Tumour dormancy: findings and hypotheses from clinical research on breast cancer

Decoding melanoma metastasis

Metastasis accounts for the vast majority of morbidity and mortality associated with melanoma. Evidence suggests melanoma has a predilection for metastasis to particular organs. Experimental analyses have begun to shed light on the mechanisms regulating melanoma metastasis and organ specificity, but these analyses are complicated by observations of metastatic dormancy and dissemination of melanocytes that are not yet fully malignant. Additionally, tumor extrinsic factors in the microenvironment, both at the site of the primary tumor and the site of metastasis, play important roles in mediating the metastatic process. As metastasis research moves forward, paradigms explaining melanoma metastasis as a step-wise process must also reflect the temporal complexity and heterogeneity in progression of this disease. Genetic drivers of melanoma as well as extrinsic regulators of disease spread, particularly those that mediate metastasis to specific organs, must also be incorporated into newer models of melanoma metastasis.

The ROCO kinase QkgA is necessary for proliferation inhibition by autocrine signals in Dictyostelium discoideum

AprA and CfaD are secreted proteins that function as autocrine signals to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells slows proliferation. Cells lacking the ROCO kinase QkgA proliferate rapidly, with a doubling time 83% of that of the wild type, and overexpression of a QkgA-green fluorescent protein (GFP) fusion protein slows cell proliferation. We found that qkgA(-) cells accumulate normal levels of extracellular AprA and CfaD. Exogenous AprA or CfaD does not slow the proliferation of cells lacking qkgA, and expression of QkgA-GFP in qkgA(-) cells rescues this insensitivity. Like cells lacking AprA or CfaD, cells lacking QkgA tend to be multinucleate, accumulate nuclei rapidly, and show a mass and protein accumulation per nucleus like those of the wild type, suggesting that QkgA negatively regulates proliferation but not growth. Despite their rapid proliferation, cells lacking AprA, CfaD, or QkgA expand as a colony on bacteria less rapidly than the wild type. Unlike AprA and CfaD, QkgA does not affect spore viability following multicellular development. Together, these results indicate that QkgA is necessary for proliferation inhibition by AprA and CfaD, that QkgA mediates some but not all of the effects of AprA and CfaD, and that QkgA may function downstream of these proteins in a signal transduction pathway regulating proliferation.

Long-term outcomes in stage IIIB breast cancer patients who achieved less than a pathological complete response (<pCR) after primary chemotherapy

PURPOSE

Pathological complete response (pCR) to primary chemotherapy is the main determinant for improved disease-free survival (DFS) and overall survival (OS). The primary endpoints of our study were the long-term DFS and OS rates in homogeneously treated stage IIIB breast cancer patients who failed to achieve a pCR (<pCR), in relation to residual tumor burden. The secondary endpoint was the prognostic relevance of hormone receptor (HR) and human epidermal growth factor receptor (HER)-2 status.

METHODS

We analyzed 58 of 74 consecutive stage IIIB patients treated between 1996 and 2001 who achieved <pCR following a primary cisplatin, epirubicin, and vinorelbine regimen for up to six cycles. At the time of patient accrual, trastuzumab was not available. After definitive surgery, pathological residual disease remained in 40 (69%) patients in both the breast and axilla, in 14 (24%) patients in only the breast, and in four (7%) patients in only the axilla.

RESULTS

Fifty-eight (78%) of 74 patients achieved <pCR and 16 (22%) had pCR both in the breast and axilla. After a median follow-up of 99 months (range, 72-134 months), in patients with <pCR the estimated 10-year DFS and OS rates were 37.6% and 50.3%, respectively, significantly worse than in the pCR group (p = .003 and p = .008, respectively). Patients with four or more axillary nodes involved had a significantly worse 10-year DFS rate (28.9% versus 62.7%; p = .036). Patients with HR(-) tumors had significantly lower 10-year DFS (17.3% versus 46.4%; p = .018) and OS (17.3% versus 70.2%; p = .002) rates. Overall, the triple-negative (TN) group showed only a marginally significantly worse OS rate (p = .048). HER-2 status alone, in the absence of trastuzumab, did not appear to significantly affect outcomes.

