Liver metastasis of pancreatic cancer: the hepatic microenvironment impacts differentiation and self-renewal capacity of pancreatic ductal epithelial cells

Epithelial and Mesenchymal-like Pancreatic Cancer Cells Exhibit Different Stem Cell Phenotypes Associated with Different Metastatic Propensities

Pancreatic ductal adenocarcinoma (PDAC) is mostly diagnosed at advanced or even metastasized stages, limiting the prognoses of patients. Metastasis requires high tumor cell plasticity, implying phenotypic switching in response to changing environments. Here, epithelial-mesenchymal transition (EMT), being associated with an increase in cancer stem cell (CSC) properties, and its reversion are important. Since it is poorly understood whether different CSC phenotypes exist along the EMT axis and how these impact malignancy-associated properties, we aimed to characterize CSC populations of epithelial and mesenchymal-like PDAC cells. Single-cell cloning revealed CSC (Holoclone) and non-CSC (Paraclone) clones from the PDAC cell lines Panc1 and Panc89. The Panc1 Holoclone cells showed a mesenchymal-like phenotype, dominated by a high expression of the stemness marker Nestin, while the Panc89 Holoclone cells exhibited a SOX2-dominated epithelial phenotype. The Panc89 Holoclone cells showed enhanced cell growth and a self-renewal capacity but slow cluster-like invasion. Contrarily, the Panc1 Holoclone cells showed slower cell growth and self-renewal ability but were highly invasive. Moreover, cell variants differentially responded to chemotherapy. In vivo, the Panc1 and Panc89 cell variants significantly differed regarding the number and size of metastases, as well as organ manifestation, leading to different survival outcomes. Overall, these data support the existence of different CSC phenotypes along the EMT axis in PDAC, manifesting different metastatic propensities.

Sequential therapy for pancreatic cancer patients with synchronous oligo-hepatic metastatic lesions

BACKGROUND

Treatments for patients suffering from pancreatic cancer with oligo-hepatic metastasis have always been a cause of certain controversy. Herein, we reported 15 pancreatic cancer patients with oligo-hepatic metastasis who accepted sequential therapy of chemotherapy, radiofrequency ablation (RFA), and radical resection of the primary tumor.

METHODS

A total of 87 pancreatic cancer patients with synchronous oligo-metastatic hepatic lesions who received treatments in the 2nd Affiliated Hospital of Zhejiang University between January 2017 and July 2020 were enrolled. The chemotherapy regimens included modified folfirinox (54/87) and gemcitabine plus nab-paclitaxel (33/87). Test of blood tumor markers and contrast-enhanced computed tomography (CT) or magnetic resonance (MR) scan was performed at diagnosis and after eight weeks of chemotherapy.

RESULTS

Thirty-five patients received just chemotherapy because of poor reaction to the first round of chemotherapy(Overall survival (OS), 6.47±1.80 months); 15 patients reassessed as stable disease (SD)/partial response (PR) continued chemotherapy (OS, 10.35±3.15); nine patients reassessed as progressive disease (PD) after RFA and continued chemotherapy (OS, 10.90±2.60). The primary tumors in 13 patients were unresectable after chemotherapy and RFA (OS, 12.92±2.47), while 15 patients completed the sequential therapy of chemotherapy, radio-frequency ablation, and radical resection (OS, 16.76±6.55).

CONCLUSIONS

Sequential chemotherapy and RFA is a good treatment strategy to select the best candidates for surgical treatment among patients with pancreatic cancer with oligo-hepatic metastasis.

Breast cancer liver metastasis: Pathogenesis and clinical implications

Breast cancer is the most common malignant disease in female patients worldwide and can spread to almost every place in the human body, most frequently metastasizing to lymph nodes, bones, lungs, liver and brain. The liver is a common metastatic location for solid cancers as a whole, and it is also the third most common metastatic site for breast cancer. Breast cancer liver metastasis (BCLM) is a complex process. Although the hepatic microenvironment and liver sinusoidal structure are crucial factors for the initial arrest of breast cancer and progression within the liver, the biological basis of BCLM remains to be elucidated. Importantly, further understanding of the interaction between breast cancer cells and hepatic microenvironment in the liver metastasis of breast cancer will suggest ways for the development of effective therapy and prevention strategies for BCLM. In this review, we provide an overview of the recent advances in the understanding of the molecular mechanisms of the hepatic microenvironment in BCLM formation and discuss current systemic therapies for treating patients with BCLM as well as potential therapeutic development based on the liver microenvironment-associated signaling proteins governing BCLM.

