When breast tumor cells encounter stress due to cancer therapies, they may enter a dormant state, escaping from treatment-induced apoptosis. Dormant cells may eventually regain proliferative capabilities and cause recurrent metastatic disease, which is the leading cause of mortality in breast cancer patients. We sought to determine if a high dose of radiation therapy (RT) or combined chemo-immunotherapy, with and without the blockade of autophagy by chloroquine (CQ), could overcome treatment-induced tumor dormancy or relapse. We found that autophagy contributes in part to treatment-induced tumor dormancy. We also found that three therapeutic strategies were successful in inhibiting or preventing tumor relapse. These include: 18Gy/day RT, chemotherapy combined with the blockade of autophagy, and combined chemo-immunotherapy. Follow-up studies are needed to determine the feasibility of preventing tumor relapse by prolonging tumor dormancy versus eliminating dormant tumor cells.
Breast cancer mortality is mainly due to distant recurrence of the disease arising from dormant tumor cells established by cancer therapies. Patients who initially respond to cancer therapies often succumb to distant recurrence of the disease. It is not clear why people with the same type of breast cancer respond to treatments differently; some escape from dormancy and relapse earlier than others. In addition, some tumor clones respond to immunotherapy while others do not. We investigated how autophagy plays a role in accelerating or delaying recurrence of neu overexpressing mouse mammary carcinoma (MMC) following adriamycin (ADR) treatment, and in affecting response to immunotherapy. We explored two strategies: 1) transient blockade of autophagy with chloroquine (CQ), which blocks fusion of autophagosomes and lysosomes during ADR treatment, and 2) permanent inhibition of autophagy by a stable knockdown of ATG5 (ATG5KD), which inhibits the formation of autophagosomes in MMC during and after ADR treatment. We found that while CQ prolonged tumor dormancy, but that stable knockdown of autophagy resulted in early escape from dormancy and recurrence. Interestingly, ATG5KD MMC contained an increased frequency of ADR-induced polyploid-like cells and rendered MMC resistant to immunotherapy. On the other hand, a transient blockade of autophagy did not affect the sensitivity of MMC to immunotherapy. Our observations suggest that while chemotherapy-induced autophagy may facilitate tumor relapse, cell-intrinsic autophagy delays tumor relapse, in part, by inhibiting the formation of polyploid-like tumor dormancy. Although immunotherapy of breast cancer by means of anti-HER2 antibodies prolongs survival of breast cancer patients, disease recurrence remains a major challenge. On the other hand administration of human vaccines against infectious disease in a preventive setting or during latency/dormancy has been successful in offering a cure. Here, we sought to use adoptive immunotherapy (AIT) at the time of tumor dormancy in order to prevent progression of breast cancer. We used a low dose immunogenic chemotherapy by means of 5-FU, Adriamycin, and Cyclophosphamide (FAC) in order to stabilize tumor progression prior to AIT using autologous tumor-reactive lymphocytes. Low dose FAC established local tumor dormancy, inhibited distant tumor dormancy occurring long before distant metastasis, and induced predominate a Ki67- quiescent type of tumor dormancy, which is less susceptible to tumor immunoediting. Dormant tumor cells expressed the cell survival pathways, including the endothelin receptor/ligand (ETRA, ETRB and ET-1) and PD-L1, thereby protecting them from elimination by AIT. In addition, tumor-reactive CD8+ T cells also produced ET-1 as a survival ligand for ETRA positive tumor cells. A combination of AIT with the blockade of tumor cell survival pathways resulted in a significant improvement of AIT against tumor dormancy. We also showed that the inhibition Bcl-xL downstream of the tumor cell survival pathways is specifically effective against dormant tumor cells, suggesting a combination of AIT with small molecules inhibitors of Bcl-xL. Altogether, we showed that distant tumor dormancy is established long before distant recurrence of breast cancer, and that the expression of several tumor cell survival pathways in dormant cells protects them from immunotherapy. Our results suggest that immunotherapeutic targeting of tumor dormancy combined with the blockade of a common downstream cell survival pathway could prevent tumor progression and recurrence of the disease.
