Loss of RAB25 expression in breast cancer

Abstract

A novel breast cancer cell line (RAO-3) was established by transduction of the Q61L mutant RAS into human mammary epithelial cells that were immortalized with catalytic subunit of telomerase (hTERT). The cells displayed anchorage-independent growth and proliferation, and formed human mammary spindle cell carcinoma when injected into nude mice. Chromosome locus 1q22-23 was partially duplicated and inverted on one of the 3 chromosomes present in the cell line. We report here that mutations of chromosome 1q22-23 locus have resulted in the loss of RAB25 expression in the breast cancer cell line. Transduction of RAB25 into the breast cancer cell line arrests anchorage-independent growth. We have also demonstrated loss of RAB25 in human breast tumor tissue. These data suggest that loss of RAB25 might contribute to tumorigenesis of breast cancer, and RAB25 is likely to be an important factor in the development of breast cancer. RAB25 could be used as biological marker of breast cancer and provides a target for gene replacement therapy. ' 2006 Wiley-Liss, Inc. Key words: RAS; RAB25; breast cancerBreast cancer is the most common cancer in North American women. Many genes are considered to contribute to tumorigenesis of the mammary gland, such as RAS, BCL-2 (B-cell Leukemia-2) and NRG1 (Neuregulin1). 1-3 A novel series of human breast cancer cell lines has been established through the use of defined genetic elements in an effort to better define the role of various oncogenes in a stepwise model to tumor progression. 4 Human mammary epithelial cells (HMEC) from healthy individuals undergoing reduction mammoplasty were immortalized by transduction of either the catalytic subunit of telomerase (hTERT) after passage through stasis (RAO-1 cell line) or the human papilloma virus type16 (HPV16) E6/E7 genes. The RAO-1 cell line was then transduced with the Q61L mutant H-RAS gene; RAO-2 is a RAS-transduced derivative cell line of RAO-1 that does not show anchorageindependent growth in soft agar and is not tumorigenic in nude mice. RAO-3 and RAO-4 are human breast cancer cell lines that were derived from RAO-1 after RAS transduction. RAO-3 exclusively gives rise to human mammary spindle cell carcinomas when injected into nude mice. RAO-4 exclusively generates human mammary epithelial carcinoma when injected into nude mice. Previous studies suggested that a critical cytogenetic event on chromosome locus 1q23 was the last significant step to transformation in our RAS-driven model. 4 We confirmed the rearrangement of chromosome 1q22-23 by FISH (fluorescence in situ hybridization) in the RAO-3 cell line. The expression of RAB25, one of the genes that are located in this region, was lost in some of the tumorigenic cell lines that we tested, including RAO-3 and RAO-4.The RAB guanosine triphosphatases (GTPases) (RAS-related in brain) 5 belong to the RAS superfamily of small GTPases. More than 60 different RAB family members have been identified in the human genome. 6,7 The human RAS family consists of 3 protooncogenes, H-RAS, K-RAS and N...

Vimentin regulates EMT induction by Slug and oncogenic H-Ras and migration by governing Axl expression in breast cancer

“…These genes have earlier been linked with breast cancer invasion and the basal-like phenotype (Neve et al, 2006;Schuetz et al, 2006;Lu et al, 2008a). Moreover, knocking down vimentin induced expression of genes abundant in normal mammary epithelium (RAB25, small GTPase Rab25 and EHF, Ese3 transcription factor) (Galang et al, 2004;Cheng et al, 2006). We studied further the interplay between vimentin, EMT induction and the receptor tyrosine kinase Axl, which is associated with a wide variety of malignancies (Linger et al, 2008).…”

The role of endocytic Rab GTPases in regulation of growth factor signaling and the migration and invasion of tumor cells

“…76,77 Similarly Rab25 has differing expression levels with increased expression in estrogen and progesterone receptor positive breast cancer, 78 and suppression in colon and head and neck tumors. 79,80 Down-regulation of Rab38 may be associated with metastasis in melanoma.…”

“…96 Interestingly, it has also been shown that loss of the Rab25 (function or expression) increased turmorigenesis in mammary epithelial cells. 77 However, Rab25 is also said to be an oncogene given its role in advanced stages of ovarian and breast cancers and is linked to an increase in malignancy and migration of the epithelial cells by modulating cell proliferation (both anchorage dependent and independent cells), trafficking of integrin and suppressing apoptosis. 75 Specifically, Rab25 promotes cell survival by increasing PI3-Kinase signaling through the interaction with the Rab-coupling protein, which in turn sustains the recycling of both EGFR and the fibronectin receptor (integrin a5b1).…”

The secretory small GTPase Rab27B as a marker for breast cancer progression

“…It has been demonstrated that in ER-positive breast cancer cells, Rab25 overexpression increases proliferation and anchorage-independent growth [18]. In ER-negative breast cancer cells, re-expression of Rab25 reduced proliferation and invasive growth, and increased apoptosis [19,20].…”