PI3 kinase blockade by Ad-PTEN inhibits invasion and induces apoptosis in RGP and metastatic melanoma cells.
BACKGROUND
Melanoma is an aggressive tumor with a propensity to rapidly metastasize. The PTEN gene encodes a phosphatase with an unusual dual specificity for proteins and lipids. Mutations of PTEN have been found in various human cancers, including glioblastoma, prostate, breast, lung, and melanoma. Here we investigate in vitro the effects of blocking PI3K signaling using adenoviral-delivered PTEN (Ad-PTEN) in cell lines derived from both early- and late-stage melanoma.


METHODS
Ad-PTEN transduced melanoma cell lines or normal cells were assayed for cell death, apoptosis, gene expression, invasion and migration, and regulation of angiogenesis.


RESULTS
The PTEN locus from RGP and metastatic melanoma cell lines was sequenced; no coding region mutations were found. Adenoviral transfer of PTEN into melanoma cells containing wild-type PTEN alleles led to tumor-specific apoptosis and growth inhibition, with coordinate inhibition of AKT phosphorylation. Ad-PTEN suppressed cell migration by metastatic melanoma cells with concomitant increase in the level of cell surface E-cadherin. Immunohistochemical and confocal analyses localized PTEN to the cytoplasm and demonstrated enrichment at the cell membrane. Ad-PTEN inhibited angiogenesis as demonstrated by the tube formation assay using human vascular endothelial cells.


CONCLUSIONS
These studies indicate that Ad-PTEN can inhibit tumor cells via multiple mechanisms and has pro-apoptotic, anti-metastatic, and anti-angiogenic properties. Thus, PI3K blockade via Ad-PTEN may be a promising approach for the treatment of early- and late-stage melanoma, even in tumors that do not harbor PTEN mutations.
Stewart
Alexis L
AL
Department of Research, Introgen Therapeutics, Inc., Houston, Texas 77030, USA.
Mhashilkar
Abner M
AM
Yang
Xiaohong Helena
XH
Ekmekcioglu
Suhendan
S
Saito
Yuji
Y
Sieger
Kerry
K
Schrock
Robert
R
Onishi
Eric
E
Swanson
Xin
X
Mumm
John B
JB
Zumstein
Lou
L
Watson
Graham J
GJ
Snary
David
D
Roth
Jack A
JA
Grimm
Elizabeth A
EA
Ramesh
Rajagopal
R
Chada
Sunil
S
D000256:Adenoviridae; D017209:Apoptosis / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D004727:Endothelium / Q000503:physiopathology; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D009389:Neovascularization, Pathologic / Q000503:physiopathology; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases; D025521:Tumor Suppressor Proteins; C494929:PTEN protein, human