Erratum to: Antitumor activity of the ERK inhibitor SCH722984 against BRAF mutant, NRAS mutant and wild-type melanoma

High throughput application of the NanoBiT Biochemical Assay for the discovery of selective inhibitors of the interaction of PI3K-p110α with KRAS

The NanoBiT Biochemical Assay (NBBA) was designed as a biochemical format of the NanoBiT cellular assay, aiming to screen weak protein-protein interactions (PPIs) in mammalian cell lysates. Here we present a High Throughput Screening (HTS) application of the NBBA to screen small molecule and fragment libraries to identify compounds that block the interaction of KRAS-G12D with phosphatidylinositol 3-kinase (PI3K) p110α. This interaction promotes PI3K activity, resulting in the promotion of cell growth, proliferation and survival, and is required for tumour initiation and growth in mouse lung cancer models, whilst having little effect on the health of normal adult mice, establishing the significance of the p110α/KRAS interaction as an oncology drug target. Despite the weak binding affinity of the p110α/KRAS interaction (KD = 3 μM), the NBBA proved to be robust and displayed excellent Z'-factor statistics during the HTS primary screening of 726,000 compounds, which led to the identification of 8,000 active compounds. A concentration response screen comparing KRAS/p110α with two closely related PI3K isoforms, p110δ and p110γ, identified selective p110α-specific compounds and enabled derivation of an IC50 for these hits. We identified around 30 compounds showing greater than 20-fold selectivity towards p110α versus p110δ and p110γ with IC50 < 2 μM. By using Differential Scanning Fluorimetry (DSF) we confirmed several compounds that bind directly to purified p110α. The most potent hits will be followed up by co-crystallization with p110α to aid further elucidation of the nature of the interaction and extended optimisation of these compounds.

Calothrixin B derivatives induce apoptosis and cell cycle arrest on HEL cells through the ERK/Ras/Raf/MEK pathway

BACKGROUND

Acute erythroleukemia (AEL) is acute myeloid leukemia characterized by malignant erythroid proliferation. AEL has a low survival rate, which has seriously threatened the health of older adults. Calothrixin B is a carbazole alkaloid isolated from the cyanobacteria Calothrix and exhibits anti-cancer activity. To discover more potential anti-erythroleukemia compounds, we used calothrixin B as the structural skeleton to synthesize a series of new compounds.

METHODS

In the cell culture model, we evaluated apoptosis and cell cycle arrest using MTT assay, flow cytometry analysis, JC-1 staining, Hoechst 33258 staining, and Western blot. Additionally, assessing the curative effect in the animal model included observation of the spleen, HE staining, flow cytometry analysis, and detection of serum biochemical indexes.

RESULTS

Among the Calothrixin B derivatives, H-107 had the best activity against leukemic cell lines. H-107 significantly inhibited the proliferation of HEL cells with an IC50 value of 3.63 ± 0.33 μM. H-107 induced apoptosis of HEL cells by damaging mitochondria and activating the caspase cascade and arrested HEL cells in the G0/G1 phase. Furthermore, H-107 downregulated the protein levels Ras, p-Raf, p-MEK, p-ERK and c-Myc. Pretreatment with ERK inhibitor (U0126) increased H-107-induced apoptosis. Thus, H-107 inhibited the proliferation of HEL cells by the ERK /Ras/Raf/MEK signal pathways. Interestingly, H-107 promoted erythroid differentiation into the maturation of erythrocytes and effectively activated the immune cells in erythroleukemia mice.

CONCLUSION

Overall, our findings suggest that H-107 can potentially be a novel chemotherapy for erythroleukemia.

Application of shear stress for enhanced osteogenic differentiation of mouse induced pluripotent stem cells

The self-organizing potential of induced pluripotent stem cells (iPSCs) represents a promising tool for bone tissue engineering. Shear stress promotes the osteogenic differentiation of mesenchymal stem cells, leading us to hypothesize that specific shear stress could enhance the osteogenic differentiation of iPSCs. For osteogenesis, embryoid bodies were formed for two days and then maintained in medium supplemented with retinoic acid for three days, followed by adherent culture in osteogenic induction medium for one day. The cells were then subjected to shear loading (0.15, 0.5, or 1.5 Pa) for two days. Among different magnitudes tested, 0.5 Pa induced the highest levels of osteogenic gene expression and greatest mineral deposition, corresponding to upregulated connexin 43 (Cx43) and phosphorylated Erk1/2 expression. Erk1/2 inhibition during shear loading resulted in decreased osteogenic gene expression and the suppression of mineral deposition. These results suggest that shear stress (0.5 Pa) enhances the osteogenic differentiation of iPSCs, partly through Cx43 and Erk1/2 signaling. Our findings shed light on the application of shear-stress technology to improve iPSC-based tissue-engineered bone for regenerative bone therapy.

