An Immunofluorescence-Based Method to Quantify Replication Stress in Cancer Cells

Abstract

Source: Ramakrishnan, N. et al., Quantifying Replication Stress in Ovarian Cancer Cells Using Single-Stranded DNA Immunofluorescence. J. Vis. Exp. (2023)

The video demonstrates an immunofluorescence-based approach for quantifying replication stress in cancer cells. Hydroxyurea-treated cells produce single-stranded DNA, detected through immunofluorescence. The count of green fluorescence foci indicates the level of replication stress in cancer cells.

Protocol

NOTE: The ovarian cancer cell line, OVCAR3, was used in these steps, but this protocol is broadly applicable to multiple other cell lines, including those derived from non-ovarian sources. A schematic of the protocol is shown in Figure 1.

1. Plating the cells

1. Make poly-L-lysine coated coverslips.
   1. Add autoclaved 12 mm diameter coverslips to a 50 mL conical tube with poly-L-lysine solution, and place on a rocker for 15 min.
   2. Aspirate the solution in a tissue culture hood. Wash the coverslips by adding sterile water and place the tube containing the coverslips....

Results

Figure 1: IdU labeling schematic. Cells are pulsed with IdU for two population doublings. If any drug treatment is needed, it should be administered after the first population doubling in the presence of IdU.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3% Paraformaldehyde (PFA)	Fisher Scientific	NC0179595	10 g sucrose + 100 mL 10X PBS + water to make volume to 925 mL. Add 75 mL 40% Methanol free PFA, mix, and make aliquots of 50 mL before storage Storage: Store in -20 °C
5-iodo-2'-deoxyuridine (IdU)	Sigma Aldrich	I7125-5G	MW = 354.10 g/mol.For 10 mM stock: dissolve 3.541 mg IdU to 1 mL 1 N liquid ammonia
Anti-BrdU antibody	BD Biosciences	347580	Storage: Store in 4 °C
Anti-mouse Alexa Fluor Plus 488 secondary antibody	Thermo Scientific	A32766	Light sensitive - keep in dark
Bovine Serum Albumin (BSA)	Sigma Aldrich	A7906-100G	Made by adding specific mass to volume of PBS Storage: Store in 4 °C
Circular Cover Glass	Electron Microscopy Sciences	72230-01
OVCAR3	ATCC	HTB-161	Growth Media: RPMI supplemented with L-glutamine, 0.01 mg/mL bovine insulin; fetal bovine serum to a final concentration of 20% and 1X Pen Strep Storage: Freezing Media: growth media + 5% DMSO and stored in -80 °C
Poly-L-Lysine solution	Sigma Aldrich	P4832-50ML	Storage: Store in 4 °C
ProLong Diamond Antifade Mountant with DAPI	Thermo Scientific	P36962	Storage: Store in 4 °C
Trypsin-EDTA, 0.25%	Genesee Scientific	25-510	Storage: Store in 4 °C
Water, sterile-filtered	Sigma Aldrich	W3500-6X500ML	Storage: Store in 4 °C