Francesca Montani

Protein phosphatases take the mitotic stage

Following the identification of cyclin-dependent kinases in the 1980s, kinases were hailed as the directors of mitosis. Although the action of kinases must necessarily be reversible, only recently has the involvement of specific phosphatases in mitosis become appreciated. Studies are now revealing how the timely execution of mitotic events depends on the delicate interplay between kinases and phosphatases. To date, the best-characterized mitotic phosphatases are Cdc25, that is required for entry into mitosis and Cdc14, that controls exit from mitosis in budding yeast. Recent work has now exposed the conserved serine-threonine phosphatases PP1 and PP2A as key regulators of various mitotic processes.

Oscillations in Cdc14 release and sequestration reveal a circuit underlying mitotic exit.

The phosphatase Cdc14 exerts negative feedback on its upstream regulators to limit its release from the nucleolus to once per cell cycle.

DEPDC1B coordinates de-adhesion events and cell-cycle progression at mitosis.

Summary Cells entering mitosis become rounded, lose attachment to the substrate, and increase their cortical rigidity. Pivotal to these events is the dismantling of focal adhesions (FAs). How mitotic reshaping is linked to commitment to divide is unclear. Here, we show that DEPDC1B, a protein that accumulates in G2, coordinates de-adhesion events and cell-cycle progression at mitosis. DEPDC1B functions as an inhibitor of a RhoA-based signaling complex, which assembles on the FA-associated protein tyrosine phosphatase, receptor type, F (PTPRF) and mediates the integrity of FAs. By competing with RhoA for the interaction with PTPRF, DEPDC1B promotes the dismantling of FAs, which is necessary for the morphological changes preceding mitosis. The circuitry is relevant in whole organisms, as shown by the control exerted by the DEPDC1B/RhoA/PTPRF axis on mitotic dynamics during zebrafish development. Our results uncover an adhesion-dependent signaling mechanism that coordinates adhesion events with the control of cell-cycle progression.

Optimization and Standardization of Circulating MicroRNA Detection for Clinical Application: The miR-Test Case.

BACKGROUND The identification of circulating microRNAs (miRNAs) in the blood has been recently exploited for the development of minimally invasive tests for the early detection of cancer. Nevertheless, the clinical transferability of such tests is uncertain due to still-insufficient standardization and optimization of methods to detect circulating miRNAs in the clinical setting. METHODS We performed a series of tests to optimize the quantification of serum miRNAs that compose the miR-Test, a signature for lung cancer early detection, and systematically analyzed variables that could affect the performance of the test. We took advantage of a large-scale (>1000 samples) validation study of the miR-Test that we recently published, to evaluate, in clinical samples, the effects of analytical and preanalytical variables on the quantification of circulating miRNAs and the clinical output of the signature (risk score). RESULTS We developed a streamlined and standardized pipeline for the processing of clinical serum samples that allows the isolation and analysis of circulating miRNAs by quantitative reverse-transcription PCR, with a throughput compatible with screening trials. The major source of analytical variation came from RNA isolation from serum, which could be corrected by use of external (spike-in) or endogenous miRNAs as a reference for normalization. We also introduced standard operating procedures and QC steps to check for unspecific fluctuations that arise from the lack of standardized criteria in the collection or handling of the samples (preanalytical factors). CONCLUSIONS We propose our methodology as a reference for the development of clinical-grade blood tests on the basis of miRNA detection.

Recessive Cancer Genes Engage in Negative Genetic Interactions with Their Functional Paralogs

Cancer genetic heterogeneity offers a wide repertoire of molecular determinants to be screened as therapeutic targets. Here, we identify potential anticancer targets by exploiting negative genetic interactions between genes with driver loss-of-function mutations (recessive cancer genes) and their functionally redundant paralogs. We identify recessive genes with additional copies and experimentally test our predictions on three paralogous pairs. We confirm digenic negative interactions between two cancer genes (SMARCA4 and CDH1) and their corresponding paralogs (SMARCA2 and CDH3). Furthermore, we identify a trigenic negative interaction between the cancer gene DNMT3A, its functional paralog DNMT3B, and a third gene, DNMT1, which encodes the only other human DNA-methylase domain. Although our study does not exclude other causes of synthetic lethality, it suggests that functionally redundant paralogs of cancer genes could be targets in anticancer therapy.

