Fibroblastic FAP promotes intrahepatic cholangiocarcinoma growth via MDSCs recruitment

CCL2: An Important Mediator Between Tumor Cells and Host Cells in Tumor Microenvironment

Tumor microenvironment (TME) formation is a major cause of immunosuppression. The TME consists of a considerable number of macrophages and stromal cells that have been identified in multiple tumor types. CCL2 is the strongest chemoattractant involved in macrophage recruitment and a powerful initiator of inflammation. Evidence indicates that CCL2 can attract other host cells in the TME and direct their differentiation in cooperation with other cytokines. Overall, CCL2 has an unfavorable effect on prognosis in tumor patients because of the accumulation of immunosuppressive cell subtypes. However, there is also evidence demonstrating that CCL2 enhances the anti-tumor capability of specific cell types such as inflammatory monocytes and neutrophils. The inflammation state of the tumor seems to have a bi-lateral role in tumor progression. Here, we review works focusing on the interactions between cancer cells and host cells, and on the biological role of CCL2 in these processes.

Collagenase-Expressing Salmonella Targets Major Collagens in Pancreatic Cancer Leading to Reductions in Immunosuppressive Subsets and Tumor Growth

Therapeutic resistance in pancreatic ductal adenocarcinoma (PDAC) can be attributed, in part, to a dense extracellular matrix containing excessive collagen deposition. Here, we describe a novel Salmonella typhimurium (ST) vector expressing the bacterial collagenase Streptomyces omiyaensis trypsin (SOT), a serine protease known to hydrolyze collagens I and IV, which are predominantly found in PDAC. Utilizing aggressive models of PDAC, we show that ST-SOT selectively degrades intratumoral collagen leading to decreases in immunosuppressive subsets, tumor proliferation and viability. Ultimately, we found that ST-SOT treatment significantly modifies the intratumoral immune landscape to generate a microenvironment that may be more conducive to immunotherapy.

Therapeutic cancer vaccines

Therapeutic cancer vaccines have undergone a resurgence in the past decade. A better understanding of the breadth of tumour-associated antigens, the native immune response and development of novel technologies for antigen delivery has facilitated improved vaccine design. The goal of therapeutic cancer vaccines is to induce tumour regression, eradicate minimal residual disease, establish lasting antitumour memory and avoid non-specific or adverse reactions. However, tumour-induced immunosuppression and immunoresistance pose significant challenges to achieving this goal. In this Review, we deliberate on how to improve and expand the antigen repertoire for vaccines, consider developments in vaccine platforms and explore antigen-agnostic in situ vaccines. Furthermore, we summarize the reasons for failure of cancer vaccines in the past and provide an overview of various mechanisms of resistance posed by the tumour. Finally, we propose strategies for combining suitable vaccine platforms with novel immunomodulatory approaches and standard-of-care treatments for overcoming tumour resistance and enhancing clinical efficacy.

The Emerging Role of Immunotherapy in Intrahepatic Cholangiocarcinoma

Biliary tract cancer, and intrahepatic cholangiocarcinoma (iCC) in particular, represents a rather uncommon, highly aggressive malignancy with unfavorable prognosis. Therapeutic options remain scarce, with platinum-based chemotherapy is being considered as the gold standard for the management of advanced disease. Comprehensive molecular profiling of tumor tissue biopsies, utilizing multi-omics approaches, enabled the identification of iCC’s intratumor heterogeneity and paved the way for the introduction of novel targeted therapies under the scope of precision medicine. Yet, the unmet need for optimal care of patients with chemo-refractory disease or without targetable mutations still exists. Immunotherapy has provided a paradigm shift in cancer care over the past decade. Currently, immunotherapeutic strategies for the management of iCC are under intense research. Intrinsic factors of the tumor, including programmed death-ligand 1 (PD-L1) expression and mismatch repair (MMR) status, are simply the tip of the proverbial iceberg with regard to resistance to immunotherapy. Acknowledging the significance of the tumor microenvironment (TME) in both cancer growth and drug response, we broadly discuss about its diverse immune components. We further review the emerging role of immunotherapy in this rare disease, summarizing the results of completed and ongoing phase I–III clinical trials, expounding current challenges and future directions.

In Vitro and In Situ Activity-Based Labeling of Fibroblast Activation Protein with UAMC1110-Derived Probes

Fibroblast activation protein (FAP) is a proline-selective protease that belongs to the S9 family of serine proteases. It is typically highly expressed in the tumor microenvironment (TME) and especially in cancer-associated fibroblasts, the main cell components of the tumor stroma. The exact role of its enzymatic activity in the TME remains largely unknown. Hence, tools that enable selective, activity-based visualization of FAP within the TME can help to unravel FAP’s function. We describe the synthesis, biochemical characterization, and application of three different activity-based probes (biotin-, Cy3-, and Cy5-labeled) based on the FAP-inhibitor UAMC1110, an in-house developed molecule considered to be the most potent and selective FAP inhibitor available. We demonstrate that the three probes have subnanomolar FAP affinity and pronounced selectivity with respect to the related S9 family members. Furthermore, we report that the fluorescent Cy3- and Cy5-labeled probes are capable of selectively detecting FAP in a cellular context, making these chemical probes highly suitable for further biological studies. Moreover, proof of concept is provided for in situ FAP activity staining in patient-derived cryosections of urothelial tumors.

