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MMP-9 expression varies according to molecular subtypes of breast cancer.

Yousef EM, Tahir MR, St-Pierre Y, Gaboury LA - BMC Cancer (2014)

Bottom Line: We next ascertained MMP-9 expression in both normal breast tissue and in human breast carcinoma tissue microarrays.Significant increase in MMP-9 expression was found in breast cancer cells where compared to normal breast tissue.Lastly, the clinical relevance of MMP-9 overexpression is strongly supported by its significant association with a higher incidence of metastasis and relapse.

View Article: PubMed Central - PubMed

Affiliation: Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Canada. louis.gaboury@umontreal.ca.

ABSTRACT

Background: In 2014, breast cancer remains a major cause of mortality worldwide mostly due to tumor relapse and metastasis. There is currently a great interest in identifying cancer biomarkers and signalling pathways mechanistically related to breast cancer progression. Matrix metalloproteinase-9 (MMP-9) is a member of matrix degrading enzymes involved in cancer development, invasion and metastasis. Our objective was to investigate MMP-9 expression in normal human breast tissue and to compare it to that of breast cancer of various histological grades and molecular subtypes. We also sought to correlate MMP-9 expression with the incidence of metastasis, survival rates and relapse in breast cancer patients.

Methods: MMP-9 was first studied using in silico analysis on available DNA microarray and RNA sequencing data of human breast cancer tissues and human breast cancer cell lines. We next ascertained MMP-9 expression in both normal breast tissue and in human breast carcinoma tissue microarrays.

Results: Significant increase in MMP-9 expression was found in breast cancer cells where compared to normal breast tissue. A positive correlation could also be established between elevated levels of MMP-9 and breast cancer of high histological grade. Furthermore, our results indicate that not only MMP-9 is differentially expressed between each molecular subset but also, more importantly MMP-9 overexpression revealed itself as a startling feature of triple-negative and HER2-positive breast cancers. Lastly, the clinical relevance of MMP-9 overexpression is strongly supported by its significant association with a higher incidence of metastasis and relapse.

Conclusions: Differential expression of MMP-9 reflects the extent of cellular differentiation in breast cancer cells and is closely related to the most aggressive subtypes of breast cancer. Hence, MMP-9 is a promising prognostic biomarker of high-grade breast cancer. In our opinion, MMP-9 expression could help segregate subsets of aggressive breast cancer into clinically meaningful subtypes.

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Related in: MedlinePlus

Overexpression of MMP-9 is associated with triple-negative, HER2-positive breast tumors and nodal metastases. (A) Histogram showing percentage of breast cancer patients in each molecular subtype category that express low and high level of MMP-9. Both HER2-positive and triple-negative subtypes demonstrate elevated levels of MMP-9 that are significantly different from those observed in normal breast tissue. The number of patients in each group was mentioned over each bar. The overall relationship between MMP-9 scores and molecular subtypes was evaluated using the chi-square test. (B) Luminal A and (C) Luminal B subtypes showing low level of MMP-9 expression. (D) HER2-positive and (E) Triple-negative subtypes displaying strong cytoplasmic labeling in cancer cells and surrounding stromal cells. (F) Metastatic lymph node demonstrating elevated levels of MMP-9 expression in the cytoplasm of metastatic breast cancer cells. The surrounding lymphocytic and stromal cells did not stain with anti-MMP-9 antibody. Magnification 20X (B-E), 5X (F), 40X inset in Figure 5F.
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Fig5: Overexpression of MMP-9 is associated with triple-negative, HER2-positive breast tumors and nodal metastases. (A) Histogram showing percentage of breast cancer patients in each molecular subtype category that express low and high level of MMP-9. Both HER2-positive and triple-negative subtypes demonstrate elevated levels of MMP-9 that are significantly different from those observed in normal breast tissue. The number of patients in each group was mentioned over each bar. The overall relationship between MMP-9 scores and molecular subtypes was evaluated using the chi-square test. (B) Luminal A and (C) Luminal B subtypes showing low level of MMP-9 expression. (D) HER2-positive and (E) Triple-negative subtypes displaying strong cytoplasmic labeling in cancer cells and surrounding stromal cells. (F) Metastatic lymph node demonstrating elevated levels of MMP-9 expression in the cytoplasm of metastatic breast cancer cells. The surrounding lymphocytic and stromal cells did not stain with anti-MMP-9 antibody. Magnification 20X (B-E), 5X (F), 40X inset in Figure 5F.