The Transcription Factors Zeb1 and Snail Induce Cell Malignancy and Cancer Stem Cell Phenotype in Prostate Cells, Increasing Androgen Synthesis Capacity and Therapy Resistance

Prostate cancer (PCa) incidence has increased during the last decades, becoming one of the leading causes of death by cancer in men worldwide. During an extended period of prostate cancer, malignant cells are androgen-sensitive being testosterone the main responsible for tumor growth. Accordingly, treatments blocking production and action of testosterone are mostly used. However, during disease progression, PCa cells become androgen insensitive producing a castration-resistant stage with a worse prognosis. Overcoming castration-resistant prostate cancer (CRPC) has become a great challenge in the management of this disease. In the search for molecular pathways leading to therapy resistance, the epithelial-mesenchymal transition (EMT), and particularly the transcription factors zinc finger E-box-binding homeobox 1 (Zeb1) and zinc finger protein SNAI1 (Snail), master genes of the EMT, have shown to have pivotal roles. Also, the discovery that cancer stem cells (CSCs) can be generated de novo from their non-CSCs counterpart has led to the question whereas these EMT transcription factors could be implicated in this dynamic conversion between non-CSC and CSC. In this review, we analyze evidence supporting the idea that Zeb1 and Snail induce cell malignancy and cancer stem cell phenotype in prostate cells, increasing androgen synthesis capacity and therapy resistance.

Autophagy and Hepatic Tumor Microenvironment Associated Dormancy

The goal of successful cancer treatment is targeting the eradication of cancer cells. Although surgical removal of the primary tumors and several rounds of chemo- and radiotherapy reduce the disease burden, in some cases, asymptomatic dormant cancer cells may still exist in the body. Dormant cells arise from the disseminated tumor cells (DTCs) from the primary lesion. DTCs escape from immune system and cancer therapy and reside at the secondary organ without showing no sign of proliferation. However, under some conditions. dormant cells can be re-activated and enter a proliferative state even after decades. As a stress response mechanism, autophagy may help the adaptation of DTCs at this futile foreign microenvironment and may control the survival and re-activation of dormant cells. Studies indicate that hepatic microenvironment serves a favorable condition for cancer cell dormancy. Although, no direct study was pointing out the role of autophagy in liver-assisted dormancy, involvement of autophagy in both liver microenvironment, health, and disease conditions has been indicated. Therefore, in this review article, we will summarize cancer dormancy and discuss the role and importance of autophagy and hepatic microenvironment in this context.

Pre-clinical Models of Metastasis in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a hostile solid malignancy coupled with an extremely high mortality rate. Metastatic disease is already found in most patients at the time of diagnosis, resulting in a 5-year survival rate below 5%. Improved comprehension of the mechanisms leading to metastasis is pivotal for the development of new targeted therapies. A key field to be improved are modeling strategies applied in assessing cancer progression, since traditional platforms fail in recapitulating the complexity of PDAC. Consequently, there is a compelling demand for new preclinical models that mirror tumor progression incorporating the pressure of the immune system, tumor microenvironment, as well as molecular aspects of PDAC. We suggest the incorporation of 3D organoids derived from genetically engineered mouse models or patients as promising new tools capable to transform PDAC pre-clinical modeling and access new frontiers in personalized medicine.

The Microbiome Tumor Axis: How the Microbiome Could Contribute to Clonal Heterogeneity and Disease Outcome in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant cancers. It is characterized by a poor prognosis with a 5-year survival rate of only around 10% and an ongoing increase in death rate. Due to the lack of early and specific symptoms, most patients are diagnosed at an advanced or even metastasized stage, essentially limiting curative treatment options. However, even curative resection of the primary tumor and adjuvant therapy often fails to provide a long-term survival benefit. One reason for this dismal situation can be seen in the evolution of therapy resistances. Furthermore, PDAC is characterized by high intratumor heterogeneity, pointing towards an abundance of cancer stem cells (CSCs), which are regarded as essential for tumor initiation and drug resistance. Additionally, it was shown that the gut microbiome is altered in PDAC patients, promotes Epithelial-Mesenchymal-Transition (EMT), determines responses towards chemotherapy, and affects survival in PDAC patients. Given the established links between CSCs and EMT as well as drug resistance, and the emerging role of the microbiome in PDAC, we postulate that the composition of the microbiome of PDAC patients is a critical determinant for the abundance and plasticity of CSC populations and thus tumor heterogeneity in PDAC. Unravelling this complex interplay might pave the way for novel treatment strategies.

