A novel auxin-inducible degron system for rapid, cell cycle-specific targeted proteolysis.

The discrimination of protein biological functions in different phases of the cell cycle is limited by the lack of experimental approaches that do not require pre-treatment with compounds affecting the cell cycle progression. Therefore, potential cycle-specific biological functions of a protein of interest could be biased by the effects of cell treatments. The OsTIR1/auxin-inducible degron (AID) system allows "on demand" selective and reversible protein degradation upon exposure to the phytohormone auxin. In the current format, this technology does not allow to study the effect of acute protein depletion selectively in one phase of the cell cycle, as auxin similarly affects all the treated cells irrespectively of their proliferation status. Therefore, the AID system requires coupling with cell synchronization techniques, which can alter the basal biological status of the studied cell population, as with previously available approaches. Here, we introduce a new AID system to Regulate OsTIR1 Levels based on the Cell Cycle Status (ROLECCS system), which induces proteolysis of both exogenously transfected and endogenous gene-edited targets in specific phases of the cell cycle. We validated the ROLECCS technology by down regulating the protein levels of TP53, one of the most studied tumor suppressor genes, with a widely known role in cell cycle progression. By using our novel tool, we observed that TP53 degradation is associated with increased number of micronuclei, and this phenotype is specifically achieved when TP53 is lost in S/G2/M phases of the cell cycle, but not in G1. Therefore, we propose the use of the ROLECCS system as a new improved way of studying the differential roles that target proteins may have in specific phases of the cell cycle.

Downregulation of miR-223 Expression Is an Early Event during Mammary Transformation and Confers Resistance to CDK4/6 Inhibitors in Luminal Breast Cancer.

miR-223 is an anti-inflammatory miRNA that in cancer acts either as an oncosuppressor or oncopromoter, in a context-dependent manner. In breast cancer, we demonstrated that it dampens the activation of the EGF pathway. However, little is known on the role of miR-223 during breast cancer onset and progression. miR-223 expression was decreased in breast cancer of luminal and HER2 subtypes and inversely correlated with patients' prognosis. In normal luminal mammary epithelial cells, miR-223 acted cell autonomously in the control of their growth and morphology in three-dimensional context. In the MMTV-Δ16HER2 transgenic mouse model, oncogene transformation resulted in a timely abrogation of miR-223 expression, likely due to activation of E2F1, a known repressor of miR-223 transcription. Accordingly, treatment with CDK4/6 inhibitors, which eventually results in restraining E2F1 activity, restored miR-223 expression and miR-223 ablation induced luminal breast cancer resistance to CDK4/6 inhibition, both in vitro and in vivo. Notably, miR-223 expression was lost in microdissected ductal carcinoma in situ (DCIS) from patients with luminal and HER2-positive breast cancer. Altogether, these results identify downmodulation of miR-223 as an early step in luminal breast cancer onset and suggest that it could be used to identify aggressive DCIS and predict the response to targeted therapy. SIGNIFICANCE: miR-223 may represent a predictive biomarker of response to CDK4/6 inhibitors and its loss could identify DCIS lesions that are likely to progress into invasive breast cancer.

TIMP-1 is Overexpressed and Secreted by Platinum Resistant Epithelial Ovarian Cancer Cells.

Epithelial Ovarian Cancer (EOC) is the most lethal gynecological cancer in developed countries, and the development of new strategies to overcome chemoresistance is an awaited clinical need. Angiogenesis, the development of new blood vessels from pre-existing vasculature, has been validated as a therapeutic target in this tumor type. The aim of this study is to verify if EOC cells with acquired resistance to platinum (PT) treatment display an altered angiogenic potential. Using a proteomic approach, we identified the tissue inhibitor of metalloproteinases 1 (TIMP-1) as the only secreted factor whose expression was up-regulated in PT-resistant TOV-112D and OVSAHO EOC cells used as study models. We report that TIMP-1 acts as a double-edged sword in the EOC microenvironment, directly affecting the response to PT treatment on tumor cells and indirectly altering migration and proliferation of endothelial cells. Interestingly, we found that high TIMP-1 levels in stage III-IV EOC patients associate with decreased overall survival, especially if they were treated with PT or bevacizumab. Taken together, these results pinpoint TIMP-1 as a key molecule involved in the regulation of EOC PT-resistance and progression disclosing the possibility that it could be used as a new biomarker of PT-resistance and/or therapeutic target.

USP1 links platinum resistance to cancer cell dissemination by regulating Snail stability.

Resistance to platinum-based chemotherapy is a common event in patients with cancer, generally associated with tumor dissemination and metastasis. Whether platinum treatment per se activates molecular pathways linked to tumor spreading is not known. Here, we report that the ubiquitin-specific protease 1 (USP1) mediates ovarian cancer cell resistance to platinum, by regulating the stability of Snail, which, in turn, promotes tumor dissemination. At the molecular level, we observed that upon platinum treatment, USP1 is phosphorylated by ATM and ATR and binds to Snail. Then, USP1 de-ubiquitinates and stabilizes Snail expression, conferring resistance to platinum, increased stem cell-like features, and metastatic ability. Consistently, knockout or pharmacological inhibition of USP1 increased platinum sensitivity and decreased metastatic dissemination in a Snail-dependent manner. Our findings identify Snail as a USP1 target and open the way to a novel strategy to overcome platinum resistance and more successfully treat patients with ovarian cancer.

