Table 1.

The chemo-sensitizing effect of natural and synthetic retinoids on MDR cell lines.

retinoid	class	resistant cancer cell line	cancer origin	resistance to chemotherapeutic agent(s)	IC50 (µM)	Ref.
ATRA	retinoic acid receptor (RAR) Pan-agonist	MDA-MB-231	breast	paclitaxel (PTX) and 5-fluorouracil (5-FU)	34.1b,c	[15,16]
		LoVo/MDR	colon	doxorubicin (Dox)	NAd	[17]
		HEN-16-2/CDDP	cervical	cisplatin (CDDP)	NAd	[18]
		L1210/VCR	mouse lymphocytic leukaemia	vincristine (VCR)	NAd	[19,20]
		mS-0.5	melanoma	colchicine	NAd	[21]
		J82-NVB	bladder	navelbine	NAd	[22]
		HL60/DNR	acute promyelocytic leukaemia (APL)	daunorubicin	NAd	[23]
retinol	—	SW620	colorectal	etoposide	NAd	[24]
isoxazole retinoid 15b	RAR pan-agonist	HL60R	APL	ATRA	1.4b,c	[25]
		K562	leukaemia	ATRA	2.3b,c	[25]
		HUT78	T-cell lymphoma	ATRA	0.8b,c	[25]
fenretinide or 4-HPR	RAR-β selective agonist	Bel-7402	HCC	Dox and VCR	13.1a	[26,27]
		MDA-MB-231	breast	PTX and 5-FU	6.5b,c	[28]
		CHLA-119	neuroblastoma	ABT-737 (small-molecule BH3- mimetic) alone	NAd	[29]
ABPN (or CBG41)	RAR pan-agonist	MDA-MB-231	breast	PTX and 5-FU	3.3b,c	[28]
ATPR	RAR pan-agonist	MDA-MB-231	breast	PTX and 5-FU	18.1b,c	[15]

^aIC₅₀ (concentration of the compound caused 50% reduction in comparison to untreated cells) was calculated after 72 h of treatment.

^bIC₅₀ was calculated after 48 h of treatment.

^cIC₅₀ was calculated after 24 h of treatment.

^dNA = not available.