Formation of an invasion-permissive matrix requires TGFβ/SNAIL1-regulated alternative splicing of fibronectin

BACKGROUND

As in most solid cancers, the emergence of cells with oncogenic mutations in the mammary epithelium alters the tissue homeostasis. Some soluble factors, such as TGFβ, potently modify the behavior of healthy stromal cells. A subpopulation of cancer-associated fibroblasts expressing a TGFβ target, the SNAIL1 transcription factor, display myofibroblastic abilities that rearrange the stromal architecture. Breast tumors with the presence of SNAIL1 in the stromal compartment, and with aligned extracellular fiber, are associated with poor survival prognoses.

METHODS

We used deep RNA sequencing and biochemical techniques to study alternative splicing and human tumor databases to test for associations (correlation t-test) between SNAIL1 and fibronectin isoforms. Three-dimensional extracellular matrices generated from fibroblasts were used to study the mechanical properties and actions of the extracellular matrices on tumor cell and fibroblast behaviors. A metastatic mouse model of breast cancer was used to test the action of fibronectin isoforms on lung metastasis.

RESULTS

In silico studies showed that SNAIL1 correlates with the expression of the extra domain A (EDA)-containing (EDA+) fibronectin in advanced human breast cancer and other types of epithelial cancers. In TGFβ-activated fibroblasts, alternative splicing of fibronectin as well as of 500 other genes was modified by eliminating SNAIL1. Biochemical analyses demonstrated that SNAIL1 favors the inclusion of the EDA exon by modulating the activity of the SRSF1 splicing factor. Similar to Snai1 knockout fibroblasts, EDA- fibronectin fibroblasts produce an extracellular matrix  that does not sustain TGFβ-induced fiber organization, rigidity, fibroblast activation, or tumor cell invasion. The presence of EDA+ fibronectin changes the action of metalloproteinases on fibronectin fibers. Critically, in an mouse orthotopic breast cancer model, the absence of the fibronectin EDA domain completely prevents lung metastasis.

CONCLUSIONS

Our results support the requirement of EDA+ fibronectin in the generation of a metastasis permissive stromal architecture in breast cancers and its molecular control by SNAIL1. From a pharmacological point of view, specifically blocking EDA+ fibronectin deposition could be included in studies to reduce the formation of a pro-metastatic environment.

Splicing of a non-coding antisense transcript controls LEF1 gene expression

In this report we have analyzed the role of antisense transcription in the control of LEF1 transcription factor expression. A natural antisense transcript (NAT) is transcribed from a promoter present in the first intron of LEF1 gene and undergoes splicing in mesenchymal cells. Although this locus is silent in epithelial cells, and neither NAT transcript nor LEF1 mRNA are expressed, in cell lines with an intermediate epithelial-mesenchymal phenotype presenting low LEF1 expression, the NAT is synthesized and remains unprocessed. Contrarily to the spliced NAT, this unspliced NAT down-regulates the main LEF1 promoter activity and attenuates LEF1 mRNA transcription. Unspliced LEF1 NAT interacts with LEF1 promoter and facilitates PRC2 binding to the LEF1 promoter and trimethylation of lysine 27 in histone 3. Expression of the spliced form of LEF1 NAT in trans prevents the action of unspliced NAT by competing for interaction with the promoter. Thus, these results indicate that LEF1 gene expression is attenuated by an antisense non-coding RNA and that this NAT function is regulated by the balance between its spliced and unspliced forms.

[Primary amyloidosis associated to severe factor X deficiency]

Amyloidosis is a systemic disease characterized by generalized deposition of beta-organized proteic fibrillar material with green birefringence under polarized light, in different tissues and organs, the most frequent kidney, liver and heart, with important clinical repercussion. Primary or AL amyloidosis is the most common subtype of amyloidosis (1), confirmed by biopsy-proved amyloid deposition in abdominal fat pad, rectum, kidney or liver, if necessary, in which fragments of monoclonal light chains are deposited. Cases with factor X (Stuart factor) of coagulation deficiency associated are described, due to adsorption of this factor to amyloid fibrills. Normally, evolution is fatal, with only few months of survival. We report a case of primary amyloidosis with nephrotic syndrome, severe factor X deficiency (without bleeding complications), possible heart affection and short-term good response to chemotherapic treatment.

Leiomioma de vejiga. análisis de agregación de 90 casos

INTRODUCTION

Bladder leiomyomas (BL) are rare. Most publications regarding these tumours are reports of isolated cases; therefore they don't allow an evaluation of diagnostic and treatment procedures.

MATERIAL & METHODS

We preformed a pooled analysis of 90 cases of BL reported in the literature.

RESULTS

Mean age was 45.3 (19 to 85 years), 68 (75.6%) were women. Filling symptoms were the most frequently reported (50%), followed by voiding symptoms (24.4%). Twenty four patients (26.7%) were asymptomatic. Tumours were endoluminal in 46 patients (51.1%), intramural in 27 (30%) and extravesical in 15 (16.7%). A laparotomy was performed in 56 patients (62.2%), with enucleation in 29 (32.2%), partial cystectomy in 25 (27.8%) and total cystectomy in 2 (2.2%). A transurethral resection was preformed in 27 (30%) and a transvaginal resection in 5 (5.6%). Two patients underwent conservative treatment. In 3 cases there were reports of recurrence and one patient got a vesicovaginal fistula.

CONCLUSIONS

Although BL are rare, when evaluating bladder tumours, imaging techniques can make suspect of this neoplasm. Surgical treatment of these tumours has a very high success rate. Usually an enucleation or a transurethral resection is sufficient to render the patient tumour free, avoiding a more iatrogenic surgery.

Waldenström macroglobulinaemia: presenting features and outcome in a series with 217 cases

In this report we analyse the presenting features of a series of patients diagnosed with Waldenström macroglobulinaemia (WM) in Spain over the last 10 years. Criteria for diagnosis required a serum monoclonal IgM protein > or = 30 g/l and > 20% bone marrow lymphocytes. Two hundred and seventeen patients were included in the study, with a median age of 69 years and male/female ratio of 2:1. The most common symptoms at diagnosis were anaemia (38%), hyperviscosity (31%), B symptoms (23%), bleeding (23%) and neurological symptoms (22%). Sixty-one patients (27%) were asymptomatic at diagnosis and, to date, 32 of them have not received chemotherapy. Variables predicting a shorter survival free of therapy were haemoglobin < 12.5 g/dl and high beta2microglobulin (beta2M). The 83% of patients who did receive treatment were distributed as follows: chlorambucil/prednisone (43%), intermittent chlorambucil (11%), continuous chlorambucil (26%), cyclophosphamide/vincristine/prednisone (COP, 13.5%) and other (6.5%). Response to therapy was complete in 2%, partial in 48% and minor in 10%. Finally, 28% and 13% of patients presented stable and progressive disease, respectively, which was more common among patients treated with COP. Progression-free survival was 43% at 5 years, with three independent predictors for shorter progression-free survival (PFS): COP treatment, age > 65 and B symptoms at diagnosis. The 10-year projected overall survival (OS) was 55%. The two most frequent causes of death were development of second malignancies (31%), or infections (19%). The two main variables predicting a poor OS were hyperviscosity and high beta2M. In summary, this study favours the use of chlorambucil-based therapy as the standard treatment for WM, and describes a subset of patients who should be considered as suffering a smouldering form and who therefore do not require treatment for a long period of time.