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Aims: To discern the differences in expression profiling of two histological subtypes of colorectal carcinoma (CRC) arising from the serrated route (serrated adenocarcinoma (SAC) and CRC showing histological and molecular features of a high level of microsatellite instability (hmMSI‐H) both sharing common features (female gender, right‐sided location, mucinous histology, and altered CpG methylation), but dramatically differing in terms of prognosis, development of an immune response, and treatment options. Methods and results: Molecular signatures of SAC and hmMSI‐H were obtained by the use of transcriptomic arrays; quantitative polymerase chain reaction (qPCR) and immunohistochemistry (IHC) were used to validate differentially expressed genes. An over‐representation of innate immunity functions (granulomonocytic recruitment, chemokine production, Toll‐like receptor signalling, and antigen processing and presentation) was obtained from this comparison, and intercellular cell adhesion molecule‐1 (ICAM1) was more highly expressed in hmMSI‐H, whereas two genes [those encoding calcitonin gene‐related peptide‐receptor component protein and C‐X‐C motif chemokine ligand 14 (CXCL14)] were more highly expressed in SAC. These array results were subsequently validated by qPCR, and by IHC for CXCL14 and ICAM1. Information retrieved from public databanks confirmed our findings. Conclusions: Our findings highlight specific functions and genes that provide a better understanding of the role of the immune response in the serrated pathological route and may be of help in identifying actionable molecules. [ABSTRACT FROM AUTHOR]

Background: Serrated adenocarcinoma (SAC) is a recently recognized colorectal cancer (CRC) subtype accounting for 7.5-8.7% of CRCs. It has been shown that SAC has a worse prognosis and different histological and molecular features compared to conventional carcinoma (CC) but, to date, there is no study analysing its methylome profile. Results: The methylation status of 450,000 CpG sites using the Infinium Human Methylation 450 BeadChip array was investigated in 103 colorectal specimens, including 39 SACs and 34 matched CCs, from Spanish and Finnish patients. Microarray data showed a higher representation of morphogenesis-, neurogenesis-, cytoskeleton- and vesicle transport-related functions and also significant differential methylation of 15 genes, including the iodothyronine deiodinase DIO3 and the forkhead family transcription factor FOXD2 genes which were validated at the CpG, mRNA and protein level using pyrosequencing, methylation-specific PCR, quantitative polymerase chain reaction (qPCR) and immunohistochemistry. A quantification study of the methylation status of CpG sequences in FOXD2 demonstrated a novel region controlling gene expression. Moreover, differences in these markers were also evident when comparing SAC with CRC showing molecular and histological features of high-level microsatellite instability. Conclusions: This methylome study demonstrates distinct epigenetic regulation patterns in SAC which are consistent to previous expression profile studies and that DIO3 and FOXD2 might be molecular targets for a specific histologyoriented treatment of CRC. [ABSTRACT FROM AUTHOR]

Serrated adenocarcinoma (SAC) is a recently recognized colorectal cancer (CRC) subtype accounting for 7.5 to 8.7% of CRCs. It has been shown that SAC has a poorer prognosis and has different molecular and immunohistochemical features compared with conventional carcinoma (CC) but, to date, only one previous study has analyzed its mRNA expression profile by microarray. Using a different microarray platform, we have studied the molecular signature of 11 SACs and compared it with that of 15 matched CC with the aim of discerning the functions which characterize SAC biology and validating, at the mRNA and protein level, the most differentially expressed genes which were also tested using a validation set of 70 SACs and 70 CCs to assess their diagnostic and prognostic values. Microarray data showed a higher representation of morphogenesis-, hypoxia-, cytoskeleton- and vesicle transport-related functions and also an overexpression of fascin1 (actin-bundling protein associated with invasion) and the antiapoptotic gene hippocalcin in SAC all of which were validated both by quantitative real-time PCR (qPCR) and immunohistochemistry. Fascin1 expression was statistically associated with KRAS mutation with 88.6% sensitivity and 85.7% specificity for SAC diagnosis and the positivity of fascin1 or hippocalcin was highly suggestive of SAC diagnosis (sensitivity = 100%). Evaluation of these markers in CRCs showing histological and molecular characteristics of high-level microsatellite instability (MSI-H) also helped to distinguish SACs from MSI-H CRCs. Molecular profiling demonstrates that SAC shows activation of distinct signaling pathways and that immunohistochemical fascin1 and hippocalcin expression can be reliably used for its differentiation from other CRC subtypes. [ABSTRACT FROM AUTHOR]

The early mechanisms of spontaneous tumor initiation that precede malignancy are largely unknown. We show that reduced aPKC levels correlate with stem cell loss and the induction of revival and metaplastic programs in serrated- and conventional-initiated premalignant lesions, which is perpetuated in colorectal cancers (CRCs). Acute inactivation of PKCλ/ι in vivo and in mouse organoids is sufficient to stimulate JNK in non-transformed intestinal epithelial cells (IECs), which promotes cell death and the rapid loss of the intestinal stem cells (ISCs), including those that are LGR5+. This is followed by the accumulation of revival stem cells (RSCs) at the bottom of the crypt and fetal-metaplastic cells (FMCs) at the top, creating two spatiotemporally distinct cell populations that depend on JNK-induced AP-1 and YAP. These cell lineage changes are maintained during cancer initiation and progression and determine the aggressive phenotype of human CRC, irrespective of their serrated or conventional origin. [Display omitted] • aPKC deficiency acutely drives intrinsic stem cell loss in the intestinal epithelium • Stem cells are lost before metaplasia and in aPKC-low dysplasia and CRC • Revival stem and fetal metaplasia cells are two spatiotemporally distinct populations • JNK activation by low aPKC leads to stem cell loss and metaplasia through AP-1/YAP Kinoshita and Martinez-Ordoñez et al. demonstrate that aPKC loss is an early event in the initiation of colorectal cancer through the conventional and serrated pathways. This is associated with impaired intestinal stem cells, preceding the activation of the revival and metaplastic cell programs through a JNK-driven AP-1/YAP cascade. [ABSTRACT FROM AUTHOR]