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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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Survival of patients with primary breast cancers. Patient survival was assessed using the Kaplan-Meier method. Clinical breast cancer patients were followed for more than 120 months and classified into groups based on the expression of DSS1 mRNA, which was determined using qRT-PCR of total RNAs from 289 primary invasive breast cancer patients. (A) BCSS (left) and RFS (right) of the DSS1 low (n = 248) and high (n = 41) groups are shown. Statistical significance was calculated as log-rank: n.s.P = 0.25 (left) and *P = 0.011 (right), respectively. (B) The patient survival was compared using double markers with p53 and DSS1 mRNAs as p53low/DSS1low (n = 120), p53low/DSS1high (n = 31), p53high/DSS1low (n = 85), and p53high/DSS1high (n = 10) groups. Statistical significance was calculated as log-rank: n.s.P = 0.49 (left) and *P = 0.045 (right), respectively.
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Figure 1: Survival of patients with primary breast cancers. Patient survival was assessed using the Kaplan-Meier method. Clinical breast cancer patients were followed for more than 120 months and classified into groups based on the expression of DSS1 mRNA, which was determined using qRT-PCR of total RNAs from 289 primary invasive breast cancer patients. (A) BCSS (left) and RFS (right) of the DSS1 low (n = 248) and high (n = 41) groups are shown. Statistical significance was calculated as log-rank: n.s.P = 0.25 (left) and *P = 0.011 (right), respectively. (B) The patient survival was compared using double markers with p53 and DSS1 mRNAs as p53low/DSS1low (n = 120), p53low/DSS1high (n = 31), p53high/DSS1low (n = 85), and p53high/DSS1high (n = 10) groups. Statistical significance was calculated as log-rank: n.s.P = 0.49 (left) and *P = 0.045 (right), respectively.

Mentions: We examined the survival of breast cancer patients using the Kaplan-Meier method. We analyzed the expression level of DSS1 mRNA by qRT-PCR from the tumor samples obtained at surgery using primers for DSS1 mRNA (Additional file1: Figure S1). The relative expression level was arbitrarily determined and used for classification of breast cancer cases into DSS1-high (DSS1high) and DSS1-low (DSS1low) groups. The DSS1high group showed a significant shorter survival time (*P = 0.011) on the RFS curve, while the difference in the breast cancer specific survival (BCSS) curves was not significant (n.s.; P = 0.25) (Figure 1A). DSS1 physically interacts with the RPN3/S3 proteasomal subunit, which increases the degradation of ubiquitinated p53[20]. In a large cohort, over-expression of p53 was significantly associated with poor prognosis in premenopausal women treated with tamoxifen after chemotherapy[21]. The p53 expression was used for classification by arbitrarily determined conditions (see Methods). We compared RFS among p53low/DSS1low, p53high/DSS1low, p53low/DSS1high, and p53high/DSS1high groups (Figure 1B). While the number of cases was small, no change of the survival curve was observed when p53 expression was low; however, the DSS1high group showed a worse prognosis in comparison with the DSS1low group in breast cancer cases with high p53 expression (*P = 0.045). Other parameters and markers were compared in the DSS1high and DSS1low groups (Table 1). No significant differences were observed in the groups of pre- or post-menopausal women, positive or negative nodal status, tumor size < 20 or ≥ 20 mm, nuclear grade I to III, positive or negative vessel invasion score, ERα status, and PgR status. However, DSS1 expression showed a significant difference (*P = 0.0255) based on HER2 status, which is presumably associated with effective treatment using trastuzumab as the standard regimen for HER2-positive breast cancer cases. Interestingly, DSS1 expression was markedly increased (55.6; median of DSS1 relative expression) in the group of breast cancer cases with low Ki67 labeling indices (< 20%) compared with the expression (36.0; median of DSS1 relative expression) in the group with high Ki67 labeling indices (≥ 20%).


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)

Survival of patients with primary breast cancers. Patient survival was assessed using the Kaplan-Meier method. Clinical breast cancer patients were followed for more than 120 months and classified into groups based on the expression of DSS1 mRNA, which was determined using qRT-PCR of total RNAs from 289 primary invasive breast cancer patients. (A) BCSS (left) and RFS (right) of the DSS1 low (n = 248) and high (n = 41) groups are shown. Statistical significance was calculated as log-rank: n.s.P = 0.25 (left) and *P = 0.011 (right), respectively. (B) The patient survival was compared using double markers with p53 and DSS1 mRNAs as p53low/DSS1low (n = 120), p53low/DSS1high (n = 31), p53high/DSS1low (n = 85), and p53high/DSS1high (n = 10) groups. Statistical significance was calculated as log-rank: n.s.P = 0.49 (left) and *P = 0.045 (right), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 1: Survival of patients with primary breast cancers. Patient survival was assessed using the Kaplan-Meier method. Clinical breast cancer patients were followed for more than 120 months and classified into groups based on the expression of DSS1 mRNA, which was determined using qRT-PCR of total RNAs from 289 primary invasive breast cancer patients. (A) BCSS (left) and RFS (right) of the DSS1 low (n = 248) and high (n = 41) groups are shown. Statistical significance was calculated as log-rank: n.s.P = 0.25 (left) and *P = 0.011 (right), respectively. (B) The patient survival was compared using double markers with p53 and DSS1 mRNAs as p53low/DSS1low (n = 120), p53low/DSS1high (n = 31), p53high/DSS1low (n = 85), and p53high/DSS1high (n = 10) groups. Statistical significance was calculated as log-rank: n.s.P = 0.49 (left) and *P = 0.045 (right), respectively.
Mentions: We examined the survival of breast cancer patients using the Kaplan-Meier method. We analyzed the expression level of DSS1 mRNA by qRT-PCR from the tumor samples obtained at surgery using primers for DSS1 mRNA (Additional file1: Figure S1). The relative expression level was arbitrarily determined and used for classification of breast cancer cases into DSS1-high (DSS1high) and DSS1-low (DSS1low) groups. The DSS1high group showed a significant shorter survival time (*P = 0.011) on the RFS curve, while the difference in the breast cancer specific survival (BCSS) curves was not significant (n.s.; P = 0.25) (Figure 1A). DSS1 physically interacts with the RPN3/S3 proteasomal subunit, which increases the degradation of ubiquitinated p53[20]. In a large cohort, over-expression of p53 was significantly associated with poor prognosis in premenopausal women treated with tamoxifen after chemotherapy[21]. The p53 expression was used for classification by arbitrarily determined conditions (see Methods). We compared RFS among p53low/DSS1low, p53high/DSS1low, p53low/DSS1high, and p53high/DSS1high groups (Figure 1B). While the number of cases was small, no change of the survival curve was observed when p53 expression was low; however, the DSS1high group showed a worse prognosis in comparison with the DSS1low group in breast cancer cases with high p53 expression (*P = 0.045). Other parameters and markers were compared in the DSS1high and DSS1low groups (Table 1). No significant differences were observed in the groups of pre- or post-menopausal women, positive or negative nodal status, tumor size < 20 or ≥ 20 mm, nuclear grade I to III, positive or negative vessel invasion score, ERα status, and PgR status. However, DSS1 expression showed a significant difference (*P = 0.0255) based on HER2 status, which is presumably associated with effective treatment using trastuzumab as the standard regimen for HER2-positive breast cancer cases. Interestingly, DSS1 expression was markedly increased (55.6; median of DSS1 relative expression) in the group of breast cancer cases with low Ki67 labeling indices (< 20%) compared with the expression (36.0; median of DSS1 relative expression) in the group with high Ki67 labeling indices (≥ 20%).

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