There is increasing evidence that the physical environment is a critical mediator of tumor behavior. Hepatocellular carcinoma (HCC) develops within an altered biomechanical environment, and increasing matrix stiffness is a strong predictor of HCC development. The aim of this study was to establish whether changes in matrix stiffness, which are characteristic of inflammation and fibrosis, regulate HCC cell proliferation and chemotherapeutic response. Using an in vitro system of “mechanically tunable” matrix-coated polyacrylamide gels, matrix stiffness was modeled across a pathophysiologically relevant range, corresponding to values encountered in normal and fibrotic livers. Increasing matrix stiffness was found to promote HCC cell proliferation. The proliferative index (assessed by Ki67 staining) of Huh7 and HepG2 cells was 2.7-fold and 12.2-fold higher, respectively, when the cells were cultured on stiff (12 kPa) versus soft (1 kPa) supports. This was associated with stiffness-dependent regulation of basal and hepatocyte growth factor-stimulated mitogenic signaling through extracellular signal-regulated kinase, protein kinase B (PKB/Akt), and signal transducer and activator of transcription 3. β1-Integrin and focal adhesion kinase were found to modulate stiffness-dependent HCC cell proliferation. Following treatment with cisplatin, we observed reduced apoptosis in HCC cells cultured on stiff versus soft (physiological) supports. Interestingly, however, surviving cells from soft supports had significantly higher clonogenic capacity than surviving cells from a stiff microenvironment. This was associated with enhanced expression of cancer stem cell markers, including clusters of differentiation 44 (CD44), CD133, c-kit, cysteine-X-cysteine receptor 4, octamer-4 (CXCR4), and NANOG. Conclusion: Increasing matrix stiffness promotes proliferation and chemotherapeutic resistance, whereas a soft environment induces reversible cellular dormancy and stem cell characteristics in HCC. This has implications for both the treatment of primary HCC and the prevention of tumor outgrowth from disseminated tumor cells. (HEPATOLOGY 2011;)

Studies of the role of the cytokine macrophage-migration-inhibitory-factor (MIF) in malignant tumors have revealed its stimulating influence on cell-cycle progression, angiogenesis and anti-apoptosis. Here we show that in vitro targeting MIF in cultures of human malignant glioblastoma cells by either antisense plasmid introduction or anti-MIF antibody treatment reduced the growth rates of tumor cells. Of note is the marked decrease of proliferation under confluent and over-confluent conditions, implying a role of MIF in overcoming contact inhibition. Several proteins involved in contact inhibition including p27, p21, p53 and CEBPalpha are upregulated in the MIF antisense clones indicating a restoration of contact inhibition in the tumor cells. Correspondingly, we observed a marked increase in MIF mRNA and protein content under higher cell densities in LN18 cells. Furthermore, we showed the relevance of the enzymatic active site of MIF for the proliferation of glioblastoma cells by using the MIF-tautomerase inhibitor ISO-1. Our study adds another puzzle stone to the role of MIF in tumor growth and progression by showing the importance of MIF for overcoming contact inhibition.

A key role of chronic hepatocyte damage, leading to liver inflammation, fibrosis, and eventually cirrhosis, in the development of hepatocellular carcinoma (HCC) has been long established. Although the chronic stimulation of liver regeneration is one of the main contributors to HCC development, the accompayning inflammation has also been established as a pivotal component [ 1 x [1] El-Serag, H.B. and Rudolph, K.L. Hepatocellular carcinoma: epidemiology and molecular carcinogenesis. Gastroenterology. 2007; 132: 2557–2576 Abstract | Full Text | Full Text PDF | PubMed | Scopus (3302) | Google Scholar See all References , 2 x [2] Berasain, C., Castillo, J., Perugorria, M.J., Latasa, M.U., Prieto, J., and Avila, M.A. Inflammation and liver cancer: new molecular links. Ann NY Acad Sci. 2009; 1155: 206–221 Crossref | PubMed | Scopus (246) | Google Scholar See all References ]. Less is known about the role of ongoing inflammation with regard to disease progression once HCC has developed. A first hint of the relevance of the inflammatory response in tumour progression came from a seminal study from Budhu et al., linking a pro-inflammatory peritumoural cytokine milieu with the prognosis and metastatic spread of HCC [ 3 x [3] Budhu, A., Forgues, M., Ye, Q.H., Jia, H.L., He, P., Zanetti, K.A. et al. Prediction of venous metastases, recurrence, and prognosis in hepatocellular carcinoma based on a unique immune response signature of the liver microenvironment. Cancer Cell. 2006; 10: 99–111 Abstract | Full Text | Full Text PDF | PubMed | Scopus (478) | Google Scholar See all References ] [3] . There is increasing evidence that the inflammatory milieu, by virtue of both its soluble signals, cellular infiltrates, and physical properties, may alter the behaviour of HCC [ 4 x [4] Kuang, D.M., Peng, C., Zhao, Q., Wu, Y., Chen, M.S., and Zheng, L. Activated monocytes in peritumoral stroma of hepatocellular carcinoma promote expansion of memory T helper 17 cells. Hepatology. 2010; 51: 154–164 Crossref | PubMed | Scopus (152) | Google Scholar See all References , 5 x [5] Ju, M.J., Qiu, S.J., Fan, J., Xiao, Y.S., Gao, Q., Zhou, J. et al. Peritumoral activated hepatic stellate cells predict poor clinical outcome in hepatocellular carcinoma after curative resection. Am J Clin Pathol. 2009; 131: 498–510 Crossref | PubMed | Scopus (59) | Google Scholar See all References , 6 x [6] Schrader J, Gordon-Walker TT, van Deemter M, Aucott RL, Quaas A, Walsh S, et al. Matrix stiffness modulates proliferation, chemotherapeutic response and dormancy in hepatocellular carcinoma cells. Hepatology, in press. Google Scholar See all References ].