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Breast cancers with high DSS1 expression that potentially maintains BRCA2 stability have poor prognosis in the relapse-free survival.

Rezano A, Kuwahara K, Yamamoto-Ibusuki M, Kitabatake M, Moolthiya P, Phimsen S, Suda T, Tone S, Yamamoto Y, Iwase H, Sakaguchi N - BMC Cancer (2013)

Bottom Line: Patient survival was compared using Kaplan-Meier method.DSS1 high-expression reduces the susceptibility of MCF7 cells to DNA-damaging drugs, as observed in cell cycle and apoptosis analyses.DSS1 is necessary to rescue cells from DNA damage, but high DSS1 expression increases drug resistance.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Immunology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1, Honjo, Chuo-ku, Kumamoto 860-8556, Japan. nobusaka@kumamoto-u.ac.jp.

ABSTRACT

Background: Genetic BRCA2 insufficiency is associated with breast cancer development; however, in sporadic breast cancer cases, high BRCA2 expression is paradoxically correlated with poor prognosis. Because DSS1, a mammalian component of the transcription/RNA export complex, is known to stabilize BRCA2, we investigated how the expression of DSS1 is associated with clinical parameters in breast cancers.

Methods: DSS1 mRNA and p53 protein were examined by RT-PCR and immunohistochemical staining of breast cancer specimens to classify DSS1(high) and DSS1(low) or p53(high) and p53(low) groups. Patient survival was compared using Kaplan-Meier method. DSS1(high) or DSS1(low) breast cancer cells were prepared by retroviral cDNA transfection or DSS1 siRNA on proliferation, cell cycle progression, and survival by flow cytometric analyses with or without anti-cancer drugs.

Results: In comparison to patients with low levels of DSS1, high-DSS1 patients showed a poorer prognosis, with respect to relapse-free survival period. The effect of DSS1 was examined in breast cancer cells in vitro. DSS1 high-expression reduces the susceptibility of MCF7 cells to DNA-damaging drugs, as observed in cell cycle and apoptosis analyses. DSS1 knockdown, however, increased the susceptibility to the DNA-damaging drugs camptothecin and etoposide and caused early apoptosis in p53 wild type MCF7 and p53-insufficient MDA-MB-231 cells. DSS1 knockdown suppresses the proliferation of drug-resistant MDA-MB-231 breast cancer cells, particularly effectively in combination with DNA-damaging agents.

Conclusion: Breast cancers with high DSS1 expression have worse prognosis and shorter relapse-free survival times. DSS1 is necessary to rescue cells from DNA damage, but high DSS1 expression increases drug resistance. We suggest that DSS1 expression could be a useful marker for drug resistance in breast cancers, and DSS1 knockdown can induce tumor apoptosis when used in combination with DNA-damaging drugs.

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Effect of DSS1 knockdown on the drug sensitivity of MCF7 and MDA-MB-231 cells. Drug sensitivity was examined in DSS1 knockdown cells with an optimized dose of CPT (50 μM) and ETP (50 μM). MCF7 and MDA-MB-231 cells were first treated with siDSS1 for 2 days and then cultured with CPT (A) or ETP (B) for 2 days. (A) and (B) The number of cells in the sub-G1 (dead) cell populations was compared between siDSS1-(a)- or siCtrl-treated cells. The results of cell cycle profiling (left) were converted into the graph, which represents more than three independent experiments (right). Statistical significance was assessed by Student’s t-test, with **P < 0.01 and ***P < 0.001.
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Figure 6: Effect of DSS1 knockdown on the drug sensitivity of MCF7 and MDA-MB-231 cells. Drug sensitivity was examined in DSS1 knockdown cells with an optimized dose of CPT (50 μM) and ETP (50 μM). MCF7 and MDA-MB-231 cells were first treated with siDSS1 for 2 days and then cultured with CPT (A) or ETP (B) for 2 days. (A) and (B) The number of cells in the sub-G1 (dead) cell populations was compared between siDSS1-(a)- or siCtrl-treated cells. The results of cell cycle profiling (left) were converted into the graph, which represents more than three independent experiments (right). Statistical significance was assessed by Student’s t-test, with **P < 0.01 and ***P < 0.001.

Mentions: To confirm the effect of DSS1 on breast cancer cells, we investigated the effect of DSS1 knockdown on cell cycle and cell death in breast cancer cells during early stages of treatment with CPT or ETP. DSS1 knockdown markedly increased the number of cells in the sub-G1 apoptotic population in both MCF7 and MDA-MB-231 cells treated with CPT as early as day 2 (Figure 6A). Similarly, DSS1 knockdown increased the sub-G1 population in both breast cancer cell lines treated with ETP (Figure 6B). Because MDA-MB-231 cells, which are of mesenchymal origin and have a triple-negative phenotype[22], are well known to be resistant to several DNA-damaging agents, these data suggested that DSS1 depletion can increase chemosensitivity in drug-resistant breast cancer cells with either wild type or mutant p53.