Targeting the tumor microenvironment in cholangiocarcinoma: implications for therapy

Introduction: Cholangiocarcinomas (CCAs) are biliary epithelial tumors with rising incidence over the past 3 decades. Early diagnosis of CCAs remains a significant challenge and the majority of patients present at an advanced stage. CCAs are heterogeneous tumors and currently available standard systemic therapy options are of limited effectiveness. Immune checkpoint inhibition (ICI) has transformed cancer therapy across a spectrum of malignancies. However, the response rate to ICI has been relatively disappointing in CCAs owing to its desmoplastic tumor microenvironment (TME).Areas covered: Tumor microenvironment of CCAs consists of innate and adaptive cells, stromal cells, and extracellular components (cytokines, chemokines, exosomes, etc.). This intricate microenvironment has multiple immunosuppressive elements that promote tumor cell survival and therapeutic resistance. Accordingly, there is a need for the development of effective therapeutic strategies that target the TME. Herein, we review the components of the CCA TME, and potential therapies targeting the CCA TME.Expert opinion: CCAs are desmoplastic tumors with a dense tumor microenvironment. An enhanced understanding of the various components of the CCA TME is essential in the effort to develop novel biomarkers for patient stratification as well as combination therapeutic strategies that target the tumor plus the TME.

Targeting the tumor microenvironment in cholangiocarcinoma: implications for therapy

Introduction: Cholangiocarcinoma (CCA) is a rare, deadly cancer that is characterized by an abundant desmoplastic stroma. Late diagnoses and limited available effective treatments are major problems with this malignancy. Targeting of the tumor microenvironment (TME) has emerged as a potential therapeutic strategy.Areas covered: In this review, we describe the role of the various compartments of the TME in CCA and focus on the preclinical rationale for the development of innovative therapies. Relevant literature was identified by a PubMed search covering the last decade (2010-2020).Expert opinion: Low efficacy of surgery and cytotoxic chemotherapy emphasizes the need for new therapeutic strategies and companion biomarkers. Single-cell RNA sequencing of the stroma is yielding a critical functional characterization of TME in CCA and is paving the way for immunotherapies and cancer-associated fibroblast and extracellular matrix-oriented treatments. We believe that the development of treatments targeting the components of the TME will produce the best results if in combination with cytotoxic chemotherapy. Biomarkers should be developed to define the patient population of interest for each combination strategy.

MDSCs in liver cancer: A critical tumor-promoting player and a potential therapeutic target

Liver cancer is a leading cause of cancer deaths worldwide. Hepatocellular carcinoma (~75-85%) and cholangiocarcinoma (~10-15%) account for the majority of primary liver malignancies. Patients with primary liver cancer are often diagnosed with unresectable diseases and do not respond well to current therapies. The liver is also a common site of metastasis. Liver metastasis is difficult to treat, and the prognosis is poor. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells with immunosuppressive activity. MDSCs are an important component of the tumor microenvironment and promote tumor progression through various mechanisms. MDSCs expand in both liver cancer patients and mouse liver cancer models. Importantly, MDSCs correlate with poor clinical outcomes for liver cancer patients. The tumor-promoting functions of MDSCs have also been shown in mouse liver cancer models. All these studies suggest that targeting MDSCs can potentially benefit liver cancer treatment. This review summarizes the current findings of MDSC regulation in liver cancer and related disease conditions.

Intrahepatic cholangiocarcinoma: Morpho-molecular pathology, tumor reactive microenvironment, and malignant progression

Intrahepatic cholangiocarcinoma (iCCA) is a relatively rare, but highly lethal and biologically complex primary biliary epithelial cancer arising within liver. After hepatocellular carcinoma, iCCA is the second most common primary liver cancer, accounting for approximately 10-20% of all primary hepatic malignancies. Over the last 10-20 years, iCCA has become the focus of increasing concern largely due to its rising incidence and high mortality rates in various parts of the world, including the United States. The challenges posed by iCCA are daunting and despite recent progress in the standard of care and management options for iCCA, the prognosis for this cancer continues to be dismal. In an effort to provide a framework for advancing our understanding of iCCA malignant aggressiveness and therapy resistance, this review will highlight key etiological, biological, molecular, and microenvironmental factors hindering more effective management of this hepatobiliary cancer. Particular focus will be on critically reviewing the cell origins and morpho-molecular heterogeneity of iCCAs, providing mechanistic insights into high risk fibroinflammatory cholangiopathies associated with iCCA development, and notably discussing the deleterious role played by the tumor reactive desmoplastic stroma in regulating iCCA malignant progression, lymphangiogenesis, and tumor immunobiology.

