Introduction

The research program coordinated by Professor Giannino Del Sal encompasses both basic and translational aspects of cancer cell molecular biology. The research interests of Del Sal’s team are focused on the crosstalks of oncogenic and tumor suppressor pathways with local stromal cues, and on understanding how these pathways act to pace tumor progression by promoting metabolic reprogramming, epigenetic rewiring, protein modification and alteration of the local and distal microenvironment. Thorough understanding of these mechanisms is expected to highlight tumor dependencies and vulnerabilities, helping to design strategies for more effective patient treatment.

Research in Del Sal’s lab is conducted by combination of molecular and omics approaches, cell biology, use of mouse and fly models, bioinformatics and integrative methods.

At the centerpiece of these investigations are the roles of p53 tumor suppressor and mutant p53 oncogenic networks, YAP/TAZ and Notch pathways, phosphorylation-dependent isomerization signaling, regulation of cell metabolism, chromatin structure and non coding RNAs in physiology and disease.

The activities within this program are organized in various lines of research:

1) Function and dysfunction of TP53

Mutations in the TP53 gene are among the most common alterations found in human cancer cells, and missense mutations account for the vast majority of these alterations. While p53 is a central tumor suppressor, p53 missense mutants (mutp53) are powerful drivers of cancer initiation and progression. In addition to losing the wt tumor suppressive abilities, mutp53 strongly promote tumor development by driving cancer cell proliferation and survival, migration/invasion, metastasis and chemoresistance. This relies on the ability of mutp53 to establish interactions with transcription regulators, enzymes and other cellular proteins (Mantovani et al., 2016).

Del Sal’s team investigates how mutp53 subverts cellular processes by regulating cancer-related gene expression programs (Girardini et al., 2011) including coding and non-coding genes, and reshaping the tumor cell’s proteome (Walerych et al., 2016). Activities within this task include the characterization of key effectors of mutp53 and of their contribution in promoting cancer cell’s aggressive features as well as the ability to cope with transformation-related stress conditions, such as oxidative stress (Lisek et al., 2018). The ultimate aim of this line of research is to identify new targets and biomarkers within the mutp53 molecular network that can help improving patient care.

Of particular interest are the mechanisms leading to mutp53 accumulation and oncogenic activation in tumors. We have recently demonstrated that mechanical inputs, transduced by RhoA-dependent cytoskeletal tension, sustain mutp53 protein stability, thus implying that tumor-associated fibrosis may drive mutp53 accumulation. Importantly, blocking RhoA activation with mevalonate pathway (MVP) inhibitors curbs mutp53 accumulation in tumors (Ingallina et al., 2017).

2) Cancer metabolism

Reprogramming of cell metabolism is a hallmark of cancer that is promoted by multiple oncogenic pathways to sustain tumor cell biosynthetic requirements for continuous growth and proliferation and to cope with the changing environment. Del Sal’s research is focused on identifying metabolic processes altered during tumorigenesis and on understanding the crosstalk between cellular metabolites and oncogenes (such as mutant p53, YAP/TAZ and Notch).

By a cell-based High-Content Screening we identified the MVP as an important metabolic regulator of the nuclear activities of the YAP/TAZ oncogenes, master regulators of cancer cell proliferation, stemness and metastasis (Sorrentino et al., Nature Cell Biology 2014), as well as of mutp53 accumulation (Ingallina et al., Nature Cell Biology 2017). Through the MVP cells synthesize fundamental biomolecules required for membrane synthesis, signal transduction and protein prenylation. Del Sal’s findings demonstrated how cancer cells, by altering cell metabolism, can drive unscheduled activation of YAP/TAZ as well as mutp53 accumulation, thus sustaining proliferation, migration, resistance to apoptosis and stem cell traits appearance.

These findings open the unprecedented opportunity to blunt this pro-oncogenic axis with drugs acting at different steps of this metabolic route: statins, bisphosphonates and GGTI inhibitors. Given that statins and bisphosphonates are FDA-approved and already used in clinics, Del Sal’s team is testing the efficacy of atorvastatin and zoledronate in preoperative neoadjuvant chemotherapy regimen in triple negative breast cancer TNBC, in a large prospective randomized controlled trial (RCT).

Moreover, the team addresses the synergistic anticancer potential of combination of drugs selected on the base of their inhibitory activity on pathways impinging on these oncogenic axes, and tests their ability to induce chemosensitization of different tumors to standard chemotherapeutic treatments. This research stream benefits of a living biobank of patient-derived tumor organoids of breast, colon and lung tumors, that is being generated in the lab within an ongoing Italian-Austrian cross-border collaboration (PreCanMed http://www.precanmed.eu/en/).

3) Insights into cancer and neurodegeneration co-morbidity

Statistics on the top ten causes of death suggest that certain forms of highly aggressive cancers (namely lung, colon, breast cancer) and neurodegenerative diseases like Alzheimer’s Disease and others are among the most powerful killers in high income countries (WHO, 2011 release). Interestingly these two classes of disease display an inverse relationship in the way that several epidemiologic studies have pointed out an inverse comorbidity pattern associated with cancer and Alzheimer’s Disease (AD), Parkinson’s Disease (PD), multiple sclerosis, Huntington’s Disease (HD), amyotrophic lateral sclerosis (ALS) and others. The molecular circuitries proposed to be responsible for this inverse relationship are still unknown. Different experimental evidence indicates that common fundamental cellular processes, such as the cell cycle, are subverted in both. In the extent and direction of these deregulations it may rely the inverse relationship inter-occurring between such highly impacting classes of disease.

