Methylation of the <Emphasis Type="Italic">RASSF1A</Emphasis> promoter region and the allelic imbalance frequencies in chromosome 3 critical regions correlate with progression of clear cell renal carcinoma

The short arm of chromosome 3 (3p) contains several critical regions that have increased frequencies of allelic deletions and harbor a set of tumor suppressor genes. In particular, the range of functions performed by RASSF1A (LUCA region, 3p21.31) includes those potentially associated with carcinogenesis. Among 3p genes, RASSF1A has the highest methylation frequency in epithelial tumors of various locations. For the first time, two different methods (methylation-specific PCR and methylation-sensitive restriction analysis) independently showed that the methylation level of the CpG island in the RASSF1A promoter region significantly correlated with grade and clinical stage of clear cell renal cell carcinoma (RCC). An analysis of 23 3p polymorphic markers in a representative set of 80 RCC cases characterized clinically and histologically revealed that RCC progression significantly correlated with the frequency of allelic imbalances in some critical regions of 3p (LUCA and AP20), but not in 3p as a whole. These data suggest that RCC progression is associated with the methylation of the RASSF1A promoter and, possibly, with structural and functional alterations in other 3p genes. In addition, significant correlation between RASSF1A methylation and allelic losses at the nearby polymorphic marker locus suggests the “two hit” model for the inactivation of this tumor suppressor gene in RCC.     

Met amplification and tumor progression in Cdkn2a‐deficient melanocytes

While many genetic alterations have been identified in melanoma, the relevant molecular events that contribute to disease progression are poorly understood. Most primary human melanomas exhibit loss of expression of the CDKN2A locus in addition to activation of the canonical mitogen‐activated protein kinase signaling pathway. In this study, we used a Cdkn2a‐deficient mouse melanocyte cell line to screen for secondary genetic events in melanoma tumor progression. Upon investigation, intrachromosomal gene amplification of Met, a receptor tyrosine kinase implicated in melanoma progression, was identified in Cdkn2a‐deficient tumors. RNA interference targeting Met in these tumor cells resulted in a significant delay in tumor growth in vivo compared with the control cells. MET expression is rarely detected in primary human melanoma but is frequently observed in metastatic disease. This study validates a role for Met activation in melanoma tumor progression in the context of Cdkn2a deficiency.     

The role of the microenvironment in tumor growth and invasion

Mathematical modeling and computational analysis are essential for understanding the dynamics of the complex gene networks that control normal development and homeostasis, and can help to understand how circumvention of that control leads to abnormal outcomes such as cancer. Our objectives here are to discuss the different mechanisms by which the local biochemical and mechanical microenvironment, which is comprised of various signaling molecules, cell types and the extracellular matrix (ECM), affects the progression of potentially-cancerous cells, and to present new results on two aspects of these effects. We first deal with the major processes involved in the progression from a normal cell to a cancerous cell at a level accessible to a general scientific readership, and we then outline a number of mathematical and computational issues that arise in cancer modeling. In Section 2 we present results from a model that deals with the effects of the mechanical properties of the environment on tumor growth, and in Section 3 we report results from a model of the signaling pathways and the tumor microenvironment (TME), and how their interactions affect the development of breast cancer. The results emphasize anew the complexities of the interactions within the TME and their effect on tumor growth, and show that tumor progression is not solely determined by the presence of a clone of mutated immortal cells, but rather that it can be ‘community-controlled’.     

