The mannose 6‐phosphate/insulin‐like growth factor II receptor restricts the tumourigenicity and invasiveness of squamous cell carcinoma cells

Abstract

The mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) mediates biosynthetic sorting and endocytosis of various factors that impinge on the proliferation, migration and invasiveness of tumour cells. The gene encoding M6P/IGF2R is frequently lost or mutated in a wide range of malignant tumours including squamous cell carcinomas. We have previously shown that M6P/IGF2R-deficient SCC-VII murine squamous cell carcinoma cells secrete large amounts of pro-invasive lysosomal proteinases. Furthermore, the formation of mature lysosomes is impaired in SCC-VII cells. To assess the link between M6P/ IGF2R status and tumour invasion, we have now generated SCC-VII lines stably transfected with human M6P/IGF2R cDNA. Reconstitution of functional M6P/IGF2R expression in SCC-VII cells strongly improves the intracellular retention of lysosomal proteinases and restores the formation of mature lysosomes. In addition, the presence of heterologous M6P/IGF2R compromises the growth of SCC-VII cells both in vitro and in vivo. Remarkably, M6P/IGF2R expression also reduces the invasive capacity of SCC-VII cells in response to various chemoattractants. These results indicate that the M6P/IGF2R status influences the metastatic propensity of squamous cell carcinomas. ' 2008 Wiley-Liss, Inc.Key words: cathepsin; lysosome; proteolysis; squamous cell carcinoma; tumour invasion A key requirement for metastatic cancer cell invasion is the penetration of extracellular matrix (ECM) barriers. This process involves the degradation of different ECM proteins and proteoglycans. 1,2 Various proteinases have been implicated in ECM degradation associated with tumour invasion and metastasis, including urokinase-type plasminogen activator, matrix metalloproteinases and cathepsins. [3][4][5] The involvement of the latter enzymes in ECM proteolysis is perplexing, since cathepsins are normally localized in lysosomes. However, tumour cells often secrete significant amounts of these proteinases into the pericellular fluid, as first observed for cathepsin B. 6 As typical for lysosomal enzymes, the N-glycan moieties of cathepsins are modified during their biosynthesis with mannose 6-phosphate (M6P) residues which permit interaction with the main lysosomal sorting receptors, the 300-kDa mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) and the 46-kDa mannose 6-phosphate receptor (MPR46). 7 Evidence has been provided that excessive secretion of cathepsins by tumour cells may be due to transformation-induced changes to the M6P receptor pathway. [8][9][10] Lysosomal sorting via M6P/IGF2R is generally far more efficient than by MPR46, demonstrating that the former is the main lysosomal targeting receptor in mammalian cells. 11,12 However, M6P/IGF2R also binds a variety of other factors that impinge on the proliferation, migration and invasiveness of tumour cells, including insulin-like growth factor II (IGF-II), 13 transforming growth factor b, 14 urokinase-type plasminogen activator receptor 15 and plasminogen. 16 Hence, it is o...

M6P/IGF2R modulates the invasiveness of liver cells via its capacity to bind mannose 6-phosphate residues

“…4). These results demonstrate that ectopic expression of M6P/IGF2R in FRL14 cells leads to improved intracellular retention of lysosomal enzymes and restoration of dense lysosome formation, as previously shown for receptor-deficient squamous cell carcinoma cells [25].…”

“…When the efficacy of physiological proteinase inhibitors was tested, it was found that the potent serine proteinase inhibitor aprotinin had a much weaker effect on cell invasion (22% reduction) than the cysteine proteinase inhibitor cystatin C (49% reduction). We have earlier observed a similar proteinase inhibition profile for the invasive properties of M6P/IGF2R-deficient murine squamous cell carcinoma cells [25]. When FRL14 extracts were immunoblotted with antibodies recognizing rat M6P/IGF2R, it became evident that these cells lack expression of the receptor (Fig.…”

Knockdown of IGF2R suppresses proliferation and induces apoptosis in hemangioma cells in vitro and in vivo

“…M6P/IGF2R also functions as a growth suppressor, but the loss or mutation of this gene contributes to development and progression of some cancers (15,16) and is involved in HBV-associated hepatocarcinogenesis (17). Moreover, M6P/ IGF2R controls cell adhesion and invasion by regulating αv integrin expression and accelerating uPAR cleavage (18), and restricts the metastatic propensity of squamous cell carcinomas (19). These studies thereby support that M6P/IGF2R may act as the tumor suppressor in carcinogenesis.…”

IGF2 and cancer

“…They often occur early in carcinogenesis, predisposing to cancer presumably via loss of restraint on IGF2 (Biliya & Bulla 2010). Polymorphisms of IGF2R are also linked to increased risk of oral cancer (Yoon et al 2012), colonic cancer (Probst et al 2009) and HCC (Morcavallo et al 2012) possibly because of impaired IGF2 clearance.…”

“…Loss of IGF2R is associated with a poor prognosis (Jamieson et al 2003, Pavelic et al 2003. The aggressive phenotype may be caused both by excessive IGF2 and over secretion of lysozomal proteases that promote tumour invasion (Probst et al 2009). Conversely, increased IGF2R expression is associated with a better outcome from disease, possibly because of enhanced clearance of IGF2 (Kalla Singh et al 2010b).…”