Stathmin Is Required for Normal Mouse Mammary Gland Development and Δ16HER2-Driven Tumorigenesis.

Postnatal development of the mammary gland relies on the maintenance of oriented cell division and apicobasal polarity, both of which are often deregulated in cancer. The microtubule (MT) network contributes to control these processes; however, very little is known about the impact of altered MT dynamics in the development of a complex organ and on the role played by MT-interacting proteins such as stathmin. In this study, we report that female stathmin knock-out (STM KO) mice are unable to nurse their litters due to frank impairment of mammary gland development. In mouse mammary epithelial cells, loss of stathmin compromised the trafficking of polarized proteins and the achievement of proper apicobasal polarity. In particular, prolactin receptor internalization and localization was altered in STM KO mammary epithelial cells, leading to decreased protein stability and downmodulation of the Prl/PrlR/STAT5 signaling pathway. Absence of stathmin induced alterations in mitotic spindle orientation, accumulation of mitotic defects, and apoptosis, overall contributing to tissue disorganization and further decreasing the expansion of the mammary epithelial compartment. Loss of stathmin in MMTV-Δ16HER2 transgenic mice decreased the incidence and increased the latency of these very aggressive mammary carcinomas. Collectively, these data identify the essential mammary protein stathmin as protumorigenic and suggest it may serve as a potential therapeutic target in breast cancer. SIGNIFICANCE: Stathmin expression is critical to maintain oriented cell division and apicobasal polarity in normal mammary glands and to establish a protumorigenic program that eventually sustains HER2-positive breast cancer formation in mice.

Optimized immunohistochemistry using the D5F3 antibody provides a reliable test for identification of ALK-positive lung adenocarcinomas.

We used optimized immunohistochemistry (IHC) with the D5F3 antibody for detection of tumours in a prospective study of 307 pulmonary adenocarcinomas. Cases positive by IHC (1+, 2+, 3+) were further investigated by fluorescent in situ hybridization (FISH). Of 307 cases, 22 (7.2%) were moderately intensely positive (2+/3+); 18 of these (82%) were also positive by FISH. Of the four IHC-positive/FISH-negative cases, one was unsuitable for FISH and three had abnormalities of the ALK gene. All cases with weak reactivity with D5F3 (1+) were FISH-negative. The FISH positive/IHC-positive cases with moderately intense reactivity had the typical clinicopathologic features of ALK-positive patients (younger age, p < 0.01; higher frequency in metastatic sites, p < 0.01; cribriform/mucinous/signet histology, p < 0.01; stage IV disease, p < 0.01). In conclusion, our findings indicate that optimized IHC using the D5F3 antibody provides a reliable and inexpensive test for identification of ALK-positive adenocarcinomas. Inclusion of this information in the pathology report at the time of the histological diagnosis might significantly shorten time to treatment.

Diffuse Follicular Variant of Papillary Thyroid Carcinoma: A Case Report with a Revision of Literature.

The diffuse follicular variant of papillary thyroid carcinoma (DFV-PTC) is a rare malignant thyroid condition. It represents an uncommon variant of papillary carcinoma characterized by a diffuse involvement of thyroid parenchyma, follicular architecture and nuclear features of PTC in absence of a surrounding capsule. Up to date few data have been collected about this entity and, at the best of our knowledge, only 24 cases have been reported in the literature. According to these reports DFV-PTC seems to occur preferentially in young women and shows more aggressive behavior than other papillary thyroid tumors. Herein we present an unusual case of DFV-PTC occurring in an 83 years old woman, involving the entire thyroid gland, without distinct or prevalent thyroid nodules. The tumor was clinically misdiagnosed as obstructive goiter.

Oncocytic Variant of Medullary Thyroid Carcinoma: A Rare Case of Sporadic Multifocal and Bilateral RET Wild-Type Neoplasm with Revision of the Literature.

Oncocytic variant of medullary thyroid carcinoma (OV-MTC) is a very unusual entity, up to date only 17 cases have been reported in the literature. MTC is a neuro-endocrine malignancy arising from the para-follicular C cells of the thyroid gland. It generally has a slight female predominance and appears as a single lesion. However in the Multiple Endocrine Neoplasia Syndrome 2, linked to the point mutation of RET oncogene, multifocal MTCs may also occur. Herein, we report the case of a 75 years old man with a rare form of sporadic multifocal and bilateral OV-MTC expressing wild-type RET gene. The histological and molecular features of this rare entity are presented and discussed with revision of the pertinent literature.

Transitional cell carcinoma of the retrorectal space arisen in tailgut cyst: a case report and review of the literature.

Tailgut cysts, also known as retrorectal cystic hamartomas, are congenital lesions derived by an abnormal remnant of the postanal primitive hindgut, consisting of unilocular or multilocular cysts usually lined by squamous, transitional, or glandular epithelium. Malignant transformation is an uncommon event, and it mainly involves the neuroendocrine or glandular epithelium; other histotypes are sporadic. Here, we report, for the first time, the clinicopathological features of a transitional cell carcinoma that arose in a tailgut cyst.