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CD147 as potential therapeutic target in AML
lar carcinoma cells, and that ERK/STAT3 signaling plays a significant role in promoting AML cell proliferation, sur- vival and autophagy,22,23,32,33 we also investigated the effect of AC-73 on ERK1/2 and STAT3 activation in leukemic cells. In line with previous studies,31,32 western blot analy- sis showed that ERK and STAT3 are constitutively phos- phorylated in all leukemic cell lines [Online Supplementary Figure S3, lanes (-)]. We then found that AC-73 (5 mM, for 3 days) notably decreases both pERK and pSTAT3 (S727) levels without affecting the levels of total ERK and STAT3, in leukemic cells (lanes 5 mM) (Online Supplementary Figure S3, lower panels).
Altogether, our data demonstrate that AC-73 inhibits leukemic cell proliferation, in part by suppressing the ERK/STAT3 activation pathway in these cells, in part by activating a non-apoptotic, autophagic form of cell death, which may account for the efficacy of AC-73 in leukemic cells.
AC-73 has an additive anti-proliferative effect on chemotherapeutic treatment of leukemic cells and increases ATO-induced autophagy in leukemic cells
To evaluate the effect of AC-73 in combination with standard drugs used for AML treatment, AML cell lines
Figure 2. Over-expressed in acute myeloid leukemia (AML), CD147 expression is down-regulated during monocytic and granulocytic differentiation of leukemic cells. (A) qRT-PCR analysis of CD147 mRNA expression in primary leukemic cells of AMLs pertaining from M0 to M5 subtypes of the French-American-British (FAB) classi- fication, as compared to normal CD34+ hematopoietic progenitor cells (HPCs) (left panel); CD147 mRNA expression data from AML samples generated by TCGA Research Network (right panel). (B) Western blot analysis of CD147 protein expression level in AML cell lines; densitometry analysis [arbitrary units (AU)] of CD147 protein expression levels compared with actin lev- els is indicated. (C) qRT-PCR analysis of CD147 mRNA expression in leukemic cell lines, as compared to normal CD34+ HPCs. (D-G) Western blot (left panels) and flow cytometry (right panels) analysis of CD147 total and membrane protein expression levels during vitamin D3-induced monocyt- ic differentiation of U937 cell (D), ATRA- induced granulocytic differentiation of HL- 60 cells (E), ATRA-induced differentiation of NB4 cells (F), and in NB4-R4 cells, resistant to ATRA treatment (G). (A and C) Mean±Standard Error of Mean (SEM) of three independent experiments is shown. *P<0.05; **P<0.01; ***P<0.001. (B, D-G, left panels) One representative western blot experiment out of three is shown. High (HG) and Low (LG) glycosylated CD147 iso- forms are indicated. Actin is shown as inter- nal control. (D-G, right panels) Mean±SEM of three independent experiments by flow cytometry analysis is shown. *P<0.05; **P<0.01; ***P<0.001. ns: not signifi- cant; RPKM: Reads Per Kilobase Million; MFI: mean fluorescence intensity.
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