Using real-time impedance-based assays to monitor the effects of fibroblast-derived media on the adhesion,proliferation, migration and invasion of colon cancer cells

Increasing our knowledge of the mechanisms regulating cell proliferation, migration and invasion are central to understanding tumour progression and metastasis. The local tumour microenvironment contributes to the transformed phenotype in cancer by providing specific environmental cues that alter the cells behaviour and promotes metastasis. Fibroblasts have a strong association with cancer and in recent times there has been some emphasis in designing novel therapeutic strategies that alter fibroblast behaviour in the tumour microenvironment. Fibroblasts produce growth factors, chemokines and many of the proteins laid down in the ECM (extracellular matrix) that promote angiogenesis, inflammation and tumour progression. In this study, we use a label-free RTCA (real-time cell analysis) platform (xCELLigence) to investigate how media derived from human fibroblasts alters cancer cell behaviour. We used a series of complimentary and novel experimental approaches to show HCT116 cells adhere, proliferate and migrate significantly faster in the presence of media from human fibroblasts. As well as this, we used the xCELLigence CIM-plates system to show that HCT116 cells invade matrigel layers aggressively when migrating towards media derived from human fibroblasts. These data strongly suggest that fibroblasts have the ability to increase the migratory and invasive properties of HCT116 cells. This is the first study that provides real-time data on fibroblast-mediated migration and invasion kinetics of colon cancer cells.     

Targeted therapy for gastric cancer: Molecular pathways and ongoing investigations

Gastric cancer is currently the second leading cause of worldwide cancer mortality. Ongoing collaborative sequencing efforts have highlighted recurrent somatic genomic aberrations in gastric cancer, however, despite advances in characterizing the genomic landscape, there have been few advances in patient outcomes. Prognosis remains poor with a median overall survival of 12 months for advanced disease. The improved survival with trastuzumab, and more recently ramucirumab, underscore the promise of targeted and biologic therapies and the importance of molecular tumor characterization in gastric cancer. Here we review the most frequent actionable alterations in gastric cancer and highlight ongoing clinical investigations attempting to translate biologic understanding into improved clinical outcomes.     

Regulatory B cells correlate with HIV disease progression

A rare subset of IL‐10‐producing B cells, named Breg, was recently identified in mice and humans. Currently, there are no unified cell surface markers to identify Breg, and the relationship between the frequency of Breg and HIV disease progression in chronic HIV infection is unclear. In the present study, we determined whether the cell surface markers of Breg reported for other diseases are suitable for identifying Breg in HIV‐infected patients. In addition, we examined the relationship between Breg and HIV disease progression. We found that Breg frequency correlated positively with viral load and negatively with CD4 count in chronic HIV infection. Following antiretroviral treatment, the CD4 count increased and the frequency of Breg decreased stepwise. There was no difference in IL‐10 expression of CD1d^hi or CD1d^lo cells isolated from HIV‐infected patients. Therefore, CD1d may not be a marker of Breg in HIV‐infected patients.     

Viral Cyclin promotes KSHV-induced cellular transformation and tumorigenesis by overriding contact inhibition

Kaposi sarcoma-associated herpesvirus (KSHV) is a tumor virus encoding several proto-oncogenes. However, the roles of these viral genes in KSHV-induced tumorigenesis have not been defined. In this study, we used a recently developed model of KSHV-induced cellular transformation and tumorigenesis combining with a reverse genetic system to examine the role of a KSHV latent gene vCyclin (ORF72), a cellular Cyclin D2 homolog, in KSHV-induced oncogenesis. Deletion of vCyclin did not affect cell proliferation and cell cycle progression at a low-density condition, when cells were at an active proliferation state. However, vCyclin mutant cells were contact-inhibited and arrested at G₁ phase at a high-density condition. As a result, vCyclin mutant cells formed less and smaller colonies in soft agar assay. Nude mice inoculated with vCyclin mutant cells had reduced tumor incidence and extended tumor latency and survival compared with mice inoculated with wild-type (WT) virus-infected cells. WT but not mutant virus effectively induced Cyclin-dependent kinase inhibitor p27/Kip1 Ser10 phosphorylation and cytoplasmic relocalization. shRNA knockdown of p27 released the blockage of the mutant cells from cell cycle arrest at G₁ phase at a high-density condition. Together, these results indicate that vCyclin primarily functions to enhance cellular transformation and tumorigenesis by promoting cell cycle progression and cell proliferation at a contact-inhibited condition.