Intratumor Heterogeneity of K-Ras and p53 Mutations among Human Colorectal Adenomas Containing Early Cancer

The molecular pathways and the timing of genetic events during human colorectal carcinogenesis are still not fully understood. We have addressed the intratumor heterogeneity of the mutational status of the k‐ras oncogene and of the p53 oncosuppressor gene during the adenoma–carcinoma sequence by investigating 26 human colorectal adenomas containing early cancer. An intratumor comparative analysis was obtained among the adenomatous and carcinomatous component pairs. Additionally, we have analyzed 17 adenomas having cancer in the near vicinity. The adenomatous components of the adenomas containing early cancer and the adenomas having cancer in the near vicinity had comparable frequencies for k‐ras mutations (28 and 47%) but different for p53 mutations (52 and 7%, p‐value = 0.01). Interestingly, the adenomatous and carcinomatous components of the adenomas containing early cancer were rarely heterogeneous for the k‐ras mutational status (only in 13% of the cases) but were characterized by heterogeneity of the p53 status in 59% of the cases (p‐value < 0.01). In addition, the mutations of p53 for the adenomatous components of the adenomas containing early cancer were statistically significantly associated with severe dysplasia (p-value = 0.01). Intratumor homogeneity of k‐ras status during the human colorectal adenoma–carcinoma sequence suggests that the role of k‐ras is more related to tumor initiation than to tumor progression. On the contrary, intratumor heterogeneity of p53 mutations indicates that the type of the p53 mutations may also be relevant for selection and expansion of new subclones leading to tumor progression

Gene expression deregulation by KRAS G12D and G12V in a BRAF V600E context

<p>Abstract</p> <p>Background</p> <p><it>KRAS </it>and <it>BRAF </it>mutations appear of relevance in the genesis and progression of several solid tumor types but the co-occurrence and interaction of these mutations have not yet been fully elucidated. Using a microsatellite stable (MSS) colorectal cancer (CRC) cell line (Colo741) having mutated <it>BRAF </it>and <it>KRAS</it>^<it>WT</it>, we also aimed to investigate the <it>KRAS-BRAF </it>interaction. Gene expression profiles for control <it>KRAS</it>^<it>WT</it>, <it>KRAS</it>^{<it>G</it>12<it>V </it>}and <it>KRAS</it>^{<it>G</it>12<it>D </it>}transfected cells were obtained after cell clone selection and RT-PCR screening. Extensive qPCR was performed to confirm microarray data.</p> <p>Results</p> <p>We found that the <it>KRAS</it>^{<it>G</it>12<it>V </it>}state deregulated several genes associated to cell cycle, apoptosis and nitrogen metabolism. These findings indicated a reduced survival and proliferation with respect to the <it>KRAS</it>^{<it>WT </it>}state. The <it>KRAS</it>^{<it>G</it>12<it>D </it>}state was, instead, characterized by several other distinct functional changes as for example those related to chromatin organization and cell-cell adhesion without affecting apoptosis related genes.</p> <p>Conclusion</p> <p>These data predict that the G12D mutation may be more likely selected in a <it>BRAF </it>mutated context. At the same time, the presence of the <it>KRAS</it>^{<it>G</it>12<it>V </it>}mutation in the cells escaping apoptosis and inducing angiogenesis via IL8 may confer a more aggressive phenotype. The present results get along with the observations that CRCs with G12V are associated with a worse prognosis with respect to the WT and G12D states and may help identifying novel CRC pathways and biomarkers of clinical relevance.</p

K-ras2 Activation and Genome Instability Increase Proliferation and Size of FAP Adenomas

