Signal transducer and activator of transcription 3 inhibition enhances vemurafenib sensitivity in colon cancers harboring the BRAFV600E mutation

Single-cell multi-omics reveals insights into differentiation of rare cell types in mucinous colorectal cancer

Neuroendocrine cells have been implicated in therapeutic resistance and worse overall survival in many cancer types. Mucinous colorectal cancer (mCRC) is uniquely enriched for enteroendocrine cells (EECs), the neuroendocrine cell of the normal colon epithelium, as compared to non-mucinous CRC. Therefore, targeting EEC differentiation may have clinical value in mCRC. Here, single cell multi-omics was used to uncover epigenetic alterations that accompany EEC differentiation, identify STAT3 as a novel regulator of EEC specification, and discover a rare cancer-specific cell type with enteric neuron-like characteristics. Further experiments demonstrated that lysine-specific demethylase 1 (LSD1) and CoREST2 mediate STAT3 demethylation and regulate STAT3 chromatin binding. Knockdown of CoREST2 in an orthotopic xenograft mouse model resulted in decreased primary tumor growth and lung metastases. In culmination, these results provide rationale for new LSD1 inhibitors that target the interaction between LSD1 with STAT3 or CoREST2, which may improve clinical outcomes for patients with mCRC.

Identification of HMGCR as the anticancer target of physapubenolide against melanoma cells by in silico target prediction

Physapubenolide (PB), a withanolide-type compound extracted from the traditional herb Physalis minima L., has been demonstrated to exert remarkable cytotoxicity against cancer cells; however, its molecular mechanisms are still unclear. In this study, we demonstrated that PB inhibited cell proliferation and migration in melanoma cells by inducing cell apoptosis. The anticancer activity of PB was further verified in a melanoma xenograft model. To explore the mechanism underlying the anticancer effects of PB, we carried out an in silico target prediction study, which combined three approaches (chemical similarity searching, quantitative structure-activity relationship (QSAR), and molecular docking) to identify the targets of PB, and found that PB likely targets 3-hydroxy-methylglutaryl CoA reductase (HMGCR), the rate-limiting enzyme of the mevalonate pathway, which promotes cancer cell proliferation, migration, and metastasis. We further demonstrated that PB interacted with HMGCR, decreased its protein expression and inhibited the HMGCR/YAP pathway in melanoma cells. In addition, we found that PB could restore vemurafenib sensitivity in vemurafenib-resistant A-375 cells, which was correlated with the downregulation of HMGCR. In conclusion, we demonstrate that PB elicits anticancer action and enhances sensitivity to vemurafenib by targeting HMGCR.

Signal transducer and activator of transcription 3 inhibition alleviates resistance to BRAF inhibition in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is a rare type of thyroid cancer (TC) with no effective therapeutic strategy. Although surgery, chemotherapy and radiation are all available for ATC treatment, the median survival for ATC patients is less than 6 months. In this study, we aimed to study on resistant mechanisms to B-Raf proto-oncogene serine/threonine kinase (BRAF) inhibitor and identify effective combinational therapy for ATC patients. TC cells were treated with Vemurafenib and cell apoptosis and viability were analyzed by flow cytometry and MTT assay. Monolayer and sphere cells were isolated from ATC cells to detect the mRNA level of stem cell markers and differentiation markers by RT-PCR. Phosphor-STAT3 level in sphere and monolayer cells was tested by Western blotting. The xenotransplantation animal model has established to analyze the anti-tumor effect of Vemurafenib and Stattic combinational therapy. Undifferentiated TC cells were resistant to Vemurafenib treatment. Sphere cells isolated from ATC showed no significant change in cell viability and apoptosis upon Vemurafenib treatment, and expressed a high level of stem cell marker and phosphor-STAT3. STAT3 inhibition enhanced the tumorigenic capacity and increased Vemurafenib sensitivity in ATC cell lines. Stattic significantly enhanced anti-tumor effect of Vemurafenib in mouse model. Our findings demonstrate that the combinational therapy of Vemurafenib and Stattic is an effective therapeutic treatment for ATC patients.

Yes-activated protein promotes primary resistance of BRAF V600E mutant metastatic colorectal cancer cells to mitogen-activated protein kinase pathway inhibitors

Background

Most colorectal cancer (CRC) patients with the BRAF V600E mutation display resistance to chemotherapy and targeted medicinal treatments. Thus, exploring new drugs and drug resistance mechanisms for the BRAF V600E mutation has become an urgent clinical priority.

Methods

MTS experiment, cell cloning experiment, cell scratching experiment, Transwell experiment, chromatin immunoprecipitation (ChIP), quantitative polymerase chain reaction (qPCR) and flow cytometry are used. Detect the transcription and protein expression of YAP in colorectal cancer cell lines, establish a transient cell line with YAP gene overexpression and knockdown, and detect the effect of YAP gene expression on the biological functions of colorectal cancer cells RKO and HT-29. And further study the mechanism of YAP regulating the response of RAF and MEK targeted therapy.

Results

In this study, for the first time, we verified that the expression of transcription factor yes-associated protein (YAP) was upregulated in BRAF V600E mutant CRC cells. After knocking down YAP, we observed a reduction in the growth rate, proliferation, and invasion ability of colon cancer cells. We further verified that YAP knockdown increased sensitivity of BRAF V600E mutant CRC cells to mitogen-activated protein kinase (MAPK) pathway inhibitors. In addition, we clarified the mechanism underlying YAP regulation of RAF and MAPK/extracellular signal-regulated kinase (MEK)-targeted therapy response: YAP cooperates with RAF→MEK pathway inhibitors to regulate the cell cycle, increase cell G1/S phase arrest, and increase apoptosis.

