Histone H3K27M is a driving mutation in diffuse intrinsic pontine glioma (DIPG), a deadly pediatric brain tumor. The malignant and treatment-resistant brain tumor is a target for anti-cancer studies.

Through a global inhibition of PRC2 catalytic activity and displacement of H3K27me2/3, H3K27M reshapes the epigenome and promotes oncogenesis of DIPG. Consequentially, the histone modification H3K36me2, antagonistic to H3K27me2/3, is elevated. The relationship and role of H3K36me2 in H3K27M-DIPG was investigated by approaches to its upstream catalyzing enzymes, NSD1 and NSD2, the “writers”, and its downstream binding factors, LEDGF and HDGF2, the “readers”.

Tumor-promoting transcriptional programs in H3K27M-DIPG were found to be disrupted by loss of NSD1 and NSD2, thus impeding cellular proliferation and tumorigenesis.
Downstream, a chemically modified peptide mimicking endogenous H3K36me2 was found to dislodge LEDGF and HDGF2 from chromatin. As LEDGF and HDGF2 are the main readers mediating the protumorigenic effects downstream of NSD1/2-H3K36me2, dislodging them resulted in inhibition of H3K27M-DIPG proliferation.

In this study, the chemically modified peptides used were cell penetrating peptides purchased from LifeTein.

Reference: Sci. Adv. 2021 Jul 14; 7(29)

BRAF is the most frequently mutated kinase in human cancers and is one of the major effectors of oncogenic RAS. So BRAF is a target of interest for anti-cancer drug development.

Two FDA-approved inhibitors, dabrafenib and vemurafenib have been developed as inhibitors for BRAF. These ATP-competitive inhibitors potently inhibit the most common BRAF variant V600E. However, current BRAF inhibitors could induce drug resistance and paradoxical activation. New approaches and drug candidates are needed to disrupt the intact dimer interface of BRAF. The 10-mer peptide inhibitor braftide was designed using a computational approach to block RAF dimerization. It was found that the peptide inhibitor triggers selective protein degradation of BRAF and MEK through proteasome-mediated protein degradation in cells.

The combination of ATP competitive inhibitors and braftide eliminates paradoxical activation. This alternative strategy will improve the efficacy of current ATP-competitive inhibitors. The RAF dimer interface could be a promising therapeutic target.

Braftide is a 10-mer peptide TRHVNILLFM. Braftide disrupts BRAF dimers and inhibits BRAF kinase activity. Braftide causes degradation of BRAF leading to destabilized MAPK complexes. Braftide synergizes with ATP-competitive inhibitors like Dabrafenib to mitigate paradoxical MAPK activation and downregulate MAPK signaling.

In this study, the Braftide, Null-Braftide, TAT-PEGlinker-Braftide, and TAT peptides were purchased from LifeTein with TFA removal.

Reference: ACS Chem Biol. 2019 Jul 19; 14(7): 1471–1480.