Mentions: Next we aimed to validate the results obtained from the in silico analysis on human breast tissue. We studied the expression of MMP-9 at the protein level and assessed the cellular and subcellular localization of MMP-9. MMP-9 expression was evaluated in 300 human tumor tissues representative of each molecular subtypes of breast cancer whose definition was based on the use of the following surrogate markers: ER, PR, HER2 and Ki-67 [22]. As shown in Figure 5A, only 33.3% of luminal A (p = 0.05) and 43.3% of luminal B (p < 0.01) expressed elevated levels of MMP-9. In contrast, high levels of MMP-9 expression were found in 87.9% of HER2-positive and 79.4% of triple-negative breast cancer when compared to normal (p < 0.001). Low levels of MMP-9 expression were detected in the cytoplasm of cancer cells in both luminal A and B breast tumors. Indigenous stromal cells surrounding cancer cells in luminal A and B revealed only faint levels of MMP-9 expression (Figure 5B and C). On the other hand, elevated levels of MMP-9 expression were detected in the stroma surrounding cancer cells in both triple-negative and HER2-positive breast cancer. Nevertheless, the level of MMP-9 in the cytoplasm of cancer cells always exceeded that found in adjacent stromal cells (Figure 5D and E). Furthermore, when MMP-9 levels were evaluated in the cytoplasm of carcinoma cells present in 13 metastatic lymph nodes, it was found that all tumor cells (100%) displayed elevated levels of MMP-9 whereas the surrounding lymphocytic and stromal cells failed to express MMP-9 (Figure 5F).Figure 5


MMP-9 expression varies according to molecular subtypes of breast cancer.

Yousef EM, Tahir MR, St-Pierre Y, Gaboury LA - BMC Cancer (2014)

Overexpression of MMP-9 is associated with triple-negative, HER2-positive breast tumors and nodal metastases. (A) Histogram showing percentage of breast cancer patients in each molecular subtype category that express low and high level of MMP-9. Both HER2-positive and triple-negative subtypes demonstrate elevated levels of MMP-9 that are significantly different from those observed in normal breast tissue. The number of patients in each group was mentioned over each bar. The overall relationship between MMP-9 scores and molecular subtypes was evaluated using the chi-square test. (B) Luminal A and (C) Luminal B subtypes showing low level of MMP-9 expression. (D) HER2-positive and (E) Triple-negative subtypes displaying strong cytoplasmic labeling in cancer cells and surrounding stromal cells. (F) Metastatic lymph node demonstrating elevated levels of MMP-9 expression in the cytoplasm of metastatic breast cancer cells. The surrounding lymphocytic and stromal cells did not stain with anti-MMP-9 antibody. Magnification 20X (B-E), 5X (F), 40X inset in Figure 5F.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4150970&req=5