Conclusions

These results suggest that YAP expression may be related to the primary resistance of MAPK inhibitors in metastatic CRC with the BRAF V600E mutation. Therefore, the combination of YAP and MAPK pathway inhibitors in BRAF V600E mutant metastatic CRC may present a promising treatment method.

Tumor-Derived Exosome-Educated Hepatic Stellate Cells Regulate Lactate Metabolism of Hypoxic Colorectal Tumor Cells via the IL-6/STAT3 Pathway to Confer Drug Resistance

Purpose

Colorectal cancer cells spread to the liver and crosstalk with the microenvironment, and hepatic stellate cells (HSCs) are the major stromal components in the liver. However, the role of the interaction between colorectal tumor cells and HSCs in chemotherapeutic resistance remains unclear. The present study aimed to determine the mechanism of colorectal tumor cells educating the HSCs to reprogram the metabolism of adjacent tumor cells and fuel themselves in the metastatic microenvironment of the liver.

Patients and Methods

Immunohistochemistry (IHC) examined the expression of the monocarboxylate transporters 1 (MCT1) and lactate dehydrogenase B (LDHB) in colorectal liver metastases (CRLM). The Mann–Whitney U-tests analyzed the association between IL-6 levels and clinical parameters. The mechanisms of normoxic tumor-derived exosomes in the education of HSCs were investigated using IHC and ELISA. The conditioned medium of activated HSCs in the regulation of hypoxic tumor cells was analyzed by CCK-8 and cell apoptosis assays.

Results

The expression of MCT1 and LDHB was high in the liver metastases of irinotecan-resistant patients, and the high level of IL-6 in the plasma of patients with CRLM was associated with poor response to irinotecan-based chemotherapy. The colorectal tumor-derived exosomes activated HSCs to secrete excessive IL-6. Furthermore, the conditioned medium of activated HSCs enhanced the lactate metabolism of hypoxic tumor cells by activating the IL-6/STAT3 pathway and upregulating the downstream MCT1 and LDHB, in order to confer the resistance of SN38, which is the active metabolite of irinotecan.

Conclusion

Taken together, the cultured supernatant of normoxic exosome-educated HSCs enhances the lactate metabolism of hypoxic tumor cells via the IL-6/STAT3 pathway, in order to confer the SN38 resistance in a mimic liver metastatic microenvironment.

Epithelioid glioblastoma with microglia features: potential for novel therapy

Epithelioid glioblastoma (E‐GBM) was recently designated as a subtype of glioblastoma (GBM) by the World Health Organization (2016). E‐GBM is an aggressive and rare variant of GBM that primarily occurs in children and young adults. Although most characterized cases of E‐GBM harbor a mutation of the BRAF gene in which valine (V) is substituted by glutamic acid (E) at amino acid 600 (BRAF‐V600E), in addition to telomerase reverse transcriptase promoter mutations and homozygous CDKN2A/B deletions, the origins and cellular nature of E‐GBM remain uncertain. Here, we present a case of E‐GBM that exhibits antigenic and functional traits suggestive of microglia. Although no epithelial [e.g., CKAE1/3, epithelial membrane antigen (EMA)] or glial (e.g., GFAP, Olig2) markers were detected by immunohistochemical staining, the microglial markers CD68 and Iba1 were readily apparent. Furthermore, isolated E‐GBM‐derived tumor cells expressed microglial/macrophage‐related genes including cytokines, chemokines, MHC class II antigens, lysozyme and the critical functional receptor, CSF‐1R. Isolated E‐GBM‐derived tumor cells were also capable of phagocytosis and cytokine production. Treating E‐GBM‐derived tumor cells with the BRAF‐V600E inhibitor, PLX4032 (vemurafenib), resulted in a dose‐dependent reduction in cell viability that was amplified by addition of the CSF‐1R inhibitor, BLZ945. The present case provides insight into the cellular nature of E‐GBM and introduces several possibilities for effective targeted therapy for these patients.

Dihydroartemisinin Prevents Distant Metastasis of Laryngeal Carcinoma by Inactivating STAT3 in Cancer Stem Cells

Background

Accumulating evidence indicates that cancer stem cells (CSCs) are a minor subpopulation of cancer cells that may be the primary source of cancer invasion, migration, and widespread metastasis.

Material/Methods

We investigated the effects of dihydroartemisinin (DHA) on distant metastasis of laryngeal carcinoma and the relevant mechanism. In vitro, we used the Hep-2 human laryngeal squamous carcinoma cell line (Hep-2 cells) to assemble CSCs, using CD133 as the cell surface marker. Our data demonstrate that the CD133⁺ subpopulation of Hep-2 cells has greater invasion and migration capabilities than CD133⁻ cells. We also evaluated the effects of DHA, a newly defined STAT3 inhibitor, on the invasion and migration of CD133⁺ Hep-2 cells under hypoxia and IL-6 stimulation, both of which can activate STAT3 phosphorylation.

Results

CSCs exhibited a significant decrease in the ability of migration and invasion upon the application of DHA, along with simultaneous alterations in related proteins, both in cultured cells and in xenograft tumors. The associated signaling proteins included phosphorylated STAT3 (p-STAT3), matrix metalloproteinase-9 (MMP-9), and E-cadherin, which are closely involved in cancer invasion and metastasis. In vivo, we found that DHA can reduce lung metastasis formation caused by CSCs and prolong survival in mice, and can inhibit STAT3 activation, downregulate MMP-9, and upregulate E-cadherin in lung metastatic tumors.

Conclusions

Taken together, our findings indicate that CSCs possess stronger invasive and metastatic capabilities than non-CSCs, and DHA inhibits invasion and prevents metastasis induced by CSCs by inhibiting STAT3 activation.