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A distinct macrophage population mediates metastatic breast cancer cell extravasation, establishment and growth.

Qian B, Deng Y, Im JH, Muschel RJ, Zou Y, Li J, Lang RA, Pollard JW - PLoS ONE (2009)

Bottom Line: Using animal models of breast cancer metastasis, we show that a population of host macrophages displaying a distinct phenotype is recruited to extravasating pulmonary metastatic cells regardless of species of origin.Furthermore, imaging of intact lungs revealed that macrophages are required for efficient tumor cell extravasation.These data indicate a direct enhancement of metastatic growth by macrophages through their effects on tumor cell extravasation, survival and subsequent growth and identifies these cells as a new therapeutic target for treatment of metastatic disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental and Molecular Biology and the Department of Obstetrics/Gynecology and Woman's Health, Center for the Study of Reproductive Biology and Woman's Health, Albert Einstein College of Medicine, Bronx, NY, USA.

ABSTRACT

Background: The stromal microenvironment and particularly the macrophage component of primary tumors influence their malignant potential. However, at the metastatic site the role of these cells and their mechanism of actions for establishment and growth of metastases remain largely unknown.

Methodology/principal findings: Using animal models of breast cancer metastasis, we show that a population of host macrophages displaying a distinct phenotype is recruited to extravasating pulmonary metastatic cells regardless of species of origin. Ablation of this macrophage population through three independent means (genetic and chemical) showed that these macrophages are required for efficient metastatic seeding and growth. Importantly, even after metastatic growth is established, ablation of this macrophage population inhibited subsequent growth. Furthermore, imaging of intact lungs revealed that macrophages are required for efficient tumor cell extravasation.

Conclusion/significance: These data indicate a direct enhancement of metastatic growth by macrophages through their effects on tumor cell extravasation, survival and subsequent growth and identifies these cells as a new therapeutic target for treatment of metastatic disease.

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Related in: MedlinePlus

Recruitment of a distinct macrophage population in metastasis bearing lungs.(A–D) Pulmonary metastasis of breast cancer cells are highly infiltrated with macrophages. Representative Mac3 immunohistochemistry staining of transverse sections of lung metastatic lesions from different tumor models: (A) experimental metastasis of primary PyMT tumor cells; (B) spontaneous metastasis derived from a MMTV-PyMT induced mammary tumor; (C) experimental metastasis of Met-1 cells and (D) spontaneous metastasis derived from subcutaneously implanted MDA-231 cells. Bar equals 20 um. (E) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and metastasis bearing lung from experimental metastasis assay of Met-1 cells (lower panel). n = 5 (F) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and lung bearing spontaneous metastasis from MMTV-PyMT induced mouse mammary tumor (lower panel). n = 3 (G) Recruitment of CD11b+Gr1- macrophages (F4/80+) in lungs with experimentally induced metastasis with Met-1 cells. Lungs were harvested at time indicated after tumor cell i.v. injection. Data are shown as mean+SEM. n = 3, *p<0.05 and **P<0.01. (H) Representative flow histograms of normal lung macrophages (F4/80+, blue dashed line) versus recruited macrophage population (F4/80+CD11b+Gr1-, red solid line) from lungs bearing Met-1 cell metastases stained with antibodies of different cell surface makers (indicated at the right side of the histogram). X axis indicates the fluorescent intensity, Y axis indicates the percentage of maximum cell number, MFI (top right panel) denotes representative mean fluorescent intensity (n = 3).
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pone-0006562-g003: Recruitment of a distinct macrophage population in metastasis bearing lungs.(A–D) Pulmonary metastasis of breast cancer cells are highly infiltrated with macrophages. Representative Mac3 immunohistochemistry staining of transverse sections of lung metastatic lesions from different tumor models: (A) experimental metastasis of primary PyMT tumor cells; (B) spontaneous metastasis derived from a MMTV-PyMT induced mammary tumor; (C) experimental metastasis of Met-1 cells and (D) spontaneous metastasis derived from subcutaneously implanted MDA-231 cells. Bar equals 20 um. (E) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and metastasis bearing lung from experimental metastasis assay of Met-1 cells (lower panel). n = 5 (F) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and lung bearing spontaneous metastasis from MMTV-PyMT induced mouse mammary tumor (lower panel). n = 3 (G) Recruitment of CD11b+Gr1- macrophages (F4/80+) in lungs with experimentally induced metastasis with Met-1 cells. Lungs were harvested at time indicated after tumor cell i.v. injection. Data are shown as mean+SEM. n = 3, *p<0.05 and **P<0.01. (H) Representative flow histograms of normal lung macrophages (F4/80+, blue dashed line) versus recruited macrophage population (F4/80+CD11b+Gr1-, red solid line) from lungs bearing Met-1 cell metastases stained with antibodies of different cell surface makers (indicated at the right side of the histogram). X axis indicates the fluorescent intensity, Y axis indicates the percentage of maximum cell number, MFI (top right panel) denotes representative mean fluorescent intensity (n = 3).