The possible role of K‐ras2 mutations and aneuploidy toward increase of proliferation and adenoma size in Familial Adenomatous Polyposis (FAP) adenomas is not known. The present study addresses these issues by investigating 147 colorectal adenomas obtained from four FAP patients. The majority of adenomas had size lower than or equal to 10 mm (86%), low grade dysplasia (63%), and were preferentially located in the right colon (60%). Normal mucosa samples were obtained from 19 healthy donors. Three synchronous adenocarcinomas were also investigated. K‐ras2 mutation spectrum was analysed by PCR and Sequence Specific Oligonucleotide (SSO) hybridization, while flow cytometry (FCM) was used for evaluating degree of DNA ploidy and S‐phase fraction. Overall, incidences of K‐ras2 mutations, DNA aneuploidy and high S‐phase values (>7.2%) were 6.6%, 5.4% and 10.5%, respectively. In particular, among the adenomas with size lower than 5 mm, K‐ras2 mutation and DNA aneuploidy frequencies were only slightly above 1%. Statistically significant correlations were found between K‐ras2 and size, DNA ploidy and size and K‐ras2 and S‐phase (p). In particular, among the wild type K‐ras2 adenomas, high S‐phase values were detected in 8% of the cases versus 57% among the K‐ras2 mutated adenomas (p=0.0005). The present series of FAP adenomas indicates that K‐ras2 activation and gross genomic changes play a role toward a proliferative gain and tumour growth in size

p53 Mutations and DNA Ploidy in Colorectal Adenocarcinomas

The p53 tumour suppressor gene has an important role in the the maintenance of genome stability and its mutational inactivation may be at the origin of aneuploidy in cancer cells. The aim of this study was to determine whether p53 mutations were associated to DNA aneuploidy, as assessed by flow cytometry, in colorectal adenocarcinomas. Analysis of p53 mutations spectrum of the sorted nuclei was done by Denaturing Gradient Gel Electrophoresis (DGGE) and DNA sequencing. Overall, we studied 20 adenocarcinomas, the corresponding control mucosa, and 7 lymph node metastases

Chromosomal aberrations and aneuploidy in oral potentially malignant lesions: distinctive features for tongue

<p>Abstract</p> <p>Background</p> <p>The mucosae of the oral cavity are different at the histological level but appear all equally exposed to common genotoxic agents. As a result of this exposure, changes in the mucosal epithelia may develop giving rise to Oral Potentially Malignant Lesions (OPMLs), which with time may in turn progress to Oral Squamous Cell Carcinomas (OSCCs). Therefore, much effort should be devoted to identify features able to predict the likeliness of progression associated with an OPML. Such features may be helpful in assisting the clinician to establish both appropriate therapies and follow-up schedules. Here, we report a pilot study that compared the occurrence of DNA aneuploidy and chromosomal copy number aberrations (CNAs) in the OPMLs from different oral anatomical subsites.</p> <p>Methods</p> <p>Samples from histologically diagnosed OPMLs were processed for high resolution DNA flow cytometry (hr DNA-FCM) in order to determine the relative DNA content expressed by the DNA index (DI). Additionally, array-Comparative Genomic Hybridization (a-CGH) analysis was performed on DNA obtained from diploid nuclei suspensions directly. When aneuploid nuclei were detected, these were physically separated from diploid nuclei on the base of their DI values by means of a DNA-FCM-Sorter in order to improve the a-CGH analysis.</p> <p>Results</p> <p>Tongue OPMLs were more frequently associated with DNA aneuploidy and CNAs than OPMLs arising from all the other mucosal subsites.</p> <p>Conclusions</p> <p>We suggest that the follow-up and the management of the patients with tongue OPMLs should receive a distinctive special attention. Clearly, this hypothesis should be validated in a prospective clinical study.</p

Aneuploidy Mechanisms in Human Colorectal Preneoplastic Lesions and Barrett’s Esophagus. Is There a Role for K-Ras and p53 Mutations?

The link of aneuploidy and heteroploidy in human solid tumours with early genetic events is poorly understood. The study of human preneoplastic precursor lesions, i.e., colorectal adenomas, chronic ulcerative colitis lesions, and Barrett’s esophagus, as considered in this review, appears particularly useful to achieve this aim. Literature data examined here on aneuploidy were obtained by image and flow cytometry, classical cytogenetics, and in situ hybridization based cytogenetics. It appears that aneuploidy is linked with specific gene mutations, i.e., of the tumour suppressor gene p53 in chronic ulcerative colitis and in Barrett’s esophagus, and of the protooncogene K‐ras in colorectal adenomas. These data and data from experiments using in vitro and mouse models, suggest that chromosome instability, tetraploidization, and asymmetrical chromosome segregation during cell division are the result of deregulated cell cycle genes with multiple functions that normally exert active checks on the cell cycle processes including apoptosis and chromosome stability