Lorena Bottarelli

Distinct molecular patterns based on proximal and distal sporadic colorectal cancer: arguments for different mechanisms in the tumorigenesis

Background and aimsColorectal cancer (CRC) ranks as the fourth most frequently diagnosed cancer worldwide. CRCs that arise proximally or distally to the splenic flexure show differences in epidemiologic incidence, morphology, and molecular alterations, suggesting the existence of two categories of CRC based on the site of origin. The aim of the present work is to investigate the histological and molecular differences between CRCs located proximally and distally to the splenic flexure, and their potential involvement in tumor prognosis and therapeutic strategies.MethodsWe evaluated 120 patients affected by sporadic CRC for clinicopathologic features, microsatellite instability (MSI), loss of heterozygosity (LOH) of chromosomes 18q, 8p, and 4p; they were also investigated for hMlh1, hMsh2, Fhit, p27, and Cox-2 immunostaining.ResultsThe mucinous histotype was more frequent in the proximal than in the distal CRCs (p<0.004). The frequency of MSI phenotype was higher in proximal than in distal tumors (p<0.001); moreover, reduced or absent hMlh1, Fhit, p27 immunohistochemical expressions were more frequent in proximal than in distal tumors (p<0.001 and 0.01 for p27). In contrast, the frequency of LOH in 18q was higher in distal than in proximal tumors (p=0.002). No significant differences were observed between proximal and distal tumors in the frequency of LOH in 8p and altered expression of hMsh2 and p53 protein.ConclusionThese different features may reflect different genetic pathways of carcinogenesis and support the hypothesis of a different mechanism of cancer development between the proximal and the distal colon, with potential implications in the therapeutic approach.

RASSF1A promoter methylation and 3p21.3 loss of heterozygosity are features of foregut, but not midgut and hindgut, malignant endocrine tumours.

The Ras‐association domain family 1A (RASSF1A) tumour suppressor gene is inactivated in a variety of solid tumours, usually by epigenetic silencing of the promoter and/or allelic loss of its locus at 3p21.3. RASSF1A induces cell cycle arrest through inhibition of cyclin D1 accumulation. In this work, 62 endocrine tumours from different sites in the gut were investigated for methylation of the RASSF1A promoter using the polymerase chain reaction, the presence of 3p21.3 deletions by loss of heterozygosity analysis, and cyclin D1 expression by immunohistochemistry. Methylation was found in 20/62 (32%) cases and was restricted to foregut tumours; deletion at 3p21.3 was found in 15/58 (26%) informative cases and restricted to malignant foregut tumours; cyclin D1 hyperexpression was found in 31/58 (53%) cases and correlated with RASSF1A methylation. Our data suggest that RASSF1A is involved in the development of endocrine tumours derived from the foregut only, and that the presence of both RASSF1A methylation and 3p21.3 deletion is associated with malignancy. These results may provide a rationale for foregut‐targeted therapy for aggressive endocrine carcinomas entailing the use of demethylating agents. Copyright

Genetic alterations in poorly differentiated endocrine carcinomas of the gastrointestinal tract.

The molecular pathogenesis of poorly differentiated endocrine carcinomas of the gastrointestinal tract (GI PDECs) remains unclear. It has been suggested that these lesions either originate from multipotent stem cells that also can serve as the origin of nonendocrine adenocarcinomas or arise due to the dedifferentiation of well‐differentiated endocrine carcinomas (WDECs).

L718Q Mutation as New Mechanism of Acquired Resistance to AZD9291 in EGFR-Mutated NSCLC

Abstract With the advent of third-generation epidermal growth-factor receptor (EGFR) tyrosine kinase inhibitors, such as AZD9291 and CO-1686, new mechanisms of drug resistance are emerging, like C797S and L884V EGFR mutations, in patients with EGFR T790M-positive non-small cell lung cancer (NSCLC). Here we present a case of advanced NSCLC with coexisting primary L585R and secondary T790M EGFR mutations that acquired resistance to AZD9291 (osimertinib) due to the occurrence of the tertiary L718Q mutation. This is the first clinical report for this new mutation as EGFR-dependent mechanism of resistance to AZD9291.

Association Between Recurrence of Sporadic Colorectal Cancer, High Level of Microsatellite Instability, and Loss of Heterozygosity at Chromosome 18q

