Learn this "tumor research" method, and you will be one step closer to the country!

As the world's population ages, most cancers occur in people over the age of 60, and cancer is becoming a major public health problem
.

Cancer and aging seem to be the opposite process: cancer is the result of abnormal enhancement of cellular fitness, while aging is characterized by a loss
of adaptation.

How to moderately induce cell aging and inhibit cancer is a hot research content
in the field of oncology.

Today's analysis of an article published in Cell Death and Disea.

First, the research background

Polycomb Repressive Complex 2 (PRC2) is the only histone H3 lysine 27 (H3K27) methyltransferase identified from yeast to mammals
.

2.

The research ideas of this paper are:

(1) Experiments were conducted in a variety of tumor cells to verify that PCR2 inhibitors can increase the level of H3K27 acetylation

(2) Genome-wide bisulfite sequencing and ACAT-seq analysis proved that PRC2 inhibitors can upregulate the expression of H3K27me3z

(3) It was proved by gene enrichment analysis that PRC2 inhibitors induce tumor cell senescence

1.

After treating tumor cells using PRC2 inhibitors (MAK683, EED226, and EPZ26438), the authors found that these inhibitors could dose-dependently reduce H3K27me3 expression in HeLa cells and inhibit the proliferation
of lymphoma cells (WSU).

The authors then tested MAK683 for antiproliferative effects
in a group of cancer cells.

2.

Next, the authors investigated what
happens to sensitive tumors after PRC2 suppression.

To find out the epigenetic characteristics of the PRC2 inhibition upregulation gene, the authors used data from mRNA expression, DNA methylation, H3K4me3, and ATAC-seq for cluster analysis and obtained five different gene types: type 2 exhibits high DNA methylation, type 4 exhibits high H3K4me3 levels, and type 5 enriches most of the upregulated genes
.

3.

Since genes upregulated by PRC2 inhibitors may be drivers of tumor sensitivity, the authors focused on transcriptome data and performed gene set enrichment analysis (GSEA
).

Next, the authors continued to look at cells in the G401 xenograft and found that MAK683 showed good efficacy
in inhibiting tumor growth.

4.

CDKN2A/p16 is considered a key PRC2 target for inhibiting proliferation blockade
after PRC2 in many cancers, including nasopharyngeal, breast, leukemia, and ovarian cancers.
But the researchers verified that p16 deficiency did not change the level
of H3K27me3.
Shows that p16 KO does not hinder the deinhibition of the SASP gene, which is independently regulated
by PRC2.

Next, the authors conducted a study
of in vivo xenografting.
The p16 KO G401 xenograft grows more strongly
than the WT xenograft.
Because MAK683 treatment lasted longer in this study, it effectively blocked the growth of WT tumors (T/C% = 7.
21%, TGI reached 91.
25% of the treatment endpoint).

In addition, p16 KO xenografts also respond to MAK683 therapy (T/C% = 35.
81%, TGI at the end of treatment 54.
18%)
.
Ki67 positive is strongly correlated with tumor size, is expressed higher in the p16 KO vector than in the WT vector group, and is inhibited
by MAK683 in WT and p16 KO tumors.
SA-β-gal signal is increased after treatment by MAK683 in WT tumors, but no change
in p16KO xenografts.
Up-tuning of classic SASP, including MMP2, MMP10, BMP6, IGFBP3, IGFBP5, and IL1B, was statistically significant and unaffected by p16 KO, and the same trend
towards CCL2 was observed.
Together, these results suggest that a class of SASP genes is directly regulated
by PRC2.
They inhibit upregulation by PRC2 independent of p16 and help inhibit tumors
through PRC2 inhibitors.

5.
PRC2 inhibitors promote tumor differentiation, aging and immune infiltration in vivo

In MAK683-treated tumors, GSEA showed significant enrichment of ECM components, synaptic membrane components, and basement membrane pathways, and both the SASP pathway and ECM were significantly upregulated
in MAK683-treated tumors.
qPCR analysis also confirmed that they were upregulated in MAK683-treated WT and p16 KO tumors, and that the expression of ITGA2 and GBP1 proteins (SASP-associated proteins) was also significantly increased
.
These results suggest that PRC2 inhibitors promote the differentiation of tumor cells in the body, aging-related inflammation, and the occurrence
of immune infiltration.

III.
Summary

Deciphering the molecular pharmacological mechanisms of targeted therapies is critical
for their proper clinical application and maximizing their potential benefit to patients.
In this study, the authors address a fundamental question about PRC2 inhibitors, namely how they function
in reactive tumors.
By combining single-cell sequencing, gene enrichment analysis, and other methods, the pharmacological mechanism of PRC2 inhibitors - that is, inducing tumor cells to undergo aging changes to exert their anti-cancer effects - and proposed that the combination of PRC2 inhibitors with PD-1 therapy and/or CDK4/6 inhibitors may be an effective clinical strategy
.