Initiation of Pancreatic Cancer: The Interplay of Hyperglycemia and Macrophages Promotes the Acquisition of Malignancy-Associated Properties in Pancreatic Ductal Epithelial Cells

Pancreatic ductal adenocarcinoma (PDAC) is still one of the most aggressive solid malignancies with a poor prognosis. Obesity and type 2 diabetes mellitus (T2DM) are two major risk factors linked to the development and progression of PDAC, both often characterized by high blood glucose levels. Macrophages represent the main immune cell population in PDAC contributing to PDAC development. It has already been shown that pancreatic ductal epithelial cells (PDEC) undergo epithelial–mesenchymal transition (EMT) when exposed to hyperglycemia or macrophages. Thus, this study aimed to investigate whether concomitant exposure to hyperglycemia and macrophages aggravates EMT-associated alterations in PDEC. Exposure to macrophages and elevated glucose levels (25 mM glucose) impacted gene expression of EMT inducers such as IL-6 and TNF-α as well as EMT transcription factors in benign (H6c7-pBp) and premalignant (H6c7-kras) PDEC. Most strikingly, exposure to hyperglycemic coculture with macrophages promoted downregulation of the epithelial marker E-cadherin, which was associated with an elevated migratory potential of PDEC. While blocking IL-6 activity by tocilizumab only partially reverted the EMT phenotype in H6c7-kras cells, neutralization of TNF-α by etanercept was able to clearly impair EMT-associated properties in premalignant PDEC. Altogether, the current study attributes a role to a T2DM-related hyperglycemic, inflammatory micromilieu in the acquisition of malignancy-associated alterations in premalignant PDEC, thus providing new insights on how metabolic diseases might promote PDAC initiation.

Oxygen-Carrying Polymer Nanoconstructs for Radiodynamic Therapy of Deep Hypoxic Malignant Tumors

Radiodynamic therapy (RDT) is an emerging non-invasive anti-cancer treatment based on the generation of the reactive oxygen species (ROS) at the lesion site following the interaction between X-rays and a photosensitizer drug (PS). The broader application of RDT is impeded by the tumor-associated hypoxia that results in low availability of oxygen for the generation of sufficient amounts of ROS. Herein, a novel nanoparticle drug formulation for RDT, which addresses the problem of low oxygen availability, is reported. It consists of poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) co-loaded with a PS drug verteporfin (VP), and the clinically approved oxygen-carrying molecule, perfluorooctylbromide (PFOB). When triggered by X-rays (4 Gy), under both normoxic and hypoxic conditions, PLGA-VP-PFOB nanoconstructs (NCs) induced a significant increase of the ROS production compared with matching PLGA-VP nanoparticles. The RDT with NCs effectively killed ~60% of human pancreatic cancer cells in monolayer cultures, and almost completely suppressed the outgrowth of tumor cells in 2-weeks clonogenic assay. In a 3D engineered model of pancreatic cancer metastasis to the liver, RDT with NCs destroyed ~35% of tumor cells, demonstrating an exceptional efficiency at a tissue level. These results show that PLGA-VP-PFOB is a promising agent for RDT of deep-seated hypoxic tumors.

