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Period-2: a tumor suppressor gene in breast cancer.

Xiang S, Coffelt SB, Mao L, Yuan L, Cheng Q, Hill SM - J Circadian Rhythms (2008)

Bottom Line: The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies.A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2.Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Structural and Cellular Biology, Tulane University Health Sciences Center, New Orleans, LA 70112, USA. smhill@tulane.edu.

ABSTRACT
Previous reports have suggested that the ablation of the Period 2 gene (Per 2) leads to enhanced development of lymphoma and leukemia in mice. Employing immunoblot analyses, we have demonstrated that PER 2 is endogenously expressed in human breast epithelial cell lines but is not expressed or is expressed at significantly reduced level in human breast cancer cell lines. Expression of PER 2 in MCF-7 breast cancer cells significantly inhibited the growth of MCF-7 human breast cancer cells, and, when PER 2 was co-expressed with the Crytochrome 2 (Cry 2) gene, an even greater growth-inhibitory effect was observed. The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies. A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2. Expression of PER 2 also induced apoptosis of MCF-7 breast cancer cells as demonstrated by an increase in PARP [poly (ADP-ribose) polymerase] cleavage. Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels.

No MeSH data available.


Related in: MedlinePlus

PER 2 expression induces apoptosis in MCF-7 breast cancer cells. (A) MCF-7 cells were transiently transfected with empty vector, vector expressing PER 2, or both vectors expressing PER 2 or CRY 2. After 72 hours, total cell extracts were prepared and subjected to Western blot analysis using an antibody directed against the 85 kDa cleaved fragment of PARP [poly (ADP-ribose) polymerase] (representative of three independent studies). (B) Densitometric analysis of cleaved PARP protein (average value of three independent studies). a. PER 2 or PER 2 + CRY 2 vs vector control, p < 0.001, b PER 2 + CRY 2 vs PER 2, p < 0.01
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Figure 4: PER 2 expression induces apoptosis in MCF-7 breast cancer cells. (A) MCF-7 cells were transiently transfected with empty vector, vector expressing PER 2, or both vectors expressing PER 2 or CRY 2. After 72 hours, total cell extracts were prepared and subjected to Western blot analysis using an antibody directed against the 85 kDa cleaved fragment of PARP [poly (ADP-ribose) polymerase] (representative of three independent studies). (B) Densitometric analysis of cleaved PARP protein (average value of three independent studies). a. PER 2 or PER 2 + CRY 2 vs vector control, p < 0.001, b PER 2 + CRY 2 vs PER 2, p < 0.01

Mentions: To determine if the decreased growth in MCF-7 cells transfected with Per 2 or Per 2 and Cry 2 was the result of increased apoptosis we conduced PARP-cleavage assays. Seventy two hours post transfection cells were harvested and total cell extracts prepared and subjected to Western blot analysis using an antibody directed against the 85 kDa cleaved fragment of PARP [poly (ADP-ribose) polymerase] (Figure 4). MCF-7 cells transfected and expressing Per 2 displayed a significant increase (p < 0.001) in cleaved PARP protein levels by 714.2% when compared to control vector transfected cells. These results show that expression of PER 2 induces apoptosis in MCF-7 human breast cancer cells and that concomitant expression of PER 2 and CRY 2 further increase apoptosis in MCF-7 human breast cancer cells by 689.5% (p < 0.001) compared to transfection controls and 74% (p < 0.01) compared to cells expressing PER 2 alone.


Period-2: a tumor suppressor gene in breast cancer.

Xiang S, Coffelt SB, Mao L, Yuan L, Cheng Q, Hill SM - J Circadian Rhythms (2008)

PER 2 expression induces apoptosis in MCF-7 breast cancer cells. (A) MCF-7 cells were transiently transfected with empty vector, vector expressing PER 2, or both vectors expressing PER 2 or CRY 2. After 72 hours, total cell extracts were prepared and subjected to Western blot analysis using an antibody directed against the 85 kDa cleaved fragment of PARP [poly (ADP-ribose) polymerase] (representative of three independent studies). (B) Densitometric analysis of cleaved PARP protein (average value of three independent studies). a. PER 2 or PER 2 + CRY 2 vs vector control, p < 0.001, b PER 2 + CRY 2 vs PER 2, p < 0.01
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2365929&req=5

Figure 4: PER 2 expression induces apoptosis in MCF-7 breast cancer cells. (A) MCF-7 cells were transiently transfected with empty vector, vector expressing PER 2, or both vectors expressing PER 2 or CRY 2. After 72 hours, total cell extracts were prepared and subjected to Western blot analysis using an antibody directed against the 85 kDa cleaved fragment of PARP [poly (ADP-ribose) polymerase] (representative of three independent studies). (B) Densitometric analysis of cleaved PARP protein (average value of three independent studies). a. PER 2 or PER 2 + CRY 2 vs vector control, p < 0.001, b PER 2 + CRY 2 vs PER 2, p < 0.01
Mentions: To determine if the decreased growth in MCF-7 cells transfected with Per 2 or Per 2 and Cry 2 was the result of increased apoptosis we conduced PARP-cleavage assays. Seventy two hours post transfection cells were harvested and total cell extracts prepared and subjected to Western blot analysis using an antibody directed against the 85 kDa cleaved fragment of PARP [poly (ADP-ribose) polymerase] (Figure 4). MCF-7 cells transfected and expressing Per 2 displayed a significant increase (p < 0.001) in cleaved PARP protein levels by 714.2% when compared to control vector transfected cells. These results show that expression of PER 2 induces apoptosis in MCF-7 human breast cancer cells and that concomitant expression of PER 2 and CRY 2 further increase apoptosis in MCF-7 human breast cancer cells by 689.5% (p < 0.001) compared to transfection controls and 74% (p < 0.01) compared to cells expressing PER 2 alone.

Bottom Line: The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies.A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2.Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Structural and Cellular Biology, Tulane University Health Sciences Center, New Orleans, LA 70112, USA. smhill@tulane.edu.

ABSTRACT
Previous reports have suggested that the ablation of the Period 2 gene (Per 2) leads to enhanced development of lymphoma and leukemia in mice. Employing immunoblot analyses, we have demonstrated that PER 2 is endogenously expressed in human breast epithelial cell lines but is not expressed or is expressed at significantly reduced level in human breast cancer cell lines. Expression of PER 2 in MCF-7 breast cancer cells significantly inhibited the growth of MCF-7 human breast cancer cells, and, when PER 2 was co-expressed with the Crytochrome 2 (Cry 2) gene, an even greater growth-inhibitory effect was observed. The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies. A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2. Expression of PER 2 also induced apoptosis of MCF-7 breast cancer cells as demonstrated by an increase in PARP [poly (ADP-ribose) polymerase] cleavage. Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels.

No MeSH data available.


Related in: MedlinePlus