Mentions: The above data strongly argues for a macrophage population enhancing both seeding and persistent growth of metastatic cells. In mice homozygous for the Csf1op mutation the lung resident macrophage population is relatively normal in tissue distribution, morphology, number and cell surface markers (Figure S3), consistent with previous reports [28]. This is probably due to the fact that the lung resident macrophages are largely regulated by GM-CSF instead of CSF-1 [29]. In addition, deletion of alveolar macrophage by intra-tracheal injection of L-Clodronate does not affect Met-1 cell metastatic efficiency (data not shown). These data strongly suggest that a distinct macrophage population is recruited from the blood to the metastatic cells in lung. First to establish whether macrophages are recruited to the pulmonary metastases, immunohistochemical staining using anti-Mac3 (a macrophage specific marker [30]) antibody was performed. In the experimentally induced metastasis formed either by primary PyMT tumor cells or Met-1 cells (Figure 3A, C), there was an abundant infiltration of macrophages. This was not a cell-type or route of injection specific phenomena because an intensive macrophage infiltration was also seen in the spontaneous metastases derived from late stage primary tumors of PyMT mice (Figure 3B) and in spontaneous metastasis derived from a subcutaneously implanted human breast cancer cell (MDA-231) in nude mice (Figure 3D). These data show that macrophages are recruited to metastatic lesions regardless of their origin.


A distinct macrophage population mediates metastatic breast cancer cell extravasation, establishment and growth.

Qian B, Deng Y, Im JH, Muschel RJ, Zou Y, Li J, Lang RA, Pollard JW - PLoS ONE (2009)

Recruitment of a distinct macrophage population in metastasis bearing lungs.(A–D) Pulmonary metastasis of breast cancer cells are highly infiltrated with macrophages. Representative Mac3 immunohistochemistry staining of transverse sections of lung metastatic lesions from different tumor models: (A) experimental metastasis of primary PyMT tumor cells; (B) spontaneous metastasis derived from a MMTV-PyMT induced mammary tumor; (C) experimental metastasis of Met-1 cells and (D) spontaneous metastasis derived from subcutaneously implanted MDA-231 cells. Bar equals 20 um. (E) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and metastasis bearing lung from experimental metastasis assay of Met-1 cells (lower panel). n = 5 (F) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and lung bearing spontaneous metastasis from MMTV-PyMT induced mouse mammary tumor (lower panel). n = 3 (G) Recruitment of CD11b+Gr1- macrophages (F4/80+) in lungs with experimentally induced metastasis with Met-1 cells. Lungs were harvested at time indicated after tumor cell i.v. injection. Data are shown as mean+SEM. n = 3, *p<0.05 and **P<0.01. (H) Representative flow histograms of normal lung macrophages (F4/80+, blue dashed line) versus recruited macrophage population (F4/80+CD11b+Gr1-, red solid line) from lungs bearing Met-1 cell metastases stained with antibodies of different cell surface makers (indicated at the right side of the histogram). X axis indicates the fluorescent intensity, Y axis indicates the percentage of maximum cell number, MFI (top right panel) denotes representative mean fluorescent intensity (n = 3).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2721818&req=5

