bims-pimaco 2022-07-10 papers

Issue of 2022‒07‒10
five papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research

Nat Cell Biol. 2022 Jul 07.

A p53-phosphoinositide signalosome regulates nuclear AKT activation.

Mo Chen, Suyong Choi, Tianmu Wen, Changliang Chen, Narendra Thapa, Jeong Hyo Lee, Vincent L Cryns, Richard A Anderson.

The tumour suppressor p53 and PI3K-AKT pathways have fundamental roles in the regulation of cell growth and apoptosis, and are frequently mutated in cancer. Here, we show that genotoxic stress induces nuclear AKT activation through a p53-dependent mechanism that is distinct from the canonical membrane-localized PI3K-AKT pathway. Following genotoxic stress, a nuclear PI3K binds p53 in the non-membranous nucleoplasm to generate a complex of p53 and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), which recruits AKT, PDK1 and mTORC2 to activate AKT and phosphorylate FOXO proteins, thereby inhibiting DNA damage-induced apoptosis. Wild-type p53 activates nuclear AKT in an on/off fashion following stress, whereas mutant p53 dose-dependently stimulates high basal AKT activity. The p53-PtdIns(3,4,5)P3 complex is dephosphorylated to p53-phosphatidylinositol 4,5-bisphosphate by PTEN to inhibit AKT activation. The nuclear p53-phosphoinositide signalosome is distinct from the canonical membrane-localized pathway and insensitive to PI3K inhibitors currently in the clinic, which underscores its therapeutic relevance.

DOI: https://doi.org/10.1038/s41556-022-00949-1

Cancer Res. 2022 Jul 08. pii: can.21.2519. [Epub ahead of print]

Efficient correction of oncogenic KRAS and TP53 mutations through CRISPR base editing.

Shady Sayed, Olga Alexandra Sidorova, Alexander Hennig, Martina Augsburg, Catherine P Cortes Vesga, Moustafa Abohawya, Lukas Theo Schmitt, Duran S R N, Daniel E Stange, Jovan Mircetic, Frank Buchholz.

KRAS is the most frequently mutated oncogene in human cancer, and its activating mutations represent long-sought therapeutic targets. Programmable nucleases, particularly the CRISPR-Cas9 system, provide an attractive tool for genetically targeting KRAS mutations in cancer cells. Here, we show that cleavage of a panel of KRAS driver mutations suppresses growth in various human cancer cell lines, revealing their dependence on mutant KRAS. However, analysis of the remaining cell population after long-term Cas9 expression unmasked the occurence of oncogenic KRAS escape variants that were resistant to Cas9-cleavage. In contrast, the use of an adenine base editor (ABE) to correct oncogenic KRAS mutations progressively depleted the targeted cells without the appearance of escape variants and allowed efficient and simultaneous correction of a cancer-associated TP53 mutation. Oncogenic KRAS and TP53 base editing was possible in patient-derived cancer organoids, suggesting that base editor approaches to correct oncogenic mutations could be developed for functional interrogation of vulnerabilities in a personalized manner for future precision oncology applications.

DOI: https://doi.org/10.1158/0008-5472.CAN-21-2519

Cell Mol Life Sci. 2022 Jul 02. 79(7): 393

Aspirin sensitivity of PIK3CA-mutated Colorectal Cancer: potential mechanisms revisited.

Daniella C N Hall, Ralf A Benndorf.

PIK3CA mutations are amongst the most prevalent somatic mutations in cancer and are associated with resistance to first-line treatment along with low survival rates in a variety of malignancies. There is evidence that patients carrying PIK3CA mutations may benefit from treatment with acetylsalicylic acid, commonly known as aspirin, particularly in the setting of colorectal cancer. In this regard, it has been clarified that Class IA Phosphatidylinositol 3-kinases (PI3K), whose catalytic subunit p110α is encoded by the PIK3CA gene, are involved in signal transduction that regulates cell cycle, cell growth, and metabolism and, if disturbed, induces carcinogenic effects. Although PI3K is associated with pro-inflammatory cyclooxygenase-2 (COX-2) expression and signaling, and COX-2 is among the best-studied targets of aspirin, the mechanisms behind this clinically relevant phenomenon are still unclear. Indeed, there is further evidence that the protective, anti-carcinogenic effect of aspirin in this setting may be mediated in a COX-independent manner. However, until now the understanding of aspirin's prostaglandin-independent mode of action is poor. This review will provide an overview of the current literature on this topic and aims to analyze possible mechanisms and targets behind the aspirin sensitivity of PIK3CA-mutated cancers.

