Tumor reactive stroma in cholangiocarcinoma: The fuel behind cancer aggressiveness

The tumour microenvironment and immune milieu of cholangiocarcinoma

Tumour microenvironment is a complex, multicellular functional compartment that, particularly when assembled as an abundant desmoplastic reaction, may profoundly affect the proliferative and invasive abilities of epithelial cancer cells. Tumour microenvironment comprises not only stromal cells, mainly cancer-associated fibroblasts, but also immune cells of both the innate and adaptive system (tumour-associated macrophages, neutrophils, natural killer cells, and T and B lymphocytes), and endothelial cells. This results in an intricate web of mutual communications regulated by an extensively remodelled extracellular matrix, where the tumour cells are centrally engaged. In this regard, cholangiocarcinoma, in particular the intrahepatic variant, has become the focus of mounting interest in the last years, largely because of the lack of effective therapies despite its rising incidence and high mortality rates worldwide. On the other hand, recent studies in pancreatic cancer, which similarly to cholangiocarcinoma, is highly desmoplastic, have argued against a tumour-promoting function of the tumour microenvironment. In this review, we will discuss recent developments concerning the role of each cellular population and their multifaceted interplay with the malignant biliary epithelial counterpart. We ultimately hope to provide the working knowledge on how their manipulation may lead to a therapeutic gain in cholangiocarcinoma.

Animal models of cholangiocarcinoma: What they teach us about the human disease

Despite recent advances, pathogenesis of cholangiocarcinoma, a highly lethal cancer, remains enigmatic. Furthermore, treatment options are still limited and often disappointing. For this reason, in the last few years there has been a mounting interest towards the generation of experimental models able to reproduce the main features associated with this aggressive behavior. Toxic and infestation-induced, genetically engineered and cell implantation rodent models have been generated, contributing to a deeper understanding of the complex cell biology of the tumor, sustained by multiple cell interactions and driven by a huge variety of molecular perturbations. Herein, we will overview the most relevant animal models of biliary carcinogenesis, highlighting the methodological strategy, the molecular, histological and clinical phenotypes consistent with the human condition, their particular strengths and weaknesses and the novel therapeutic approaches that have been developed.

High-grade precursor lesions can be used as surrogate markers to identify the epicenter of periampullary carcinomas

Identifying the accurate origin of periampullary cancers is important because different origins may trigger different clinicopathological behaviors. The presence of intraepithelial precursor lesions, including high-grade pancreatic intraepithelial neoplasias (PanINs) and/or high-grade biliary intraepithelial neoplasias (BilINs), may be suggestive of the origin of the periampullary carcinoma in challenging cases. To prove the usefulness of high-grade intraepithelial precursor lesions in identifying the origin of ambiguous periampullary cancers, the status and grades of PanINs and BilINs were evaluated in 256 periampullary carcinomas with a well-defined cancer origin as a test set, including 114 pancreatic cancers, 82 distal bile duct cancers, 54 ampullary cancers, and 6 duodenal cancers. One hundred twelve periampullary carcinomas with clinically equivocal epicenter either by radiologic imaging or by endoscopic finding used as a validation set. High-grade PanINs were found more commonly in pancreatic cancers than in distal bile duct, ampullary, and duodenal cancers both in test (P = .002) and validation sets (P < .001). Similarly, high-grade BilINs were identified more frequently in distal bile duct cancers than in ampullary, pancreatic, and duodenal cancers both in test (P < .001) and validation sets (P = .039). High-grade PanINs were found most commonly in pancreatic cancers, whereas high-grade BilINs were seen most frequently in distal bile duct cancers. In addition, both high-grade PanINs and high-grade BilINs are uncommonly noted in ampullary or duodenal cancers. The recognition of high-grade intraepithelial lesions can help identify the primary origin of periampullary cancers, especially when the epicenter of the periampullary cancer is ambiguous.