Breast cancers with high DSS1 expression that potentially maintains BRCA2 stability have poor prognosis in the relapse-free survival.

Rezano A, Kuwahara K, Yamamoto-Ibusuki M, Kitabatake M, Moolthiya P, Phimsen S, Suda T, Tone S, Yamamoto Y, Iwase H, Sakaguchi N - BMC Cancer (2013)

Effect of DSS1 knockdown on the drug sensitivity of MCF7 and MDA-MB-231 cells. Drug sensitivity was examined in DSS1 knockdown cells with an optimized dose of CPT (50 μM) and ETP (50 μM). MCF7 and MDA-MB-231 cells were first treated with siDSS1 for 2 days and then cultured with CPT (A) or ETP (B) for 2 days. (A) and (B) The number of cells in the sub-G1 (dead) cell populations was compared between siDSS1-(a)- or siCtrl-treated cells. The results of cell cycle profiling (left) were converted into the graph, which represents more than three independent experiments (right). Statistical significance was assessed by Student’s t-test, with **P < 0.01 and ***P < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219476&req=5

Figure 6: Effect of DSS1 knockdown on the drug sensitivity of MCF7 and MDA-MB-231 cells. Drug sensitivity was examined in DSS1 knockdown cells with an optimized dose of CPT (50 μM) and ETP (50 μM). MCF7 and MDA-MB-231 cells were first treated with siDSS1 for 2 days and then cultured with CPT (A) or ETP (B) for 2 days. (A) and (B) The number of cells in the sub-G1 (dead) cell populations was compared between siDSS1-(a)- or siCtrl-treated cells. The results of cell cycle profiling (left) were converted into the graph, which represents more than three independent experiments (right). Statistical significance was assessed by Student’s t-test, with **P < 0.01 and ***P < 0.001.
Mentions: To confirm the effect of DSS1 on breast cancer cells, we investigated the effect of DSS1 knockdown on cell cycle and cell death in breast cancer cells during early stages of treatment with CPT or ETP. DSS1 knockdown markedly increased the number of cells in the sub-G1 apoptotic population in both MCF7 and MDA-MB-231 cells treated with CPT as early as day 2 (Figure 6A). Similarly, DSS1 knockdown increased the sub-G1 population in both breast cancer cell lines treated with ETP (Figure 6B). Because MDA-MB-231 cells, which are of mesenchymal origin and have a triple-negative phenotype[22], are well known to be resistant to several DNA-damaging agents, these data suggested that DSS1 depletion can increase chemosensitivity in drug-resistant breast cancer cells with either wild type or mutant p53.

Bottom Line: Patient survival was compared using Kaplan-Meier method.DSS1 high-expression reduces the susceptibility of MCF7 cells to DNA-damaging drugs, as observed in cell cycle and apoptosis analyses.DSS1 is necessary to rescue cells from DNA damage, but high DSS1 expression increases drug resistance.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Immunology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1, Honjo, Chuo-ku, Kumamoto 860-8556, Japan. nobusaka@kumamoto-u.ac.jp.

ABSTRACT

Background: Genetic BRCA2 insufficiency is associated with breast cancer development; however, in sporadic breast cancer cases, high BRCA2 expression is paradoxically correlated with poor prognosis. Because DSS1, a mammalian component of the transcription/RNA export complex, is known to stabilize BRCA2, we investigated how the expression of DSS1 is associated with clinical parameters in breast cancers.

Methods: DSS1 mRNA and p53 protein were examined by RT-PCR and immunohistochemical staining of breast cancer specimens to classify DSS1(high) and DSS1(low) or p53(high) and p53(low) groups. Patient survival was compared using Kaplan-Meier method. DSS1(high) or DSS1(low) breast cancer cells were prepared by retroviral cDNA transfection or DSS1 siRNA on proliferation, cell cycle progression, and survival by flow cytometric analyses with or without anti-cancer drugs.

Results: In comparison to patients with low levels of DSS1, high-DSS1 patients showed a poorer prognosis, with respect to relapse-free survival period. The effect of DSS1 was examined in breast cancer cells in vitro. DSS1 high-expression reduces the susceptibility of MCF7 cells to DNA-damaging drugs, as observed in cell cycle and apoptosis analyses. DSS1 knockdown, however, increased the susceptibility to the DNA-damaging drugs camptothecin and etoposide and caused early apoptosis in p53 wild type MCF7 and p53-insufficient MDA-MB-231 cells. DSS1 knockdown suppresses the proliferation of drug-resistant MDA-MB-231 breast cancer cells, particularly effectively in combination with DNA-damaging agents.

Conclusion: Breast cancers with high DSS1 expression have worse prognosis and shorter relapse-free survival times. DSS1 is necessary to rescue cells from DNA damage, but high DSS1 expression increases drug resistance. We suggest that DSS1 expression could be a useful marker for drug resistance in breast cancers, and DSS1 knockdown can induce tumor apoptosis when used in combination with DNA-damaging drugs.

Show MeSH
Related in: MedlinePlus