Cancer-associated fibroblasts as abettors of tumor progression at the crossroads of EMT and therapy resistance

In the last decades, the role of the microenvironment in tumor progression and therapeutic outcome has gained increasing attention. Cancer-associated fibroblasts (CAFs) have emerged as key players among stromal cells, owing to their abundance in most solid tumors and their diverse tumor-restraining/promoting roles. The interplay between tumor cells and neighboring CAFs takes place by both paracrine signals (cytokines, exosomes and metabolites) or by the multifaceted functions of the surrounding extracellular matrix. Here, we dissect the most recent identified mechanisms underlying CAF-mediated control of tumor progression and therapy resistance, which include induction of the epithelial-to-mesenchymal transition (EMT), activation of survival pathways or stemness-related programs and metabolic reprogramming in tumor cells. Importantly, the recently unveiled heterogeneity in CAFs claims tailored therapeutic efforts aimed at eradicating the specific subset facilitating tumor progression, therapy resistance and relapse. However, despite the large amount of pre-clinical data, much effort is still needed to translate CAF-directed anti-cancer strategies from the bench to the clinic

CHK1 inhibitor sensitizes resistant colorectal cancer stem cells to nortopsentin

Limited therapeutic options are available for advanced colorectal cancer (CRC). Herein, we report that exposure to a neo-synthetic bis(indolyl)thiazole alkaloid analog, nortopsentin 234 (NORA234), leads to an initial reduction of proliferative and clonogenic potential of CRC sphere cells (CR-CSphCs), followed by an adaptive response selecting the CR-CSphC-resistant compartment. Cells spared by the treatment with NORA234 express high levels of CD44v6, associated with a constitutive activation of Wnt pathway. In CR-CSphC-based organoids, NORA234 causes a genotoxic stress paralleled by G2-M cell cycle arrest and activation of CHK1, driving the DNA damage repair of CR-CSphCs, regardless of the mutational background, microsatellite stability, and consensus molecular subtype. Synergistic combination of NORA234 and CHK1 (rabusertib) targeting is synthetic lethal inducing death of both CD44v6-negative and CD44v6-positive CRC stem cell fractions, aside from Wnt pathway activity. These data could provide a rational basis to develop an effective strategy for the treatment of patients with CRC

Proinflammatory and Cancer-Promoting Pathobiont Fusobacterium nucleatum Directly Targets Colorectal Cancer Stem Cells

Intestinal bacterial communities participate in gut homeostasis and are recognized as crucial in bowel inflammation and colorectal cancer (CRC). Fusobacterium nucleatum (Fn), a pathobiont of the oral microflora, has recently emerged as a CRC-associated microbe linked to disease progression, metastasis, and a poor clinical outcome; however, the primary cellular and/or microenvironmental targets of this agent remain elusive. We report here that Fn directly targets putative colorectal cancer stem cells (CR-CSCs), a tumor cell subset endowed with cancer re-initiating capacity after surgery and chemotherapy. A patient-derived CSC line, highly enriched (70%) for the stem marker CD133, was expanded as tumor spheroids, dissociated, and exposed in vitro to varying amounts (range 100-500 MOI) of Fn. We found that Fn stably adheres to CSCs, likely by multiple interactions involving the tumor-associated Gal-GalNac disaccharide and the Fn-docking protein CEA-family cell adhesion molecule 1 (CEACAM-1), robustly expressed on CSCs. Importantly, Fn elicited innate immune responses in CSCs and triggered a growth factor-like, protein tyrosine phosphorylation cascade largely dependent on CEACAM-1 and culminating in the activation of p42/44 MAP kinase. Thus, the direct stimulation of CSCs by Fn may contribute to microbiota-driven colorectal carcinogenesis and represent a target for innovative therapies

Integrin α7 Is a Functional Marker and Potential Therapeutic Target in Glioblastoma

Functionally relevant markers of glioblastoma stem-like cells (GSCs) have potential for therapeutic targeting to treat this aggressive disease. Here we used generation and screening of thousands of monoclonal antibodies to search for receptors and signaling pathways preferentially enriched in GSCs. We identified integrin α7 (ITGA7) as a major laminin receptor in GSCs and in primary high-grade glioma specimens. Analyses of mRNA profiles in comprehensive datasets revealed that high ITGA7 expression negatively correlated with survival of patients with both low- and high-grade glioma. In vitro and in vivo analyses showed that ITGA7 plays a key functional role in growth and invasiveness of GSCs. We also found that targeting of ITGA7 by RNAi or blocking mAbs impaired laminin-induced signaling, and it led to a significant delay in tumor engraftment plus a strong reduction in tumor size and invasion. Our data, therefore, highlight ITGA7 as a glioblastoma biomarker and candidate therapeutic target

