Caspases are intracellular proteases that function as initiators and effectors of apoptosis. The kinase Akt and p21-Ras, an Akt activator, induced phosphorylation of pro-caspase-9 (pro-Casp9) in cells. Cytochrome c-induced proteolytic processing of pro-Casp9 was defective in cytosolic extracts from cells expressing either active Ras or Akt. Akt phosphorylated recombinant Casp9 in vitro on serine-196 and inhibited its protease activity. Mutant pro-Casp9(Ser196Ala) was resistant to Akt-mediated phosphorylation and inhibition in vitro and in cells, resulting in Akt-resistant induction of apoptosis. Thus, caspases can be directly regulated by protein phosphorylation.

https://science.sciencemag.org/content/sci/282/5392/1318.full.pdf

Regulation of Cell Death Protease Caspase-9 by Phosphorylation

http://sdjohnston.faculty.noctrl.edu/360/oncogene%20addiction.pdf

Principles of Cancer Therapy: Oncogene and Non-oncogene Addiction

Over the past three decades, molecular genetic studies have revealed some critical mutations underlying the pathogenesis of the sporadic and inherited forms of colorectal cancer (CRC). A relatively limited number of oncogenes and tumor-suppressor genes—most prominently the APC, KRAS, and p53 genes—are mutated in a sizeable fraction of CRCs, and a larger collection of genes that are mutated in subsets of CRC have begun to be defined. Together with DNA-methylation and chromatin-structure changes, the mutations act to dysregulate conserved signaling networks that exert context-dependent effects on critical cell phenotypes, including the regulation of cellular metabolism, proliferation, differentiation, and survival. Much work remains to be done to fully understand the nature and significance of the individual and collective genetic and epigenetic defects in CRC. Some key concepts for the field have emerged, two of which are emphasized in this review. Specifically, the gene defects in CRC often target protein...

Molecular Genetics of Colorectal Cancer

A Genome-wide RNAi Screen Identifies Multiple Synthetic Lethal Interactions with the Ras Oncogene

Advanced malignancy in tumours represents the phenotypic endpoint of successive genetic lesions that affect the function and regulation of oncogenes and tumour-suppressor genes. The established tumour is maintained through complex and poorly understood host-tumour interactions that guide processes such as angiogenesis and immune sequestration. The many different genetic alterations that accompany tumour genesis raise questions as to whether experimental cancer-promoting mutations remain relevant during tumour maintenance. Here we show that melanoma genesis and maintenance are strictly dependent upon expression of H-RasV12G in a doxycycline-inducible H-Ras12G mouse melanoma model null for the tumour suppressor INK4a. Withdrawal of doxycycline and H-RasV12G down-regulation resulted in clinical and histological regression of primary and explanted tumours. The initial stages of regression involved marked apoptosis in the tumour cells and host-derived endothelial cells. Although the regulation of vascular endothelial growth factor (VEGF) was found to be Ras-dependent in vitro, the failure of persistent endogenous and enforced VEGF expression to sustain tumour viability indicates that the tumour-maintaining actions of activated Ras extend beyond the regulation of VEGF expression in vivo. Our results provide genetic evidence that H-RasV12G is important in both the genesis and maintenance of solid tumours.

Essential role for oncogenic Ras in tumour maintenance

Point mutations that activate the Ki-ras proto-oncogene are presented in about 50 percent of human colorectal tumors. To study the functional significance of these mutations, the activated Ki-ras genes in two human colon carcinoma cell lines, DLD-1 and HCT 116, were disrupted by homologous recombination. Compared with parental cells, cells disrupted at the activated Ki-ras gene were morphologically altered, lost the capacity for anchorage-independent growth, grew more slowly both in vitro and in nude mice, and showed reduced expression of c-myc. Thus, the activated Ki-ras gene plays a key role in colorectal tumorigenesis through altered cell differentiation and cell growth.