Breast cancer is the most common cause of cancer-related death and is the most frequently diagnosed cancer in women worldwide. Mortality from breast cancer is principally due to tumor recurrence, which may be diagnosed up to 20 years after treatment of the primary tumor. Since relapse is a consequence of the persistence of residual tumor cells, identifying the mechanisms involved in tumor cell survival and escape from therapy is essential for the development of more effective strategies for improving patient outcomes. Using a genetically-engineered mouse model for breast cancer dormancy and recurrence, we now report that inhibition of HER2/neu signaling in primary tumors induces cellular senescence and that this process may serve as a barrier to tumor relapse. We find that the ETS-domain transcription factor Ehf is up-regulated following acute HER2/neu signaling inhibition and induces senescence in mouse mammary tumor cells. Notably, Ehf expression is lost in residual breast cancer cells that survive tumor regression, as well as in recurrent tumors. Analogous to its behavior in response to targeted down-regulation of the HER2/neu pathway, EHF is acutely up-regulated in human breast cancer cells following Adriamycin treatment, but down-regulated in tumor cells that survive neoadjuvant chemotherapy in breast cancer patients. Consistent with a model in which EHF down-regulation promotes tumor cell survival following therapy, low EHF expression in primary breast cancers is associated with a poor response to neoadjuvant chemotherapy and an increased risk of relapse in women with breast cancer. Collectively, our findings demonstrate that senescence is a conserved response to HER2/neu signaling inhibition in oncogene-addicted breast cancer cells and identify EHF as a potential regulator of HER2/neu inactivation-induced senescence and tumor cell survival following targeted therapy and chemotherapy.
Breast cancer recurrence is the primary cause of mortality in breast cancer, and although advances have been made in the treatment of primary breast cancer, recurrent breast cancer remains uncurable. Targeted therapy has had a major impact on survival across multiple cancer types, including breast cancer, however patients who respond to targeted therapy ultimately relapse. Residual disease, the tumor cells that survive initial therapy, represent an attractive therapeutic target, however little is known about the biology of these cells. We use mouse models of breast cancer to investigate the phenotype of residual disease that survives targeted therapy, and to explore approaches to inhibit tumor recurrence. Residual disease exhibits cellular dormancy in models driven by distinct oncogenic pathways. Gene expression profiling reveals that residual tumor cells are enriched for a phenotype associated with normal and neoplastic stem-like cells, but are not enriched for tumor initiative cells. Interventions that inhibit inflammatory signaling inhibit tumor recurrence, however increasing inflammation promotes tumor recurrence. Inflammatory macrophages may be leukocytes that promote inflammation and drive recurrence in these models. Together, our findings present a more comprehensive picture of residual tumor cells surviving targeted therapy, and suggest possible therapeutic strategies for targeting residual disease that gives rise to cancer recurrence.
This important book provides up-to-date information on a series of topical issues relating to the approach to minimal residual disease in breast cancer patients. It first explains how the study of minimal residual disease and circulating and disseminated tumor cells (CTCs/DTCs) can assist in the understanding of breast cancer metastasis. A series of chapters then discuss the various technologies available for the detection and characterization of CTCs and DTCs, pinpointing their merits and limitations. Detailed consideration is given to the relevance of CTCs and DTCs, and their detection, to clinical research and practice. The role of other blood-based biomarkers is also addressed, and the closing chapters debate the challenges facing drug and biomarker co-development and the use of CTCs for companion diagnostic development. This book will be of interest and assistance to all who are engaged in the modern management of breast cancer.
