A Dominant-Negative Mutant of ANXA7 Impairs Calcium Signaling and Enhances the Proliferation of Prostate Cancer Cells by Downregulating the IP3 Receptor and the PI3K/mTOR Pathway.

Annexin A7/ANXA7 is a calcium-dependent membrane fusion protein with tumor suppressor gene (TSG) properties, which is located on chromosome 10q21 and is thought to function in the regulation of calcium homeostasis and tumorigenesis. However, whether the molecular mechanisms for tumor suppression are also involved in the calcium- and phospholipid-binding properties of ANXA7 remain to be elucidated. We hypothesized that the 4 C-terminal endonexin-fold repeats in ANXA7 (GX(X)GT), which are contained within each of the 4 annexin repeats with 70 amino acids, are responsible for both calcium- and GTP-dependent membrane fusion and the tumor suppressor function.

Distinct effects of annexin A7 and p53 on arachidonate lipoxygenation in prostate cancer cells involve 5-lipoxygenase transcription.

Tumor suppressor function for Annexin A7 (ANXA7; 10q21) is based on cancer-prone phenotype in Anxa7(+/-) mouse and ANXA7 prognostic role in human cancers. Because ANXA7-caused liposome aggregation can be promoted by arachidonic acid (AA), we hypothesized that the phospholipid-binding tumor suppressor ANXA7 is associated with AA cascade. In a comparative study of ANXA7 versus canonical tumor suppressor p53 effects on AA lipoxygenation pathway in the p53-mutant and androgen-insensitive DU145 prostate cancer cells, both tumor suppressors altered gene expression of major 5-lipoxygenase (LOX) and 15-LOXs, including response to T helper 2 (Th2)-cytokine [interleukin-4 (IL-4)] and endogenous steroids (mimicked by dexamethasone).

Cardiac glycosides inhibit TNF-alpha/NF-kappaB signaling by blocking recruitment of TNF receptor-associated death domain to the TNF receptor.

Digitoxin and structurally related cardiac glycoside drugs potently block activation of the TNF-alpha/NF-kappaB signaling pathway. We have hypothesized that the mechanism might be discovered by searching systematically for selective inhibitory action through the entire pathway. We report that the common action of these drugs is to block the TNF-alpha-dependent binding of TNF receptor 1 to TNF receptor-associated death domain.

Haploinsufficiency of Anx7 tumor suppressor gene and consequent genomic instability promotes tumorigenesis in the Anx7(+/-) mouse.

Annexin 7 (ANX7) acts as a tumor suppressor gene in prostate cancer, where loss of heterozygosity and reduction of ANX7 protein expression is associated with aggressive metastatic tumors. To investigate the mechanism by which this gene controls tumor development, we have developed an Anx7(+/-) knockout mouse. As hypothesized, the Anx7(+/-) mouse has a cancer-prone phenotype.

Anx7 is required for nutritional control of gene expression in mouse pancreatic islets of Langerhans.

Background: Gene expression in islets of Langerhans is profoundly sensitive to glucose and other nutrients. Islets of Langerhans in the Anx7(+/-) knockout mouse exhibit a profound reduction in ITPR3 protein expression, defective intracellular calcium signaling, and defective insulin secretion. Additional data presented here also show that mRNA for ITPR3 is virtually undetectable in isolated Anx7(+/-) islets.

Influence of the Anx7 (+/-) knockout mutation and fasting stress on the genomics of the mouse adrenal gland.

The Anx7 gene codes for a Ca(2+)/GTPase with calcium channel and membrane fusion properties that has been proposed to regulate exocytotic secretion in chromaffin and other cell types. We have previously reported that the homozygous Anx7 (+/-) knockout mouse has an embryonically lethal phenotype. However, the viable heterozygous Anx7 (+/-) mouse displays a complex phenotype that includes adrenal gland hypertrophy, chromaffin cell hyperplasia, and defective IP(3) receptor (IP(3)R) expression.