Systemic Cancer Progression and Tumor Dormancy: Mathematical Models Meet Single Cell Genomics

Metastatic progression is thought to result from genetically advanced ?fully-malignant“ tumor cells. Within the concept the prevailing view holds that such cells disseminate mostly from large tumors and are capable of growing into metastases once they arrive at a distant site. Support for this scenario comes from numerous mouse models in which transplanted tumor cells grow into metastases within days or weeks. However, the assumption of such fully-malignant disseminating cells in human cancer is misleading and is neither supported by mathematical modeling of survival data from cancer patients nor by ex-vivo genomic data from disseminated cancer cells. For example, in breast cancer the growth of metastases is highly homogeneous and takes on average six years, the number of disseminated tumor cells before diagnosis of metastasis is similar for different tumor stages, and the genomic aberrations of disseminated cancer cells do rarely correspond to those in the primary tumor. Since these facts question conventional concepts of metastatic progression we provide a model of cancer progression in which time considerations and direct ex-vivo data form a starting point. In the proposed model tumor dormancy is a characteristic of almost all migrated tumor cells and metastatic growth is a rare, stochastic, evolutionary process of selection and mutation of cells that often disseminate shortly after transformation at the primary site.     

A paradigm for the treatment of prostate cancer bone metastases based on an understanding of tumor cell-microenvironment interactions

The pliability of cancer cells to mutate into several different phenotypes in an attempt to find one that will survive and colonize at the metastatic site is a tremendous "hurdle" to overcome in designing novel cancer therapeutics. New targets of therapy are essential if we are to effectively overcome the evasiveness of cancer. The interaction between the tumor cell and the surrounding microenvironment creates a vicious cycle that perpetuates disease survival and progression. The future of cancer therapy resides in the ability to focus on the recruited and exploited relationships of the cancer cell with the host environment. These therapies target cancer cell growth early and interrupt the vicious cycle that is created by the tumor cells interacting with bone components by inhibiting osteoclasts, osteoblasts, stromal cells, and endothelial cells. They alter the bone microenvironment, creating a hostile "soil" that prevents the "seed" from developing into bone metastases and represent a potential new platform for the development of prostate cancer therapeutics.     

Stochastic dynamics of metastasis formation

Tumor metastasis accounts for the majority of deaths in cancer patients. The metastatic behavior of cancer cells is promoted by mutations in many genes, including activation of oncogenes such as RAS and MYC. Here, we develop a mathematical framework to analyse the dynamics of mutations enabling cells to metastasize. We consider situations in which one mutation is necessary to confer metastatic ability to the cell. We study different population sizes of the main tumor and different somatic fitness values of metastatic cells. We compare mutations that are positively selected in the main tumor with those that are neutral or negatively selected, but faster at forming metastases. We study whether metastatic potential is the property of all (or the majority of) cells in the main tumor or only the property of a small subset. Our theory shows how to calculate the expected number of metastases that are formed by a tumor.     

Computational modeling of pancreatic cancer reveals kinetics of metastasis suggesting optimum treatment strategies

Pancreatic cancer is a leading cause of cancer-related death, largely due to metastatic dissemination. We investigated pancreatic cancer progression by utilizing a mathematical framework of metastasis formation together with comprehensive data of 228 patients, 101 of whom had autopsies. We found that pancreatic cancer growth is initially exponential. After estimating the rates of pancreatic cancer growth and dissemination, we determined that patients likely harbor metastases at diagnosis and predicted the number and size distribution of metastases as well as patient survival. These findings were validated in an independent database. Finally, we analyzed the effects of different treatment modalities, finding that therapies that efficiently reduce the growth rate of cells earlier in the course of treatment appear to be superior to upfront tumor resection. These predictions can be validated in the clinic. Our interdisciplinary approach provides insights into the dynamics of pancreatic cancer metastasis and identifies optimum therapeutic interventions.     

Angiopoietin-2, an angiogenic regulator, promotes initial growth and survival of breast cancer metastases to the lung through the integrin-linked kinase (ILK)-AKT-B cell lymphoma 2 (Bcl-2) pathway

