Comparison of IgG diffusion and extracellular matrix composition in rhabdomyosarcomas grown in mice versus in vitro as spheroids reveals the role of host stromal cells

Abstract

The tumour extracellular matrix acts as a barrier to the delivery of therapeutic agents. To test the hypothesis that extracellular matrix composition governs the penetration rate of macromolecules in tumour tissue, we measured the diffusion coefficient of nonspecific IgG in three rhabdomyosarcoma subclones growing as multicellular spheroids in vitro or as subcutaneous tumours in dorsal windows in vivo. In subcutaneous tumours, the diffusion coefficient decreased with increasing content of collagen and sulphated glycosaminoglycans. When grown as multicellular spheroids, no differences in either extracellular matrix composition or diffusion coefficient were found. Comparison of in vitro vs in vivo results suggests an over-riding role of host stromal cells in extracellular matrix production subjected to modulation by tumour cells. Penetration of therapeutic macromolecules through tumour extracellular matrix might thus be largely determined by the host organ. Hence, caution must be exercised in extrapolating drug penetrability from spheroids and multilayer cellular sandwiches consisting of only tumour cells to tumours in vivo. British Journal of Cancer (2002) The extracellular matrix (ECM) is a potent barrier to the delivery and penetration of complex biopharmaceuticals such as monoclonal antibodies, therapeutic proteins, or genes. Due to the elevated interstitial fluid pressure in tumours , the therapeutic agents must reach the tumour cells by interstitial diffusion. It is not clear whether the network of fibrillar collage or the glycosaminoglycan (GAG) gel plays the most important role in limiting the diffusion of macromolecules through the ECM, and what the role of the host stromal cells is. Netti et al (2000) found that the amount of collagen in tumours correlated inversely with the diffusion coefficient of macromolecules, and collagenase treatment of the tumour increased the diffusion coefficient. Pluen et al (2001) provided further support for the role of collagen by measuring diffusion in tumours grown in subcutaneous tissue and the cranium. Hyaluronidase, on the other hand, is reported to reduce the diffusion coefficient of albumin in lung interstitium (Qiu et al, 1999).We postulated that diffusion of macromolecules is hindered both by the collagen network and by the hydrophilic gel of GAG and proteoglycans. To test this hypothesis we used three distinct clones with different degrees of differentiation and ECM (Groeschel et al, 1994) derived from a rat rhabdomyosarcoma, growing as multicellular spheroids in vitro or subcutaneously in dorsal chambers in mice in vivo. The production of ECM in tumours is the result of an active interaction between the tumour cells and stromal cells of the host (Gullino and Grantham, 1962;Knudson et al, 1984), whereas the extracellular matrix of multicellular spheroids is solely produced by the tumour cells. Comparison of the ECM composition in tumours growing as xenografts in vivo and as multicellular spheroids in vitro, is likely to reveal the influence of the host stromal ce...

Predictive Models of Diffusive Nanoparticle Transport in 3-Dimensional Tumor Cell Spheroids

“…We assumed negligible nanoparticle binding to ECM, based on the following literature findings and our own unpublished results: (a) low ECM content in spheroids (less than 10% of the level in tumors) (28), (b) pegylation of liposomes diminishes interaction with ECM (29),(c) minimal interaction between positively charged liposomes and collagen (positively charge at physiological pH) (30), and (d) treatment of FaDu spheroids with collagenase did not significantly enhance the penetration of negatively charged polystyrene beads (20 nm; unpublished results), suggesting inconsequential interactions between beads and collagen in spheroids.…”

“…Because the major component of tumor matrix materials is collagen (36), we used values for collagen to calculate φ int , which equals the multiplication product of (interstitial collagen concentration) and (effective specific volume of collagen fibers, which equals 1.89 cm 3 /g) (37). The collagen concentration in the interstitium of a solid tumor is 0.35 g/cm 3 (37), and the collagen content in a spheroid is about one eleventh of the value in a tumor (28). Accordingly, the collagen concentration in a spheroid was 0.032 g/cm 3 and φ int was 0.06. r f is the radius of the tumor matrix proteins/fibers and equals 20 nm for collagen (37).…”

Biodistribution Mechanisms of Therapeutic Monoclonal Antibodies in Health and Disease

“…While pericytes are present on most tumor vessels, studies indicate that these cells exhibit a loose association with endothelial cells and have cytoplasmic processes that extend deep into the tumor tissue (60). The composition and structure of the extracellular matrix is another contributing factor that can retard the movement of molecules within the tumor (66)(67)(68).…”

Microfluidic synthesis of multifunctional liposomes for tumour targeting

“…Tumour spheroids are three-dimensional (3D) tumour cell clusters [41], which possess similar characteristics of tumour xenografts, such as extracellular matrix, cell-cell interactions [42], spatial geometry [43] and hypoxic or necrotic regions [44]. Similar to 2D cell monolayer, Plain-Lip could be internalised into both the MCF-7 and SKOV3 tumour spheroids through non-specific binding while sterically stabilised PEG-Lips were not able to interact with any spheroids due to the effect of the PEG, which was in accordance with previously reported work using tumour spheroids [45].…”