CONCLUSIONS

Our data suggest that, in stage IIIB patients who achieve <pCR, the number of residual nodes and HR(-) status are strong predictors of poor outcomes. After a long follow-up time, HER-2 expression does not appear to significantly affect DFS and OS. TN patients showed a trend toward early recurrence and death.

Dormancy of metastatic melanoma

Metastatic dormancy of melanoma has not received sufficient attention, most likely because once detectable, metastasis is almost invariably fatal and, understandably, the focus has been on finding ways to prolong life of patients with overt recurrences. Nevertheless, analysis of the published clinical and experimental data on melanoma indicates that some aspect of melanoma biology imitate traits recently associated with dormancy in other solid cancers. Among them the ability of some melanomas to disseminate early during primary tumor progression and once disseminated, to remain undetected (dormant) for years. Comparison of cutaneous and uveal melanoma indicates that, in spite of being of the same origin, they differ profoundly in their clinical progression. Importantly for this discussion, between 40 and 50% of uveal melanoma remain undetected for longer than a decade, while less than 5% of cutaneous melanoma show this behavior. Both types of melanoma have activating oncogene mutations that provide autonomous pro-proliferative signals, yet the consensus is that those are not sufficient for tumor progression. If that is the case, it is possible to envision that signals from outside the tumor cell, (microenvironment) shape the fate of an individual disseminated cell, regardless of an oncogene mutation, to progress or to pause in a state of dormancy. To stimulate further debate and inquiry we describe here a few examples of potential signals that might modify the fate of disseminated cell and provide brief description of the current knowledge on dormancy in other cancers. Our hope is to convince the reader that disseminated melanoma cells do enter periods of prolonged dormancy and that finding ways to induce it, or to prolong it, might mean an extension of symptoms-free life for melanoma patients. Ultimately, understanding the biology of dormancy and the mechanisms of dormant cell survival, might allow for their specific targeting and elimination.

Metastasis: from dissemination to organ-specific colonization

Metastasis to distant organs is an ominous feature of most malignant tumours but the natural history of this process varies in different cancers. The cellular origin, intrinsic properties of the tumour, tissue affinities and circulation patterns determine not only the sites of tumour spread, but also the temporal course and severity of metastasis to vital organs. Striking disparities in the natural progression of different cancers raise important questions about the evolution of metastatic traits, the genetic determinants of these properties and the mechanisms that lead to the selection of metastatic cells.

The tumor suppressor gene ARHI regulates autophagy and tumor dormancy in human ovarian cancer cells

The role of autophagy in oncogenesis remains ambiguous, and mechanisms that induce autophagy and regulate its outcome in human cancers are poorly understood. The maternally imprinted Ras-related tumor suppressor gene aplasia Ras homolog member I (ARHI; also known as DIRAS3) is downregulated in more than 60% of ovarian cancers, and here we show that re-expression of ARHI in multiple human ovarian cancer cell lines induces autophagy by blocking PI3K signaling and inhibiting mammalian target of rapamycin (mTOR), upregulating ATG4, and colocalizing with cleaved microtubule-associated protein light chain 3 (LC3) in autophagosomes. Furthermore, ARHI is required for spontaneous and rapamycin-induced autophagy in normal and malignant cells. Although ARHI re-expression led to autophagic cell death when SKOv3 ovarian cancer cells were grown in culture, it enabled the cells to remain dormant when they were grown in mice as xenografts. When ARHI levels were reduced in dormant cells, xenografts grew rapidly. However, inhibition of ARHI-induced autophagy with chloroquine dramatically reduced regrowth of xenografted tumors upon reduction of ARHI levels, suggesting that autophagy contributed to the survival of dormant cells. Further analysis revealed that autophagic cell death was reduced when cultured human ovarian cancer cells in which ARHI had been re-expressed were treated with growth factors (IGF-1, M-CSF), angiogenic factors (VEGF, IL-8), and matrix proteins found in xenografts. Thus, ARHI can induce autophagic cell death, but can also promote tumor dormancy in the presence of factors that promote survival in the cancer microenvironment.

