based detection, digital image analysis, and PCR-based marker detection from soft agar cultures.

The clonogenic (colony formation) assay measures the ability of a single cell to retain reproductive viability and form a macroscopic colony, typically defined as a cluster derived from one progenitor cell after a defined growth period. This assay is widely used to evaluate cell survival after exposure to ionizing radiation or cytotoxic treatments and is considered a standard method in radiation biology for generating dose-response relationships of reproductive cell death. Colony formation reflects long-term proliferative capacity rather than short-term metabolic activity, and survival is quantified by comparing treated versus untreated conditions based on colony number and derived survival fractions.

The following protocol uses the MTT colorimetric assay as a classic literature-established method for assessing cell viability/metabolic activity in cultured mammalian cells. MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] is reduced by metabolically active cells to a colored formazan product; the amount of formazan is quantified spectrophotometrically and provides an indirect measure of metabolically active viable cells. Importantly, MTT reduction reflects cellular oxidoreductase/metabolic activity rather than an absolute direct count of living cells, so changes in cellular metabolism can alter the signal independently of cell number.