Lentivirus-mediated RNA interference targeting FAMLF-1 inhibits cell growth and enhances cell differentiation of acute myeloid leukemia partially differentiated cells via inhibition of AKT and c-MYC

Trametinib enhances ATRA-induced differentiation in AML cells

All-trans retinoic acid (ATRA) is only clinically useful in acute promyelocytic leukemia (APL), but not other subtypes of acute myeloid leukemia (AML). In the present study, a clinically achievable concentration of trametinib, a highly selective inhibitor of MEK, enhanced ATRA-induced differentiation in AML cell lines, HL-60 and U937 as well as AML primary cells. Moreover, trametinib-ATRA (tra-ATRA) co-treatment restored ATRA sensitivity in ATRA-resistant AML cell line, HL-60Res. The protein level of STAT3 and the phosphorylation of Akt or JNK were enhanced with tra-ATRA treatment in HL-60, U937, and HL-60Res cells, respectively. Furthermore, tra-ATRA-induced differentiation in HL-60, U937, and HL-60Res cells was inhibited by STAT3, PI3K, and JNK inhibitors, respectively. Therefore, STAT3, Akt, and JNK signaling pathways were involved in tra-ATRA-induced differentiation in HL-60, U937, and HL-60Res cells, respectively. Taken together, our findings may provide novel therapeutic strategies for AML patients.

Platelet-derived growth factor-B signalling might promote epithelial-mesenchymal transition in gastric carcinoma cells through activation of the MAPK/ERK pathway

Introduction

Epithelial-mesenchymal transition (EMT) is important in the metastasis of tumours and is triggered by several key growth factors, including platelet-derived growth factor-B (PDGF-B). But, whether PDGF-B signalling promotes EMT in gastric carcinoma cells is still unknown.

Material and methods

We established 2 gastric carcinoma cell lines (MKN28 and MKN45) to stably overexpress PDGF-B by lentiviral vectors, and expression of E-cadherin, N-cadherin, and ERK-1 were detected by western blot assay. Then, PDGF-B overexpression and normal MKN28 and MKN45 cells were cocultured with PDGFR-b positive fibroblast (hs738) and MAPK inhibitors were added; also, the expressions of ERK-1, E-cadherin, and N-cadherin were detected by western blot assay.

Results

After being cocultured with hs738 cells, expressions of ERK-1 and N-cadherin protein in PDGF-B overexpression MKN28 and MKN45 cells were much higher than normal MKN28 and MKN45 cells (p < 0.05), and those could be decreased by MAPK inhibitor. Also, expressions of E-cadherin protein in PDGF-B overexpression MKN28 and MKN45 cells were much lower than normal MKN28 and MKN45 cells (p < 0.05), and they could be increased by MAPK inhibitor.

Conclusions

Our data indicate that PDGF-B signalling can induce EMT in gastric carcinoma cells. Thr tumour microenvironment is imperative in the process of PDGF-B signalling inducing EMT in gastric carcinoma cells. Also, activation of MAPK/ERK pathway, which is a downstream pathway of PDGF-B signalling, might participate in this process.

Enzastaurin enhances ATRA-induced differentiation of acute myeloid leukemia cells

All-trans retinoic acid (ATRA) is considered to be the sole clinically-useful differentiating agent in the treatment of acute myeloid leukemia (AML). However, ATRA has been effective only in acute promyelocytic leukemia (APL) but not other subtypes of AML. Therefore, discovering strategies to sensitize cells to ATRA may lead to the development of ATRA-based treatments in non-APL AML patients. In the present study, a clinically-achievable concentration of enzastaurin enhanced ATRA-induced differentiation in AML cell lines, HL-60 and U937 as well as non-APL AML primary cells. Furthermore, it also restored ATRA sensitivity in ATRA-resistant cell line, HL-60Res. Mechanistically, in all these cell lines, enzastaurin-ATRA (enz-ATRA) co-treatment enhanced the protein levels of PU.1, CCAAT/enhancer-binding protein β (C/EBPβ) and C/EBPε. The activity of protein kinase C β (PKCβ) was suppressed by enz-ATRA treatment in HL-60 and HL-60Res cells. However, another PKCβ-selective inhibitor mimicked the cellular and molecular effects of enzastaurin only in HL-60 cells. Furthermore, in U937 cells, enz-ATRA activated MEK and ERK, and a MEK-specific inhibitor suppressed enz-ATRA-triggered differentiation and reduced the protein levels of PU.1, C/EBPβ and C/EBPε. Enz-ATRA activated Akt in HL-60 and HL-60Res cells. However, an Akt inhibitor blocked enz-ATRA-triggered differentiation and restored the protein levels of PU.1, C/EBPβ and C/EBPε only in HL-60Res cells. Therefore, PKCβ inhibition, MEK/ERK and Akt activation were involved in enz-ATRA-induced differentiation in HL-60, U937 and HL-60Res cells, respectively, via modulation of the protein levels of C/EBPβ, C/EBPε and PU.1. Taken together, our findings may help to guide novel therapeutic strategies for AML patients.