pone-0006562-g003: Recruitment of a distinct macrophage population in metastasis bearing lungs.(A–D) Pulmonary metastasis of breast cancer cells are highly infiltrated with macrophages. Representative Mac3 immunohistochemistry staining of transverse sections of lung metastatic lesions from different tumor models: (A) experimental metastasis of primary PyMT tumor cells; (B) spontaneous metastasis derived from a MMTV-PyMT induced mammary tumor; (C) experimental metastasis of Met-1 cells and (D) spontaneous metastasis derived from subcutaneously implanted MDA-231 cells. Bar equals 20 um. (E) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and metastasis bearing lung from experimental metastasis assay of Met-1 cells (lower panel). n = 5 (F) Representative flow diagram of CSF-1R-GFP positive cells from normal lung (upper panel) and lung bearing spontaneous metastasis from MMTV-PyMT induced mouse mammary tumor (lower panel). n = 3 (G) Recruitment of CD11b+Gr1- macrophages (F4/80+) in lungs with experimentally induced metastasis with Met-1 cells. Lungs were harvested at time indicated after tumor cell i.v. injection. Data are shown as mean+SEM. n = 3, *p<0.05 and **P<0.01. (H) Representative flow histograms of normal lung macrophages (F4/80+, blue dashed line) versus recruited macrophage population (F4/80+CD11b+Gr1-, red solid line) from lungs bearing Met-1 cell metastases stained with antibodies of different cell surface makers (indicated at the right side of the histogram). X axis indicates the fluorescent intensity, Y axis indicates the percentage of maximum cell number, MFI (top right panel) denotes representative mean fluorescent intensity (n = 3).
Mentions: The above data strongly argues for a macrophage population enhancing both seeding and persistent growth of metastatic cells. In mice homozygous for the Csf1op mutation the lung resident macrophage population is relatively normal in tissue distribution, morphology, number and cell surface markers (Figure S3), consistent with previous reports [28]. This is probably due to the fact that the lung resident macrophages are largely regulated by GM-CSF instead of CSF-1 [29]. In addition, deletion of alveolar macrophage by intra-tracheal injection of L-Clodronate does not affect Met-1 cell metastatic efficiency (data not shown). These data strongly suggest that a distinct macrophage population is recruited from the blood to the metastatic cells in lung. First to establish whether macrophages are recruited to the pulmonary metastases, immunohistochemical staining using anti-Mac3 (a macrophage specific marker [30]) antibody was performed. In the experimentally induced metastasis formed either by primary PyMT tumor cells or Met-1 cells (Figure 3A, C), there was an abundant infiltration of macrophages. This was not a cell-type or route of injection specific phenomena because an intensive macrophage infiltration was also seen in the spontaneous metastases derived from late stage primary tumors of PyMT mice (Figure 3B) and in spontaneous metastasis derived from a subcutaneously implanted human breast cancer cell (MDA-231) in nude mice (Figure 3D). These data show that macrophages are recruited to metastatic lesions regardless of their origin.

Bottom Line: Using animal models of breast cancer metastasis, we show that a population of host macrophages displaying a distinct phenotype is recruited to extravasating pulmonary metastatic cells regardless of species of origin.Furthermore, imaging of intact lungs revealed that macrophages are required for efficient tumor cell extravasation.These data indicate a direct enhancement of metastatic growth by macrophages through their effects on tumor cell extravasation, survival and subsequent growth and identifies these cells as a new therapeutic target for treatment of metastatic disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental and Molecular Biology and the Department of Obstetrics/Gynecology and Woman's Health, Center for the Study of Reproductive Biology and Woman's Health, Albert Einstein College of Medicine, Bronx, NY, USA.

ABSTRACT

Background: The stromal microenvironment and particularly the macrophage component of primary tumors influence their malignant potential. However, at the metastatic site the role of these cells and their mechanism of actions for establishment and growth of metastases remain largely unknown.

Methodology/principal findings: Using animal models of breast cancer metastasis, we show that a population of host macrophages displaying a distinct phenotype is recruited to extravasating pulmonary metastatic cells regardless of species of origin. Ablation of this macrophage population through three independent means (genetic and chemical) showed that these macrophages are required for efficient metastatic seeding and growth. Importantly, even after metastatic growth is established, ablation of this macrophage population inhibited subsequent growth. Furthermore, imaging of intact lungs revealed that macrophages are required for efficient tumor cell extravasation.

Conclusion/significance: These data indicate a direct enhancement of metastatic growth by macrophages through their effects on tumor cell extravasation, survival and subsequent growth and identifies these cells as a new therapeutic target for treatment of metastatic disease.

Show MeSH
Related in: MedlinePlus