Transcriptome profiling reveals liver metastasis-associated genes in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies worldwide. However, the mechanisms underlying the acquisition of the metastatic potential in PDAC has not been well understood. In this study, we identified a total of 154 genes upregulated in primary tissues of PDAC with liver metastasis using the Genome Cancer Atlas (TCGA) and GSE151580 cohorts. The epithelial-mesenchymal transition and glycolysis were enriched by the liver metastasis-related genes, indicating that the liver metastasis-related genes might be functionally relevant to liver metastasis in PDAC. Moreover, we also found that the liver metastasis-related genes were primarily regulated at epigenetic level. Particularly, SFN, a cell cycle checkpoint protein, and KRT19, a marker gene for ductal cells, were predicted to be regulated by multiple methylation sites at the promoter. Clinically, we for the first time defined a liver metastasis score (LMS), which was derived from liver metastasis-related genes, and closely associated with clinical characteristics such as disease type and tumor grade, in PDAC. Furthermore, we also divided the samples into high and low LMS groups using three cohorts with long-term follow-up (TCGA, GSE71729, and E-MTAB-6134), which exhibited significantly different prognostic outcomes across three PDAC cohorts, suggesting that the LMS might be a good indicator for risk stratification in PDAC. Furthermore, we also found that the liver metastasis-related genes were primarily expressed in malignant ductal cells by integrative analysis of the bulk and single-cell gene expression data. Moreover, the malignant ductal cells and M0 macrophages were highly correlated with LMS, indicating that the two cell types might function as tumor-promoting cells in PDAC. In summary, the systematic analysis for the first time defined an LMS score to evaluate the risk of liver metastasis in PDAC and revealed that malignant ductal cells might promote PDAC liver metastasis, which greatly improves our understanding of the liver metastasis-related genes, their underlying mechanisms, and association with prognosis in PDAC.

The fibrotic and immune microenvironments as targetable drivers of metastasis

Although substantial progress has been made over the past 40 years in treating patients with cancer, effective therapies for those who are diagnosed with advanced metastatic disease are still few and far between. Cancer cells do not exist in isolation: rather, they exist within a complex microenvironment composed of stromal cells and extracellular matrix. Within this tumour microenvironment exists an interplay between the two main stromal cell subtypes, cancer-associated fibroblasts (CAFs) and immune cells, that are important in controlling metastasis. A complex network of paracrine signalling pathways between CAFs, immune cells and tumour cells are involved at multiple stages of the metastatic process, from invasion and intravasation at the primary tumour site to extravasation and colonisation in the metastatic site. Heterogeneity and plasticity within stromal cell populations also contribute to the complexity. Although many of these processes are likely to be common to a number of metastatic sites, we will describe in detail the interplay within the liver, a preferred site of metastasis for many tumours. A greater understanding of these networks provides opportunities for the design of new therapeutic approaches for targeting the metastatic disease.

Space of Disse: a stem cell niche in the liver

Recent evidence indicates that the plasticity of preexisting hepatocytes and bile duct cells is responsible for the appearance of intermediate progenitor cells capable of restoring liver mass after injury without the need of a stem cell compartment. However, mesenchymal stem cells (MSCs) exist in all organs and are associated with blood vessels which represent their perivascular stem cell niche. MSCs are multipotent and can differentiate into several cell types and are known to support regenerative processes by the release of immunomodulatory and trophic factors. In the liver, the space of Disse constitutes a stem cell niche that harbors stellate cells as liver resident MSCs. This perivascular niche is created by extracellular matrix proteins, sinusoidal endothelial cells, liver parenchymal cells and sympathetic nerve endings and establishes a microenvironment that is suitable to maintain stellate cells and to control their fate. The stem cell niche integrity is important for the behavior of stellate cells in the normal, regenerative, aged and diseased liver. The niche character of the space of Disse may further explain why the liver can become an organ of extra-medullar hematopoiesis and why this organ is frequently prone to tumor metastasis.

A Phase Ib Study of Single-Agent Idelalisib Followed by Idelalisib in Combination with Chemotherapy in Patients with Metastatic Pancreatic Ductal Adenocarcinoma

LESSONS LEARNED

Although this study of idelalisib in patients with PDAC was limited in size and duration because of early termination, idelalisib exposure resulted in an overall safety profile consistent with studies in hematological malignancies, except that the incidences of diarrhea and colitis were reduced in patients with PDAC. Preclinical studies of the PI3K pathway in PDAC and positive clinical results of PI3K inhibition in other cancers support the continued development of PI3K inhibitors in PDAC.

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal solid tumors and is often refractory to treatment. Phosphatidylinositol-3 kinase (PI3K) δ inhibition influences regulatory immune cell function and improves survival in preclinical PDAC models. Here, idelalisib, an inhibitor of PI3Kδ, was investigated as treatment for metastatic PDAC.

