BACKGROUND: The majority of patients with non-small cell lung cancer (NSCLC) harboring activating epidermal growth factor receptor (EGFR) mutations respond well to osimertinib (AZD9291), a third-generation, mutation-selective EGFR inhibitor. The current study focuses on determining whether targeting MEK/ERK signaling prevents or delays the development of acquired resistance to osimertinib. METHODS: Drug effects on cell survival were determined by measuring cell number alterations. Apoptosis was assessed with flow cytometry for the detection of annexin V-positive cells and with Western blotting for protein cleavage. Alterations of proteins in cells were detected with Western blotting. Drug effects on delaying the emergence of osimertinib resistance were evaluated with colony formation in vitro and xenografts in nude mice in vivo. RESULTS: Osimertinib combined with an MEK or ERK inhibitor synergistically decreased cell survival with enhanced induction of apoptosis in EGFR-mutant NSCLC cells but not in EGFR wild-type NSCLC cells. These combinations were also very effective in killing cell clones with primary intrinsic resistance to osimertinib. Continuous and intermittent pharmacologic inhibition of MEK/ERK signaling delayed the emergence of osimertinib resistance both in vitro and in vivo. CONCLUSIONS: These results provide strong preclinical evidence in support of targeting MEK/ERK signaling as a strategy for delaying or preventing acquired resistance to osimertinib in the clinic to improve the long-term therapeutic efficacy of osimertinib. From a clinical standpoint, the data support the evaluation of an intermittent treatment schedule of osimertinib in combination with an MEK or ERK inhibitor in patients with EGFR-mutated NSCLC.
) is reported to be overexpressed in colorectal carcinoma (CRC), but the role of miR-191 in CRC progress remained unclear. This study demonstrated that High miR-191 expression was associated with clinical stage, lymph node metastasis, liver metastasis and depth of tumor invasion. Kaplan-Meier analysis indicated that patients with high miR-191 expression had a poor overall survival. Moreover, multivariate analysis showed that miR-191 was an independent prognostic factor in patients with CRC. Furthermore, we found that tissue inhibitor of metalloprotease 3 (TIMP3) was a direct target of miR-191 in colorectal cancer SW620 cells. TIMP3 downregulation mediated by miR-191 activated matrix metalloproteinases (MMPs) and thus promoted invasiveness of cancer cells. Anti-miR-191 could attenuate the invasiveness, suppress proliferation and induce apoptosis by restoring TIMP3 expression. Our results suggested that miR-191 might be a potential diagnostic and therapeutic target in patients with colorectal cancer.
Human non-small cell lung cancer (NSCLC) displays activated MEK/ERK signaling due to a high frequency of K-Ras mutation and is thus a potential candidate for MEK-targeted therapy. The current study focuses on demonstrating the activity of MEK162, a MEK inhibitor under clinical testing, against NSCLC and exploring possible mechanism-driven strategies to enhance its therapeutic efficacy. MEK162 inhibits the growth of human NSCLC cell lines with varied potencies through induction of G1 cell cycle arrest and apoptosis. Moreover, it induces autophagy and accordingly the combination of MEK162 with the autophagy inhibitor, chloroquine, synergistically inhibits the growth of NSCLC cells and enhances apoptosis. MEK162 activates Akt signaling while effectively inhibiting MEK/ERK signaling. Accordingly, the combination of MEK162 and BKM120, a pan PI3K inhibitor, abrogates induced Akt activation and significantly augments therapeutic efficacy against the growth of NSCLC cells both in vitro and in vivo. Hence our findings warrant further evaluation of these rational combinations in the clinic.
Carfilzomib (CFZ) is a second generation proteasome inhibitor approved for the treatment of patients with multiple myeloma. It induces apoptosis in human cancer cells; but the underlying mechanisms remain undefined. In the present study, we show that CFZ decreases the survival of several human cancer cell lines and induces apoptosis. Induction of apoptosis by CFZ occurs, at least in part, due to activation of the extrinsic apoptotic pathway, since FADD deficiency protected cancer cells from undergoing apoptosis. CFZ increased total and cell surface levels of DR5 in different cancer cell lines; accordingly it enhanced TRAIL-induced apoptosis. DR5 deficiency protected cancer cells from induction of apoptosis by CFZ either alone or in combination with TRAIL. These data together convincingly demonstrate that DR5 upregulation is a critical mechanism accounting for CFZ-induced apoptosis and enhancement of TRAIL-induced apoptosis. CFZ inhibited the degradation of DR5, suggesting that DR5 stabilization contributes to CFZ-induced DR5 upregulation. In summary, the present study highlights the important role of DR5 upregulation in CFZ-induced apoptosis and enhancement of TRAIL-induced apoptosis in human cancer cells.
