Characterization of F3II, a sarcomatoid mammary carcinoma cell line originated from a clonal subpopulation of a mouse adenocarcinoma

We characterized a new mammary tumor cell line, F3II, previously established in vitro from a clonal subpopulation of the BALB/c transplantable mammary adenocarcinoma M3, moderately metastatic to lung. The F3II cell line has been passaged > 50 times. It has grown as elongated cells adherent to the bottom of the flask. Cytogenetic studies showed that F3II cultures were nearly triploid. Tumor cells expressed fibronectin and showed high levels of cell-surface urokinase, a key protease in invasion and metastasis. F3II cells grew as poorly differentiated, spindle-cell carcinoma tumors (sarcomatoid carcinomas) with a prominent local invasiveness, a high angiogenic response, and a 90-100% incidence of lung metastases when inoculated s.c. into syngeneic mice. Ultrastructural and immunocytochemical analysis revealed characteristic features of carcinomas. Our data suggest that F3II is less differentiated and more aggressive than the original tumor line, supporting the notion that mammary carcinomas are heterogeneous neoplasms and contain subpopulations with diverse biologic behavior. The F3II mouse mammary sarcomatoid carcinoma line is a suitable model to examine antiinvasive, antiangiogenic, and antimetastatic agents.

Genomewide Association Studies of LRRK2 Modifiers of Parkinson's Disease

Objective

The aim of this study was to search for genes/variants that modify the effect of LRRK2 mutations in terms of penetrance and age‐at‐onset of Parkinson's disease.

Methods

We performed the first genomewide association study of penetrance and age‐at‐onset of Parkinson's disease in LRRK2 mutation carriers (776 cases and 1,103 non‐cases at their last evaluation). Cox proportional hazard models and linear mixed models were used to identify modifiers of penetrance and age‐at‐onset of LRRK2 mutations, respectively. We also investigated whether a polygenic risk score derived from a published genomewide association study of Parkinson's disease was able to explain variability in penetrance and age‐at‐onset in LRRK2 mutation carriers.

Results

A variant located in the intronic region of CORO1C on chromosome 12 (rs77395454; p value = 2.5E‐08, beta = 1.27, SE = 0.23, risk allele: C) met genomewide significance for the penetrance model. Co‐immunoprecipitation analyses of LRRK2 and CORO1C supported an interaction between these 2 proteins. A region on chromosome 3, within a previously reported linkage peak for Parkinson's disease susceptibility, showed suggestive associations in both models (penetrance top variant: p value = 1.1E‐07; age‐at‐onset top variant: p value = 9.3E‐07). A polygenic risk score derived from publicly available Parkinson's disease summary statistics was a significant predictor of penetrance, but not of age‐at‐onset.

Interpretation

This study suggests that variants within or near CORO1C may modify the penetrance of LRRK2 mutations. In addition, common Parkinson's disease associated variants collectively increase the penetrance of LRRK2 mutations. ANN NEUROL 2021;90:82–94

Modulation of fibronectin expression and proteolytic activity associated with the invasive and metastatic phenotype in two new murine mammary tumor cell lines

Two cell lines obtained by sequential subcultures from primary cultures of the murine mammary adenocarcinomas M3 and MM3 were characterized. During LM3 cell line evolution an increase in the anchorage-independent growth ability, a displacement towards a triploid level in the chromosomic distribution and a loss of fibronectin (FN) expression were observed. LMM3 cell line showed a tetraploid chromosomic number and was unable to produce FN, behaving in a similar way as its parental tumor MM3. The local invasive ability as well as the spontaneous metastatic capacity of LM3 cells inoculated subcutaneously (s.c.) increased with the passage number and were associated with the progressive loss of FN expression as well as to the appearence of membrane bound uPA. LMM3 cells, which did not express FN, maintained the high spontaneous metastasic capacity already shown by the parental tumor MM3 but acquired a higher local invasive phenotype.

Expression of RGD minus fibronectin that does not form extracellular matrix fibrils is sufficient to decrease tumor metastasis

Fibronectin (FN) is a plasma and extracellular matrix (ECM) glycoprotein, the expression of which may modulate the invasive and metastatic abilities of cancer cells. LMM3 is a cell line derived from the highly metastatic mouse mammary adenocarcinoma MM3 and is unable to express FN both at protein and mRNA levels. To study the role of FN in the metastatic process, LMM3 cells were stably transfected with 2 variants (wt and RGD-minus) of a full length human FN cDNA. All analyzed clones secreted recombinant FN and although none assembled FN in the ECM they showed an in vitro reduced migratory ability and an increased adhesive capacity. FN-producing cells were assayed for experimental and spontaneous metastasis. All clones tested showed a significant reduction in the number of experimental lung metastasis when compared with a control clone. Similar trends were observed for spontaneous metastatic ability. Our results indicate that the expression of FN that lacks the well-recognized RGD cell-binding site and that does not form ECM fibrils, is sufficient to decrease the metastatic potential of cancer cells. Our results also suggest that an RGD-independent mechanism may be acting in the prevention of metastasis.

TTP as Tumor Suppressor and Inflammatory Regulator in Oral Carcinogenesis

The stability of messenger RNA (mRNA) is controlled by proteins that bind to adenosine-uridine-rich sequences (AREs) in their 3' untranslated regions (3'UTR), known as AU-binding proteins. One of these proteins is tristetraprolin (TTP; encoded by Zfp36), which promotes degradation of mRNAs with AREs in their 3'UTR. TTP accelerates the decay of its target transcripts, many of which encode proinflammatory mediators that promote tumorigenesis. TTP underexpression has been reported in multiple cancer types. Oral squamous cell carcinoma is an aggressive disease characterized by high morbidity and few therapeutic options. The role of TTP has not been studied in oral epithelium homeostasis nor in its carcinogenesis. Herein, using tissue-specific TTP knockout mice (TTP-KO), we show that TTP expression is relevant for oral epithelium homeostasis. TTP-KO mice developed dysplastic lesions in the tongue along with inflammatory infiltrates in the connective tissue. Analysis of the inflammatory infiltrate revealed the presence of mast cells (MCs), CD45+ cells, and CD11b+ cells, with the MCs being the most abundant cell type and associated with cyclooxygenase-2 expression. Recruitment of MCs was dependent on tumor necrosis factor-α (TNFα) upon TTP ablation in the tongue. Although the infiltration of MCs was dependent on TNFα activity, this did not affect the development of tongue dysplasia. We analyzed the status of the NF-κB pathway, finding its activation. In addition, we demonstrate that K-ras activation combined with Zfp36 deletion leads to the rapid onset of the oral tongue phenotype and significantly reduces mouse survival. Our results support the notion that TTP expression protects against oral carcinogenesis, regulates the inflammatory infiltrate, and maintains the epithelial microenvironment, potentially serving as a barrier to tumorigenesis.