Harvard scientists discovered an anti-cancer target that can not only affect tumor cells and improve the immune microenvironment, but also improve the anti-cancer activity of immune cells 丨 scientific discovery

Recently, the latest discovery by the team of Kai W Wucherpfennig of Harvard Medical School is expected to break the predicament of cancer patients who are resistant to immunotherapy.

They screened a magical protein-CARM1.

If the activity of CARM1 is inhibited in tumor cells, it will induce an increase in the level of double-stranded DNA breaks, activate tumor cells to respond to DNA damage, increase the expression level of interferon-stimulating genes (ISGs), improve the tumor microenvironment, and promote innate immunity The aggregation of cells.

Inhibiting the activity of CARM1 in killer T cells will increase the activity of killer T cells and maintain the level of memory anti-tumor T cells.

This means that drugs that inhibit CARM1 activity on the one hand can subdue tumor cells, on the other hand, it can also improve the anti-tumor ability of T cells.

It really kills two birds with one stone.

Researchers believe that this is a very important breakthrough for immunotherapy, and related research results have been published in the well-known journal Cancer Discovery [1].

▲ Screenshot of the first page of the paper The emergence of immunotherapy is a major milestone in the history of cancer treatment and has changed the fate of many cancer patients.

However, from the current curative effect, only a small proportion of patients have benefited, and most patients do not respond to immunotherapy or will develop resistance after treatment.

In recent years, in order to further expand the beneficiaries of immunotherapy, scientists and doctors have hoped to use immunotherapy in combination with chemotherapy and other therapies.
Some combination therapies have even been approved by the FDA.

However, only a small number of patients can benefit from combination therapy [2].

The reason behind this is partly because chemotherapy and other treatments that kill tumor cells can also damage the survival, function, and even production of immune cells [3, 4].

Therefore, in the opinion of Wucherpfennig and his colleagues, it would be great if there was a drug that could subdue tumor cells without damaging immune cells, or even enhance the anti-cancer activity of immune cells.

▲ Kai W Wucherpfennig, in order to find drugs that meet the above conditions, first started with tumor-specific T cells and used CRISPR/Cas9 technology to screen negative regulators of anti-tumor immunity.

Soon, a gene called Carm1 surfaced.

The Carm1 gene encodes an arginine methyltransferase, which can add methyl groups to the R17 and R26 residues of histone H3 and other nucleoproteins.

▲ Found that the Carm1 gene Since Carm1 has been delivered to the door, let's study its effect on T cells.

Wucherpfennig first knocked out the Carm1 gene of T cells in vitro.
Compared with the control group, T cells whose Carm1 gene was knocked out had stronger lethality on the melanoma cell B16F10-Ova.

Moreover, after coexisting in a culture vessel with B16F10-Ova, the expression levels of CD69 activation markers, granzyme B cytotoxic protein and cytokines IL-2, IFNg and TNFa of T cells whose Carm1 gene was knocked out were higher; in addition, It also showed stronger antigen-induced proliferation ability.

In other words, knocking out the Carm1 gene of the T cell makes the T cell stronger.

In this view, the Carm1 gene is undoubtedly a negative regulator of tumor-specific T cells.

Subsequent in vivo experiments in model mice once again found that T cells whose Carm1 gene was knocked out had a stronger inhibitory effect on tumors formed by melanoma cells B16F10-Ova.

Specifically, not only has the anti-cancer activity of T cells increased, but also the ability of T cells whose Carm1 gene has been knocked out to enter tumors has also increased.

In order to clarify the effect of knocking out the Carm1 gene on the T cell transcriptome, the researchers further performed RNA sequencing analysis.

The results showed that knocking out the Carm1 gene had an amazing effect on T cells, with 1143 genes up-regulated and 1199 genes down-regulated.

The up-regulated genes include genes encoding chemokine receptors that mediate T cell recruitment into tumors, as well as key genes required to maintain memory T cell populations.

Down-regulated genes include genes related to terminal differentiation, suppression of cytokine signaling, and T cell dysfunction in tumors.

This confirms the above findings again.

▲ The effect of knocking out the Carm1 gene on the T cell transcriptome The next research question is critical: What effect does knocking out the Carm1 gene have on cancer cells? The Wucherpfennig team first analyzed RNA sequencing data from the 1208 human cancer cell line (Cancer Cell Line Encyclopedia, CCLE) and found that different human cancer cell lines have high levels of Carm1 expression.

For this study, this is a good phenomenon.
It at least implies that Carm1 is very important to cancer cells and should be beneficial to the growth or development of cancer cells.

Immediately afterwards, the researchers plan to use B16F10 melanoma and 4T1 breast cancer models that are resistant to immune checkpoint inhibitors to explore the effects of Carm1 on cancer cells.

After knocking out the Carm1 gene of B16F10 and 4T1, the results of in vitro studies may make them sweat.

Because knocking out the Carm1 gene does not affect the proliferation and survival of B16F10 and 4T1 in vitro.

The good news is that after knocking out the Carm1 gene, the growth ability of B16F10 and 4T1 in the body is greatly reduced.

However, if the CD8+ T cells in the mice are depleted, the growth ability of B16F10 and 4T1 cancer cells in which the Carm1 gene is deleted will be restored.

▲ What does the expression level of Carm1 gene in various cancers indicate? This shows that Carm1 in cancer cells is inactivated, which stimulates the powerful anti-tumor immunity mediated by T cells.

