Impact of tumor-associated macrophages in LH(BETA)T(AG) mice on retinal tumor progression: relation to macrophage subtype.
OBJECTIVE
To determine the distribution of tumor-associated macrophages (TAMs) during retinoblastoma tumor development, examine the contribution of bone marrow-derived TAMs in retinoblastoma tumors, and evaluate the supportive role of TAMs in tumor growth in a transgenic retinoblastoma mouse model.


METHODS
The time course of macrophage infiltration in transgenic retinoblastoma tumors was assessed by immunohistochemistry at different time points in tumorigenesis. The origin of TAMs in transgenic retinoblastoma tumors was determined by transplanting 10(7) bone marrow cells from green fluorescent protein (GFP)-positive 16-week-old mice into age-matched, irradiated LH(BETA)T(AG) mice via tail vein injections. Macrophage depletion was performed by subconjunctival (SC) delivery of liposomal clodronate.


RESULTS
The density of TAMs increased from 4 to 12 weeks of age in mice with small to medium tumors (P = 0.037) and remained stable in the later stages of disease (i.e., 16 weeks old with large tumors; P = 0.20). In 16-week-old mice, 38% (2.5 +/- 3.2 cells per 400x high-power field) of TAMs were GFP-positive, bone marrow-derived macrophages. Total TAM depletion was associated with a significant decrease in the expression levels of MMP-9 (P = 0.014) and mature vessels (P < 0.001) and a nonsignificant decrease in the density of neovessels (P = 0.94). The density of M2-polarized TAMs did not change significantly after TAM depletion (P = 0.68). After M1-polarized TAM depletion, the tumor burden increased (P = 0.056).


CONCLUSIONS
This work extends understanding of the complex role that macrophages play in retinoblastoma. Macrophage modulation in the tumor microenvironment is a critical factor in retinoblastoma tumor progression.
Piña
Yolanda
Y
Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
Boutrid
Hinda
H
Murray
Timothy G
TG
Jager
Martine J
MJ
Cebulla
Colleen M
CM
Schefler
Amy
A
Ly
Long V
LV
Alegret
Armando
A
Celdran
Magda
M
Feuer
William
W
Jockovich
Maria-Elena
ME
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D016026:Bone Marrow Transplantation; D002452:Cell Count; D004195:Disease Models, Animal; D018450:Disease Progression; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008264:Macrophages / Q000502:physiology*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D017628:Microglia / Q000166:cytology; D009389:Neovascularization, Pathologic / Q000473:pathology; D019572:Retinal Neoplasms / Q000098:blood supply / Q000473:pathology*; D012175:Retinoblastoma / Q000098:blood supply / Q000473:pathology*
D020780:Matrix Metalloproteinase 9