Abstract
Evasion of apoptosis plays an important role in colon cancer progression. Following loss of the Apc tumor suppressor gene in mice, the gene encoding Fem1b is upregulated early in neoplastic intestinal epithelium. Fem1b is a pro-apoptotic protein that interacts with Fas, TNFR1 and apaf-1, and increased expression of Fem1b induces apoptosis of cancer cells. Fem1b is a homolog of FeM-1, a protein in Caenorhabditis elegans that is negatively regulated by ubiquitination and proteasomal degradation. To study Fem1b regulation in colon cancer progression, we used apoptotis-sensitive SW480 cells, derived from a primary colon cancer, and their isogenic, apoptosis-resistant counterparts sW620 cells, derived from a subsequent metastatic lesion in the same patient. Treatment with proteasome inhibitor increased Fem1b protein levels in SW620 cells, but not in SW480 cells. In SW620 cells we found that endogenous Fem1b co-immunoprecipitates in complexes with RACK1, a protein known to mediate ubiquitination and proteasomal degradation of other pro-apoptotic proteins and to be upregulated in colon cancer. Full-length Fem1b, or the N-terminal region of Fem1b, associated with RACK1 when co-expressed in HEK293T cells, and RACK1 stimulated ubiquitination of Fem1b. RACK1 overexpression in SW620 cells led to downregulation of Fem1b protein levels. Conversely, downregulation of RACK1 led to upregulation of Fem1b protein levels, associated with induction of apoptosis, and this apoptosis was inhibited by blocking Fem1b protein upregulation. In conclusion, RACK1 downregulates levels of the pro-apoptotic protein Fem1b in metastatic, apoptosis-resistant colon cancer cells, which may promote apoptosis-resistance during progression of colon cancer.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2297-2305 |
| Number of pages | 9 |
| Journal | Cancer Biology and Therapy |
| Volume | 8 |
| Issue number | 23 |
| State | Published - Dec 1 2009 |
| Externally published | Yes |
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Keywords
- Colon cancer
- Fem1b
- Proteasome
- RACK1
- SW480
- SW620
- Ubiquitin
ASJC Scopus subject areas
- Cancer Research
- Oncology
- Molecular Medicine
- Pharmacology
Cite this
RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells. / Subauste, M. Cecilia; Ventura-Holman, T.; Du, L.; Subauste, Jose S.; Chan, Shing Leng; Yu, Victor C.; Maher, Joseph F.
In: Cancer Biology and Therapy, Vol. 8, No. 23, 01.12.2009, p. 2297-2305.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - RACK1 downregulates levels of the pro-apoptotic protein Fem1b in apoptosis-resistant colon cancer cells
AU - Subauste, M. Cecilia
AU - Ventura-Holman, T.
AU - Du, L.
AU - Subauste, Jose S.
AU - Chan, Shing Leng
AU - Yu, Victor C.
AU - Maher, Joseph F.
PY - 2009/12/1
Y1 - 2009/12/1
N2 - Evasion of apoptosis plays an important role in colon cancer progression. Following loss of the Apc tumor suppressor gene in mice, the gene encoding Fem1b is upregulated early in neoplastic intestinal epithelium. Fem1b is a pro-apoptotic protein that interacts with Fas, TNFR1 and apaf-1, and increased expression of Fem1b induces apoptosis of cancer cells. Fem1b is a homolog of FeM-1, a protein in Caenorhabditis elegans that is negatively regulated by ubiquitination and proteasomal degradation. To study Fem1b regulation in colon cancer progression, we used apoptotis-sensitive SW480 cells, derived from a primary colon cancer, and their isogenic, apoptosis-resistant counterparts sW620 cells, derived from a subsequent metastatic lesion in the same patient. Treatment with proteasome inhibitor increased Fem1b protein levels in SW620 cells, but not in SW480 cells. In SW620 cells we found that endogenous Fem1b co-immunoprecipitates in complexes with RACK1, a protein known to mediate ubiquitination and proteasomal degradation of other pro-apoptotic proteins and to be upregulated in colon cancer. Full-length Fem1b, or the N-terminal region of Fem1b, associated with RACK1 when co-expressed in HEK293T cells, and RACK1 stimulated ubiquitination of Fem1b. RACK1 overexpression in SW620 cells led to downregulation of Fem1b protein levels. Conversely, downregulation of RACK1 led to upregulation of Fem1b protein levels, associated with induction of apoptosis, and this apoptosis was inhibited by blocking Fem1b protein upregulation. In conclusion, RACK1 downregulates levels of the pro-apoptotic protein Fem1b in metastatic, apoptosis-resistant colon cancer cells, which may promote apoptosis-resistance during progression of colon cancer.
AB - Evasion of apoptosis plays an important role in colon cancer progression. Following loss of the Apc tumor suppressor gene in mice, the gene encoding Fem1b is upregulated early in neoplastic intestinal epithelium. Fem1b is a pro-apoptotic protein that interacts with Fas, TNFR1 and apaf-1, and increased expression of Fem1b induces apoptosis of cancer cells. Fem1b is a homolog of FeM-1, a protein in Caenorhabditis elegans that is negatively regulated by ubiquitination and proteasomal degradation. To study Fem1b regulation in colon cancer progression, we used apoptotis-sensitive SW480 cells, derived from a primary colon cancer, and their isogenic, apoptosis-resistant counterparts sW620 cells, derived from a subsequent metastatic lesion in the same patient. Treatment with proteasome inhibitor increased Fem1b protein levels in SW620 cells, but not in SW480 cells. In SW620 cells we found that endogenous Fem1b co-immunoprecipitates in complexes with RACK1, a protein known to mediate ubiquitination and proteasomal degradation of other pro-apoptotic proteins and to be upregulated in colon cancer. Full-length Fem1b, or the N-terminal region of Fem1b, associated with RACK1 when co-expressed in HEK293T cells, and RACK1 stimulated ubiquitination of Fem1b. RACK1 overexpression in SW620 cells led to downregulation of Fem1b protein levels. Conversely, downregulation of RACK1 led to upregulation of Fem1b protein levels, associated with induction of apoptosis, and this apoptosis was inhibited by blocking Fem1b protein upregulation. In conclusion, RACK1 downregulates levels of the pro-apoptotic protein Fem1b in metastatic, apoptosis-resistant colon cancer cells, which may promote apoptosis-resistance during progression of colon cancer.
KW - Colon cancer
KW - Fem1b
KW - Proteasome
KW - RACK1
KW - SW480
KW - SW620
KW - Ubiquitin
UR - http://www.scopus.com/inward/record.url?scp=73949109266&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=73949109266&partnerID=8YFLogxK
M3 - Article
C2 - 19855191
AN - SCOPUS:73949109266
VL - 8
SP - 2297
EP - 2305
JO - Cancer Biology and Therapy
JF - Cancer Biology and Therapy
SN - 1538-4047
IS - 23
ER -