Not only that, but subsequent studies also confirmed that cancer cells lacking the Carm1 gene are more sensitive to CD8+ T cells.

This is very powerful, not only strengthening immune cells, but also weakening cancer cells.

Isn't this what the Wucherpfennig team wanted? So after knocking out the Carm1 gene, what happened in the cancer cells? They first found that cancer cells lacking the Carm1 gene are more sensitive to CD8+ T cells, which is related to the cGAS-STING pathway that recognizes free DNA fragments.

This implies that the deletion of the Carm1 gene enhances the DNA damage response of cancer cells.

This response induces a type 1 interferon response, which ultimately leads to a substantial increase in the number of tumor-infiltrating CD8 T cells, NK cells and dendritic cells.

 Through the fluorescent labeling of DNA break sites, the researchers found that cancer cells with missing Carm1 gene have more DNA breaks.

▲ How to explain the effect of knocking out the Carm1 gene on the gene expression of cancer cells? Looking at the previous literature, the Wucherpfennig team found that: Previous studies have shown that the CARM1 protein encoded by the Carm1 gene can cooperate with BRCA1 and p53 to induce the expression of the cell cycle inhibitor p21CIP1 (CDKN1A) [5].

In other words, CARM1 protein can cooperate with p53 to prevent cancer cells from collapsing, especially in the case of DNA breaks.

Because double-stranded DNA breaks can induce the wrong separation of chromosomes and the formation of cell micronuclei during mitosis [6], this micronucleus often has a fragile nuclear envelope, which causes its double-stranded DNA to be exposed to cGAS [7, 8] ].

In other words, knocking out the Carm1 gene will result in the failure of cell cycle inhibition after DNA damage, which will lead to chromosome separation and the formation of micronuclei during mitosis, and the cGAS-STING pathway will be activated.

That's it! ▲ The study of the difference in the effect of knocking out the Carm1 gene on the gene expression of cancer cells and T cells is done here.
Many readers may have a question.
How can the effects of CARM1 protein on cancer cells and T cells be completely opposite? Wucherpfennig and his colleagues also discussed this issue at the end of the paper.

In fact, this problem is not difficult to understand.
The difference is mainly due to DNA damage and repair.

There is no large amount of DNA break damage in T cells.
Although the deletion of Carm1 gene will speed up the cell cycle, free DNA fragments will not activate downstream pathways.

Now it seems that this coincidence is really wonderful.

In order to test the anti-cancer effect of CARM1 inhibitors, the researchers tested the resistance of CARM1 inhibitors (EZM2302) monotherapy and combined PD-1 inhibitors or CTLA-4 inhibitors with cold tumors with poorly infiltrated CD8+ T cells.
Cancer effect.

In general, not only do CARM1 inhibitors have a certain anti-cancer effect, but also CARM1 inhibitors combined with immune checkpoint inhibitors have a strong anti-cancer effect.

▲ Anti-cancer effect Wucherpfennig team believes that their research results are of great significance, because the exhaustion of T cells and the lack of memory immune cells are the main obstacles facing immunotherapy.

The use of CARM1 inhibitors can turn cold tumors into hot tumors, make drug-resistant solid tumors sensitive to cytotoxic T cells, and can also enhance the memory and persistence of T cells.

In terms of these points alone, CARM1 inhibitors are really the golden partner of immunotherapy.

I look forward to the transformation of the Wucherpfennig team's research results as soon as possible, so that CARM1 inhibitors can help immunotherapy, so that more cancer patients can benefit from it.

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Please send your resume and works (if any) to: hr@geekheal.
com We are waiting for you at Singularity.  References: [1].
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The author of this article | BioTalker warms it upNatarajan AT, et al.
Molecular mechanisms of micronucleus, nucleoplasmic bridge and nuclear bud formation in mammalian and human cells[J].
Mutagenesis, 2011, 26(1): 125-132.
[7].
Mackenzie KJ, Carroll P, Martin CA, et al.
cGAS surveillance of micronuclei links genome instability to innate immunity[J].
Nature, 2017, 548(7668): 461-465.
[8].
Bakhoum SF, Cantley L C.
The multifaceted role of chromosomal instability in cancer and its microenvironment[J].
Cell, 2018, 174(6): 1347-1360.
The author of this article | BioTalkerNatarajan AT, et al.
Molecular mechanisms of micronucleus, nucleoplasmic bridge and nuclear bud formation in mammalian and human cells[J].
Mutagenesis, 2011, 26(1): 125-132.
[7].
Mackenzie KJ, Carroll P, Martin CA, et al.
cGAS surveillance of micronuclei links genome instability to innate immunity[J].
Nature, 2017, 548(7668): 461-465.
[8].
Bakhoum SF, Cantley L C.
The multifaceted role of chromosomal instability in cancer and its microenvironment[J].
Cell, 2018, 174(6): 1347-1360.
The author of this article | BioTalkerBakhoum SF, Cantley L C.
The multifaceted role of chromosomal instability in cancer and its microenvironment[J].
Cell, 2018, 174(6): 1347-1360.
Author of this article | BioTalkerBakhoum SF, Cantley L C.
The multifaceted role of chromosomal instability in cancer and its microenvironment[J].
Cell, 2018, 174(6): 1347-1360.
Author of this article | BioTalker