Loss of S6K1 But Not S6K2 in the Tumor Microenvironment Suppresses Tumor Growth by Attenuating Tumor Angiogenesis.

Two isoforms of the 70-kDa ribosomal protein S6 kinase, S6K1 and S6K2, have been identified and are considered key downstream effectors of the mTOR signaling pathway, which is involved in tumor growth and progression. However, their biological roles in the tumor microenvironment are poorly understood. In this study, utilizing tumor xenograft models in S6k1-/- and S6k2-/- mice, we show that loss of S6K1 but not S6K2 in the tumor stroma suppresses tumor growth, accompanied by attenuated tumor angiogenesis. We found that while S6K1 depletion had no effect on the proangiogenic phenotype of endothelial cells, the growth and angiogenesis of tumor xenografts were significantly reduced in wild-type mice upon reconstitution with S6K1-deficient bone marrow cells. Furthermore, upon S6K1 loss, induction of both mRNA and protein levels of Hif-1α and those of the downstream target, Vegf, was compromised in bone marrow-derived macrophages stimulated with lactate. These findings indicate that S6K1 but not S6K2 contributes to establishing a microenvironment that favors tumor growth through mediating angiogenesis, and suggest that attenuated tumor angiogenesis upon loss of S6K1 in the tumor stroma is, at least in part, attributable to impaired upregulation of Vegf in tumor-associated macrophages.

Cytotoxic Constituents from the Sclerotia of Poria cocos against Human Lung Adenocarcinoma Cells by Inducing Mitochondrial Apoptosis.

Previous studies have revealed the antitumor potential of Poria cocos Wolf against a broad spectrum of cancers. However, the biological activity of P. cocos against lung cancer, which is known as the leading cause of cancer mortality worldwide, and its underlying chemical and molecular basis, remain to be investigated. We aimed to evaluate the in vitro cytotoxicity of P. cocos toward human lung adenocarcinoma cells with different p53 statuses, to identify the bioactive constituents of P. cocos, and explicate the molecular mechanisms underlying the cytotoxicity of these constituents in human lung adenocarcinoma cells. An EtOH extract of the sclerotia of P. cocos exhibited cytotoxicity toward four human lung cancer cell lines: A549, H1264, H1299, and Calu-6, regardless of their p53 status. Chemical investigation of the extract resulted in the isolation of two triterpenoids, dehydroeburicoic acid monoacetate (1) and acetyl eburicoic acid (4); a sterol, 9,11-dehydroergosterol peroxide (2); and a diterpenoid, dehydroabietic acid (3). All of the isolated compounds were cytotoxic to the lung adenocarcinoma cell lines, exhibiting IC50 values ranging from 63.6 µM to 171.0 µM at 48 h of treatment. The cytotoxicity of the extract and the isolated compounds were found to be mediated by apoptosis, and accompanied by elevated Bax expression and/or Bcl-2 phosphorylation along with caspase-3 activation. Our data demonstrate that the sclerotium of P. cocos and its four bioactive constituents (1⁻4) exert cytotoxicity against human lung adenocarcinoma cells, regardless of their p53 status, by inducing apoptosis associated with mitochondrial perturbation, and proposing the potential to employ P. cocos in the treatment of lung cancer.

Bioactivity-based analysis and chemical characterization of cytotoxic constituents from Chaga mushroom (Inonotus obliquus) that induce apoptosis in human lung adenocarcinoma cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Inonotus obliquus, also known as Chaga mushroom, is one of the most widely appreciated wild edible mushrooms in Russia and northern European countries and is renowned for its use in cancer treatment. Indeed, recently published in vitro and in vivo studies have demonstrated its anticancer activity in various types of cancer and support its potential application for therapeutic intervention in cancer. However, its activity against lung cancer, the most commonly diagnosed cancer and the leading cause of cancer death worldwide, and the underlying molecular basis of its action remain to be fully elucidated. OBJECTIVE: This study aimed to evaluate the cytotoxic activity of I. obliquus in four human lung adenocarcinoma cell lines with different p53 status (A549, H1264, H1299, and Calu-6) and identify its active constituents by bioactivity-based analysis and the underlying molecular basis of their cytotoxicity on lung cancer cells. MATERIALS AND METHODS: Bioactivity-guided fractionation and preparative/semi-preparative HPLC purification were used with LC/MS analysis to separate the bioactive constituents. Cell viability and apoptosis in human lung cancer cell lines (A549, H1264, H1299, and Calu-6) were assessed using the WST-1 assay and TUNEL staining, respectively. Caspase activation was assessed by detecting its surrogate markers, cleaved poly (ADP-ribose) polymerase (PARP) and caspase-3, using an immunoblot assay. RESULTS: The MeOH extract of I. obliquus reduced cell viability in all lung cancer cell lines tested through induction of apoptosis accompanied by caspase-3 cleavage. Bioactivity-guided fractionation of the MeOH extract and chemical investigation of its cytotoxic hexane-soluble and CH2Cl2-soluble fractions led to the isolation of eight triterpenoids (1-8), including a new lanostane-type triterpenoid named chagabusone A (7). The structures of the isolates were elucidated based on spectroscopic analysis, including 1D and 2D NMR and high-resolution ESIMS. Among isolated compounds, compounds 1, 6, and 7 showed the most potent cytotoxic activity in all human lung cancer cell lines examined, with IC50 values ranging from 75.1 to 227.4 µM. Cytotoxicity of these compounds was mediated by apoptosis with caspase-3 activation. CONCLUSION: These findings provide experimental evidence supporting the potential application of I. obliquus in lung cancer treatment and reveal the molecular basis underlying its cytotoxic activity against human lung cancer cells.