Fractionated radiation therapy alters energy metabolism and induces cellular quiescence exit in patient-derived orthotopic xenograft models of high-grade glioma.

Radiation is one of the standard therapies for pediatric high-grade glioma (pHGG), of which the prognosis remains poor. To gain an in-depth understanding of biological consequences beyond the classic DNA damage, we treated 9 patient-derived orthotopic xenograft (PDOX) models, including one with DNA mismatch repair (MMR) deficiency, with fractionated radiations (2 Gy/day x 5 days). Extension of survival time was noted in 5 PDOX models (P < 0.05) accompanied by γH2AX positivity in >95 % tumor cells in tumor core and >85 % in the invasive foci as well as ∼30 % apoptotic and mitotic catastrophic cell death. The model with DNA MMR (IC-1406HGG) was the most responsive to radiation with a reduction of Ki-67(+) cells. Altered metabolism, including mitochondria number elevation, COX IV activation and reactive oxygen species accumulation, were detected together with the enrichment of CD133+ tumor cells. The latter was caused by the entry of quiescent G0 cells into cell cycle and the activation of self-renewal (SOX2 and BMI1) and epithelial mesenchymal transition (fibronectin) genes. These novel insights about the cellular and molecular mechanisms of fractionated radiation in vivo should support the development of new radio-sensitizing therapies.

Mislocalized cytoplasmic p27 activates PAK1-mediated metastasis and is a prognostic factor in osteosarcoma.

The development of pulmonary metastasis is the leading cause of death in osteosarcoma (OS), which is the most common malignant bone tumor in children. We have previously reported that the tumor suppressor p27 (KIP1, CDKN1B) is frequently mislocalized to the cytoplasm of OS. However, its prognostic significance and metastatic mechanism are still elusive. Here, we show that cytoplasmic p27 significantly correlated with a higher metastatic status and poorer survival of OS patients (n = 136, P < 0.05), highlighting the clinical significance of p27 mislocalization in OS. Mechanistically, cytoplasmic p27 is co-immunoprecipitated with p21-activated kinase 1 (PAK1), which resulted in higher PAK1 phosphorylations, actin polymerization, and cell motility in p27-mislocalized OS cells. Silencing PAK1 expression in different p27-mislocalized OS cell lines decreased the migratory and adhesion abilities in vitro, as well as the development of pulmonary metastases in vivo. Similar PAK1-dependent motility was also observed in other p27-mislocalized cancer cell lines. In summary, our study suggests that cytoplasmic p27-mediated PAK1 activation is crucial for OS metastasis. A biomarker-guided targeted therapeutic approach for metastatic OS and other cancers harboring p27 mislocalization can be developed, where cytoplasmic p27 is used for risk stratification and PAK1 can be exploited as a potential therapeutic target.

The dual functions of YAP-1 to promote and inhibit cell growth in human malignancy.

The major functions of Hippo (Hpo) signaling pathway are to control cell growth, proliferation, and apoptosis. As its important downstream player, yes-associated protein (YAP)-1 was originally found to promote cell proliferation and transformation. Overexpression of YAP-1 has been linked to tumor progression and worse survival in certain malignancies. However, it has been recently recognized as a tumor suppressor gene as well since it also induces apoptosis. Decreased or absent expression of YAP-1 is highly correlated with tumor progression and worse survival in other tumors such as breast cancer. It is clear that YAP-1 plays a dual role as oncogene and tumor suppressor gene in human oncogenesis, depending on the specific tissue type involved. Here, we reviewed the recent research on both the oncogenic and tumor suppressor function of YAP-1 and its significance in human malignancy. The clinical implication of YAP-1 expression in cancer prognosis and the development of targeted therapy will also be discussed.

Prostaglandin E2, Wnt, and BMP in gastric tumor mouse models.

The development of gastric cancer is closely associated with Helicobacter pylori (H. pylori) infection. The expression of cylooxigenase-2 (COX-2), a rate-limiting enzyme for prostaglandin biosynthesis, is induced in H. pylori-associated chronic gastritis, which thus results in the induction of proinflammatory prostaglandin, PGE(2). The COX-2/PGE(2) pathway plays a key role in gastric tumorigenesis. On the other hand, several oncogenic pathways have been shown to trigger gastric tumorigenesis. The activation of Wnt/beta-catenin signaling is found in 30-50% of gastric cancers, thus suggesting that Wnt signaling plays a causal role in gastric cancer development. Mutations in the bone morphogenetic protein (BMP) signaling pathway are responsible for the subset of juvenile polyposis syndrome (JPS) that develops hamartomas in the gastrointestinal tract. BMP suppression appears to contribute to gastric cancer development because gastric cancer risk is increased in JPS. Wnt signaling is important for the maintenance of gastrointestinal stem cells, while BMP promotes epithelial cell differentiation. Accordingly, it is possible that both Wnt activation and BMP suppression can cause gastric tumorigenesis through enhancement of the undifferentiated status of epithelial cells. Recent mouse model studies have indicated that induction of the PGE(2) pathway is required for the development of both gastric adenocarcinoma and hamartoma in the Wnt-activated and BMP-suppressed gastric mucosa, respectively. This article reviews the involvement of the PGE(2), Wnt, and BMP pathways in the development of gastric cancer, and gastric phenotypes that are found in transgenic mouse models of PGE(2) induction, Wnt activation, BMP suppression, or a combination of these pathways.