Fig5: Overexpression of MMP-9 is associated with triple-negative, HER2-positive breast tumors and nodal metastases. (A) Histogram showing percentage of breast cancer patients in each molecular subtype category that express low and high level of MMP-9. Both HER2-positive and triple-negative subtypes demonstrate elevated levels of MMP-9 that are significantly different from those observed in normal breast tissue. The number of patients in each group was mentioned over each bar. The overall relationship between MMP-9 scores and molecular subtypes was evaluated using the chi-square test. (B) Luminal A and (C) Luminal B subtypes showing low level of MMP-9 expression. (D) HER2-positive and (E) Triple-negative subtypes displaying strong cytoplasmic labeling in cancer cells and surrounding stromal cells. (F) Metastatic lymph node demonstrating elevated levels of MMP-9 expression in the cytoplasm of metastatic breast cancer cells. The surrounding lymphocytic and stromal cells did not stain with anti-MMP-9 antibody. Magnification 20X (B-E), 5X (F), 40X inset in Figure 5F.
Mentions: Next we aimed to validate the results obtained from the in silico analysis on human breast tissue. We studied the expression of MMP-9 at the protein level and assessed the cellular and subcellular localization of MMP-9. MMP-9 expression was evaluated in 300 human tumor tissues representative of each molecular subtypes of breast cancer whose definition was based on the use of the following surrogate markers: ER, PR, HER2 and Ki-67 [22]. As shown in Figure 5A, only 33.3% of luminal A (p = 0.05) and 43.3% of luminal B (p < 0.01) expressed elevated levels of MMP-9. In contrast, high levels of MMP-9 expression were found in 87.9% of HER2-positive and 79.4% of triple-negative breast cancer when compared to normal (p < 0.001). Low levels of MMP-9 expression were detected in the cytoplasm of cancer cells in both luminal A and B breast tumors. Indigenous stromal cells surrounding cancer cells in luminal A and B revealed only faint levels of MMP-9 expression (Figure 5B and C). On the other hand, elevated levels of MMP-9 expression were detected in the stroma surrounding cancer cells in both triple-negative and HER2-positive breast cancer. Nevertheless, the level of MMP-9 in the cytoplasm of cancer cells always exceeded that found in adjacent stromal cells (Figure 5D and E). Furthermore, when MMP-9 levels were evaluated in the cytoplasm of carcinoma cells present in 13 metastatic lymph nodes, it was found that all tumor cells (100%) displayed elevated levels of MMP-9 whereas the surrounding lymphocytic and stromal cells failed to express MMP-9 (Figure 5F).Figure 5

Bottom Line: We next ascertained MMP-9 expression in both normal breast tissue and in human breast carcinoma tissue microarrays.Significant increase in MMP-9 expression was found in breast cancer cells where compared to normal breast tissue.Lastly, the clinical relevance of MMP-9 overexpression is strongly supported by its significant association with a higher incidence of metastasis and relapse.

View Article: PubMed Central - PubMed

Affiliation: Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Canada. louis.gaboury@umontreal.ca.

ABSTRACT

Background: In 2014, breast cancer remains a major cause of mortality worldwide mostly due to tumor relapse and metastasis. There is currently a great interest in identifying cancer biomarkers and signalling pathways mechanistically related to breast cancer progression. Matrix metalloproteinase-9 (MMP-9) is a member of matrix degrading enzymes involved in cancer development, invasion and metastasis. Our objective was to investigate MMP-9 expression in normal human breast tissue and to compare it to that of breast cancer of various histological grades and molecular subtypes. We also sought to correlate MMP-9 expression with the incidence of metastasis, survival rates and relapse in breast cancer patients.

Methods: MMP-9 was first studied using in silico analysis on available DNA microarray and RNA sequencing data of human breast cancer tissues and human breast cancer cell lines. We next ascertained MMP-9 expression in both normal breast tissue and in human breast carcinoma tissue microarrays.

Results: Significant increase in MMP-9 expression was found in breast cancer cells where compared to normal breast tissue. A positive correlation could also be established between elevated levels of MMP-9 and breast cancer of high histological grade. Furthermore, our results indicate that not only MMP-9 is differentially expressed between each molecular subset but also, more importantly MMP-9 overexpression revealed itself as a startling feature of triple-negative and HER2-positive breast cancers. Lastly, the clinical relevance of MMP-9 overexpression is strongly supported by its significant association with a higher incidence of metastasis and relapse.

Conclusions: Differential expression of MMP-9 reflects the extent of cellular differentiation in breast cancer cells and is closely related to the most aggressive subtypes of breast cancer. Hence, MMP-9 is a promising prognostic biomarker of high-grade breast cancer. In our opinion, MMP-9 expression could help segregate subsets of aggressive breast cancer into clinically meaningful subtypes.

Show MeSH
Related in: MedlinePlus