Ras-association domain family 1C protein promotes breast cancer cell migration and attenuates apoptosis.
BACKGROUND
The Ras association domain family 1 (RASSF1) gene is a Ras effector encoding two major mRNA forms, RASSF1A and RASSF1C, derived by alternative promoter selection and alternative mRNA splicing. RASSF1A is a tumor suppressor gene. However, very little is known about the function of RASSF1C both in normal and transformed cells.


METHODS
Gene silencing and over-expression techniques were used to modulate RASSF1C expression in human breast cancer cells. Affymetrix-microarray analysis was performed using T47D cells over-expressing RASSF1C to identify RASSF1C target genes. RT-PCR and western blot techniques were used to validate target gene expression. Cell invasion and apoptosis assays were also performed.


RESULTS
In this article, we report the effects of altering RASSF1C expression in human breast cancer cells. We found that silencing RASSF1C mRNA in breast cancer cell lines (MDA-MB231 and T47D) caused a small but significant decrease in cell proliferation. Conversely, inducible over-expression of RASSF1C in breast cancer cells (MDA-MB231 and T47D) resulted in a small increase in cell proliferation. We also report on the identification of novel RASSF1C target genes. RASSF1C down-regulates several pro-apoptotic and tumor suppressor genes and up-regulates several growth promoting genes in breast cancer cells. We further show that down-regulation of caspase 3 via overexpression of RASSF1C reduces breast cancer cells' sensitivity to the apoptosis inducing agent, etoposide. Furthermore, we found that RASSF1C over-expression enhances T47D cell invasion/migration in vitro.


CONCLUSIONS
Together, our findings suggest that RASSF1C, unlike RASSF1A, is not a tumor suppressor, but instead may play a role in stimulating metastasis and survival in breast cancer cells.
Reeves
Mark E
ME
Surgical Oncology Laboratory, 11201 Benton Street (151), Loma Linda VA Medical Center, California 92350, USA.
Baldwin
Scott W
SW
Baldwin
Melissa L
ML
Chen
Shin-Tai
ST
Moretz
Jeremy M
JM
Aragon
Robert J
RJ
Li
Xinmin
X
Strong
Donna D
DD
Mohan
Subburaman
S
Amaar
Yousef G
YG
D017209:Apoptosis; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D020411:Oligonucleotide Array Sequence Analysis; D010957:Plasmids / Q000378:metabolism; D016896:Treatment Outcome; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000502:physiology*
C411762:RASSF1 protein, human; D025521:Tumor Suppressor Proteins