Epigenetic Regulation of Dlg1, via Kaiso, Alters Mitotic Spindle Polarity and Promotes Intestinal Tumorigenesis

Abstract

Both alterations to the epigenome and loss of polarity have been linked to cancer initiation, progression, and metastasis. It has previously been demonstrated that loss of the epigenetic reader protein Kaiso suppresses intestinal tumorigenesis in the Apc þ/min mouse model, in which altered polarity plays a key role. Thus, we investigated the link between Kaiso deficiency, polarity, and suppression of intestinal tumorigenesis. We used Kaiso-deficient mice to conditionally delete Apc within the intestinal epithelia and demonstrated upregulation of the spindle polarity genes Dlg1 and Dlgap1. To understand the role of Dlg1, we generated Villin-creApc þ/min Dlg1 flx/flx Kaiso À/y mice to analyze gene expression, survival, tumor burden, and spindle orientation. In vivo analysis of the Dlg1-deficient intestine revealed improper orientation of mitotic spindles and a decreased rate of cellular migration.Loss of Dlg1 decreased survival in Apc þ/min mice, validating its role as a tumor suppressor in the intestine. Significantly, the increased survival of Apc þ/min Kaiso y/À mice was shown to be dependent on Dlg1 expression. Taken together, these data indicate that maintenance of spindle polarity in the intestinal crypt requires appropriate regulation of Dlg1 expression. As Dlg1 loss leads to incorrect spindle orientation and a delay in cells transiting the intestinal crypt. We propose that the delayed exit from the crypt increase the window in which spontaneous mutations can become fixed, producing a "tumor-permissive" environment, without an increase in mutation rate.Implications: Loss of mitotic spindle polarity delays the exit of cells from the intestinal crypt and promotes a tumorigenic environment.

The interaction between CASK and the tumour suppressor Dlg1 regulates mitotic spindle orientation in mammalian epithelia

“…Recently, Dlg1 loss has been shown to cooperate with APC mutations to promote intestinal carcinogenesis in a mouse model (Young et al, 2019), an effect thought to be mediated by spindle misorientation due to loss of Dlg1. While a clear causal link between spindle misorientation and tumourigenesis remains elusive (see recent review in Seldin and Macara, 2017), it remains a plausible hypothesis that disruption to the spindle orientation machinery could play a role in tumour initiation or progression.…”

Downregulation of hsa-microRNA-204-5p and identification of its potential regulatory network in non-small cell lung cancer: RT-qPCR, bioinformatic- and meta-analyses

“…DLG1 is a vital participant in the control of cellular processes like polarity, proliferation and migration, so its dysregulation and mutation give rise to pathologies that include oncogenic processes [76]. DLG1 is mainly identified as a tumor suppressor, since overexpression is observed early in the onset of cervical cancer (CeCa) [77] and elevated DLG1 promotes intestinal tumorigenesis [78], predicts poor prognosis in people with CRC [79] and increases the invasiveness of NSCLC cell lines [80]. Increased phosphorylation of the DLG1 SH3-Hook region promotes interaction with the PDZ ligand of PKCα and accelerates cell migration [80].…”

“…The lncRNA DLG1-AS1 acts as a competitive inhibitor that influences the activity of miR-107 on its target gene ZHX1, thereby inducing cancer cell proliferation [81]. Moreover, DLG1 deficiency results in incorrect spindle polarity and a delay in cells transiting orientation [78], which disrupts cellular structure and distribution [82]. Interestingly, DLG1 protein levels are significantly lower in NSCLC and hepatocellular carcinoma (HCC) than in the corresponding normal tissues [83,84], but are nearly undetectable in poorly differentiated stages of colon adenocarcinoma [85], in contrast to our findings and the existing literature.…”

Insights Into Mechanisms of Oriented Division From Studies in 3D Cellular Models

“…Ablation of Dlg-1 from the murine intestinal crypts has been shown to result in misoriented divisions of the intestinal stem cells with a consequent delay in cell migration from the crypts bottom to the villi that promotes tumorigenic events ( Young et al, 2019 ). Similarly, depletion from the murine crypts of the protein Tacc3, which is involved in MT crosslinking and stabilization of the Aurora-A dependent kinetochore-microtubules attachment ( LeRoy et al, 2007 ; Burgess et al, 2015 ), blocks proliferation ( Yao et al, 2016 ).…”