Interaction between circulating galectin-3 and cancer-associated MUC1 enhances tumour cell homotypic aggregation and prevents anoikis

Zhao Qicheng, Barclay Monica, Hilkens John, Guo Xiuli, Barrow Hannah, Rhodes, Yu, Yu Lu-Gang

Description

Formation of tumour cell aggregation/emboli prolongs the survival of circulating tumour cells in the circulation, enhances their physical trapping in the micro-vasculature and thus increases metastatic spread of the cancer cells to remote sites. Results It shows here that the presence of the galactoside-binding galectin-3, whose concentration is markedly increased in the blood circulation of cancer patients, increases cancer cell homotypic aggregation under anchorage-independent conditions by interaction with the oncofetal Thomsen-Friedenreich carbohydrate (Galβ1,3GalNAcα-, TF) antigen on the cancer-associated transmembrane mucin protein MUC1. The galectin-3-MUC1 interaction induces MUC1 cell surface polarization and exposure of the cell surface adhesion molecules including E-cadherin. The enhanced cancer cell homotypic aggregation by galectin-MUC1 interaction increases the survival of the tumour cells under anchorage-independent conditions by allowing them to avoid initiation of anoikis (suspension-induced apoptosis). Conclusion These results suggest that the interaction between free circulating galectin-3 and cancer-associated MUC1 promotes embolus formation and survival of disseminating tumour cells in the circulation. This provides new information into our understanding of the molecular mechanisms of cancer cell haematogenous dissemination and suggests that targeting the interaction of circulating galectin-3 with MUC1 in the circulation may represent an effective therapeutic approach for preventing metastasis.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2010
• Nombre de lectures: 3
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Zhao et al. Molecular Cancer 2010, 9:154
http://www.molecular-cancer.com/content/9/1/154
RESEARCH Open Access
ResearchInteraction between circulating galectin-3 and
cancer-associated MUC1 enhances tumour cell
homotypic aggregation and prevents anoikis
1 1 2 1 1 1 1Qicheng Zhao , Monica Barclay , John Hilkens , Xiuli Guo , Hannah Barrow , Jonathan M Rhodes and Lu-Gang Yu*
Abstract
Background: Formation of tumour cell aggregation/emboli prolongs the survival of circulating tumour cells in the
circulation, enhances their physical trapping in the micro-vasculature and thus increases metastatic spread of the
cancer cells to remote sites.
Results: It shows here that the presence of the galactoside-binding galectin-3, whose concentration is markedly
increased in the blood circulation of cancer patients, increases cancer cell homotypic aggregation under
anchorageindependent conditions by interaction with the oncofetal Thomsen-Friedenreich carbohydrate (Galβ1,3GalNAcα-, TF)
antigen on the cancer-associated transmembrane mucin protein MUC1. The galectin-3-MUC1 interaction induces
MUC1 cell surface polarization and exposure of the cell surface adhesion molecules including E-cadherin. The
enhanced cancer cell homotypic aggregation by galectin-MUC1 interaction increases the survival of the tumour cells
under anchorage-independent conditions by allowing them to avoid initiation of anoikis (suspension-induced
apoptosis).
Conclusion: These results suggest that the interaction between free circulating galectin-3 and cancer-associated
MUC1 promotes embolus formation and survival of disseminating tumour cells in the circulation. This provides new
information into our understanding of the molecular mechanisms of cancer cell haematogenous dissemination and
suggests that targeting the interaction of circulating galectin-3 with MUC1 in the circulation may represent an effective
therapeutic approach for preventing metastasis.
Introduction adhesion molecule in cell-cell interactions [5,6] and
proFormation of tumour cell aggregation/emboli in the cir- motes cancer progression and metastasis [7,8]. The
conculation prolongs the survival of tumour cells and allows centration of free circulating galectin-3 is markedly
their physical trapping in the micro-vasculature and con- increased in the sera of patients with breast, colorectal,
tributes to cancer cell hematogenous dissemination [1,2]. lung [9], head and neck [10] cancers and melanoma [11].
The formation of tumour emboli is heavily regulated by Patients with metastatic disease are seen to have higher
the expression, availability and activity of the cell surface concentrations of circulating galectin-3 than those with
adhesion molecules. localized tumours. Recently, we have shown that the
Galectin-3 is a multi-functional galactoside-binding transmembrane mucin protein MUC1 is an endogenous
protein that is expressed by many types of human cells. It ligand of galectin-3 in human colon cancer cells and that
is found inside and outside of the cells as well as in the the interaction between MUC1 and galectin-3 occurs via
circulation. Intracellular galectin-3 is an apoptosis inhibi- binding of galectin-3 to the oncofetal
Thomsen-Friedentor [3] and mRNA splicing promoter [4] whilst cell sur- reich carbohydrate (Galβ1,3GalNAcα-, T or TF) antigen
face-associated extracellular galectin-3 acts as an on MUC1 [12].
MUC1 is a large and heavily glycosylated
transmem* Correspondence: [e-mail] brane mucin protein that is expressed on the apical
sur1 Gastroenterology Research Unit, School of Clinical Sciences, Centre for