Circulating Cancer Biomarkers: The Macro-revolution of the Micro-RNA

MicroRNAs (miRNAs) are small non-coding RNAs that act as master regulators of many cellular processes. The expression of miRNAs is often deregulated in human tumors, causing the alteration of molecular mechanisms relevant for cancer progression. Importantly, miRNAs are detectable in the blood and their quantity fluctuations are the hallmark of pathogenic conditions, including cancer. Several groups reported the identification of circulating cell-free miRNAs (cf-miRNAs) in the human serum and plasma and demonstrated their diagnostic and prognostic utility. Other studies also shown that it may be feasible to apply such cf-miRNA signatures within screening programs in order to improve cancer early detection. Circulating cf-miRNAs therefore appear to be excellent candidates for blood-borne cancer biomarkers.

Abstract 1573: miR-Test: a blood test for lung cancer early detection

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Background: Lung cancer is the leading cause of cancer death worldwide. As lung cancer is asymptomatic in its early stages, the majority of patients are diagnosed with advanced disease, when the tumor is unresectable. Consequently, the survival rate is very low: 15% at 5 years. It is vital, therefore, that screening programs and novel diagnostic tools are developed, which will increase the detection of lung cancer in its early stages (stage I-II), when the tumor is still curable, to reduce lung cancer mortality. Recently, we described a serum microRNA signature diagnostic for asymptomatic, early stage, lung cancer. The availability of reliable biomarkers to identify high-risk individuals might help to reduce the size of the target population for LDCT-based programs, thereby reducing costs and probably increasing compliance Methods: We performed a large-scale validation study of a miRNA blood test based on our signature (the miR-Test) in a population of high-risk individuals (N = 1115) enrolled in the lung cancer screening program COSMOS (Continuous Observation of SMOking Subjects), and other 74 lung cancer patients diagnosed outside of screening. Results: The miR-Test showed overall accuracy, specificity and sensitivity of 75%, 78%, and 75%, respectively, with an AUC of 0.85. The test appears to have a dual origin: the first from epithelial cells (the epithelial-like component); the second from cells of hematopoietic origin (the inflammatory-like component). Of note, we found that both components are needed to maintain a good performance of the miR-Test. Conclusions: The relatively high sensitivity of the miR-Test in detecting asymptomatic lung cancer and its high negative predictive value (NPV > 99%), confirm the effectiveness of the test, both interms of its ability to identify asymptomatic lung cancer patients and to reduce significantly unnecessary CTs on healthy individuals. Citation Format: Francesca Montani, Matteo Jacopo Marzi, Fabio Dezi, Elisa Dama, Rose Mary Carletti, Giuseppina Bonizzi, Raffaella Bertolotti, Massimo Bellomi, Cristiano Rampinelli, Patrick Maisonneuve, Lorenzo Spaggiari, Giulia Veronesi, Francesco Nicassio, Pier Paolo Di Fiore, Fabrizio Bianchi. miR-Test: a blood test for lung cancer early detection. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1573. doi:10.1158/1538-7445.AM2015-1573

Unraveling the role of low-frequency mutated genes in breast cancer

Motivation: Breast cancer is the most commonly diagnosed malignancy in women and the second cause of cancer death in developed countries. While advancements in early detection and therapeutic options have led to a significant decrease in mortality, response to treatment is affected by the genetic heterogeneity of the disease. Recent genome‐wide DNA mutation analyses revealed the existence of hundreds of low‐frequency mutated genes, in addition to known cancer drivers: a finding that is prompting research into the impact of these genes on the pathogenesis of the disease. Results: Herein, we describe a strategy towards the characterization of the role of low‐frequency mutated genes in breast cancer. Through the combined analyses of publicly available gene expression and mutational datasets, we identified several Cancer Gene Modules (CMs) that we re‐organized in Gene Regulatory Networks (GRN) enriched in low‐frequency mutated genes. Importantly, these low‐frequency mutated genes were mutually exclusive with known cancer drivers. Finally, we provide evidence that gene expression analysis of these mutated GRNs can predict resistance/sensitivity to chemotherapeutic drugs for breast cancer treatment. Availability and implementation: Datasets are available at https://www.ncbi.nlm.nih.gov/geo/ and at https://www.ebi.ac.uk/ega/datasets/. Molecular signatures and GSEA software are available at http://www.gsea‐msigdb.org/gsea/index.jsp. Source codes are available at https://github.com/EleonoraLusito/Reverse_Engineering_BC_GRNs. Supplementary information: Supplementary data are available at Bioinformatics online.