https://science.sciencemag.org/content/sci/260/5104/85.full.pdf

Altered growth of human colon cancer cell lines disrupted at activated Ki-ras

Little is known about the temporal changes in Helicobacter pylori density and B-cell clonality during the evolution from chronic gastritis to gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Biopsied specimens from 28 patients with chronic gastritis who developed gastric MALT lymphoma (group A) and from 24 similar patients who did not (group B) during an equivalent follow-up period (mean, 42 months) were retrospectively scored for histological features of MALT lymphoma (0 to 5) and H. pylori density (0 to 3). B-cell clonality was analyzed by polymerase chain reaction (PCR). During the observation period, the H. pylori density in group A decreased significantly in comparison with group B; the mean change in H. pylori density (final minus initial density) per 1000 days was -1.4 for group A and +0.2 for group B (P < 0.005). Monoclonality was detected more frequently in group A (79%) than in group B (21%; P < 0.005), and it preceded the histological evidence of malignant transformation in 64% of those patients who showed monoclonality in group A. These results suggest that H. pylori is thus more closely associated with the precursor or initial phase in the genesis of gastric MALT lymphoma than with the later phase, as its density decreases as the tumor progresses. The detection of B-cell monoclonality by PCR is thus of possible use for predicting the histological genesis of gastric lymphoma.

/pdf/b-cell-monoclonality-precedes-the-development-of-gastric-4um08lm0yw.pdf

B-cell monoclonality precedes the development of gastric MALT lymphoma in Helicobacter pylori-associated chronic gastritis.

Background: Previous reports have shown that heat-shock protein 70 (HSP70) may be associated with Crohn disease. However, genetic analysis of the HSP70 gene in Crohn disease has not been done. The aim of this study is to investigate whether HSP70-2 gene polymorphism is involved in susceptibility to Crohn disease in the Japanese population and whether it correlates with clinical manifestation of the disease. Methods: A total of 108 genetically unrelated patients with Crohn disease and 108 healthy controls were typed for HSP70-2 PstI polymorphism by restriction fragment length polymorphism analysis (alleles A and B). Patients with Crohn disease were classified into two types: either perforating or non-perforating. Results: Genotype and allele frequency did not differ between patients and controls. In patients with Crohn disease, allele A frequency was significantly higher in the non-perforating than in the perforating type (P = 0.02). When patients with Crohn disease of more than 6.7 years' duration were as...

Polymorphism of Heat-Shock Protein Gene HSP70-2 in Crohn Disease: Possible Genetic Marker for Two Forms of Crohn Disease

The activation of c-Jun NH2-terminal kinase (JNK)/stress-activated protein kinase (SAPK) and/or extracellular signal-regulated kinase (ERK) is involved in ceramide-induced apoptosis in certain cells. To examine the relationship between activated Ki- ras -mediated signals and ceramide-induced apoptosis in human colon cancer cells, JNK/SAPK and ERK activity, as initiated by ceramide, was examined in HCT116, which has a mutation of Ki- ras at codon 13, and HCT116-derived clones, HKe-3 and HKh-2, in which activated Ki- ras was disrupted through gene targeting. In HKe-3 and HKh-2, the activity of JNK/SAPK increased significantly within 60 min following C2 ceramide stimulation, and some apoptosis followed. In contrast, C2 ceramide caused a marked apoptosis in HCT116, but activation of JNK/SAPK was not observed. C2 ceramide did not activate ERK in any of the cell lines. These results suggest that activated Ki- ras contributes to the sensitivity of ceramide-induced apoptosis without JNK/SAPK or ERK activation and that other signaling pathways involved in ceramide-induced apoptosis may be present in human colon cancer cells.

https://cancerres.aacrjournals.org/content/canres/57/21/4714.full.pdf

Activated Ki-ras Enhances Sensitivity of Ceramide-induced Apoptosis without c-Jun NH2-Terminal Kinase/Stress-activated Protein Kinase or Extracellular Signal-regulated Kinase Activation in Human Colon Cancer Cells

Masanori Furuse

Papers

Altered growth of human colon cancer cell lines disrupted at activated Ki-ras

B-cell monoclonality precedes the development of gastric MALT lymphoma in Helicobacter pylori-associated chronic gastritis.

Polymorphism of Heat-Shock Protein Gene HSP70-2 in Crohn Disease: Possible Genetic Marker for Two Forms of Crohn Disease

Activated Ki-ras Enhances Sensitivity of Ceramide-induced Apoptosis without c-Jun NH2-Terminal Kinase/Stress-activated Protein Kinase or Extracellular Signal-regulated Kinase Activation in Human Colon Cancer Cells

MHC class I bound peptides of a colon carcinoma cell line, a Ki-ras gene-targeted progeny cell line and a B cell line