Cancer stem cells: at the forefront of personalized medicine and immunotherapy

Cancer stem cells (CSCs) represent the main target of the current efforts to eradicate cancer, because of their ability to promote metastatic dissemination and survive cytotoxic therapies. Here, we highlight the potential of patient-derived CSCs as an in vitro and in vivo pre-clinical model and of liquid biopsy as a diagnostic, prognostic and predictive tool. We discuss recently developed therapeutic strategies aiming at specifically targeting the cancer stem cell population, particularly focusing on the latest advances in cancer immunotherapy. In fact, it is now widely accepted that the microenvironment plays an active role in supporting tumor progression. Hence, the crosstalk between CSCs and the host immune system is nowadays object of intensive study, with the aim to develop effective therapeutic strategies targeting the ability of CSCs to escape immune-surveillance through immunoediting

miR-1285-3p Controls Colorectal Cancer Proliferation and Escape from Apoptosis through DAPK2

MicroRNAs are tiny but powerful regulators of gene expression at the post-transcriptional level. Aberrant expression of oncogenic and tumor-suppressor microRNAs has been recognized as a common feature of human cancers. Colorectal cancer represents a major clinical challenge in the developed world and the design of innovative therapeutic approaches relies on the identification of novel biological targets. Here, we perform a functional screening in colorectal cancer cells using a library of locked nucleic acid (LNA)-modified anti-miRs in order to unveil putative oncogenic microRNAs whose inhibition yields a cytotoxic effect. We identify miR-1285-3p and further explore the effect of its targeting in both commercial cell lines and primary colorectal cancer stem cells, finding induction of cell cycle arrest and apoptosis. We show that DAPK2, a known tumor-suppressor, is a novel miR-1285 target and mediates both the anti-proliferative and the pro-apoptotic effects of miR-1285 depletion. Altogether, our findings uncover a novel oncogenic microRNA in colorectal cancer and lay the foundation for further studies aiming at the development of possible therapeutic strategies based on miR-1285 targeting

Exploiting bioactive natural products of marine origin: Evaluation of the meroterpenoid metachromin V as a novel potential therapeutic drug for colorectal cancer

Colorectal cancer (CRC) is the second most common cause of cancer death, leading to almost 1 million deaths per year. Despite constant progress in surgical and therapeutic protocols, the 5-year survival rate of advanced CRC patients remains extremely poor. Colorectal Cancer Stem Cells (CRC-CSCs) are endowed with unique stemness-related properties responsible for resistance, relapse and metastasis. The development of novel therapeutics able to tackle CSCs while avoiding undesired toxicity is a major need for cancer treatment. Natural products are a large reservoir of unexplored compounds with possible anticancer bioactivity, sustainability, and safety. The family of meroterpenoids derived from sponges share interesting bioactive properties. Bioassay-guided fractionation of a meroterpenoids extract led to the isolation of three compounds, all cytotoxic against several cancer cell lines: Metachromins U, V and W. In this study, we evaluated the anticancer potential of the most active one, Metachromins V (MV), on patient-derived CRC-CSCs. MV strongly impairs CSCs-viability regardless their mutational background and the cytotoxic effect is maintained on therapy-resistant metastatic CSCs. MV affects cell cycle progression, inducing a block in G2 phase in all the cell lines tested and more pronouncedly in CRC-CSCs. Moreover, MV triggers an important reorganization of the cytoskeleton and a strong reduction of Rho GTPases expression, impairing CRC-CSCs motility and invasion ability. By Proteomic analysis identified a potential molecular target of MV: CCAR1, that regulates apoptosis under chemotherapy treatments and affect β-catenin pathway. Further studies will be needed to confirm and validate these data in in vivo experimental model

PI3K-driven HER2 expression is a potential therapeutic target in colorectal cancer stem cells

Objective: Cancer stem cells are responsible for tumour spreading and relapse. Human epidermal growth factor receptor 2 (HER2) expression is a negative prognostic factor in colorectal cancer (CRC) and a potential target in tumours carrying the gene amplification. Our aim was to define the expression of HER2 in colorectal cancer stem cells (CR-CSCs) and its possible role as therapeutic target in CRC resistant to anti- epidermal growth factor receptor (EGFR) therapy. Design: A collection of primary sphere cell cultures obtained from 60 CRC specimens was used to generate CR-CSC mouse avatars to preclinically validate therapeutic options. We also made use of the ChIP-seq analysis for transcriptional evaluation of HER2 activation and global RNA-seq to identify the mechanisms underlying therapy resistance. Results: Here we show that in CD44v6-positive CR-CSCs, high HER2 expression levels are associated with an activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which promotes the acetylation at the regulatory elements of the Erbb2 gene. HER2 targeting in combination with phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase kinase (MEK) inhibitors induces CR-CSC death and regression of tumour xenografts, including those carrying Kras and Pik3ca mutation. Requirement for the triple targeting is due to the presence of cancer-associated fibroblasts, which release cytokines able to confer CR-CSC resistance to PI3K/AKT inhibitors. In contrast, targeting of PI3K/AKT as monotherapy is sufficient to kill liver-disseminating CR-CSCs in a model of adjuvant therapy. Conclusions: While PI3K targeting kills liver-colonising CR-CSCs, the concomitant inhibition of PI3K, HER2 and MEK is required to induce regression of tumours resistant to anti-EGFR therapies. These data may provide a rationale for designing clinical trials in the adjuvant and metastatic setting