PURPOSE:Microsatellite instability and loss of heterozygosity of chromosomes 18q, 8p, and 4p are genetic alterations commonly found in colorectal cancer. We investigated whether these genetic markers allow for the stratification of patients with Stage II to III colorectal cancer into groups with different recurrence risks, and with different prognoses.METHODS:Tumors of 113 patients were evaluated for loss of heterozygosity of chromosomes 18q, 8p, and 4p and for microsatellite instability by use of six microsatellite markers. Genetic alterations involving each of these genetic markers were examined for association with disease recurrences and survival.RESULTS:Loss of heterozygosity of chromosomes 18q, informative in 96 percent of cases, in Stage III tumors was associated with higher risk of overall recurrence (P < 0.001), local recurrence (P < 0.001), distant metastases (P < 0.001), decreased overall survival (P = 0.002), and disease-free survival (P < 0.001). The recurrence rates and survival rates among patients with Stage II colorectal cancer were independent of loss of heterozygosity of chromosome 18q. Stage III and loss of heterozygosity of chromosome 8p also were associated with a higher risk of recurrences when these factors were considered individually. In multivariate analysis, only loss of heterozygosity of chromosome 18q was independently associated with risk of recurrences (P < 0.001) and with disease-free survival (P = 0.001). No correlation was observed between microsatellite instability and recurrence rates. However, microsatellite instability was associated with improved overall survival (P = 0.04) and with a longer disease-free interval (P = 0.002). Only in five cases (16.7 percent) was it possible to perform resection of recurrences; two of these patients had microsatellite instability tumor. In no cases was it possible to resect recurrence of tumors with loss of heterozygosity of chromosome 18q.CONCLUSIONS:Loss of heterozygosity of chromosome 18q is an informative genetic marker, which in resected Stage III colorectal cancer can be used to predict recurrences and survival. Microsatellite instability identified cases that, even in the case of recurrence, have a more favorable prognosis.

Malignancy-associated X chromosome allelic losses in foregut endocrine neoplasms: further evidence from lung tumors.

Association of X chromosome allelic losses with tumor malignancy has been identified in foregut but not in midgut endocrine neoplasms. The aim of this study was to investigate the association of deletions on X chromosome with malignancy in lung neuroendocrine tumors, another family of foregut neoplasms comprising four categories with increased malignancy: typical and atypical carcinoids, large cell neuroendocrine and small cell lung carcinomas. To evaluate loss of heterozygosity, DNA extracted from nine typical carcinoids, 17 atypical carcinoids, six large cell neuroendocrine carcinomas and five small cell lung carcinomas was PCR-amplified for 18 microsatellite markers spanning the whole X chromosome. All tissue samples were formalin-fixed and paraffin-embedded. X chromosome losses were absent in typical carcinoids, whereas they were found in nine out of 17 atypical carcinoids and in five out of six large cell neuroendocrine carcinomas (involving 28 and 70% of informative loci, respectively). On the contrary, deletions on X chromosome were an extremely rare event in small cell lung carcinomas. In atypical carcinoids, the presence of losses was associated with larger tumor size, higher pT status and advanced stage. No death occurred in atypical carcinoid patients without deletions on X chromosome, whereas all atypical carcinoid patients who had died from disease showed allelic losses. In conclusion, X chromosome allelic losses, absent in benign ‘typical’ carcinoids, progressively increased in frequency from intermediate-grade ‘atypical’ carcinoids to high-grade large cell neuroendocrine carcinomas. These results extend the association of deletions on X chromosome with malignancy, already demonstrated in other foregut endocrine neoplasms, to lung neuroendocrine tumors. The absence of X chromosome allelic losses in small cell lung carcinomas underlines a striking difference from large cell neuroendocrine carcinomas, possibly linked to different pathogenetic mechanisms of these two highly aggressive neuroendocrine lung tumors.

Sex Chromosome Alterations Associate with Tumor Progression in Sporadic Colorectal Carcinomas

Purpose: The X and Y chromosomes have been associated with malignancy in different types of human tumors. This study attempts to determine the involvement of X chromosome and pseudoautosomal regions (PAR) in sporadic colorectal carcinogenesis. Experimental Design: An allelotyping of X chromosome in 20 premalignant and 22 malignant sporadic colorectal tumors (CRC) from female patients and an analysis of losses [loss of heterozygosity (LOH)] on PARs from 44 CRCs and 12 adenomas of male patients were carried out. In male tumors, a fluorescence in situ hybridization analysis was done to identify which sex chromosome was possibly lost. Results: The LOH frequency in female CRCs was 46% with higher incidence in patients with tumor recurrence than in those who were disease-free (P < 0.01) and with a significant difference from adenomas (11%; P < 0.0001). The LOH rate of PARs in male CRCs was 37% with a frequency significantly higher in patients with recurrence (P < 0.03). These results were maintained also when data from PARs of all 66 male and female patients were cumulated (P < 0.05). LOH in PARs was significantly correlated with LOH at 5q (P < 0.01) and 18q (P < 0.01), early and late events, respectively, in colorectal carcinogenesis. Fluorescence in situ hybridization analysis in male patients with extensive PAR LOH revealed a preferential loss of the Y chromosome. Conclusions: Our data suggest a role for sex chromosome deletions in the malignant progression of sporadic CRCs and support the presence in the PARs of putative tumor suppressor genes involved in the progression of human sporadic CRCs.

