ABSTRACT Background Currently, there is no direct evidence to prove the active SARS-CoV-2 replication in the intestinal tract and relevant pathological changes in the colon and rectum. We investigated the presence of virions and pathological changes in surgical rectal tissues of a clinically confirmed COVID-19 patient with rectal adenocarcinoma. Methods Here, the clinical data were collected during hospitalization and follow-up of this patient. Quantitative RT-PCR was performed on the rectal tissue specimens obtained from surgical resection, succus entericus and intestinal mucosa of ileostomy, and rectal mucosa during follow-up after recovery. Ultrathin sections of surgical samples were observed for SARS-CoV-2 virions using electron microscopy. Histopathological examination was performed using hematoxylin-eosin stain. Immunohistochemical analysis and immunofluorescence were carried out on rectal tissues to evaluate the distribution of SARS-CoV-2 antigen, and immune cell infiltrations. Results The patient had fever and cough on day 3 postoperatively, was diagnosed with COVID-19 on day 7, and was discharged from the hospital on day 41. RNA of SARS-CoV-2 was detected in surgically resected rectal specimens, but not in samples collected on 37 day after discharge. Notably, coincidence with rectal tissues of surgical specimens tested nucleic acid positive for SARS-CoV-2, typical coronavirus virions in rectal tissue were observed under electron microscopy. Moreover, abundant lymphocytes and macrophages (some are SARS-CoV-2 positive) infiltrating the lamina propria were found with no significant mucosal damage. Conclusions We firstly reported that direct evidence of the active SARS-CoV-2 replication in the patient's rectum during the incubation period, which might explain SARS-CoV-2 fecal-oral transmission.

Recent advances have highlighted profound roles of FOXO transcription factors, especially FOXO1, in bone development and remodeling. The regulation of bone development by FOXOs seems to be stage-specific or context dependent. FOXOs promote maintenance and differentiation of early progenitors of the osteoblast lineage and repress proliferation of committed osteoblast precursors; FOXO1 is vital for osteocyte survival. Considering the versatile roles played by FOXOs in bone development and tumorigenesis, it is plausible that FOXO1, the main FOXO in bone with a non-redundant role, might have influence on osteosarcoma (OS) oncogenesis. Indeed, recent results have implicated that FOXO1 has a tumor-suppressing role in OS. In the present study, we found that FOXO1 expression was generally low or absent in OS, with a minority of cases having moderate expression. Whole-genome sequencing (WGS) revealed that the FOXO1 locus was frequently involved in copy number variation and loss of heterozygosity in OS, indicating that chromosomal aberrations might be partially responsible for the heterogeneity in FOXO1 expression. FOXO1 activation in OS cell lines inhibited cancer cell survival, which can be attributed to modulation of target genes, including BIM and repressed Wnt/β-catenin signaling. FOXO1 inhibition promoted cell proliferation, enhanced colony formation and attenuated osteogenic differentiation of OS cell lines. To conclude, our results proved FOXO1 as a tumor suppressor in OS at least partially by suppression of the Wnt/β-catenin pathway.

BackgroundGenome-wide DNA copy number changes are the hallmark events in the initiation and progression of cancers. Quantitative analysis of somatic copy number alterations (CNAs) has broad applications in cancer research. With the increasing capacity of high-throughput sequencing technologies, fast and efficient segmentation algorithms are required when characterizing high density CNAs data.ResultsA fast and informative segmentation algorithm, DBS (Deviation Binary Segmentation), is developed and discussed. The DBS method is based on the least absolute error principles and is inspired by the segmentation method rooted in the circular binary segmentation procedure. DBS uses point-by-point model calculation to ensure the accuracy of segmentation and combines a binary search algorithm with heuristics derived from the Central Limit Theorem. The DBS algorithm is very efficient requiring a computational complexity of O(n*log n), and is faster than its predecessors. Moreover, DBS measures the change-point amplitude of mean values of two adjacent segments at a breakpoint, where the significant degree of change-point amplitude is determined by the weighted average deviation at breakpoints. Accordingly, using the constructed binary tree of significant degree, DBS informs whether the results of segmentation are over- or under-segmented.ConclusionDBS is implemented in a platform-independent and open-source Java application (ToolSeg), including a graphical user interface and simulation data generation, as well as various segmentation methods in the native Java language.

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The small GTPase KRAS is frequently mutated in human cancer and currently there are no targeted therapies for KRAS mutant tumors. Here, we show that the small ubiquitin-like modifier (SUMO) pathway is required for KRAS-driven transformation. RNAi depletion of the SUMO E2 ligase Ubc9 suppresses 3D growth of KRAS mutant colorectal cancer cells in vitro and attenuates tumor growth in vivo. In KRAS mutant cells, a subset of proteins exhibit elevated levels of SUMOylation. Among these proteins, KAP1, CHD1, and EIF3L collectively support anchorage-independent growth, and the SUMOylation of KAP1 is necessary for its activity in this context. Thus, the SUMO pathway critically contributes to the transformed phenotype of KRAS mutant cells and Ubc9 presents a potential target for the treatment of KRAS mutant colorectal cancer.he Ras family of small GTPases are signal transduction molecules downstream of growth factor receptors. Ras activates a number of downstream effector pathways to regulate cell proliferation, survival and motility, these effectors include the MAP kinase (MAPK) pathway, the PI3-kinase (PI3K) pathway, the small GTPases RalA, RalB, and Rho, and phospholipase-Ce (1). Activating mutations in Ras are frequently found in human malignancies, with mutations in the KRAS gene being particularly prevalent. KRAS mutations occur in ∼60% of pancreatic ductal carcinomas, 26% of lung adenocarcinomas, and 45% of colorectal carcinomas, as well as a significant fraction of ovarian, endometrial, and biliary track cancers (2, 3). A salient hallmark of the Ras oncogene is its ability to transform cells to enable anchorage-independent 3D colony growth in vitro and tumor growth in vivo. Consequently, Ras mutant cancer cells often exhibit oncogene addiction to Ras such that extinction of the Ras oncogene leads to either a reversion of the transformed phenotype or loss of viability (4, 5). Therapeutically, the Ras oncoprotein has proven pharmacologically intractable thus far: intensive drug screening efforts have not yielded high-affinity, selective Ras inhibitors. Farnesyltransferase inhibitors that aimed to block Ras membrane localization are ineffective against KRAS because of its alternative geranylgeranylation. Inhibitors targeting Ras effector kinases, including MEK, PI3K, and Akt, are currently undergoing clinical evaluations, but they have yet to demonstrate clear clinical benefits (6). Thus, KRAS mutant tumors represent a class of "recalcitrant cancer" with urgent, unmet therapeutic needs.To gain new insight into the genetic dependencies of Ras mutant cancers and discover new therapeutic targets, we and others have previously carried out genome-wide synthetic lethal screens in KRAS mutant and WT cells to identify genes whose depletion leads to greater toxicity in KRAS mutant cells. In our screen we found a wide array of genes, many of which are involved in cellular stress response, that are required to maintain the viability of KRAS mutant cells (7). We proposed the concept of "nononcogene addiction" to explain the heig...