Cancer Stem Cells and Epithelial Ovarian Cancer

Table 1

Studies that have attempted to characterise the cancer stem cell (CSC) component in the cancers are listed. Only the most relevant studies are referenced. The different experimental techniques used in the referenced studies are reviewed; this highlights the lack of consensus in the approach that can be best used to identify stem-like cells in cancers.

Cancer type	Cell surface antigen profile^a	In vitro characterization				In vivo characterisation	References
		Dye exclusion assay^b	Tumour sphere assay^c	Clonality assays^d	ALDH assay^e
Leukaemia	CD34^+/CD38^-	H 33342 (5 μg/mL) 2 hours, 37°C; Inhibitor KO143 (200 nM)	SFM	Colony forming unit assay: number of colonies from leukemic SP and haematopoetic SP compared per 10^6 cells plated	Not done	SCID	[15, 16]
			20 ng/mL Interleukin-3
			100 ng/mL stem cell factor
Brain	CD133^+	H 33342 (5 μg/mL) 90 minutes at 37°C; Inhibitors; Verapamil (50 μM) or reserpine (100 μM).	SFM	Primary spheres dissociated and plated at cell dilutions from 200 cells/well to 1 cell.	Not done	NOD-SCID	[17, 18]
			20 ng/mL EGF,
			20 ng/mL bFGF
			10 ng/mL LIF
			60 μg/mL N-acetylcysteine
Breast	CD44^+CD24^[-]/low; OCT4^+; CD133^+	H33342 (5 μg/mL) for 90 min, 37°C; Inhibitor FTC 10 μM	SFM	Single cells (1 cells per well in 96-well plate)	ALDEFLUOR-positive	NOD-SCID	[19, 20]
			10 ng/mL bFGF
			20 ng/mL EGF
			5 μg/mL insulin
			0.4% BSA
Colon	CD133^+	H33342 (5 μg/mL) for 1.5–2 hours, 37°C,; Inhibitor verapamil at 50 μM for 10 minutes at room temperature before adding H33342	SFM	Single-cell derived tumour spheres (unsorted and CD133^+, either spheroid-derived or primary)	Not done	NOD-SCID	[21, 22]
			0.6% glucose,
			9.6 μg/mL putrescine,
			6.3 ng/mL progesterone
			ITS
			20 ng/mL EGF
			10 ng/mL bFGF
Endometrial	—	H33342 (5 μg/mL) for 90 minutes, 37°C; Inhibitor verapamil (50 μM)	—	—	Not done	NOD-SCID	[23]
Head and neck	CD44^+	H33342 5 μg/mL at varying time points, 37°C; Inhibitor reserpine (5 μg/mL)	SCM	Single cells GFP^+ and GFP^-	Not done	NOD-SCID	[24–26]
Pancreas	CD133^+	—	SFM	1 cell/well in SFM by limiting dilution	Not done	Nude mice	[27]
			10 ng/mL FGF
			20 ng/mL EGF
			5 μg/mL insulin
			ITS
			0.4% BSA
Prostate	CD44^+, α 2β 1^hi, CD133^+	H33342 (5 μM) for 90 minutes, 37°C; Inhibitor verapamil (50 μM)	SFM	Single cells were plated at 1,000/mL on a plate coated with 0.5% agar	Not done	SCID	[9, 28, 29]
			B27
			10 ng/mL EGF
			10 ng/mL bFGF
Ovary	CD133^+; CD44^+CD117^+	H33342 (5 μM) for 90 minutes, 37°C; Inhibitor verapamil (50 μM)	SFM	—	Not done	BALB/c-nu/nu	[30–37]
			5 μg/mL insulin
			20 ng/mL EGF
			10 ng/mL bFGF
			0.4% BSA

^aCell surface antigen profile expression by flow cytometry and immunohistochemistry techniques
^bDye Exclusion flow cytometry assays following treatment with Hoechst, coupled with ABC multidrug transporter inhibitors to isolate side population cells
^cSphere formation assays for multicellular spheroid forming ability under nonadherent conditions, which is characteristic of stem cells
^dClonality assays measure the ability of single cells to generate spheroids/clones
^eAldehyde Dehydrogenase assays measure the levels of ALDH1 in cells
Soft agar assay measures anchorage-independent growth due to loss of contact-inhibition and is an indicator of tumourigenicity.
EGF: Epidermal growth factor
bFGF: Basic fibroblast growth factor
LIF: Leukemia inhibitory factor
NSF: Neuronal survival factor
BPE: Bovine pituitary extract
KO143: Inhibitor of breast cancer resistant protein (BRCP)
SFM: Serum-free media
SCM: Serum-containing media.