Hematopoietic transcription factor GFI1 promotes anchorage independence by sustaining ERK activity in cancer cells
Hao Wang, Zhenzhen Lin, Zhe Nian, Wei Zhang, Wenxu Liu, Fei Yan, Zengtuan Xiao, Xia Wang, Zhenfa Zhang, Zhenyi Ma, Zhe Liu
Hao Wang, Zhenzhen Lin, Zhe Nian, Wei Zhang, Wenxu Liu, Fei Yan, Zengtuan Xiao, Xia Wang, Zhenfa Zhang, Zhenyi Ma, Zhe Liu
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Research Article Cell biology Oncology

Hematopoietic transcription factor GFI1 promotes anchorage independence by sustaining ERK activity in cancer cells

Abstract

The switch from anchorage-dependent to anchorage-independent growth is essential for epithelial metastasis. The underlying mechanism, however, is not fully understood. In this study, we identified growth factor independent-1 (GFI1), a transcription factor that drives the transition from adherent endothelial cells to suspended hematopoietic cells during hematopoiesis, as a critical regulator of anchorage independence in lung cancer cells. GFI1 elevated the numbers of circulating and lung-infiltrating tumor cells in xenograft models and predicted poor prognosis of patients with lung cancer. Mechanistically, GFI1 inhibited the expression of multiple adhesion molecules and facilitated substrate detachment. Concomitantly, GFI1 reconfigured the chromatin structure of the RASGRP2 gene and increased its expression, causing Rap1 activation and subsequent sustained ERK activation upon detachment, and this led to ERK signaling dependency in tumor cells. Our studies unveiled a mechanism by which carcinoma cells hijacked a hematopoietic factor to gain anchorage independence and suggested that the intervention of ERK signaling may suppress metastasis and improve the therapeutic outcome of patients with GFI1-positive lung cancer.

Authors

Hao Wang, Zhenzhen Lin, Zhe Nian, Wei Zhang, Wenxu Liu, Fei Yan, Zengtuan Xiao, Xia Wang, Zhenfa Zhang, Zhenyi Ma, Zhe Liu

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Figure 7

GFI1 establishes the interaction between the enhancer and promoter of RASGRP2.

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GFI1 establishes the interaction between the enhancer and promoter of RA...
(A) Alignment of human, chimpanzee, Rhesus monkey, and mouse RASGRP2 genes revealed a 50 bp conserved sequence residing within the noncoding region 4 kb upstream from the RASGRP2 transcriptional start site. (B) ChIP shows distribution of H3K4me3 and H3K27ac histone modifications in H1155, H526, A549, and H460 cells. The location of primers is shown in A. (C) Bar graphs show luciferase reporter activity with ectopic placement of the 50 bp conserved DNA sequence (red line in upper diagram) adjacent to the promoter, ectopic placement of mutant GFI1 lacking DNA-binding activity, or mutation of GFI1 binding motif within the enhancer region. Luciferase activity was normalized to Renilla signals. Mean ± SD represents 3 replicates in 1 experiment. Three independent experiments were performed. ****P < 0.0001 (1-way ANOVA test with post hoc contrasts by Tukey’s test). (D) ChIP-Seq showing enrichment of GFI1 in the RASGRP2 locus (top). ChIP-QPCR analysis showing the association of GFI1-Flag in transfected A549 cells with regions 3 and regions 8–10 at the (bottom). The location of primers is shown (middle). (E) 3C was used to calculate the cross-linking frequency between chromatin segments to assess the proximity in A549, H1155, GFI1-expressing A549, and GFI1-deleted H1155 cells. Vertical lines represent Dpn II restriction sites; arrows indicate PCR primer sites and direction. Anchor symbols mark the anchoring primer. Heatmaps showing the cross-linking frequency between the RASGRP2 promoter and other Dpn II–defined segments.