The Role of Stroma in Cholangiocarcinoma: The Intriguing Interplay between Fibroblastic Component, Immune Cell Subsets and Tumor Epithelium

Cholangiocarcinoma (CCA) is a severe and mostly intractable adenocarcinoma of biliary epithelial cells. A typical feature of CCA is its highly desmoplastic microenvironment containing fibrogenic connective tissue and an abundance of immune cells (T lymphocytes, Natural Killer (NK) cells, and macrophages) infiltrating tumor epithelium. This strong desmoplasia is orchestrated by various soluble factors and signals, suggesting a critical role in shaping a tumor growth-permissive microenvironment that is responsible for CCA poor clinical outcome. Indeed stroma not only provides an abundance of factors that facilitate CCA initiation, growth and progression, but also a prejudicial impact on therapeutic outcome. This review will give an overview of tumor-stroma signaling in a microenvironment critically regulating CCA development and progression. Identification of CCA secreted factors by both the fibroblast component and immune cell subsets might provide ample opportunities for pharmacological targeting of this type of cancer.

MSI2 knockdown represses extrahepatic cholangiocarcinoma growth and invasion by inhibiting epithelial-mesenchymal transition

Purpose

To investigate the expression and functional role of Musashi2 (MSI2), an RNA-binding protein, in extrahepatic cholangiocarcinoma (eCCA).

Patients and methods

We measured MSI2 expression in human specimens and cell lines using Western blot and quantitative real-time polymerase chain reaction, and we analyzed its association with clinicopathologic features in eCCA patients. Univariate and multivariate analyses were performed to identify risk factors correlated with overall survival and disease-free survival. Functional experiments were used to study the mechanisms of MSI2 in regulating eCCA cell growth, migration, and invasion.

Results

MSI2 expression was upregulated significantly in both human specimens and cell lines, and high MSI2 expression was associated with lymph node metastasis, advanced TNM stage, and poor prognosis in eCCA patients. Additionally, MSI2 overexpression promoted eCCA cell growth, migration, and invasion, while MSI2 knockdown repressed eCCA cell migration and invasion by inhibiting epithelial–mesenchymal transition.

Conclusion

MSI2 is an independent prognostic factor for eCCA patients, and MSI2 downregulation inhibits eCCA cell growth and metastasis. MSI2 may be a potential therapeutic target for eCCA patients.

Molecular Mechanisms Driving Cholangiocarcinoma Invasiveness: An Overview

The acquisition of invasive functions by tumor cells is a first and crucial step toward the development of metastasis, which nowadays represents the main cause of cancer-related death. Cholangiocarcinoma (CCA), a primary liver cancer originating from the biliary epithelium, typically develops intrahepatic or lymph node metastases at early stages, thus preventing the majority of patients from undergoing curative treatments, consistent with their very poor prognosis. As in most carcinomas, CCA cells gradually adopt a motile, mesenchymal-like phenotype, enabling them to cross the basement membrane, detach from the primary tumor, and invade the surrounding stroma. Unfortunately, little is known about the molecular mechanisms that synergistically orchestrate this proinvasive phenotypic switch. Autocrine and paracrine signals (cyto/chemokines, growth factors, and morphogens) permeating the tumor microenvironment undoubtedly play a prominent role in this context. Moreover, a number of recently identified signaling systems are currently drawing attention as putative mechanistic determinants of CCA cell invasion. They encompass transcription factors, protein kinases and phosphatases, ubiquitin ligases, adaptor proteins, and miRNAs, whose aberrant expression may result from either stochastic mutations or the abnormal activation of upstream pro-oncogenic pathways. Herein we sought to summarize the most relevant molecules in this field and to discuss their mechanism of action and potential prognostic relevance in CCA. Hopefully, a deeper knowledge of the molecular determinants of CCA invasiveness will help to identify clinically useful biomarkers and novel druggable targets, with the ultimate goal to develop innovative approaches to the management of this devastating malignancy.

Biomarker-Driven and Molecular Targeted Therapies for Hepatobiliary Cancers

The recent accumulation of molecular profiling data for primary hepatobiliary malignancies, including hepatocellular carcinoma and biliary tract cancers, has led to a proliferation of promising therapeutic investigations in recent years. Treatment with pathway-specific targeted inhibitors and immunotherapeutic agents have demonstrated promising early clinical results. Key molecular alterations in common hepatobiliary cancers and ongoing interventional clinical trials of molecularly targeted systemic agents focusing on hepatocellular carcinoma and biliary tract cancer are reviewed.