Inhibition of BET bromodomains (BRDs) has emerged as a promising cancer therapeutic strategy. Accordingly, inhibitors of BRDs such as JQ1 have been actively developed and some have reached clinical testing. However, the mechanisms by which this group of inhibitors exerts their anticancer activity, including induction of apoptosis, have not been fully elucidated. This report reveals a previously uncovered activity of JQ1 in inducing c-FLIP degradation and enhancing TRAIL-induced apoptosis. JQ1 potently decreased c-FLIP (both long and short forms) levels in multiple cancer cell lines without apparently increasing the expression of DR5 and DR4. Consequently, JQ1, when combined with TRAIL, synergistically induced apoptosis; this enhanced apoptosis-inducing activity could be abolished by enforced expression of ectopic FLIPL or FLIPS. Hence it appears that JQ1 decreases c-FLIP levels, resulting in enhancement of TRAIL-induced apoptosis. Inhibition of proteasome with MG132 prevented JQ1-induced c-FLIP reduction. Moreover, JQ1 decreased c-FLIP stability. Therefore, JQ1 apparently decreases c-FLIP levels through facilitating its proteasomal degradation. Genetic inhibition of either BRD4 or c-Myc by knocking down their expression failed to mimic JQ1 in decreasing c-FLIP and enhancing TRAIL-induced apoptosis, suggesting that JQ1 induces c-FLIP degradation and enhances TRAIL-induced apoptosis independent of BRD4 or c-Myc inhibition. In summary, our findings in this study highlights a novel biological function of JQ1 in modulating apoptosis and warrant further study of the potential treatment of cancer with the JQ1 and TRAIL combination.
Background: Colorectal cancer (CRC) is the fourth most deadly malignancy throughout the world. Extensive studies have shown that Krüppel-like factors (KLFs) play essential roles in cancer development. However, the function of KLF13 in CRC is unclear. Methods: The Cancer Genome Atlas database was applied to analyze the expression of KLF13 in CRC and normal tissues. Lentivirus system was used to overexpress and to knock down KLF13. RT-qPCR and Western blot assays were performed to detect mRNA and protein expression. CCK-8, colony formation, cell cycle analysis and EdU staining were used to assess the in vitro function of KLF13 in CRC cells. Xenografter tumor growth was used to evaluate the in vivo effect of KLF13 in CRC. Cholesterol content was measured by indicated kit. Transcription activity was analyzed by luciferase activity measurement. ChIP-qPCR assay was performed to assess the interaction of KLF13 to HMGCS1 promoter. Results: KLF13 was downregulated in CRC tissues based on the TCGA database and our RT-qPCR and Western blot results. Comparing with normal colorectal cells NCM460, the CRC cells HT-26, HCT116 and SW480 had reduced KLF13 expression. Functional experiments showed that KLF13 knockdown enhanced the proliferation and colony formation in HT-29 and HCT116 cells. Opposite results were observed in KLF13 overexpressed cells. Furthermore, KLF13 overexpression resulted in cell cycle arrest at G0/G1 phase, reduced EdU incorporation and suppressed tumor growth of HCT116 cells in nude mice. Mechanistically, KLF13 transcriptionally inhibited HMGCS1 and the cholesterol biosynthesis. Knockdown of HMGCS1 suppressed cholesterol biosynthesis and the proliferation of CRC cells with silenced KLF13. Furthermore, cholesterol biosynthesis inhibitor significantly retarded the colony growth in both cells. Conclusions: Our study reveals that KLF13 acts as a tumor suppressor in CRC through negatively regulating HMGCS1-mediated cholesterol biosynthesis.
Disclosure of potential conflicts of interest:The University of Michigan has filed a patent application on ZBC260 and its analogues, which have been licensed to Oncopia Therapeutics.SW is a co-founder and paid consultant of Oncopia and owns stock in Oncopia. The University of Michigan also owns stock in Oncopia. No potential conflicts of interest were disclosed for other people.
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