Induction and down-regulation of Sox17 and its possible roles during the course of gastrointestinal tumorigenesis.

BACKGROUND & AIMS: The activation of Wnt/beta-catenin signaling causes the development of gastric and colon cancers. Sox17 represses Wnt/beta-catenin signaling and is down-regulated in colon cancer. This study was designed to elucidate the role of Sox17 during the course of gastrointestinal tumorigenesis. METHODS: Sox17 expression was examined in gastrointestinal tumors of mouse models and humans. The roles of Sox17 in gastric tumorigenesis were examined by cell culture experiments and by construction of Sox17 transgenic mice. RESULTS: Sox17 was induced in K19-Wnt1/C2mE mouse gastric tumors and K19-Wnt1 preneoplastic lesions, where Wnt/beta-catenin signaling was activated. Consistently, Wnt activation induced Sox17 expression in gastric cancer cells. In contrast, Sox17 was rarely detected by immunohistochemistry in gastric and colon cancers, whereas strong nuclear staining of Sox17 was found in >70% of benign gastric and intestinal tumors. Treatment with a demethylating agent induced Sox17 expression in gastric cancer cells, thus indicating the down-regulation of Sox17 by methylation. Moreover, transfection of Sox17 in gastric cancer cells suppressed both the Wnt activity and colony formation efficiency. Finally, transgenic expression of Sox17 suppressed dysplastic tumor development in K19-Wnt1/C2mE mouse stomach. CONCLUSIONS: Sox17 plays a tumor suppressor role through suppression of Wnt signaling. However, Sox17 is induced by Wnt activation in the early stage of gastrointestinal tumorigenesis, and Sox17 is down-regulated by methylation during malignant progression. It is therefore conceivable that Sox17 protects benign tumors from malignant progression at an early stage of tumorigenesis, and down-regulation of Sox17 contributes to malignant progression through promotion of Wnt activity.

Platelet-type 12-lipoxygenase accelerates tumor promotion of mouse epidermal cells through enhancement of cloning efficiency.

Accumulating evidence suggests that platelet-type 12-lipoxygenase (p12-LOX) plays an important role in tumor development. However, how p12-LOX contributes to tumorigenesis is still not understood. The role of p12-LOX was therefore examined in tumor promotion using mouse epidermal JB6 P+ cells that are sensitive to 12-O-tetradecanoylphorbol-13-acetate-induced transformation. The expression of p12-LOX was significantly higher in JB6 P+ cells than in JB6 P- cells that were resistant to transformation, and its expression was further increased by tumor necrosis factor (TNF)-alpha. Importantly, the inhibition of p12-LOX in JB6 P+ cells by baicalein, a specific inhibitor or small interfering RNA significantly suppressed TPA-induced transformation. Moreover, treatment with 12(S)-hydroxyeicosatetraenoic acid (HETE), a metabolite of p12-LOX, enhanced TPA-induced neoplastic transformation either in the presence or absence of baicalein. These results indicate that p12-LOX is required for tumor promotion of epidermal cells and that 12(S)-HETE functions as a rate-limiting factor. Notably, treatment with baicalein significantly suppressed the proliferation of JB6 P+ cells when cells were seeded at a low density in a culture plate. Moreover, the cloning efficiency of JB6 P+ cells was dramatically decreased by inhibition of p12-LOX. In contrast, baicalein treatment did not affect the cloning efficiency of most malignant cancer cells. These results indicate that p12-LOX is induced by the inflammatory cytokine TNF-alpha in the early stage of tumorigenesis, and is required for tumor promotion through enhancing efficient proliferation of a small number of initiated cells. The present results suggest that the p12-LOX pathway may be an effective target of chemoprevention for skin carcinogenesis.

[Studies on the enhancement of DC vaccine to mouse Lewis lung cancer by CpG oligonucleotides].

OBJECTIVE: To investigate whether CpG ODN can affect the antitumor responses of DC-tumor cell vaccine against Lewis lung cancer. METHODS: CpG oligonucleotides 1826 (ODN 1826) were used to promote maturation of DCs in vitro. By fusing DCs with Lewis lung carcinoma L3-8 cells, DC-based tumor cell vaccines were developed. To determine the immune responses to the vaccines, T cell proliferation and cytotoxicity were done in vitro. Therapeutic and prophylactic immunization with DC vaccines were performed in C57BL/6 mice bearing Lewis lung carcinoma. RESULTS: Bone marrow cells cultured in the presence of GM-CSF and IL-4 plus additional ODN 1862 appeared typical morphology of DCs. FACS analyses showed that the mean fluorescence index (MFI) of CD40 expression of DCs stimulated with and without CpG ODN was 24 and 11, respectively, and that of CD86 expression was 75 and 33, respectively. IL-12 secreted by DCs cultured with ODN 1826 was 10-fold as high as that without ODN 1826. Significant T-cell proliferation and T cell-mediated cytotoxicity against L3-8 was induced in vitro. Marked inhibition of tumor growth in L3-8 bearing mice was observed upon prophylactic and therapeutic immunizations with the vaccine. CONCLUSION: CpG ODN can enhance the antitumor responses of DC vaccine by promoting DC maturation.