Distal and proximal colon cancers differ in terms of molecular, pathological, and clinical features

BACKGROUND

Differences exist between the proximal and distal colon in terms of developmental origin, exposure to patterning genes, environmental mutagens, and gut flora. Little is known on how these differences may affect mechanisms of tumorigenesis, side-specific therapy response or prognosis. We explored systematic differences in pathway activation and their clinical implications.

MATERIALS AND METHODS

Detailed clinicopathological data for 3045 colon carcinoma patients enrolled in the PETACC3 adjuvant chemotherapy trial were available for analysis. A subset of 1404 samples had molecular data, including gene expression and DNA copy number profiles for 589 and 199 samples, respectively. In addition, 413 colon adenocarcinoma from TCGA collection were also analyzed. Tumor side-effect on anti-epidermal growth factor receptor (EGFR) therapy was assessed in a cohort of 325 metastatic patients. Outcome variables considered were relapse-free survival and survival after relapse (SAR).

RESULTS

Proximal carcinomas were more often mucinous, microsatellite instable (MSI)-high, mutated in key tumorigenic pathways, expressed a B-Raf proto-oncogene, serine/threonine kinase (BRAF)-like and a serrated pathway signature, regardless of histological type. Distal carcinomas were more often chromosome instable and EGFR or human epidermal growth factor receptor 2 (HER2) amplified, and more frequently overexpressed epiregulin. While risk of relapse was not different per side, SAR was much poorer for proximal than for distal stage III carcinomas in a multivariable model including BRAF mutation status [N = 285; HR 1.95, 95% CI (1.6-2.4), P < 0.001]. Only patients with metastases from a distal carcinoma responded to anti-EGFR therapy, in line with the predictions of our pathway enrichment analysis.

CONCLUSIONS

Colorectal carcinoma side is associated with differences in key molecular features, some immediately druggable, with important prognostic effects which are maintained in metastatic lesions. Although within side significant molecular heterogeneity remains, our findings justify stratification of patients by side for retrospective and prospective analyses of drug efficacy and prognosis.

Risk assessment of relapse in Swiss participants of BIG 1-98 with grade 2 early breast cancer by gene expression profiling using RNA from formalin-fixed, paraffin embedded (FFPE) tissue

Abstract #1073

BIG 1-98 is a randomized controlled clinical trial for postmenopausal patients with early, estrogen and/or progesterone receptor (ER/PgR) positive breast cancer. It compares adjuvant therapy with 5 years of tamoxifen (T) or letrozole (L), two years of T followed by 3 years of L (T→L) or vice versa (L→T). L improved disease free survival (DFS) over T by 18% (hazard ratio 0.82, JCO 2007;25:486ff). Switzerland contributed 598/8010 patients. The patient and tumor characteristics of Swiss patients was similar to the entire BIG 1-98 population. The purpose of this study was to test a prognostic score in RNA derived from FFPE tissues.&#x2028; Scores representing ER and progesterone receptor (PgR) function, proliferation (PRO14, AURKA/STK15, BIRC5/SURV, CCNB1, CCNB2, CCNE2, CDC2, ENPF, KIF20A, MKI67, MYBL2, ORC6L, PRC1, SPAG5, TOP2A), and HER-2 were built from multiple genes for each score. Genes were selected according to an analysis of publicly available cDNA array databases. In a prior set of 82 pairs of breast cancer samples the Pearson correlation coefficients of the scores between fresh frozen and FFPE tissues were at least 0.94. Cut-offs for ER and HER-2 scores were defined as the antimodes of fitted bimodal Gaussian distributions; the ER and HER-2 scores closely agreed with immunohistochemical (IHC) data (kappa(ER)=0.868, kappa(HER-2)=0.836).&#x2028; FFPE tissues were available from 437 Swiss BIG 1-98 patients. RNA of sufficient quantity and quality was extracted from 388 blocks (89%). Forty-seven genes were quantified by QRTPCR on TaqMan Low Density Arrays (TLDAs) as reported previously (Proc AACR 2008, Abstract 974).&#x2028; The PRO14 score was positively correlated with the histological grade. PRO14 scores greater than the median and PGR scores lower than the median were associated with shorter DFS. In patients with grade 2 tumors, PRO14 scores were significant predictors of DFS in univariate Cox regression analyses. Multivariate analyses will be presented. Our findings are in agreement with an analysis of fresh frozen tissues of Belgian participants in BIG 1-98 (European Breast Cancer Conference 2008, Abstract 481).We show that RNA can be extracted from FFPE in sufficient quantity and quality to be used in QRTPCR using TLDAs. This opens the possibility of using FFPE tumor banks from controlled clinical trials for the investigation of gene expression patterns.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1073.

Histopathology of the experimental tick-borne encephalitis in mice

This paper is concerned with the histopathology of the tick-borne encephalitis virus experimental infection in mice. The lesions observed in the kidneys, spleen, myocardium and especially in the encephalon are characteristic of severe vasculitis which could be the first and probably the most important event in the virus-induced encephalitis.

Isolation of Bhanja virus in Romania

The presence of Bhanja virus was notified for the first time in our country in 1986, by the serological study performed on human and domestic animals sera. In 1988 four Bhanja virus strains from Dermacentor ticks were isolated in Alba and Caraş-Severin counties. A high percent of domestic animals, originating in this region, presents antibodies to the isolated strains and also to Bhanja virus reference strain.