Transforming growth factor-beta-induced protein as a novel secreted immune check-point in colorectal cancer

We set up a LC/Mass-spectometry (Orbitrap)-based platform to identify the secreted proteome (secretome) in conditioned medium (CM) from fresh tumor and non-tumor surgery samples. By this approach, we selected a multitude of secreted proteins that were upregulated in colorectal cancer (CRC) secretome as compared to the non-tumor, in order to identify those potentially acting as secreted immune check-points (sICs). Their discovery may represent a tremendous resource for tumor specific drug targets, potentially acting as sIC inhibitors in both cold and hot tumors, unlike current IC inhibitors (e.g., IpilumumAb and NivolumAb) causing a partial or no remission in the majority of cold tumors. The transforming growth factor-beta-induced (TGFBI) protein (previously called BIG-H3) was found significantly upregulated in CRC secretome (as compared with the non-tumor). TGFBI is an RGD-containing extracellular matrix protein that binds to type I, II and IV collagens, serves as a ligand recognition sequence for several integrins, and inhibits cell adhesion. Release of TGFBI from primary tumors has been associated with increased tumor proliferation/migration/metastasis, indirectly inhibits adhesion of mononuclear cells by occupancy of various integrins on endothelial cells, but its role as sIC has not been fully investigated. We first validated by Elisa that TGFBI was overexpressed in CM from CRC tissue samples (as compared with non-tumor CM), in serum from CRC patients (as compared with HD sera), and positively correlated with the tumor stage (according to the TNM classification). Interestingly, tissue-IHC and confocal microscopy revealed that TGFBI was overexpressed by tumor cells, T cells, monocytes and plasma cells in tumors in a significantly higher extent than in non-tumor, suggesting a massive involvement of the tumor microenvironment (TME) in secreting it. These data are also confirming at the level of the same cell populations isolated from tumor tissues. Importantly, the recombinant form of TGFBI, as well as the tumor CM containing high levels of native TGFBI, significantly inhibited various functions (IFN- and TNF- production, GZB and T-bet expression…) of anti-CD3/CD28-activated CD4 and CD8 T cells, which could be restored by the addition of the neutralizing anti-TGFBI mAb in vitro. Finally, we are validating that TGFBI can act as a sIC by using human 3D CRC organoids as a surrogate of animal models in vivo. Human 3D-organoids generated from various tumor tissues allow to determine the interaction between tumor and immune system, the response (activation, cytokine production, killing…) by autologous CD8 and CD4 T cells derived from cancer patients, the role of sICs in inhibiting anti-tumor T cell response, the role of related sIC inhibitors in unlashing the anti-tumor T cell response. Human-based models, such as human organoids, can offer effective ways “to accelerate transition to a research system that does not involve testing on animals”, as the European Parliament has recently declared (see go.nature.com/3hzprhj). Anti-tumor immune responses are often unable to clear stabilized tumors due to the presence of various T cell membrane immune checkpoints (mICs) delivering inhibitory signals into tumor-infiltrating lymphocytes (TILs) (i.e., T cell exhaustion). Monoclonal antibodies (mAbs) against mICs (acting as mIC inhibitors [mICIs]) restore anti-tumor responses by TILs leading to a dramatic reduction of several metastatic tumors. This occurs mainly with the so defined “hot tumors” – including melanoma, non-small cell lung cancer, bladder, kidney, head and neck cancer – which are characterized by significant DNA instability, due to the lack of mismatching repair mechanisms, very high mutational burden and thus generating a huge repertoire of mutated (passenger) neoantigens, and a high number of TILs. However, current mICIs (e.g., IpilumumAb and NivolumAb) cause a partial or no remission in the majority of the so-called “cold tumors” expressing a low rate of somatic mutations and, as a consequence, showing low frequencies of TILs. Cold tumors are most breast, ovarian, prostate, pancreatic cancers, glioblastomas, but also the majority of colorectal or hepatocellular carcinomas (CRC or HCC), which are microsatellite stable (MSS) tumors with effective DNA mismatching repair system. In addition to poor T cell infiltration, tumor microenvironment (TEM) in “cold tumors” is characterized by low major histocompatibility complex (MHC) class I and PD-L1 expression, high infiltration of immunosuppressive (IS) cell populations (e.g., tumor-associated macrophages [TAMs], regulatory T cells [Tregs], myeloid-derived suppressor cells [MDSCs], cancer-associated fibroblasts [CAFs]), and high density of secreted IS molecules (e.g., TGF-, IL-10, IL-6, Arginase, VEGF, GM-CSF, Wnts)(3-5). Therefore, a main objective of the scientific community is the development of novel strategies addressed to restore anti-tumor immunosuppression in order to meet the medical need to cure cold tumors (e.g., to convert them into hot tumors)