Cistanche tubulosa Phenylethanoid Glycosides Induce Apoptosis of Hepatocellular Carcinoma Cells by Mitochondria-Dependent and MAPK Pathways and Enhance Antitumor Effect through Combination with Cisplatin

Cistanche tubulosa is a type of Chinese herbal medicine and exerts various biological functions. Previous studies have been demonstrated that Cistanche tubulosa phenylethanoid glycosides (CTPG) exhibit antitumor effects on a variety of tumor cells. However, the antitumor effects of CTPG on HepG2 and BEL-7404 hepatocellular carcinoma (HCC) cells are still elusive. Our study showed that CTPG significantly inhibited the growth of HepG2 and BEL-7404 cells through the induction of cell cycle arrest and apoptosis, which was associated with the activation of MAPK pathways characterized by the up-regulated phosphorylation of p38, JNK, and ERK1/2 and mitochondria-dependent pathway characterized by the reduction of mitochondrial membrane potential. The release of cytochrome c and the cleavage of caspase-3, -7, -9, and PARP were subsequently increased by CTPG treatment. Moreover, CTPG significantly suppressed the migration of HepG2 through reducing the levels of matrix metalloproteinase-2 and vascular endothelial growth factor. Interestingly, CTPG not only enhanced the proliferation of splenocytes but also reduced the apoptosis of splenocytes induced by cisplatin. In H22 tumor mouse model, CTPG combined with cisplatin further inhibited the growth of H22 cells and reduced the side effects of cisplatin. Taken together, CTPG inhibited the growth of HCC through direct antitumor effect and indirect immunoenhancement effect, and improved the antitumor efficacy of cisplatin.

Extracellular Signal-Regulated Kinase (ERK) Inhibitors in Oncology Clinical Trials

The mitogen-activated protein kinase (MAPK) pathway consists of the series of protein kinases RAS-RAF-MEK-Extracellular signal-regulated kinase (ERK), and its function is important to cell proliferation, differentiation, motility, and survival. Certain mutations in the pathway, such as KRAS or BRAF V600 mutations are associated with cancer. Inhibitors of this pathway, including some MEK and BRAF inhibitors, are already being used in the clinic, but a variety of selective ERK inhibitors are still being tested in clinical studies. To date, common adverse events associated with ERK inhibitors include diarrhea, nausea, fatigue, and rash. ERK inhibitors have demonstrated preliminary antitumor activity and may be most effective against cancers with RAS, RAF, or MAPK pathway alterations. This review discusses the MAPK pathway, the biological rationale for ERK inhibitors, and clinical trials involving ERK inhibitors.

Targeting ERK, an Achilles' Heel of the MAPK pathway, in cancer therapy

The mitogen-activated protein kinases (MAPK) pathway, often known as the RAS-RAF-MEK-ERK signal cascade, functions to transmit upstream signals to its downstream effectors to regulate physiological process such as cell proliferation, differentiation, survival and death. As the most frequently mutated signaling pathway in human cancer, targeting the MAPK pathway has long been considered a promising strategy for cancer therapy. Substantial efforts in the past decades have led to the clinical success of BRAF and MEK inhibitors. However, the clinical benefits of these inhibitors are compromised by the frequently occurring acquired resistance due to cancer heterogeneity and genomic instability. This review briefly introduces the key protein kinases involved in this pathway as well as their activation mechanisms. We also generalize the correlations between mutations of MAPK members and human cancers, followed by a summarization of progress made on the development of small molecule MAPK kinases inhibitors. In particular, this review highlights the potential advantages of ERK inhibitors in overcoming resistance to upstream targets and proposes that targeting ERK kinase may hold a promising prospect for cancer therapy.

Rational design of non-resistant targeted cancer therapies

Drug resistance is one of the major problems in targeted cancer therapy. A major cause of resistance is changes in the amino acids that form the drug-target binding site. Despite of the numerous efforts made to individually understand and overcome these mutations, there is a lack of comprehensive analysis of the mutational landscape that can prospectively estimate drug-resistance mutations. Here we describe and computationally validate a framework that combines the cancer-specific likelihood with the resistance impact to enable the detection of single point mutations with the highest chance to be responsible of resistance to a particular targeted cancer therapy. Moreover, for these treatment-threatening mutations, the model proposes alternative therapies overcoming the resistance. We exemplified the applicability of the model using EGFR-gefitinib treatment for Lung Adenocarcinoma (LUAD) and Lung Squamous Cell Cancer (LSCC) and the ERK2-VTX11e treatment for melanoma and colorectal cancer. Our model correctly identified the phenotype known resistance mutations, including the classic EGFR-T790M and the ERK2-P58L/S/T mutations. Moreover, the model predicted new previously undescribed mutations as potentially responsible of drug resistance. Finally, we provided a map of the predicted sensitivity of alternative ERK2 and EGFR inhibitors, with a particular highlight of two molecules with a low predicted resistance impact.