Lysine-Specific Demethylase 1 Mediates AKT Activity and Promotes Epithelial-to-Mesenchymal Transition in PIK3CA-Mutant Colorectal Cancer

Abstract

Activation of the epithelial-to-mesenchymal transition (EMT) program is a critical mechanism for initiating cancer progression and migration. Colorectal cancers contain many genetic and epigenetic alterations that can contribute to EMT. Mutations activating the PI3K/AKT signaling pathway are observed in >40% of patients with colorectal cancer contributing to increased invasion and metastasis. Little is known about how oncogenic signaling pathways such as PI3K/AKT synergize with chromatin modifiers to activate the EMT program. Lysine-specific demethylase 1 (LSD1) is a chromatin-modifying enzyme that is overexpressed in colorectal cancer and enhances cell migration. In this study, we determine that LSD1 expression is significantly elevated in patients with colorectal cancer with mutation of the catalytic subunit of PI3K, PIK3CA, compared with patients with colorectal cancer with WT PIK3CA. LSD1 enhances activation of the AKT kinase in colorectal cancer cells through a noncatalytic mechanism, acting as a scaffolding protein for the transcription-repressing CoREST complex. In addition, growth of PIK3CA-mutant colorectal cancer cells is uniquely dependent on LSD1. Knockdown or CRISPR knockout of LSD1 blocks AKT-mediated stabilization of the EMT-promoting transcription factor Snail and effectively blocks AKT-mediated EMT and migration. Overall, we uniquely demonstrate that LSD1 mediates AKT activation in response to growth factors and oxidative stress, and LSD1-regulated AKT activity promotes EMT-like characteristics in a subset of PIK3CA-mutant cells.Implications: Our data support the hypothesis that inhibitors targeting the CoREST complex may be clinically effective in patients with colorectal cancer harboring PIK3CA mutations.

LSD1 promotes secretory cell specification to drive BRAF mutant colorectal cancer

“…Generally, LSD1 expression was highest in early EEC and early secretory cells, lowest in differentiated EEC and goblet cells, and similar in all other clusters (Supplemental Figure 10A). We have previously demonstrated that loss of LSD1 significantly alters clonogenic growth in organotypic HT29 cells, but not in stem-like SW480 cells, which do not form secretory cells (Miller et al, 2020). Similarly, reduction of EEC or secretory cells by knockdown of NEUROG3 or ATOH1 significantly reduced clonogenic growth in HT29 cells (Supplemental Figure 10B).…”

“…Combining this observation with our LSD1 expression analysis, we hypothesized that LSD1 expression levels increase in secretory progenitors to regulate EEC progenitor and goblet cell formation in our cell lines. Additionally, loss of these populations after LSD1 KD may be responsible for our previously reported clonogenic growth phenotypes (Miller et al, 2020).…”

“…As a preliminary analysis to determine if LSD1 may be necessary for the formation of secretory lineage cells, we reanalyzed our previously published LSD1 knockdown (KD) RNA-seq data in HT29 and SW480 cells (Miller et al, 2020). LSD1 KD was associated with a significant reduction of nearly all tested EEC progenitor and goblet cell markers in HT29 cells, but no markers were reduced in SW480 cells (FDR < 0.05) (Supplemental Figure 10C).…”

“…Knockdown LSD1 (KDM1A) (TRCN0000327856, TRCN0000327932, TRCN0000046071), ATOH1 (MATH1) (TRCN0000433089, TRCN0000414973), NEUROG3 (TRCN0000427521) and SPDEF(TRCN0000274422) knockdown constructs were purchased from mission shRNA; empty plasmid was used as a vector control. Knockdowns were performed as previously described (Miller et al, 2020).…”

“…The chromatin-modifying enzyme lysine-specific demethylase 1 (LSD1) is over-expressed in many CRCs and contributes to the formation of numerous cancer types such as small cell lung cancer and acute myeloid leukemia (Mohammad et al, 2015) (Takagi et al, 2017) (Maiques-Diaz et al, 2018). While the demethylase activity of LSD1 contributes to the progression of multiple cancer types, the scaffolding function of LSD1 in the CoREST complex has recently been highlighted in CRC (Miller et al, 2020). Nevertheless, both the normal functions of LSD1 in the intestine and its potential role in intestinal cancers are poorly understood.…”