Cholangiocarcinoma - evolving concepts and therapeutic strategies

Cholangiocarcinoma is a disease entity comprising diverse epithelial tumours with features of cholangiocyte differentiation: cholangiocarcinomas are categorized according to anatomical location as intrahepatic (iCCA), perihilar (pCCA), or distal (dCCA). Each subtype has a distinct epidemiology, biology, prognosis, and strategy for clinical management. The incidence of cholangiocarcinoma, particularly iCCA, has increased globally over the past few decades. Surgical resection remains the mainstay of potentially curative treatment for all three disease subtypes, whereas liver transplantation after neoadjuvant chemoradiation is restricted to a subset of patients with early stage pCCA. For patients with advanced-stage or unresectable disease, locoregional and systemic chemotherapeutics are the primary treatment options. Improvements in external-beam radiation therapy have facilitated the treatment of cholangiocarcinoma. Moreover, advances in comprehensive whole-exome and transcriptome sequencing have defined the genetic landscape of each cholangiocarcinoma subtype. Accordingly, promising molecular targets for precision medicine have been identified, and are being evaluated in clinical trials, including those exploring immunotherapy. Biomarker-driven trials, in which patients are stratified according to anatomical cholangiocarcinoma subtype and genetic aberrations, will be essential in the development of targeted therapies. Targeting the rich tumour stroma of cholangiocarcinoma in conjunction with targeted therapies might also be useful. Herein, we review the evolving developments in the epidemiology, pathogenesis, and management of cholangiocarcinoma.

Recent Advances in Understanding Cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive malignancy that arises from damaged epithelial cells, cholangiocytes, and possibly de-differentiated hepatocytes. CCA has a poor overall survival rate and limited therapeutic options. Based on this data, it is imperative that new diagnostic and therapeutic interventions be developed. Recent work has attempted to understand the pathological mechanisms driving CCA progression. Specifically, recent publications have delved into the role of cancer stem cells (CSCs), mesenchymal stem cells (MSCs), and microRNAs (miRNAs) during CCA pathology. CSCs are a specific subset of cells within the tumor environment that are derived from a cell with stem-like properties and have been shown to influence recurrence and chemoresistance during CCA. MSCs are known for their anti-inflammatory activity and have been postulated to influence malignancy during CCA, but little is known about their exact functions. miRNAs exert various functions via gene regulation at both the transcriptional and the translational levels, giving miRNAs diverse roles in CCA progression. Additionally, current miRNA-based therapeutic approaches are in clinical trials for various liver diseases, giving hope for similar approaches for CCA. However, the interactions among these three factors in the context of CCA are unknown. In this review, we focus on recently published data (within the last 3 years) that discuss the role of CSCs, MSCs, and miRNAs and their possible interactions during CCA pathogenesis.

The deleterious interplay between tumor epithelia and stroma in cholangiocarcinoma

Prognosis of cholangiocarcinoma, a devastating liver epithelial malignancy characterized by early invasiveness, remains very dismal, though its incidence has been steadily increasing. Evidence is mounting that in cholangiocarcinoma, tumor epithelial cells establish an intricate web of mutual interactions with multiple stromal components, largely determining the pervasive behavior of the tumor. The main cellular components of the tumor microenvironment (i.e. myofibroblasts, macrophages, lymphatic endothelial cells), which has been recently termed as 'tumor reactive stroma', are recruited and activated by neoplastic cells, and in turn, deleteriously mold tumor behavior by releasing a huge variety of paracrine signals, including cyto/chemokines, growth factors, morphogens and proteinases. An abnormally remodeled and stiff extracellular matrix favors and supports these cell interactions. Although the mechanisms responsible for the generation of tumor reactive stroma are largely uncertain, hypoxia presumably plays a central role. In this review, we will dissect the intimate relationship among the different cell elements cooperating within this complex 'ecosystem', with the ultimate goal to pave the way for a deeper understanding of the mechanisms underlying cholangiocarcinoma aggressiveness, and possibly, to foster the development of innovative, combinatorial therapies aimed at halting tumor progression. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.