The early onsets of breast cancer metastasis involve cell retention, survival, and resistant to apoptosis and subsequent growth at target vascular beds and tissues in distant organs. We previously reported that angiopoietin-2 (Ang2), an angiogenic regulator stimulates MCF-7 breast tumor metastasis from their orthotopic sites to distant organs through the α(5)β(1) integrin/integrin-linked kinase (ILK)/Akt pathway. Here, by using an experimental tumor metastasis model and in vitro studies, we further dissect the underlying mechanism by which Ang2 promotes the initial growth and survival of MCF-7 breast cancer metastasis in the lung of animals. We show that Ang2 increases cell survival and suppresses cell apoptosis through ILK-induced phosphorylation of Akt1, Akt2, and up-regulation of Bcl-2 in breast cancer cells. Inhibition of ILK, Akt1, and Akt2, and their effector Bcl-2 diminishes Ang2-stimulated breast cancer cell survival and Ang2-attenuated apoptosis in vitro, and initial survival and growth of breast cancer metastasis in the lung of animals. Additionally, siRNA knockdown of endogenous Ang2 in three human metastatic breast cancer cell lines also inhibits phosphorylation of Akt, expression of Bcl-2, and tumor cell survival, migration, and increases cell apoptosis. Since increased expression of Ang2 correlates with elevated potential of human breast cancer metastasis in clinic, our data underscore the importance that up-regulated Ang2 not only stimulates breast cancer growth and metastasis at late stages of the process, but is also critical at the initiating stages of metastases onset, thereby suggesting Ang2 as a promising therapeutic target for treating patients with metastatic breast cancer.     

Biochemical mechanisms of tumor invasion and metastases

Tumor invasion and metastases is the major cause of treatment failure for cancer patients. There is a great need to develop new clinical methods to predict the clinical aggressiveness of a patient's tumor and to identify and eradicate clinically silent micrometastases. Such new methods may be derived from basic research into the biochemical mechanisms of invasion and metastases. We have isolated proteins involved in tumor cell attachment, invasion, and locomotion. The 'laminin receptor' is a tumor cell surface protein which specifically binds laminin, a glycoprotein of basement membranes. The laminin receptor may play a role in tumor cell attachment. 'Type IV collagenase' is a metalloproteinase which cleaves type IV basement membrane collagen but not interstitial collagens. The 'autocrine motility factor' is a secreted protein which binds to the cell surface and profoundly stimulates cell locomotion. All of these proteins appear to be augmented in actively metastatic tumor cells, at least in the models studied. They may provide strategies for diagnosis and therapy of metastases.     

Cell survival and metastasis regulation by Akt signaling in colorectal cancer

Dissemination of cancer cells to distant organ sites is the leading cause of death due to treatment failure in different types of cancer. Mehlen and Puisieux have reviewed the importance of the development of inappropriate cell survival signaling for various steps in the metastatic process and have noted the particular importance of aberrant cell survival to successful colonization at the metastatic site. Therefore, the understanding of mechanisms that govern cell survival fate of these metastatic cells could lead to the understanding of a new paradigm for the control of metastatic potential and could provide the basis for developing novel strategies for the treatment of metastases. Numerous studies have documented the widespread role of Akt in cell survival and metastasis in colorectal cancer, as well as many other types of cancer. Akt acts as a key signaling node that bridges the link between oncogenic receptors to many essential pro-survival cellular functions, and is perhaps the most commonly activated signaling pathway in human cancer. In recent years, Akt2 and Akt3 have emerged as significant contributors to malignancy alongside the well-characterized Akt1 isoform, with distinct non-overlapping functions. This review is aimed at gaining a better understanding of the Akt-driven cell survival mechanisms that contribute to cancer progression and metastasis and the pharmacological inhibitors in clinical trials designed to counter the Akt-driven cell survival responses in cancer.     

The membrane-cytoskeleton linker ezrin is necessary for osteosarcoma metastasis

Metastatic cancers, once established, are the primary cause of mortality associated with cancer. Previously, we used a genomic approach to identify metastasis-associated genes in cancer. From this genomic data, we selected ezrin for further study based on its role in physically and functionally connecting the actin cytoskeleton to the cell membrane. In a mouse model of osteosarcoma, a highly metastatic pediatric cancer, we found ezrin to be necessary for metastasis. By imaging metastatic cells in the lungs of mice, we showed that ezrin expression provided an early survival advantage for cancer cells that reached the lung. AKT and MAPK phosphorylation and activity were reduced when ezrin protein was suppressed. Ezrin-mediated early metastatic survival was partially dependent on activation of MAPK, but not AKT. To define the relevance of ezrin in the biology of metastasis, beyond the founding mouse model, we examined ezrin expression in dogs that naturally developed osteosarcoma. High ezrin expression in dog tumors was associated with early development of metastases. Consistent with this data, we found a significant association between high ezrin expression and poor outcome in pediatric osteosarcoma patients.     

