Paracrine factors of human fetal MSCs inhibit liver cancer growth through reduced activation of IGF-1R/PI3K/Akt signaling.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death in the world. The multikinase inhibitor sorafenib only demonstrated marginal improvement in overall survival for advanced disease prompted the search for alternative treatment options. Human mesenchymal stem cells (MSCs) have the ability to home to tumor cells. However, its functional roles on the tumor microenvironment remain controversial. Herein, we showed that conditioned media derived from human fetal MSC (CM-hfMSCs) expressed high level of the insulin growth factor binding proteins IGFBPs and can sequester free insulin-like growth factors (IGFs) to inhibit HCC cell proliferation. The inhibitory effect of IGFBPs on IGF signaling was further evident from the reduction of activated IGF-1R and PI3K/Akt, leading eventually to the induction of cell cycle arrest. We also demonstrated that CM-hfMSCs could enhance the therapeutic efficacy of sorafenib and sunitinib. To the best of our knowledge, this is the first report to show that CM-hfMSCs has a tumor-specific, antiproliferative effect that is not observed with normal human hepatocyte cells and patient-derived matched normal tissues. Our results thus suggest that CM-hfMSCs can provide a useful tool to design alternative/adjuvant treatment strategies for HCC, especially in related function to potentiate the effects of chemotherapeutic drugs.

Spontaneous thymic lymphomas in the non-obese diabetic/Shi-scid, IL-2R gamma (null) mouse.

The NOD/Shi-scid, IL-2Rgamma(null) (NOG) mouse is a severely immunodeficient mouse used for the engraftment of human tissues and cells. In this study, 2406 mice (8-62 weeks old, 503 males and 1903 females) were subcutaneously engrafted with human tissues. In 16 mice (12-26 weeks old, 1 male and 15 females), a mass was seen in the anteroventralis of the thorax on gross examination with an incidence of 0.7%. Histologically, the masses were composed of sheets of lymphoblastic cells. A 'starry sky' pattern was observed with numerous mitoses. Immunohistochemically the lymphoblastic cells were positive for Thy 1. The lymphoblastic cells were also seen in the spleen, lung, liver, kidney and heart. The gross and histopathological findings led to the diagnosis of spontaneous thymic lymphoma in NOG mice.

Interleukin-13 receptor alpha 2 cooperates with EGFRvIII signaling to promote glioblastoma multiforme.

The interleukin-13 receptor alpha2 (IL-13Rα2) is a cancer-associated receptor overexpressed in human glioblastoma multiforme (GBM). This receptor is undetectable in normal brain which makes it a highly suitable target for diagnostic and therapeutic purposes. However, the pathological role of this receptor in GBM remains to be established. Here we report that IL-13Rα2 alone induces invasiveness of human GBM cells without affecting their proliferation. In contrast, in the presence of the mutant EGFR (EGFRvIII), IL-13Rα2 promotes GBM cell proliferation in vitro and in vivo. Mechanistically, the cytoplasmic domain of IL-13Rα2 specifically binds to EGFRvIII, and this binding upregulates the tyrosine kinase activity of EGFRvIII and activates the RAS/RAF/MEK/ERK and STAT3 pathways. Our findings support the "To Go or To Grow" hypothesis whereby IL-13Rα2 serves as a molecular switch from invasion to proliferation, and suggest that targeting both receptors with STAT3 signaling inhibitor might be a therapeutic approach for the treatment of GBM.

Transcriptional profiling of dividing tumor cells detects intratumor heterogeneity linked to cell proliferation in a brain tumor model.

Intratumor heterogeneity is a primary feature of high-grade gliomas, complicating their therapy. As accumulating evidence suggests that intratumor heterogeneity is a consequence of cellular subsets with different cycling frequencies, we developed a method for transcriptional profiling of gliomas, using a novel technique to dissect the tumors into two fundamental cellular subsets, namely, the proliferating and non-proliferating cell fractions. The tumor fractions were sorted whilst maintaining their molecular integrity, by incorporating the thymidine analog 5-ethynyl-2'-deoxyuridine into actively dividing cells. We sorted the actively dividing versus non-dividing cells from cultured glioma cells, and parental and clonally derived orthotopic tumors, and analyzed them for a number of transcripts. While there was no significant difference in the transcriptional profiles between the two cellular subsets in cultured glioma cells, we demonstrate ∼2-6 fold increase in transcripts of cancer and neuronal stem cell and tumor cell migration/invasion markers, and ∼2-fold decrease in transcripts of markers of hypoxia and their target genes, in the dividing tumor cells of the orthotopic glioma when compared to their non-proliferative counterparts. This suggests the influence of the brain microenvironment in transcriptional regulation and, thereby, the physiology of glioma cells in vivo. When clonal glioma cells were derived from a parental glioma and the resultant orthotopic tumors were compared, their transcriptional profiles were closely correlated to tumor aggression and consequently, survival of the experimental animals. This study demonstrates the resolution of intratumor heterogeneity for profiling studies based on cell proliferation, a defining feature of cancers, with implications for treatment design.

Carbenoxolone enhances TRAIL-induced apoptosis through the upregulation of death receptor 5 and inhibition of gap junction intercellular communication in human glioma.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been used extensively in cancer therapy. However, more than half of glioblastoma multiforme are insensitive to the apoptotic effect of TRAIL. Improvement in therapeutic modalities that enhances the efficacy of TRAIL in glioma is much sought after. In this study, we combined the tumor selectivity of TRAIL and tumor-homing properties of mesenchymal stem cells (MSC) with gap junction (GJ) inhibitory effect of carbenoxolone (CBX) to target orthotopic glioma. MSC were engineered to express TRAIL (MSC-TRAIL) by incorporating the secretable trimeric form of TRAIL into a Herpes Simplex Virus (HSV) type I amplicon vector. Our results showed that combined treatment of MSC-TRAIL and CBX enhanced glioma cell death, especially in three primary human glioma isolates, of which two of those are marginally sensitive to TRAIL. CBX enhanced TRAIL-induced apoptosis through upregulation of death receptor 5, blockade of GJ intercellular communication, and downregulation of connexin 43. Dual arm therapy using TRAIL and CBX prolonged the survival of treated mice by ~27% when compared with the controls in an intracranial glioma model. The enhanced efficacy of TRAIL in combination with CBX coupled with the minimal cytotoxic nature of CBX suggested a favorable clinical usage of this treatment regimen.