Keywords: AKT; Acetylsalicylic acid; COX; Cyclooxygenases; NSAID; PI3 kinases; PKB; Prostaglandin; Tumor Biology; Wnt; mTOR; β-catenin

DOI: https://doi.org/10.1007/s00018-022-04430-y

Cancers (Basel). 2022 Jul 01. pii: 3252. [Epub ahead of print]14(13):

A RAS-Independent Biomarker Panel to Reliably Predict Response to MEK Inhibition in Colorectal Cancer.

Ulrike Pfohl, Jürgen Loskutov, Sanum Bashir, Ralf Kühn, Patrick Herter, Markus Templin, Soulafa Mamlouk, Sergei Belanov, Michael Linnebacher, Florian Bürtin, Marcus Vetter, Christoph Reinhard, Lena Wedeken, Christian R A Regenbrecht.

Background: In colorectal cancer (CRC), mutations of genes associated with the TGF-β/BMP signaling pathway, particularly affecting SMAD4, are known to correlate with decreased overall survival and it is assumed that this signaling axis plays a key role in chemoresistance. Methods: Using CRISPR technology on syngeneic patient-derived organoids (PDOs), we investigated the role of a loss-of-function of SMAD4 in sensitivity to MEK-inhibitors. CRISPR-engineered SMAD4R361H PDOs were subjected to drug screening, RNA-Sequencing, and multiplex protein profiling (DigiWest®). Initial observations were validated on an additional set of 62 PDOs with known mutational status. Results: We show that loss-of-function of SMAD4 renders PDOs sensitive to MEK-inhibitors. Multiomics analyses indicate that disruption of the BMP branch within the TGF-β/BMP pathway is the pivotal mechanism of increased drug sensitivity. Further investigation led to the identification of the SFAB-signature (SMAD4, FBXW7, ARID1A, or BMPR2), coherently predicting sensitivity towards MEK-inhibitors, independent of both RAS and BRAF status. Conclusion: We identified a novel mutational signature that reliably predicts sensitivity towards MEK-inhibitors, regardless of the RAS and BRAF status. This finding poses a significant step towards better-tailored cancer therapies guided by the use of molecular biomarkers.

Keywords: CRC; MEK inhibition; SMAD4; TGF-β/BMP-pathway; biomarker; colorectal cancer; intra-tumor heterogeneity; organoids; targeted therapy

DOI: https://doi.org/10.3390/cancers14133252

J Biol Chem. 2022 Jun 30. pii: S0021-9258(22)00667-6. [Epub ahead of print] 102225

Metalloprotease ADAM9 cleaves ephrin-B ligands and differentially regulates Wnt and mTOR signaling downstream of Akt kinase in colorectal cancer cells.

Pathirennehelage Chandrasekera, Mark Perfetto, Congyu Lu, Minghui Zhuo, Harinath Bahudhanapati, Jiejing Li, Wei-Chih Chen, Pallavi Kulkarni, Laura Christian, Jun Liu, Yvette Y Yien, Chundong Yu, Shuo Wei.

Ephrin-B signaling has been implicated in many normal and pathological processes, including neural crest development and tumor metastasis. We showed previously that proteolysis of ephrin-B ligands by the disintegrin metalloprotease ADAM13 is necessary for canonical Wnt signal activation and neural crest induction in Xenopus, but it was unclear if these mechanisms are conserved in mammals. Here, we report that mammalian ADAM9 cleaves ephrin-B1 and -B2 and can substitute for Xenopus ADAM13 to induce the neural crest. We found that ADAM9 expression is elevated in human colorectal cancer (CRC) tissues, and that knockdown (KD) of ADAM9 inhibits the migration and invasion of SW620 and HCT116 CRC cells by reducing the activity of Akt kinase, which is antagonized by ephrin-Bs. Akt is a signaling node that activates multiple downstream pathways, including the Wnt and mTOR pathways, both of which can promote CRC cell migration/invasion. Surprisingly, we also found that KD of ADAM9 downregulates Wnt signaling, but has negligible effects on mTOR signaling in SW620 cells; in contrast, mTOR activity is suppressed while Wnt signaling remains unaffected by ADAM9 KD in HCT116 cells. These results suggest that mammalian ADAM9 cleaves ephrin-Bs to derepress Akt and promote CRC migration and invasion; however, the signaling pathways downstream of Akt are differentially regulated by ADAM9 in different CRC cell lines, reflecting the heterogeneity of CRC cells in responding to manipulations of upstream Akt regulators.

Keywords: ADAM; Akt/PKB; Wnt signaling; colorectal cancer; ephrin; mTOR

DOI: https://doi.org/10.1016/j.jbc.2022.102225