A Mouse Tumor Model of Surgical Stress to Explore the Mechanisms of Postoperative Immunosuppression and Evaluate Novel Perioperative Immunotherapies

Surgical resection is an essential treatment for most cancer patients, but surgery induces dysfunction in the immune system and this has been linked to the development of metastatic disease in animal models and in cancer patients. Preclinical work from our group and others has demonstrated a profound suppression of innate immune function, specifically NK cells in the postoperative period and this plays a major role in the enhanced development of metastases following surgery. Relatively few animal studies and clinical trials have focused on characterizing and reversing the detrimental effects of cancer surgery. Using a rigorous animal model of spontaneously metastasizing tumors and surgical stress, the enhancement of cancer surgery on the development of lung metastases was demonstrated. In this model, 4T1 breast cancer cells are implanted in the mouse mammary fat pad. At day 14 post tumor implantation, a complete resection of the primary mammary tumor is performed in all animals. A subset of animals receives additional surgical stress in the form of an abdominal nephrectomy. At day 28, lung tumor nodules are quantified. When immunotherapy was given immediately preoperatively, a profound activation of immune cells which prevented the development of metastases following surgery was detected. While the 4T1 breast tumor surgery model allows for the simulation of the effects of abdominal surgical stress on tumor metastases, its applicability to other tumor types needs to be tested. The current challenge is to identify safe and promising immunotherapies in preclinical mouse models and to translate them into viable perioperative therapies to be given to cancer surgery patients to prevent the recurrence of metastatic disease.     

A Preclinical Murine Model of Hepatic Metastases

Numerous murine models have been developed to study human cancers and advance the understanding of cancer treatment and development. Here, a preclinical, murine pancreatic tumor model of hepatic metastases via a hemispleen injection of syngeneic murine pancreatic tumor cells is described. This model mimics many of the clinical conditions in patients with metastatic disease to the liver. Mice consistently develop metastases in the liver allowing for investigation of the metastatic process, experimental therapy testing, and tumor immunology research.     

综述与专论: 核酸适配体在肾癌中的应用

肾癌是泌尿系统最常见的肿瘤之一,发病率呈上升趋势。肾细胞癌作为肾脏肿瘤的主要类型,具有较高的局部浸润和远处转移的频率,约33%~50%的肾细胞癌患者在发现时已发生转移。由于肾细胞癌早期无特异性体征和症状,主要治疗手段是手术切除,对放化疗不敏感,治疗手段有限,因此肾细胞癌的早期诊断能够大大提高肾细胞癌有效治疗的机会,对于肾癌的有效治疗具有十分重要的意义。核酸适配体是通过指数富集的配体系统进化技术（systematic evolution of ligands by exponential enrichment,SELEX）,从核酸分子文库中得到的寡核苷酸片段,能够选择性地与小分子配体或高亲和力的蛋白质靶标结合,对靶分子或细胞具有较高的亲和力和特异性,目前已广泛应用于肿瘤影像学诊断及靶向治疗中。本文主要综述了与肾癌相关的核酸适配体,并对于适配体在肾癌诊疗中的应用进行了总结和讨论。     

Incidence of bone metastases and survival after a diagnosis of bone metastases in breast cancer patients

Background: Bone is the most common metastatic site associated with breast cancer. Using a database of women with breast cancer treated at Guy's Hospital, London 1976–2006 and followed until end 2010, we determined incidence of and survival after bone metastases. Methods: We calculated cumulative incidence of bone metastases considering death without prior bone metastases as a competing risk. Risk of bone metastases was modelled through Cox-regression. Survival after bone metastases diagnosis was calculated using Kaplan–Meier methodology. Results: Of the 7064 women, 589 (22%) developed bone metastases during 8.4 years (mean). Incidence of bone metastases was significantly higher in younger women, tumour size >5 cm, higher tumour grade, lobular carcinoma and ≥four positive nodes, but was not affected by hormone receptor status. Median survival after bone metastases diagnosis was 2.3 years in women with bone-only metastases compared with <1 year in women with visceral and bone metastases. There was a trend for decreased survival for patients who developed visceral metastases early, and proportionately fewer patients in this group. Interpretation: Incidence of bone metastases has decreased but bone metastases remain a highly relevant clinical problem due to the large number of patients being diagnosed with breast cancer.     

Gene expression sigantures, cancer cell evolution and metastatic progression

Global gene expression profiling and molecular cytogenetics for single cells provide new opportunities to resolve important questions, such as the mechanisms of tumor cell selection during cancer progression. While gene expression analyses show that metastatic progression correlates with the deregulation of certain gene sets in the primary tumor, the direct analysis of disseminated cancer cells, the putative precursors of metachronous metastases, suggests that dissemination is a very early event in the genetic development of human cancers.     

CD105 Expression on CD34-Negative Spindle-Shaped Stromal Cells of Primary Tumor Is an Unfavorable Prognostic Marker in Early Breast Cancer Patients

Several studies have confirmed that the breast tumor microenvironment drives cancer progression and metastatic development. The aim of our research was to investigate the prognostic significance of the breast tumor microenvironment in untreated early breast cancer patients. Therefore, we analyzed the association of the expression of α-SMA, FSP, CD105 and CD146 in CD34-negative spindle-shaped stromal cells, not associated with the vasculature, in primary breast tumors with classical prognostic marker levels, metastatic recurrence, local relapse, disease-free survival, metastasis-free survival and the overall survival of patients. In the same way, we evaluated the association of the amount of intra-tumor stroma, fibroblasts, collagen deposition, lymphocytic infiltration and myxoid changes in these samples with the clinical-pathological data previously described. This study is the first to demonstrate the high CD105 expression in this stromal cell type as a possible independent marker of unfavorable prognosis in early breast cancer patients. Our study suggests that this new finding can be useful prognostic marker in the clinical-pathological routine.     

