Characterization of transfected HT-29 cells expressing the oncogenic Ras isoform KrasG13D.

Point mutations in codon 12 and 13 of K-ras are frequently found in DNA of colorectal cancer. It has been suggested that particular mutations at these sites may be associated with specific tumour phenotypes. To shed light on the molecular mechanisms on which depends this specificity we set up a system of HT-29 cells stably transfected with a cDNA coding for K-rasG13D under the control of an inducible promoter. Proliferation assay performed on one of the positives clones, showed a decreased growth rate in response to K-rasG13D expression and preliminary gene expression analysis showed an up-regulation of the cell-cycle inhibitor p21 WAF1.

Effects of different ras mutations on colorectal cancer cells

Intrachromosomal recombination of the c-myc locus leading to gene amplification

Possible relation between genetic recombination and amplification within the c-myc locus in a case of primary colorectal carcinoma

Aurora-A Is Essential for the Tumorigenic Capacity and Chemoresistance of Colorectal Cancer Stem Cells

Abstract Colorectal cancer stem cells (CR-CSC) are responsible for the generation and maintenance of intestinal tumors and are highly resistant to conventional chemotherapeutic agents. Aurora-A, a serine-threonine kinase involved in mitosis regulation, plays multiple key functions in tumor initiation and progression. We found that Aurora-A is overexpressed in primary colorectal tumor cells, in the CR-CSC fraction, and in stem cell–derived differentiated cells, compared with normal colon tissue. Aurora-A expression was functionally linked to centrosome amplification in CR-CSC, as indicated by the decrease in cells with multiple centrosomes that followed Aurora-A silencing. Knockdown of Auror…

Tumorigenic and metastatic activity of human thyroid cancer stem cells

Abstract Thyroid carcinoma is the most common endocrine malignancy and the first cause of death among endocrine cancers. We show that the tumorigenic capacity in thyroid cancer is confined in a small subpopulation of stem-like cells with high aldehyde dehydrogenase (ALDHhigh) activity and unlimited replication potential. ALDHhigh cells can be expanded indefinitely in vitro as tumor spheres, which retain the tumorigenic potential upon delivery in immunocompromised mice. Orthotopic injection of minute numbers of thyroid cancer stem cells recapitulates the behavior of the parental tumor, including the aggressive metastatic features of undifferentiated thyroid carcinomas, which are sustained by…

Gene expression profiling of HT-29 cells in response to induction of oncogenic H and K-ras.

DUE DIFFERENTI MECCANISMI MOLECOLARI COINVOLTI NEL FENOMENO DELL'AMPLIFICAZIONE GENICA IN UN CASO DI CARCINOMA COLORETTALE

Survivin is regulated by interleukin-4 in colon cancer stem cells

Colorectal cancer has provided an important model to test the stem cell hypothesis of cancer origin, which implies that cancer arises as a result of genetic aberrations in stem cells leading to deregulation of the proliferation/differentiation balance. We and others have demonstrated that, similarly to other solid tumors, colon carcinogenesis and progression are dictated by highly apoptosis-resistant stem-like cells. Our data have suggested that protection from apoptosis is achieved by autocrine production of interleukin-4 (IL-4) through up-regulation of anti-apoptotic mediators. In this study, we extend our analysis to another apoptosis inhibitor widely expressed in tumors, namely survivin…

Intrachromosomal recombination of c-myc locus leading to gene amplification

Effescts of different RAS mutations on colorectal cancer cells

Two distinct amplification events of the c-myc locus in a colorectal tumour.

Southern hybridisation of genomic DNA extracted from a human primary colorectal carcinoma revealed amplification of a fragment containing the wild-type c-myc locus. Two additional rearranged DNA fragments, lying upstream of c-myc, fused to distant non-contiguous sequences from the same chromosome, with an opposite configuration (head to head vs. head to tail), were also found to be amplified. Sequences analysis suggested that these rearrangements resulted from illegitimate recombination at two distinct points within the DNA sequence just upstream of the c-myc ORF and further that these events triggered two different amplification mechanisms, only one of which, involving a strand invasion ev…

Suppressor of cytokine signaling 3 sensitizes anaplastic thyroid cancer to standard chemotherapy

We previously showed that cancer cells from papillary, follicular, and anaplastic thyroid carcinomas produce interleukin-4 and interleukin-10, which counteract the cytotoxic activity of conventional chemotherapy through the up-regulation of antiapoptotic molecules. Here, we identify Janus kinase/signal transducers and activators of transcription (STAT) and phosphatidyl inositol 3-kinase (PI3K)/AKT as the down-stream pathways through which these cytokines confer resistance to cell death in thyroid cancer. We found that the absence of suppressors of cytokine signaling (SOCS) molecules allows the propagation of the survival signaling. Exogenous expression of SOCS1, SOCS3, and SOCS5 in the high…

AMPLIFICAZIONE E RIARRANGIAMENTO NEI TUMORI COLORETTALI