Upregulation of RASSF1A in Colon Cancer by Suppression of Angiogenesis Signaling and Akt Activation

Background/Aims: Silencing of tumor suppressor genes (TSGs) and promotion of angiogenesis are associated with tumor development and metastasis. However, little is known if angiogenic molecules directly control TSGs and vice versa. Methods: A regulatory link between angiogenesis and down regulation of TSGs was evaluated using an anti-cancer agent, andrographolide (AGP) in cancer cells, mouse xenograft tissues and patient derived organoids through gene/protein expression, gene silencing, and immunohistochemical analyses. Results: AGP treatment demonstrated significant expression of RASSF1A and PTEN TSGs in colon cancer and other cancer cells, mouse tissues and organoids. Depletion of RASSF1A with siRNA limited cyclin D1 and BAX expression. SiRNA depletion of PTEN, upstream regulator of RASSF1A resulted in a 50% reduction in RASSF1A expression. Histopathological analysis of the AGP treated tumor sections showed significant reduction in vessel size, microvascular density and tumor mitotic index suggesting suppression of angiogenesis. This was corroborated by protein analysis demonstrating significant reductions in angiogenesis signaling pathway molecules VEGF165, FOXM1, and pAkt, but significant elevation of the endogenous angiogenesis inhibitor Tsp-2. Treatment of cells with exogenous VEGF prevented the suppression of angiogenesis signaling by AGP, resulting in sustained expression of pAkt, an upstream down-regulator of RASSF1A. RASSF1A expression remained low in VEGF treated cells despite the addition of AGP. Conclusion: Our results demonstrate for the first time that AGP induces RASSF1A expression in colon cancer cells and is dependent on angiogenesis signaling events. Therefore, our research may facilitate novel therapeutic options for advanced colon cancer therapy

Immunity, inflammation, and vaccines for Helicobacter pylori

Helicobacter pylori colonizes mucosa, activates Toll-like and Nod-like receptors, and usually elicits a gastric T-helper 1/17 (Th1/Th17) type of immune response. Among several bacterial factors, the secreted peptidyl prolyl cis, trans-isomerase of H. pylori represents a key factor driving Th17 inflammation. A complex and fascinating balance between H. pylon and host factors takes part in the gastric niche and is responsible for the chronicity of the infection. Novel insights into the innate and adaptive responses against H. pylori, dealing wilt gastric epithelial cells, cytokines, and immune evasion have been elucidated over the past year and are discussed for the development. of an effective vaccine

Local and Systemic Antibody Responses in Humans with Helicobacter pylori Infection

Immunization can prevent or cure an otherwise chronic helicobacter infection in several animal models despite the chronic nature of natural helicobacter infections. Differences in the antigenic specificity of the antibodies may contribute to the protection observed in these experimental animals. The goal of the present study was to compare the local and systemic antibody responses of humans with chronic Helicobacter pylori infection with those of an individual with spontaneous resolution of infection to find an immunological correlate of protection. Spontaneous resolution of infection was accompanied by a change in immunoblot profiles. Whereas a broad range of H pylori antigens was recognized in chronically infected patients (including the patient who ultimately cleared the infection spontaneously), resolution of infection in the absence of therapeutic agents resulted in the recognition of only several immunodominant antigens. The most dominant antigen was approximately 66 kDa in molecular mass. Immunoblot analysis demonstrated that these antibodies were specific for the structural subunits of the urease enzyme. These studies suggest that the success of antihelicobacter immunization may be due to the ability of vaccination to induce an immune response against antigens that are normally not immunodominant during the course of infection

Regulation of Murine Dendritic Cell Immune Responses by Helicobacter felis Antigen

Helicobacter infections are present in approximately 50% of humans, causing severe illnesses such as gastritis and malignancies. Dendritic cells (DC) are critical antigen-presenting cells which link innate and adaptive immune responses. The mechanism of dendritic cell regulation in Helicobacter-induced gastritis is poorly understood. These studies characterized DC isolated from the lamina propria of Helicobacter-infected mice and analyzed innate and adaptive immune responses elicited by Helicobacter antigen (Ag)-pulsed DC. The presence of DC was elevated in the gastric lamina propria infiltrate of infected mice in comparison with controls. After treatment with Helicobacter felis Ag, DC were polarized to secrete interleukin-6 as the dominant cytokine. In the presence of DC and Helicobacter Ag, responder allogeneic T cells in culture exhibited limited cell division. We suggest that the response of DC and T cells to Helicobacter Ag is critical to the chronic persistence of Helicobacter-induced gastritis