The successful treatment of breast cancer is limited due to a fraction of tumor cells escaping drug-treatment by entering a dormant state, only to relapse years or decades later at distant sites. Host-driven chronic inflammatory cells such as M2 macrophages play an important role in tumorigenesis, but the role of tumor-intrinsic inflammatory signaling involved in tumor dormancy and recurrence is unknown. We sought to determine the role of tumor-intrinsic inflammatory pathways in mouse mammary carcinoma cells (MMC) treated with Adriamycin (ADR), a clinically relevant chemotherapeutic drug. We found that ADR-induced dormant tumor cells autonomously produced pro-inflammatory cytokines, in vitro. MMC treated with Chloroquine (CQ) prior to ADR treatment displayed a delay in relapse, or prolonging of dormancy, when compared to ADR-treated MMC. Additional gene array data showed predicated activation of NF-[kappa]B p65 in ADR-treated dormant MMC that eventually relapsed. These data suggest that the anti-inflammatory function of CQ led to prolonged dormancy. To test this, we investigated the role of inflammatory signaling pathways directly by shRNA-mediated knockdown and CRISPR-Cas9-mediated knockout of NF-[kappa]B p65 in MMC. We found that knockdown of NF-[kappa]B p65 resulted in fewer dormant cells after ADR treatment and reduced rate of relapse, in vitro. NF-[kappa]B p65 was also found to reduce the immunomodulatory effects of ADR, with shNF-[kappa]B p65 showing increased upregulation of neu upon ADR treatment. Additionally, we found NF-[kappa]B p65 to be associated with a higher infiltration of CD8+ T cells and anti-tumor T cell responses. Our findings suggest a dual role of tumor-intrinsic NF-[kappa]B p65 pathway, allowing for escape from drug treatment through dormancy which leads to relapse, but also for proper lymphocyte infiltration and subsequent anti-tumor activity.
This book analyzes all aspects of metronomic chemotherapy, a new approach involving low-dose, long-term, and frequently administered therapy that has preclinical and clinical activity in various tumors. After an opening section on the pharmacological bases of metronomic chemotherapy, including its antiangiogenic effects and impact on immunity, preclinical studies on various classes of drug are discussed. Clinical applications of metronomic chemotherapy in a wide variety of tumors are then addressed in detail, with description of the results of all published studies. The clinical pharmacology of metronomic chemotherapy is also considered in depth, encompassing pharmacokinetics, pharmacogenetics, pharmacoeconomics, and adverse drug reactions. The book closes by describing the role of this therapy in the veterinarian clinic.
The book will explain previously unconnected clinical data such as why mammography works better for women age 50-59 than it does for women age 40-49, why adjuvant chemotherapy works best for premenopausal patients with positive lymph nodes, and it may also explain the racial disparity in outcome. In particular, it points to the perioperative period when systemic inflammation persists for a week or so. This can lead to a variety of mechanisms whereby single cancer cells (perhaps from the marrow) begin division and angiogenesis of dormant avascular micrometastases occurs leading to early relapses. With chapters presented from distinguished scientists and physicians in a variety of specialties that relate to and border the effects we present, this volume can be used as a reference for practicing physicians and as a jumping-off point for researchers to explore new therapeutic opportunities.
Cellular Immune Mechanisms and Tumor Dormancy features the work of internationally recognized experts from various disciplines as they discuss the phenomenon of tumor dormancy in humans. Animal models are described in which cellular and molecular components of the immune control of dormancy have been identified, and the relevance of these models to human cancer patients is recognized. Data derived from studies of organ transplantation, adjuvant chemotherapy, radiotherapy, anaesthesia, surgery, and whole blood transfusion is presented to show the vulnerability of cellular mechanisms maintaining dormancy. The potential for increasing the incidence of dormancy in micro metastases is also shown for non-small cell lung cancer, lymphoma, and leukemia. Cellular Immune Mechanisms and Tumor Dormancy is an important reference volume that will benefit researchers from many disciplines, including immunologists, pathologists, surgeons, and clinicians
Genetic alterations in cancer, in addition to being the fundamental drivers of tumorigenesis, can give rise to a variety of metabolic adaptations that allow cancer cells to survive and proliferate in diverse tumor microenvironments. This metabolic flexibility is different from normal cellular metabolic processes and leads to heterogeneity in cancer metabolism within the same cancer type or even within the same tumor. In this book, we delve into the complexity and diversity of cancer metabolism, and highlight how understanding the heterogeneity of cancer metabolism is fundamental to the development of effective metabolism-based therapeutic strategies. Deciphering how cancer cells utilize various nutrient resources will enable clinicians and researchers to pair specific chemotherapeutic agents with patients who are most likely to respond with positive outcomes, allowing for more cost-effective and personalized cancer therapeutic strategies.