Abstract 1575: Serum circulating miR–Test application: Standardized protocol for miR–Test clinical application

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Lung cancer is leading cause of cancer death worldwide. Being lung cancer asymptomatic in its early stages, the majority of patients are diagnosed with advanced disease. Therefore, it is vital that screening programs and novel diagnostic tools are developed to increase lung cancer early detection. The development of a minimally invasive blood-based diagnostic tool would be ideal as a first-line screening procedure. An increasing number of studies are demonstrating that fluctuations of circulating miRNAs are associated to lung cancer. Recently, we described a serum circulating miRNA signature (miR-Test) diagnostic for asymptomatic, early stage, lung cancer, that was validated in a large cohort of individuals (N = 1115) enrolled in the lung cancer screening program COSMOS (Continuous Observation of SMOking Subjects). However, the transfer to the clinic of a blood test based on circ-miRNAs requires the establishment of standardized operating procedures (SOPs), working instructions and guidelines for all pre-analytical and analytical procedures. We identified possible sources of variability affecting circulating miRNAs, analyzed their impact on the miR-Test performance, and defined a standardized protocol to optimize miR-Test application. Analysis of all possible technical and biological variation affecting circ-miRNAs level, revealed two main sources of variability: one related to analytical procedures for miRNAs extraction and quantification, and the other due to pre-analytical conditions, on how samples are prepared. The extraction causes the main source of analytical imprecision. In conclusion, we identified an optimal protocol for the application of miR-Test for lung cancer early diagnosis. Citation Format: Francesca Montani, Matteo Marzi, Fabio Dezi, Elisa Dama, Rose Mary Carletti, Giulia Veronesi, Francesco Nicassio, Pier Paolo Di Fiore, Fabrizio Bianchi. Serum circulating miR–Test application: Standardized protocol for miR–Test clinical application. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1575. doi:10.1158/1538-7445.AM2015-1575

Abstract 522: Revealing the complexity of cancer associated small non-coding RNAs by next generation sequencing (NGS) and low-density array

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background. The recent development of high-throughput sequencing technologies (Next Generation Sequencing - NGS) provided instruments to reveal the complexity of nucleic acids, highlighting the existence of numerous species of non-coding RNAs (ncRNAs) that play a significant regulatory role in complex organisms, impacting on both physiology and disease. In particular, microRNAs (miRNAs) have been proposed as “next-generation” markers for their ability to unambiguously distinguish cellular states, including SCs, progenitors and differentiated cells, as well as tumour types, even among closely related cancers or in different biological fluids. However, a comprehensive approach for the identification and characterization of small non-coding RNAs from pathological samples (blood, FFPE, primary cultures) has not been established nor compared with current available methodologies (i.e. QPCR). Aim: Our aim is to develop a simultaneous and comparative protocol for the analysis of small non-coding RNAs from pathological samples, which encompasses both high-throughput QPCR and sequencing analysis in order to reveal the complexity of cancer associated small ncRNAs. Results: An optimized protocol to analyse small ncRNAs from different pathological samples has been developed and compared with high-throughput QPCR. Both platforms resulted as highly efficient and quantitative, although NGS manages to score many molecules and RNA species that could not be analysed by current QPCR platforms, thus revealing a major complexity of cancer associated non-coding RNAs. Conclusion: We propose that the combined use of NGS and QPCR platforms would allow a wider and more detailed analysis of ncRNAs, expanding our ability to fish out robust and efficient molecular markers for diagnostic (early detection), prognostic or therapeutic use. Note: This abstract was not presented at the meeting. Citation Format: Francesca Montani, Matteo Marzi, Rose Mary Carletti, Pier Paolo Di Fiore, Francesco Nicassio. Revealing the complexity of cancer associated small non-coding RNAs by next generation sequencing (NGS) and low-density array. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 522. doi:10.1158/1538-7445.AM2014-522