Suppression of tumor growth by intra-muscular transfer of naked DNA encoding adrenomedullin antagonist

Abstract

We have recently reported that the intra-tumoral injection of adrenomedullin (AM) antagonist (AMA; AM (22-52)) peptides significantly reduced the in vivo growth of a pancreatic cancer cell line in severely combined immunodeficient (SCID) mice. In the present study, we examined the effects of intra-tumoral and intra-muscular transfers of naked DNA encoding AMA on the in vivo growth of cancer cell lines. We demonstrate that these treatments induce the regression of a pancreatic cancer cell line and a breast cancer cell line inoculated in SCID mice. Furthermore, CD31-positive cells disappear completely from tumor tissues, following treatment, indicating that neo-vascularization is entirely inhibited. These results suggest that the intra-tumoral or intra-muscular transfer of naked DNA encoding AMA might be a promising alternative modality for treating human cancers.

Adrenomedullin Is Expressed in Pancreatic Cancer and Stimulates Cell Proliferation and Invasion in an Autocrine Manner via the Adrenomedullin Receptor, ADMR

“…22), or intratumoral or i.m. transfection with an AMA-expressing plasmid (23), reduced microvascular density and growth of pancreatic tumors. These studies provide strong evidence for the angiogenic function of adrenomedullin.…”

Adrenomedullin antagonist suppresses tumor formation in renal cell carcinoma through inhibitory effects on tumor endothelial cells and endothelial progenitor mobilization

“…We showed that the intratumoral injection of AMA peptides suppressed tumor formation by human pancreatic cancer cells in nude mice (7) and that intramuscular injection of naked DNAencoding AMA almost completely suppressed tumor formation in mammary and pancreatic cancer cells in SCID mice (8). In the present study, we showed that OS-RC-2, an RCC cell line, expressed AM both under normoxia and hypoxia (data not shown).…”

“…The naked DNA-encoding AMA (AMA vector) (Fig. 1A) was injected intramuscularly using the ultrasound-microbubble method when the tumor size reached an average diameter of 4 mm (on day 13), as described previously (8). (Fig.…”

“…We demonstrated that the intratumoral injection of an adrenomedullin antagonist (AMA) inhibited tumor growth in a pancreatic cancer cell line in a xenograft mouse model (7). In addition, we recently demon-strated that naked DNA-encoding AMA suppressed the growth of pancreatic cancer and breast cancer cell lines through the inhibition of AM (8), a multifunctional polypeptide that was originally isolated from human pheochromocytoma and is a member of the family of peptides that includes calcitonin (CT), ·-and ß-calcitonin gene-related peptide (9). AM gene knockout mice have shown embryonic lethality with severe abnormalities of the vasculature (10) and subcutaneous hemorrhage indicating the significance of AM signaling in vascular development.…”

“…Tumor cells (OS-RC-2; 5x10 6 cells/mouse) were inoculated subcutaneously into the right flank of the mice. After tumor induction (day 0), naked DNA-encoding AMA was injected intramuscularly using the ultrasound-microbubble method as described previously (8) when the tumor size reached an average diameter of 4 mm (on day 13). The shortest and longest diameters of the tumor were measured on the treatment day, and tumor volume (mm 3 ) was calculated using the following standard formula: (shortest diameter) 2 x (longest diameter) x 0.5.…”