Inhibition of metastatic outgrowth from single dormant tumor cells by targeting the cytoskeleton

Metastatic breast cancer may emerge from latent tumor cells that remain dormant at disseminated sites for many years. Identifying mechanisms regulating the switch from dormancy to proliferative metastatic growth has been elusive due to the lack of experimental models of tumor cell dormancy. We characterized the in vitro growth characteristics of cells that exhibit either dormant (D2.0R, MCF-7, and K7M2AS1.46) or proliferative (D2A1, MDA-MB-231, and K7M2) metastatic behavior in vivo. Although these cells proliferate readily in two-dimensional culture, we show that when grown in three-dimensional matrix, distinct growth properties of the cells were revealed that correlate to their dormant or proliferative behavior at metastatic sites in vivo. In three-dimensional culture, cells with dormant behavior in vivo remained cell cycle arrested with elevated nuclear expression of p16 and p27. The transition from quiescence to proliferation of D2A1 cells was dependent on fibronectin production and signaling through integrin beta1, leading to cytoskeletal reorganization with filamentous actin (F-actin) stress fiber formation. We show that phosphorylation of myosin light chain (MLC) by MLC kinase (MLCK) through integrin beta1 is required for actin stress fiber formation and proliferative growth. Inhibition of integrin beta1 or MLCK prevents transition from a quiescent to proliferative state in vitro. Inhibition of MLCK significantly reduces metastatic outgrowth in vivo. These studies show that the switch from dormancy to metastatic growth may be regulated, in part, through epigenetic signaling from the microenvironment, leading to changes in the cytoskeletal architecture of dormant cells. Targeting this process may provide therapeutic strategies for inhibition of the dormant-to-proliferative metastatic switch.

Prowling wolves in sheep's clothing: the search for tumor stem cells

The importance of a subset of cells which have ‘stem like’ characteristics and are capable of tumor initiation has been reported for a range of tumors. Isolation of these tumor-initiating cells (TICs) has largely been based on differential cell surface protein expression. However, there is still much debate on the functional significance of these markers in initiating tumors, as many properties of tumor initiation are modified by cell-cell interactions. In particular, the relationship between TICs and their microenvironment is poorly understood but has therapeutic implications, as the microenvironment can maintain tumor cells in a prolonged period of quiescence. However, a major limitation in advancing our understanding of the crosstalk between TICs and their microenvironment is the lack of sensitive techniques which allow thein vivotracking and monitoring of TICs. Application of newin vivocellular and molecular imaging technologies holds much promise in uncovering the mysteries of TIC behavior at the three-dimensional level. This review will describe recent advances in our understanding of the TIC concept and how the application ofin vivoimaging techniques can advance our understanding of the biological fate of TICs. A supplementary resource guide describing TICs from different malignancies is also presented.

Linoleic-acid-induced growth suppression induces quiescent cancer cell nests in nude mice

We examined the effect of linoleic acid (LA) on tumor formation. Cell growth was suppressed by LA in a dose-dependent manner in MKN28 and Colo320 cells. Continuous treatment with LA provided growth arrest in both cells at 5-7 weeks after the treatment. LA-pretreated MKN28 and Colo320 cells showed higher tumorigenicity (9/10 and 10/10, respectively) than nontreated cells (2/10 and 3/10, respectively; p < 0.01) in nude mice. In contrast, LA-pretreated MKN28 and Colo320 cells showed more suppressed tumor growth than nontreated cells (p < 0.01). LA-pretreated MKN28 and Colo320 cells with LA administration after the inoculation did not form macroscopic tumors. Histological examination revealed small cancer cell aggregations, which showed no proliferative activity. In LA-treated MKN28 and Colo320 cells, protein production of Bcl-2 was increased, whereas Bak, EGFR and VEGF levels were decreased. These findings suggest that LA might induce quiescence and subsequent dormancy in cancer cells.

Metastatic breast cancer cells colonize and degrade three-dimensional osteoblastic tissue in vitro

Metastatic breast cancer cells (BCs) colonize a mineralized three-dimensional (3D) osteoblastic tissue (OT) grown from isolated pre-osteoblasts for up to 5 months in a specialized bioreactor. Sequential stages of BC interaction with OT include BC adhesion, penetration, colony formation, and OT reorganization into "Indian files" paralleling BC colonies, heretofore observed only in authentic pathological cancer tissue. BCs permeabilize OT by degrading the extra-cellular collagenous matrix (ECM) in which the osteoblasts are embedded. OT maturity (characterized by culture age and cell phenotype) profoundly affects the patterns of BC colonization. BCs rapidly form colonies on immature OT (higher cell/ECM ratio, osteoblastic phenotype) but fail to completely penetrate OT. By contrast, BCs efficiently penetrate mature OT (lower cell/ECM ratio, osteocytic phenotype) and reorganize OT. BC colonization provokes a strong osteoblast inflammatory response marked by increased expression of the pro-inflammatory cytokine IL-6. Furthermore, BCs inhibit osteoblastic bone formation by down-regulating synthesis of collagen and osteocalcin. Results strongly suggest that breast cancer disrupts the process of osteoblastic bone formation, in addition to upregulating osteoclastic bone resorption as widely reported. These observations may help explain why administration of bisphosphonates to humans with osteolytic metastases slows lesion progression by inhibiting osteoclasts but does not bring about osteoblast-mediated healing.

