Fig. 2

Inhibition of IRE1 reduces breast cancer cell proliferation. a Chemical structure of MKC8866. b MDA-MB-231 cells were treated with 20 μM MKC8866 for 4, 6, 12, and 24 h after which RNA was extracted and levels of XBP1s, ERDJ4, and HERP mRNA transcripts quantified by Q-PCR (n = 4). c T47D cells were treated for 24 h with 1 μg ml⁻¹ Tm alone or in combination with increasing concentrations of MKC8866 (5, 10, 20 μM) and cell lysates immunoblotted for XBP1s, PERK, CHOP, ATF6, and Actin. d MCF7 (n = 3), SKBR3 (n = 5), MDA-MB-231 (n = 2), and MCF10A (n = 3) cells were treated with 20 μM MKC8866 or an equal volume of DMSO and cell proliferation monitored by cell counts every second day for 6 days. e MCF7, SKBR3, and MDA-MB-231 cells were treated with 20 μM MKC8866 for 24 h and cell lysates immunoblotted for XBP1s and Actin. f Empty vector (EV) and XBP1shRNA MDA-MB-231 cells were treated for the indicated times with Tg (0.5 μM) after which expression of XBP1s and Actin was determined by immunoblotting. g Proliferation of empty vector (EV) and XBP1shRNA MDA-MB-231 cells was monitored by cell counts every second day for 6 days (n = 3). Results shown for c, e, and f are representative of three independent experiments. *P < 0.05, **P < 0.01 and ***P < 0.001, based on a Student’s t test. Error bars represent s.e.m.