Epidermal growth factor receptor and Kras gene expression: Reliability of mutational analysis on cytological samples

Epidermal growth factor receptor (EGFR) and Kras gene mutations are crucial for discriminating patients responsive to anti‐EGFR drugs in non‐small cell lung cancer (NSCLC) and colorectal cancer (CRC), respectively. The majority of NSCLCs come to clinical attention at an advanced stage when surgery is no longer recommended and a considerable number of them are diagnosed by cytology only. A large number of metastatic CRCs are also diagnosed by imaging and minimally invasive techniques such as fine‐needle aspiration biopsy. Here, we report our experience in the mutation analysis of EGFR and Kras on cytological material obtained from superficial and deep lesions of NSCLC and CRC. Our series included 63 cytological specimens from primary or metastatic lesions of 42 NSCLCs and 21 CRCs. The cytological material was adequate for the mutation analysis in 39/42 (93%) NSCLCs and in 20/21(95%) CRCs. EGFR and Kras mutations were found in 9 (23%) and 9 (23%) NSCLC cases, respectively. Kras mutations were found in 9/20 (45%) CRC specimens. Histological samples from the primary tumors were available in 9/42 NSCLCs and in 17/21 CRCs. The agreement of EGFR and Kras mutational status in cytological vs. histological samples was 100% for NSCLC and 88% for CRC. Our results suggest that standard cytology provides adequate material for the assessment of EGFR and Kras mutational status in NSCLC and CRC patients and could be specifically indicated in patients not eligible for surgery but candidate to anti‐EGFR therapy. Diagn. Cytopathol. 2013.

Transient expression of secretin in serotoninergic neurons of mouse brain during development

Existence of the gastro‐intestinal peptide secretin in the CNS has been a matter of debate, and contrasting results have been reported, altogether indicating that the CNS is not a major site of production of this peptide. A thorough analysis was conducted in brain of transgenic mice in which the expression of the early region of simian virus 40 large T antigen (Tag) is under control of the rat secretin gene promoter. We studied Tag expression in the brains of E14–P90 transgenic mice as well as secretin mRNA and protein expression in transgenic and control CD1 mice at corresponding developmental stages. We show here a perfect correspondence of Tag and secretin mRNA expression in the mesencephalon of transgenic and normal mice between E14 and birth. In embryos, Tag is also expressed in the spinal cord, as well as in several areas of the peripheral nervous system. Localization of Tag in P0–P90 animals becomes restricted to a single compact cellular mass in mesencephalon at the level of the dorsal raphe, raphe magnus and lateral paragigantocellular nuclei. Neurons of these nuclei display secretin mRNA from E14 to birth, in both control CD1 and transgenic mice. Approximately half of these secretin‐expressing neurons are immunoreactive for serotonin (5HT) and/or tryptophan hydroxylase. These results demonstrate that the secretin gene is transiently expressed in mouse serotoninergic mesencephalic neurons during development. In addition our data suggest a trophic role for secretin on neurons known to be involved in multiple superior functions in the normal brain, and lost in neurodegenerative disorders.

Genetic alterations in combined neuroendocrine neoplasms of the lung.

Large-cell neuroendocrine and small-cell lung carcinomas are highly aggressive neuroendocrine tumors that can be associated in a variant of ‘small-cell lung carcinoma combined with large-cell neuroendocrine carcinoma’. Little is known about this rare tumor type with biphenotypic neuroendocrine differentiation. The aim of the present study was to genetically characterize each component of a series of combined small-cell/large-cell neuroendocrine carcinomas, to gain information on their histogenesis and to compare the alterations observed with those found in their respective pure forms. To this end, 22 formalin-fixed, paraffin-embedded lung neuroendocrine tumors obtained from surgical resections were investigated: six combined small-cell/large-cell carcinomas, eight pure large-cell carcinomas and eight pure small-cell carcinomas. For the combined neuroendocrine neoplasms, DNA was extracted separately from each of the two cytologically different populations. Allelic imbalance was investigated by PCR amplification of 30 highly polymorphic microsatellite markers located at 11 different chromosomal regions. A common background of genetic alterations, similar in both components of the combined neoplasms, was demonstrated at 17p13.1, 3p14.2–3p21.2, 4q12–4q24, 5q21 and 9p21. In fact, the two components appeared to be more similar to each other than to their respective pure forms. In addition, allelic imbalances preferentially involving one of the two components were found. These alterations often appeared to be specific for this histological variant, as compared with those observed in pure forms or in the literature. In conclusion, this is the first report in which a molecular characterization of the variant of small-cell lung carcinoma combined with large-cell neuroendocrine carcinoma was performed. The finding of common alterations in the two phenotypically different neuroendocrine cell components suggests a close genetic relationship and supports the hypothesis of a monoclonal origin from a common ancestor. The genetic differences observed provide the basis for the divergent differentiation and parallel the morphological differences in the two components of these combined neuroendocrine neoplasms.