A key molecular player of both neurodegeneration and cancer is the prolyl-isomerase Pin1, a key regulator of a multitude of cellular processes. It specifically controls the conformation of key cellular proteins by catalyzing cis-trans isomerisation of Ser/Thr-Pro motifs upon phosphorylation of the Ser/Thr, having profound effects on the modulation of signal transduction. Alteration of Pin1 levels and activity, or alteration of the phosphorylation status of its direct targets, affect many cellular processes (e.g. oxidative stress, metabolism, survival, drug response, other) that, depending on the cellular context, may lead to age-related pathologies. Some of these processes are under investigation by our team.

Indeed, the group already contributed to unveil the effects of Pin1 in tumors, where it is found overexpressed and boosts tumorigenesis through key oncogenic pathways, as Notch and mutp53 (Girardini et al., Cancer Cell 2011; Rustighi et al., EMBO Mol Med 2014). Pin1 appears particularly attractive for design of small molecule inhibitors: it is highly specific, over-expressed in cancers, and essential for tumor growth and progression, while being largely dispensable for normal tissue homeostasis. Del Sal’s team has recently isolated a novel Pin1 inhibitor, able to covalently bind Pin1 and induce its degradation. This compound was shown to curb mutp53 GOF activities in vitro and decrease growth of mutp53-expressing TNBC lung metastasis in vivo (Campaner et al., Nature Communications 2017).

On the other hand, Pin1 activity appears to be required for healthy ageing and prevention of age-related diseases, most notably neurodegeneration of Alzheimer’s Disease type. Research of Del Sal team aims at using Drosophila as an efficient in vivo model to allow a deeper understanding of evolutionarily conserved molecular processes that drive development and aggressiveness of cancer, aging and neurodegeneration. In particular, this research is presently focused on studying the roles of Pin1 in regulating chromatin states, DNA repair and stress response pathways as an important key for the interpretation of the observed inverse relationship between neurodegenerative disorders and cancer. 

4) The molecular portrait of cancer stem cells

Cancer stem cells (CSCs) are proposed to drive tumor initiation and metastatic progression of chemotherapy-resistant tumors. For this reason they are considered core targets to eradicate the roots of malignancy. CSCs may origin from mutations that either occur in normal stem cells or that confer stem cell properties to more differentiated cells by deranged cellular reprogramming. Elucidation of the molecular mechanisms underpinning the attributes of normal and CSCs, i.e. self-renewal, tumorigenicity, and multilineage differentiation capacity, is important in order to develop effective therapeutic strategies.

The Del Sal’s team aims at dissecting the molecular bases of normal and CSCs using cell-based and animal models, including mice and D. melanogaster. Del Sal’s group already provided contribution to this field identifying the prolyl-isomerase Pin1 as a stem cell factor of the mammary epithelial compartment, both normal and cancerous (Rustighi et al., EMBO Mol Med 2014), whose inhibition elicits breast CSC exhaustion and chemosensitivity. Breast CSC self-renewal, chemoresistance, tumor growth and metastasis formation in vivo rely in fact on this enzyme, that sustains the deregulation of pathways, such as the Notch or mutant p53 ones, strongly implicated in development and progression of breast tumors.

Ongoing research focuses on crosstalk between different oncogenic axes and metabolic pathways in stem cell and CSC biology, with the aim to identify relevant molecular differences between adult SCs and CSCs, to define therapeutic opportunities to specifically hit CSCs, while leaving unaffected healthy SCs .

5) Epigenetics, chromatin remodelling and genome control

Epigenetic regulators play key roles in controlling gene expression by modifying the local state and architecture of chromatin at multiple levels, thus altering the execution of biological processes under specific conditions. Altered regulation and function of chromatin modifications as well as of the remodelling machinery leads to global changes of both coding and non-coding gene expression. The high frequency of such alterations in human malignancies supports a key role of epigenetic deregulation in tumor progression.

Our group already provided contribution to this field by identifying in Bromodomain-containing 7 (BRD7), a specificity factor of PBAF-specific SWI/SNF chromatin remodeling complex, a cofactor of p53 essential for transcriptional control of the cell-intrinsic tumor suppressive response named oncogene-induced senescence (Drost et al., Nat Cell Biol 2010).

We are now exploring at a genome-wide level how chromatin remodelling machineries may restrain on multiple biological processes that impinge on tumor development and aggressiveness, e.g. genome instability, acquisition of plasticity and stem-cell traits, cell metabolism and interaction with tumor microenvironment. Our interest is to understand how epigenetic regulators co-ordinately modulate the expression of various classes of mutually interacting coding and non-coding genes, including miRNAs, long ncRNAs and mobile DNA elements controlling gene expression, chromatin organization and genome structure.