METHODS

This was an open-label, multicenter, phase Ib, nonrandomized, dose-escalation study. Study aims were to investigate the maximum tolerated dose, safety, pharmacokinetics/pharmacodynamics, and efficacy of idelalisib alone and in combination with chemotherapeutics-nab-paclitaxel and modified (m)FOLFOX6.

RESULTS

Because of early termination, only 16 patients were enrolled in the single-agent idelalisib arm, 12 of whom received at least one dose of idelalisib. The most common treatment-emergent adverse events (≥25%) related to idelalisib (n = 12) were increased aspartate aminotransferase, pyrexia, and maculopapular rash. One patient presented with diarrhea; no cases of colitis were reported. One patient discontinued treatment because of pyrexia and maculopapular rash; two patients died because of disease progression.

CONCLUSION

This study was terminated because factors contributing to safety concerns in phase III studies of idelalisib for hematological malignancies were not fully understood. In this small sample of patients with metastatic PDAC, exposure to idelalisib resulted in safety findings consistent with previous studies, with reduced diarrhea/colitis.

Epithelial-Mesenchymal Transition in a Case of Metastatic Thyroid Carcinoma in a Brown Bear (Ursus arctos)

A 20-year-old male brown bear (Ursus arctos) with a 20 × 25 cm necrotic mass adjacent to the trachea was diagnosed as having an anaplastic thyroid carcinoma. Metastases were observed in the lungs and one adrenal gland and, histologically, these had anaplastic and follicular carcinoma patterns, respectively. E-cadherin labelling was observed in the adrenal mass only, while N-cadherin immunolabelling was detected in the thyroid gland and lung masses. Thyroid-specific markers (thyroid transcription factor-1, thyroglobulin) were expressed in the adrenal gland metastasis. This case illustrates an example of a primary epithelial-mesenchymal transition (EMT) enabling metastasis to distant organ sites, followed by a mesenchymal-epithelial transition within the adrenal gland microenvironment, allowing invasion and reacquisition of thyroid epithelial cell features. EMTs help to understand the phenomenon of carcinoma cell plasticity in enabling colonization and growth of metastases.

The role of liver microenvironment in hepatic metastasis

Metastasis is still poorly understood and thus further research must be conducted to provide insight into the driving factors. Novel research has revealed the significance of the microenvironment in the delegation of metastasis, expanding the field of cancer metastasis to cells and cell environments surrounding the migrated tumor cells. Research on hepatic metastasis is an ever-growing domain of this field, as several primary tumors can metastasize to the liver. The two features within the liver that promote metastasis—cellular and acellular—are found in the current interpretation of liver microenvironment. Novel findings of both are included in this review. Different hypotheses detailing the methods by which metastasis can occur must be included to understand the significance of the microenvironment, as well as a brief overview of the methods that can be used during research. This review aims to highlight the importance of liver microenvironment on the development or potential regression of hepatic metastasis through discussing both acellular and cellular components of liver microenvironment and their interaction with metastasis.

Metastasis of pancreatic cancer: An uninflamed liver micromilieu controls cell growth and cancer stem cell properties by oxidative phosphorylation in pancreatic ductal epithelial cells

Pancreatic ductal adenocarcinoma (PDAC) is commonly diagnosed when liver metastases already emerged. We recently demonstrated that hepatic stromal cells determine the dormancy status along with cancer stem cell (CSC) properties of pancreatic ductal epithelial cells (PDECs) during metastasis. This study investigated the influence of the hepatic microenvironment - and its inflammatory status - on metabolic alterations and how these impact cell growth and CSC-characteristics of PDECs. Coculture with hepatic stellate cells (HSCs), simulating a physiological liver stroma, but not with hepatic myofibroblasts (HMFs) representing liver inflammation promoted expression of Succinate Dehydrogenase subunit B (SDHB) and an oxidative metabolism along with a quiescent phenotype in PDECs. SiRNA-mediated SDHB knockdown increased cell growth and CSC-properties. Moreover, liver micrometastases of tumor bearing KPC mice strongly expressed SDHB while expression of the CSC-marker Nestin was exclusively found in macrometastases. Consistently, RNA-sequencing and in silico modeling revealed significantly altered metabolic fluxes and enhanced SDH activity predominantly in premalignant PDECs in the presence of HSC compared to HMF. Overall, these data emphasize that the hepatic microenvironment determines the metabolism of disseminated PDECs thereby controlling cell growth and CSC-properties during liver metastasis.