The E-cadherin/AmotL2 complex organizes actin filaments required for epithelial hexagonal packing and blastocyst hatching

Epithelial cells connect via cell-cell junctions to form sheets of cells with separate cellular compartments. These cellular connections are essential for the generation of cellular forms and shapes consistent with organ function. Tissue modulation is dependent on the fine-tuning of mechanical forces that are transmitted in part through the actin connection to E-cadherin as well as other components in the adherens junctions. In this report we show that p100 amotL2 forms a complex with E-cadherin that associates with radial actin filaments connecting cells over multiple layers. Genetic inactivation or depletion of amotL2 in epithelial cells in vitro or zebrafish and mouse in vivo, resulted in the loss of contractile actin filaments and perturbed epithelial packing geometry. We further showed that AMOTL2 mRNA and protein was expressed in the trophectoderm of human and mouse blastocysts. Genetic inactivation of amotL2 did not affect cellular differentiation but blocked hatching of the blastocysts from the zona pellucida. These results were mimicked by treatment with the myosin II inhibitor blebbistatin. We propose that the tension generated by the E-cadherin/AmotL2/actin filaments plays a crucial role in developmental processes such as epithelial geometrical packing as well as generation of forces required for blastocyst hatching.

AmotL2 integrates polarity and junctional cues to modulate cell shape

The assembly of individual epithelial or endothelial cells into a tight cellular sheet requires stringent control of cell packing and organization. These processes are dependent on the establishment and further integration of cellular junctions, the cytoskeleton and the formation of apical-basal polarity. However, little is known how these subcellular events are coordinated. The (Angiomotin) Amot protein family consists of scaffold proteins that interact with junctional cadherins, polarity proteins and the cytoskeleton. In this report, we have studied how these protein complexes integrate to control cellular shapes consistent with organ function. Using gene-inactivating studies in zebrafish and cell culture systems in vitro, we show that Par3 to be essential for localization of AmotL2 to cellular junctions to associate with VE/E-cadherin and subsequently the organization of radial actin filaments. Our data provide mechanistic insight in how critical processes such as aortic lumen expansion as well as epithelial packing into hexagonal shapes are controlled.

AmotL2 disrupts apical-basal cell polarity and promotes tumour invasion

The establishment and maintenance of apical-basal cell polarity is essential for the functionality of glandular epithelia. Cell polarity is often lost in advanced tumours correlating with acquisition of invasive and malignant properties. Despite extensive knowledge regarding the formation and maintenance of polarity, the mechanisms that deregulate polarity in metastasizing cells remain to be fully characterized. Here we show that AmotL2 expression correlates with loss of tissue architecture in tumours from human breast and colon cancer patients. We further show that hypoxic stress results in activation of c-Fos-dependent expression of AmotL2 leading to loss of polarity. c-Fos/hypoxia-induced p60 AmotL2 interacts with the Crb3 and Par3 polarity complexes retaining them in large vesicles and preventing them from reaching the apical membrane. The resulting loss of polarity potentiates the response to invasive cues in vitro and in vivo in mice. These data provide a molecular mechanism how hypoxic stress deregulates cell polarity during tumour progression.

Audit of PSA requesting practices in primary care compared to guidelines established by the Prostate Cancer Risk Management programme in the Avon region of the South West of England

Background

There is considerable challenge in transmitting the complicated information contained in the Prostate Cancer Risk Management (PCRM) programme in the primary care setting. 1 The practices surrounding requesting of PSA should be clearly understood by both GP and patient before requesting this investigation, and in order to further understand the needs and requirements of primary care practitioners in this regard we undertook an audit comparing practices in the Avon region of the Southwest of England compared to the guidelines of the PCRM programme. 1

Methods

Our study identified a consistent year-on-year increase in PSA requests over the study period across all age categories and regions of the southwest of England.

Results

Questionnaire review of practices surrounding the PCRM programme revealed overall good practice but with space for improvement surrounding advice regarding the limitations of prostate biopsy and the relevance of testing in the elderly.

Conclusions

Despite requesting practices generally conforming to NICE guidelines, nearly half of all abnormal primary-care PSA tests are repeated. Requests in some cases may fall short of best practice.

Abstract A12: AmotL2 linking hypoxia to invasion

Hypoxia has been shown to be a bad prognostic marker correlating with metastasis and poor survival. Furthermore, in response to antiangiogenic therapy hypoxic tumor cells become invasive and form metastasis. Malignant tumor cells undergo epithelial-mesenchymal transition (EMT) and become depolarized. A protein important for apicobasal polarity during tumor progression is Crumbs3 (crb3). Silencing of Crumbs3 disrupts epithelial cell polarity and possibly promotes metastasis. AmotL2, a gene regulated by hypoxia, associates to the Crb3/Pals/Patj polarity complex via its PDZ-binding motif (unpublished data).

Here we show that AmotL2 disrupts apicobasal polarity resulting in the development of an invasive phenotype.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A12.

Tubulin α-6 chain is a stably expressed reference gene in archival samples of normal oral tissue and oral squamous cell carcinoma

One of the most critical factors in gene expression studies using quantitative real-time PCR is the choice of reference gene. Many of the commonly used reference genes have been shown to vary during a number of biological processes as well as between tissues. It is therefore important to always verify the stability of the gene of choice for all new tissues and experimental conditions. Here, we used two publicly available computer software packages (GeNorm and NormFinder) to investigate the stability of eight potential reference genes in formalin-fixed paraffin-embedded (FFPE) samples from normal oral tissue of different origin as well as from oral squamous cell carcinomas. Both programs found the tubulin α-6 chain (TUBA6) and ribosomal protein S13 (RPS13) to have the most stable expression between malignant and non-malignant tissue. NormFinder also found TUBA6 to be the most stable gene when samples were grouped according to tissue origin. FFPE samples constitute a large research resource, which considerably increases the number of samples available for analysis, leading to more reliable conclusions. Verification of a proper reference gene in oral FFPE tissue is therefore of great importance for future studies.