face of normal secretory epithelia [13]. In epithelialGlycobiology, University of Liverpool, Liverpool L69 3GE, UK
Full list of author information is available at the end of the article cancer cells, MUC1 is over-expressed [14] and aberrantly
© 2010 Zhao et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.Zhao et al. Molecular Cancer 2010, 9:154 Page 2 of 12
http://www.molecular-cancer.com/content/9/1/154
glycosylated with short oligosaccharides such as Gal- properties of human colon cancer HT29 and HT29-5F7
NAcα- (Tn), sialylated GalNAcα- (sialyl-Tn) and TF anti- cells. HT29-5F7 is a subpopulation of HT29 cells and was
gen [15,16]. On cancer cells, MUC1 also loses its apical selected for its resistance to 5-fluorouracil and has much
polarization and becomes expressed over the entire cell higher MUC1 expression than the parental HT29 cells
surface [17,18]. TF antigen is covered in normal epithe- (Fig 1A) [25]. It was found that spontaneous aggregation
lium by extensive glycosylation, sulphation and/or sialyla- of HT29 cells was 2.8-fold greater than that of HT29-5F7
tion but expressed in unsubstituted form by most human cells (Fig 1B and 1C). Pre-treatment of HT29-5F7 cells
cancer cells [19,20]. The increased expression of MUC1 with recombinant galectin-3 at similar circulating
galecand the increased occurrence of TF antigen are both tin-3 concentrations found in the sera of colorectal
canassociated, independently, with high metastatic potential cer patients [9] resulted in a dose-dependent increase of
of the cancer cells and poor prognosis of the patients HT29-5F7 but not HT29 cell aggregation (Fig 1D). At 1.0
[21,22]. MUC1 is an extremely elongated molecule which μg/ml, galectin-3 caused a 69% increased aggregation
protrudes over 10 times further from the cell surface than [169.2 ± 24.7 (mean ± SEM), p < 0.01] of HT29-5F7 but
the typical cell surface adhesion molecules [14] and not HT29 cells (91.4 ± 5.9, p = 0.2) (Fig 1B)
therefore influences cell adhesion when is present at high Spontaneous aggregation of HBL-100 human breast
density at the cell surface [23]. Thus, over-expression of epithelial cells transfected with MUC1-cDNA (HCA1.7+)
MUC1 promotes tumour cell release from primary (5.1 ± 0.4%) was significantly less compared to
MUC1tumour sites by inhibiting E-cadherin-mediated cell-cell negative controls (HCA1.7-) (8.0 ± 0.3, p < 0.001) (Fig 2A
and integrin-mediated cancer-extracellular matrix inter- and 2B). Pre-treatment of the cells with galectin-3, at 1.0
actions [18,24]. μg/ml, caused 36% increased aggregation of HCA1.7+
We have previously shown that the interaction between (136.6 ± 7.0, p < 0.01) but not HCA1.7- cells (94.2 ± 4.2, p
cell surface MUC1 and galectin-3 at concentrations simi- = 0.2) (Fig 2C). The effect of galectin-3 on HCA1.7+ cell
lar to those found in the sera of cancer patients increases aggregation was dose-dependent (Fig 2D) and was
precancer cell heterotypic adhesion to endothelium as a vented by the presence of 10 μM lactose (Fig 2E).
Preresult of MUC1 cell surface polarization which leads to treatment of HCA1.7+ cells with streptococcal
O-glycaexposure of heterotypic cell-cell adhesion molecules that nase, that specifically removes the unsubstituted TF
are otherwise concealed by elongated structure of MUC1 disaccharide, caused a 58% reduction of TF epitope on
[12]. As change of MUC1 cell surface localization in MUC1 as assessed by PNA blotting (Fig 3A) and
attenuresponse to galectin-3 binding may also expose the adhe- ated the galectin-3-induced cell aggregation (Fig 3B).
sion molecules that are essential to homotypic cancer cell Thus, expression of MUC1 prevents homotypic cell
interactions, we hypothesised that an increased interac- aggregation but the aggregation is restored by the
interaction between circulating galectin-3 and cancer-associated tion of galectin-3 with TF/MUC1.
MUC1 expressed on the surface of circulating tumour
Galectin-3 and B27.29 anti-MUC1 mAb have similar effects cells in cancer patients may promote the formation of
on MUC1 cell surface polarization and on epithelial cancer cancer cell aggregates/emboli thus prolongs the survival
cell-cell aggregationof disseminated tumour cells in the circulation and
conOur previous study demonstrated that B27.29 anti-tributes to cancer cell haematogenous dissemination.
MUC1 mAb, directed against the PDTRPAP epitope [26]We provide evidence in this study showing that the
within the VNTR region of MUC1, induces MUC1 cellinteraction between cell surface MUC1 and recombinant
surface polarization and increases human melanoma cellgalectin-3 at pathologically-relevant circulating
galectinadhesion to endothelium [27]. We found here that addi-3 concentrations increases homotypic aggregation of
tion of B27.29 mAb to HCA1.7+ cells in suspension alsohuman colon and breast cancer cells as a result of cell
surcaused a dose-dependent increase in cell aggregation (Figface clustering of MUC1 and consequent exposure of the
4A), regardless of the presence or absence of recombinanthomotypic cell adhesion molecules including E-cadherin.
galectin-3 (Fig 4B). When the cell aggregates were furtherThe galectin-3-MUC-induced cell aggregation increases
analysed, it was found that B27.29 mAb not only inducedthe survival of the cancer cells by preventing initiation
more cell aggregates but also larger aggregates thancellular anoikis (suspension-induced apoptosis).
recombinant galectin-3 (data not shown).
Fourteen percent (71/500) of the HCA1.7+ cellsResults
showed spon