Brain metastases from stomach cancer – The role of different treatment modalities and efficacy of palliative radiotherapy

Aim

To evaluate different treatment modalities, sequences, and prognostic factors in patients with brain metastases from stomach cancer.

Background

Brain metastases from gastric cancer are rare and late manifestation of the disease, occurring in less than 1% of gastric cancer patients. The prognosis is poor and median overall survival is 1.3–2.4 months. The standard treatment scheme has not yet been described. Most studies present small sample sizes. The choice of treatment scheme is individually based on performance status, number, location and size of metastases, the status of primary tumor and the presence of other metastases.

Materials and methods

Sixteen patients diagnosed with brain metastases from gastric cancer in Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Gliwice Branch.Patients, mostly men (69%) aged 51–75 years, (median 68.5 years). Thirteen (81.25%) had treatment of primary tumor before diagnosis of brain metastases. Primary metastatic gastric cancer was diagnosed in 6 patients (37.5%), in 3 cases (18.75%) brain was the site of those metastases. Treatment schemes were individually based.

Results

We identified prognostic factors influencing OS: performance status, number of brain metastases, type of treatment. Median OS was 2.8 months. Median time to brain metastases was 12.3 months and it was shorter in patients with pretreatment metastases to other organs. Patients treated with combined treatment had median survival of 12.3 months.

Conclusions

Aggressive treatment schemes are needed to improve the outcome. Prognostic factors such as performance status, number of metastases, dissemination to other organs are helpful in considering the best treatment options.     

Tumor microenvironment – Unknown niche with powerful therapeutic potential

Head and neck squamous cell carcinomas (HNSCC) are in a group of cancers that are the most resistant to treatment. The survival rate of HNSCC patients has been still very low since last 20 years. The existence of relationship between oncogenic and surrounding cells is probably the reason for a poor response to treatment. Fibroblasts are an important element of tumor stroma which increases tumor cells ability to proliferate. Another highly resistance, tumorigenic and metastatic cell population in tumor microenvironment are cancer initiating cells (CICs). The population of cancer initiating cells can be found regardless of differentiation status of cancer and they seem to be crucial for HNSCC development.In this review, we describe the current state of knowledge about HNSCC biological and physiological tumor microenvironment.     

Significance of soluble endothelial molecule E-selectin in patients with breast cancer

Increasing evidence suggests that endothelial cells are involved in tumor growth and metastasis. E-selectin, an adhesion molecule specifically expressed or secreted by activated endothelial cells, may enhance tumor angiogenesis and the adhesion of tumor cells to endothelial cells at distant sites. The aim of this study was to assess the relationship between concentrations of circulating soluble E-selectin and clinical, pathological and biological features in patients with breast cancer (BC). sE-selectin concentrations were analyzed by an ELISA method in sera from 113 patients with metastatic BC, 30 patients with primary inflammatory BC, 105 patients with primary non-inflammatory BC, 456 patients with node-negative BC, and 42 healthy controls. sE-selectin in the metastatic BC group was significantly higher than in the healthy control group. In metastatic BC, sE-selectin was significantly higher in patients with liver metastases than in patients without liver metastases. In patients with primary non-inflammatory BC, a negative correlation was found between sE-selectin concentrations and tumoral microvessel count. In overall and disease-free survival studies performed in the node-negative population (median follow-up duration 7.5 years), multivariate analyses demonstrated a prognostic value of sE-selectin and tumor size. This study suggests that endothelial activation might play a role in the development of BC. This role seems not to be related to angiogenesis.     

Dynamics of metastasis suppressor gene inactivation

For most cancer cell types, the acquisition of metastatic ability leads to clinically incurable disease. Twelve metastasis suppressor genes (MSGs) have been identified that reduce the metastatic propensity of cancer cells. If these genes are inactivated in both alleles, metastatic ability is promoted. Here, we develop a mathematical model of the dynamics of MSG inactivation and calculate the expected number of metastases formed by a tumor. We analyse the effects of increased mutation rates and different fitness values of cells with one or two inactivated alleles on the ability of a tumor to form metastases. We find that mutations that are negatively selected in the main tumor are unlikely to be responsible for the majority of metastases produced by a tumor. Most metastases-causing mutations will be present in all (or most) cells in the main tumor.