5 research outputs found
Tyrosine 23 Phosphorylation-Dependent Cell-Surface Localization of Annexin A2 Is Required for Invasion and Metastases of Pancreatic Cancer
The aggressiveness of pancreatic ductal adenocarcinoma (PDA) is characterized by
its high metastatic potential and lack of effective therapies, which is the
result of a lack of understanding of the mechanisms involved in promoting PDA
metastases. We identified Annexin A2 (ANXA2), a member of the Annexin family of
calcium-dependent phospholipid binding proteins, as a new molecule that promotes
PDA invasion and metastases. We found ANXA2 to be a PDA-associated antigen
recognized by post-treatment sera of patients who demonstrated prolonged
survival following treatment with a PDA-specific vaccine. Cell surface ANXA2
increases with PDA development and progression. Knockdown of ANXA2 expression by
RNA interference or blocking with anti-ANXA2 antibodies inhibits in
vitro invasion of PDA cells. In addition, post-vaccination patient
sera inhibits in vitro invasion of PDA cells, suggesting that
therapeutic anti-ANXA2 antibodies are induced by the vaccine. Furthermore,
cell-surface localization of ANXA2 is tyrosine 23 phosphorylation-dependent; and
tyrosine 23 phosphorylation is required for PDA invasion. We demonstrated that
tyrosine 23 phosphorylation resulting in surface expression of ANXA2 is required
for TGFβ-induced, Rho-mediated epithelial-mesenchymal transition (EMT),
linking the cellular function of ANXA2 which was previously shown to be
associated with small GTPase-regulated cytoskeletal rearrangements, to the EMT
process in PDA. Finally, using mouse PDA models, we showed that shRNA knock-down
of ANXA2, a mutation at tyrosine 23, or anti-ANXA2 antibodies,
inhibit PDA metastases and prolong mouse survival. Thus, ANXA2 is part of a
novel molecular pathway underlying PDA metastases and a new target for
development of PDA therapeutics
Development of a Novel Preclinical Pancreatic Cancer Research Model: Bioluminescence Image-Guided Focal Irradiation and Tumor Monitoring of Orthotopic Xenografts1
PURPOSE: We report on a novel preclinical pancreatic cancer research model that uses bioluminescence imaging (BLI)-guided irradiation of orthotopic xenograft tumors, sparing of surrounding normal tissues, and quantitative, noninvasive longitudinal assessment of treatment response. MATERIALS AND METHODS: Luciferase-expressing MiaPaCa-2 pancreatic carcinoma cells were orthotopically injected in nude mice. BLI was compared to pathologic tumor volume, and photon emission was assessed over time. BLI was correlated to positron emission tomography (PET)/computed tomography (CT) to estimate tumor dimensions. BLI and cone-beam CT (CBCT) were used to compare tumor centroid location and estimate setup error. BLI and CBCT fusion was performed to guide irradiation of tumors using the small animal radiation research platform (SARRP). DNA damage was assessed by Îł-H2Ax staining. BLI was used to longitudinally monitor treatment response. RESULTS: Bioluminescence predicted tumor volume (R = 0.8984) and increased linearly as a function of time up to a 10-fold increase in tumor burden. BLI correlated with PET/CT and necropsy specimen in size (P < .05). Two-dimensional BLI centroid accuracy was 3.5 mm relative to CBCT. BLI-guided irradiated pancreatic tumors stained positively for Îł-H2Ax, whereas surrounding normal tissues were spared. Longitudinal assessment of irradiated tumors with BLI revealed significant tumor growth delay of 20 days relative to controls. CONCLUSIONS: We have successfully applied the SARRP to a bioluminescent, orthotopic preclinical pancreas cancer model to noninvasively: 1) allow the identification of tumor burden before therapy, 2) facilitate image-guided focal radiation therapy, and 3) allow normalization of tumor burden and longitudinal assessment of treatment response