Time-varying pattern of recurrence risk for Chinese breast cancer patients

PURPOSE

To analyze the rule of recurrence risk for breast cancer patients after surgery in order to get characteristics for Chinese breast cancer.

METHODS

We performed a retrospective study of 2,213 female unilateral breast cancer patients undergoing surgery in Cancer hospital of Fudan University, Shanghai, China. Survival curves were performed with Kaplan-Meier method and annual recurrence hazard was estimated by hazard function.

RESULTS

Annual recurrence hazard curve for entire population showed a double-peaked pattern, with a first major recurrence surge reaching the maximum at the second year after surgery and a second recurrence peak near the 9.5th year. The analysis according to tumor size, axillary lymph node (ALN) status (T1 + T2 versus T3, node-positive versus node-negative) and menopausal status as well as hormone receptor (HR) status proved that the double-peaked pattern was present in each subgroup. Compared with ER-positive tumors, ER-negative breast cancers were more likely to recur early. As far as Her-2/neu status was concerned, Her-2/neu-positive patients exhibited a relatively pronounced and variable pattern and tended to have more relapse across all time periods (P<0.05).

CONCLUSIONS

The double-peaked pattern observed in our patients gives further support to tumor dormancy hypothesis. It contributes to different treatment strategies (e.g. the type and timing of adjuvant therapy) for different patients, which provide the possibility to improve survival.

Radiotherapy treatment delays and their influence on tumour control achieved by various fractionation schedules

There is often a considerable delay from initial tumour diagnosis to the start of radiotherapy treatment. This paper extends the calculations of a previous paper on the effects of delays before the initiation of radiotherapy treatment to include results from a variety of practical fractionation regimes for three different types of tumour: squamous cell carcinoma (head and neck), breast and prostate. The linear quadratic model of radiation effect, logarithmic tumour growth (coupled with delay times where relevant) and the Poisson model for tumour control probability (TCP) are used to calculate the change in TCP for delays between diagnosis and treatment. Within the limitations of radiobiological modelling, these data can be used to tentatively assess the interactions between delays, dose fractionation and TCP. The results show that delays in the start of radiotherapy treatment do have an adverse effect on tumour control for fast-growing tumours. For example, calculations predict a reduction in local tumour control of up to 1.5% per week's delay for head and neck cancers treated following surgery. In addition, there may be a variety of fractionation regimes that will yield very similar clinical results for each tumour type. It is shown theoretically that, for the tumour types considered here, it is possible to increase the dose per fraction and decrease the number of fractions while maintaining or increasing TCP relative to standard 2 Gy fractionation regimes, although there may be some advantage to using hyperfractionated regimes for head and neck cancers in order to reduce normal tissue effects.

The immunomodulatory effects of laparoscopic surgery

Laparoscopic alternatives to conventional surgical procedures confer many advantages to patients including reduced postoperative pain, shortened convalescence and, perhaps, improved disease-related outcomes. The diminished degree of immune dysfunction apparent with these techniques may underpin these beneficial aspects. However, minimal access is accompanied by various ancillary anesthetic and mechanical associations (including the induction of a carbon dioxide pneumoperitoneum), which must be considered in addition to reduced tissue trauma when attempting to correlate cause with effect. Furthermore, the opportunity to establish causation between the immunomodulatory aspects of laparoscopy and subsequent clinical outcome by prospective, randomized study is difficult because of the rapid incorporation of minimal access techniques into clinical practice. Therefore, experimental in vitro and in vivo studies must be used to complement the limitations of clinical studies in this area. Although the initial investigations into the immunological effects of laparoscopy are encouraging, many of the intricacies associated with this approach still await elaboration.