FAPI PET/CT: Will It End the Hegemony of 18F-FDG in Oncology?

For over 40 years, ¹⁸F-FDG has been the dominant PET tracer in neurology, cardiology, inflammatory diseases, and, most particularly, oncology. Combined with the ability to perform whole-body scanning, ¹⁸F-FDG has revolutionized the evaluation of cancer and has stifled the adoption of other tracers, except in situations where low avidity or high background activity limits diagnostic performance. The strength of ¹⁸F-FDG has generally been its ability to detect disease in the absence of structural abnormality, thereby enhancing diagnostic sensitivity, but its simultaneous weakness has been a lack of specificity due to diverse pathologies with enhanced glycolysis. Radiotracers that leverage other hallmarks of cancer or specific cell-surface targets are gradually finding a niche in the diagnostic armamentarium. However, none have had sufficient sensitivity to realistically compete with ¹⁸F-FDG for evaluation of the broad spectrum of malignancies. Perhaps, this situation is about to change with development of a class of tracers targeting fibroblast activation protein that have low uptake in almost all normal tissues but high uptake in most cancer types. In this review, the development and exciting preliminary clinical data relating to various fibroblast activation protein-specific small-molecule inhibitor tracers in oncology will be discussed along with potential nononcologic applications.

Overcoming stromal barriers to immuno-oncological responses via fibroblast activation protein-targeted therapy

The tumor microenvironment contributes to disease progression through multiple mechanisms, including immune suppression mediated in part by fibroblast activation protein (FAP)-expressing cells. Herein, a review of FAP biology is presented, supplemented with primary data. This includes FAP expression in prostate cancer and activation of latent reservoirs of TGF-β and VEGF to produce a positive feedback loop. This collectively suggests a normal wound repair process subverted during cancer pathophysiology. There has been immense interest in targeting FAP for diagnostic, monitoring and therapeutic purposes. Until recently, this development has outpaced an understanding of the biology; impeding optimal translation into the clinic. A summary of these applications is provided with an emphasis on eliminating tumor-infiltrating FAP-positive cells to overcome stromal barriers to immuno-oncological responses.

Role of Chemokines in the Biology of Cholangiocarcinoma

Cholangiocarcinoma (CCA), a heterogeneous tumor with poor prognosis, can arise at any level in the biliary tree. It may derive from epithelial cells in the biliary tracts and peribiliary glands and possibly from progenitor cells or even hepatocytes. Several risk factors are responsible for CCA onset, however an inflammatory milieu nearby the biliary tree represents the most common condition favoring CCA development. Chemokines play a key role in driving the immunological response upon liver injury and may sustain tumor initiation and development. Chemokine receptor-dependent pathways influence the interplay among various cellular components, resulting in remodeling of the hepatic microenvironment towards a pro-inflammatory, pro-fibrogenic, pro-angiogenic and pre-neoplastic setting. Moreover, once tumor develops, chemokine signaling may influence its progression. Here we review the role of chemokines in the regulation of CCA development and progression, and the modulation of angiogenesis, metastasis and immune control. The potential role of chemokines and their receptors as possible biomarkers and/or therapeutic targets for hepatobiliary cancer is also discussed.

Molecular and Immunological Characterization of Biliary Tract Cancers: A Paradigm Shift Towards a Personalized Medicine

Biliary tract cancers (BTCs) are a group of rare cancers that account for up to 3-5% of cancer patients worldwide. BTCs include cholangiocarcinoma (CCA), gallbladder cancer (GBC), and ampulla of Vater cancer (AVC). They are frequently diagnosed at an advanced stage when the disease is often found disseminated. A late diagnosis highly compromises surgery, the only potentially curative option. Current treatment regimens include a combination of chemotherapeutic drugs gemcitabine with cisplatin that have a limited efficiency since more than 50% of patients relapse in the first year. More recently, an inhibitor of fibroblast growth factor receptor 2 (FGFR2) was approved as a second-line treatment, based on the promising results from the NCT02924376 clinical trial. However, novel secondary treatment options are urgently needed. Recent molecular characterization of CCA and GBC highlighted the molecular heterogeneity, etiology, and epidemiology in BTC development and lead to the classification of the extrahepatic CCA into four types: metabolic, proliferating, mesenchymal, and immune type. Differences in the immune infiltration and tumor microenvironment (TME) have been described as well, showing that only a small subset of BTCs could be classified as an immune "hot" and targeted with the immunotherapeutic drugs. This recent evidence has opened a way to new clinical trials for BTCs, and new drug approvals are highly expected by the medical community.