Models, mechanisms and clinical evidence for cancer dormancy

Patients with cancer can develop recurrent metastatic disease with latency periods that range from years even to decades. This pause can be explained by cancer dormancy, a stage in cancer progression in which residual disease is present but remains asymptomatic. Cancer dormancy is poorly understood, resulting in major shortcomings in our understanding of the full complexity of the disease. Here, I review experimental and clinical evidence that supports the existence of various mechanisms of cancer dormancy including angiogenic dormancy, cellular dormancy (G0-G1 arrest) and immunosurveillance. The advances in this field provide an emerging picture of how cancer dormancy can ensue and how it could be therapeutically targeted.

Tumour dormancy in breast cancer: an update

Delayed recurrences, common in breast cancer, are well explained by the concept of tumour dormancy. Numerous publications describe clinical times to disease recurrence or death, using mathematical approaches to infer mechanisms responsible for delayed recurrences. However, most of the clinical literature discussing tumour dormancy uses data from over a half century ago and much has since changed. This review explores how current breast cancer treatment could change our understanding of the biology of breast cancer tumour dormancy, and summarizes relevant experimental models to date. Current knowledge gaps are highlighted and potential areas of future research are identified.

E-cadherin cell-cell adhesion in ewing tumor cells mediates suppression of anoikis through activation of the ErbB4 tyrosine kinase

Ability to grow under anchorage-independent conditions is one of the major hallmarks of transformed cells. Key to this is the capacity of cells to suppress anoikis, or programmed cell death induced by detachment from the extracellular matrix. To model this phenomenon in vitro, we plated Ewing tumor cells under anchorage-independent conditions by transferring them to dishes coated with agar to prevent attachment to underlying plastic. This resulted in marked up-regulation of E-cadherin and rapid formation of multicellular spheroids in suspension. Addition of calcium chelators, antibodies to E-cadherin (but not to other cadherins or beta(1)-integrin), or expression of dominant negative E-cadherin led to massive apoptosis of spheroid cultures whereas adherent cultures were unaffected. This correlated with reduced activation of the phosphatidylinositol 3-kinase-Akt pathway but not the Ras-extracellular signal-regulated kinase 1/2 cascade. Furthermore, spheroid cultures showed profound chemoresistance to multiple cytotoxic agents compared with adherent cultures, which could be reversed by alpha-E-cadherin antibodies or dominant negative E-cadherin. In a screen for potential downstream effectors of spheroid cell survival, we detected E-cadherin-dependent activation of the ErbB4 receptor tyrosine kinase but not of other ErbB family members. Reduction of ErbB4 levels by RNA interference blocked Akt activation and spheroid cell survival and restored chemosensitivity to Ewing sarcoma spheroids. Our results indicate that anchorage-independent Ewing sarcoma cells suppress anoikis through a pathway involving E-cadherin cell-cell adhesion, which leads to ErbB4 activation of the phosphatidylinositol 3-kinase-Akt pathway, and that this is associated with increased resistance of cells to cytotoxic agents.

Dormant Wnt-initiated mammary cancer can participate in reconstituting functional mammary glands

The minimal residual disease foci that beget breast cancer relapse after a period of disease dormancy remain uncharacterized despite their enormous clinical importance. To model dormant breast cancer in vivo, we employed a transgenic mouse model in which Wnt1-initiated mammary cancer is doxycycline dependent. After regression of Wnt-dependent cancers, subclinical disease lesions were propagated in vivo using classical tissue recombination techniques. Surprisingly, outgrowths derived from dormant malignant tissue reconstituted morphologically normal ductal trees in wild-type mammary fat pads. Whereas hyperplasia-derived outgrowths remained benign, outgrowths derived from dormant malignancy underwent a morphological transition suggesting single-step transformation following reactivation of Wnt signaling and rapidly yielded invasive mammary tumors. Remarkably, outgrowths derived from dormant malignancy could be serially propagated in vivo and retained the potential to undergo lobuloalveolar differentiation in response to hormones of pregnancy. Matching somatic H-Ras mutations shared by antecedent tumors and descendant mammary ductal outgrowths confirmed their clonal relatedness. Thus, propagation of epithelium that possesses a latent malignant growth program reveals impressive regenerative and developmental potential, supporting the notion that dormant mammary cancers harbor transformed mammary progenitor cells. Our results define an experimental paradigm for elucidating biological properties of dormant malignancy.

Dormant cancer cells retrieved from metastasis-free organs regain tumorigenic and metastatic potency

This study shows that solitary, dormant human cancer cells, retrieved from metastasis-free organs of animals carrying spontaneously metastatic primary tumors, can reactivate their tumorigenic and metastatic potency. The tumors were produced by MDA-MB-435 CL16 breast cancer cells permanently labeled with green fluorescent protein and the neomycin resistance gene. This enabled unequivocal identification of tumor cells emerging from organ explants cultured in neomycin to eliminate nonneoplastic host cells. Rescued cells resumed proliferation and generated lines that were tumorigenic and metastatic in fresh animals. All resulting primary and secondary tumors were uniformly labeled. Cells recovered from bone marrows and spleens, where there were no metastases, were as tumorigenic and metastatic as cells recovered from lungs and lymph nodes, which are the preferred sites of colonization for this tumor line. This evidence that malignant growth of disseminated cancer cells is suspended indefinitely by microenvironmental conditions in metastasis-free organs, although it is still active in others of the same host, shows that neoplastic progression can be arrested and has far-reaching biological and clinical implications. Specifically, it predicts the existence of natural, nonimmune host mechanisms that stimulate or inactivate tumor growth in different anatomical sites, which may be exploitable for therapeutic benefit.

The problem of cancer dormancy: understanding the basic mechanisms and identifying therapeutic opportunities

The hiatus observed in the progression of cancer after diagnosis and treatment in a large proportion of patients has led to the notion that a state of cancer dormancy must exist during tumor progression. However, research on this stage of cancer has been limited due to the lack of appropriate models and clinical correlates. Fortunately, the last decade has seen the development of new cancer dormancy models, whole animal and intravital imaging techniques and the molecular characterization of minimal residual disease. These studies enabled researchers to reveal intriguing mechanisms and molecular determinants that define tumor dormancy. It is imperative to understand the basic mechanisms of dormancy, as this will accelerate the development of new markers of progression and novel therapeutic opportunities to induce dormancy and/or eradicate dormant disease. This issue of Cell Cycle includes a "Spotlight on Cancer Dormancy" highlighting major contributions to the field of cancer dormancy from basic and clinical studies. We anticipate that this will initiate a forum of discussion on the problem of cancer dormancy and stimulate investigators to study this rather unexplored but undeniably relevant clinical stage of cancer progression.

Opposing roles of mitogenic and stress signaling pathways in the induction of cancer dormancy

Cancer dormancy is a poorly understood stage of cancer progression. However, the ability to control this step of the disease offers novel therapeutic opportunities. Here we summarize recent findings that implicate the extracellular matrix and adhesion receptor signaling in the escape or induction of tumor dormancy. We further review evidence suggesting that imbalances in the activity ratio of ERK to p38 signaling may determine the fate (i.e., tumorigenicity vs. dormancy) of different carcinoma cells. Special attention is placed on the mechanisms that p38 signaling regulates during the induction of dormancy and how modulation of these pathways may offer a therapeutic opportunity. We also review evidence for a novel drug-resistance mechanism in dormant tumor cells that when blocked may enable killing of dormant tumor cells. Finally, we explore the notion that dormancy of tumor cells may be the result of a selective adaptive response that allows disseminated tumor cells to pause their growth and cope with stress signaling imposed by dissemination and/or treatment until growth can be restored.

Combined immunologic and anti-angiogenic therapy reduces hepatic micrometastases in a murine ocular melanoma model

PURPOSE

To evaluate the combined effect of neoadjuvant intracameral interferon alpha -2b and adjuvant low-dose angiostatin in reducing the number of hepatic micrometastases in a murine model of ocular melanoma.

METHODS

The posterior compartments of the right eyes of C57BL6 mice were inoculated with 5 x 10(5) cells/2.5 microl of cells from the Queens, B16F10, or B16LS9 melanoma cell lines. The right eyes were enucleated at 7 days, and the mice were sacrificed at 28 days postinoculation, respectively. Hepatic micrometastases were counted. There were four treatment groups (n = 15 each) for each cell line as follows: group 1, intraperitoneal injections of 20 KIU interferon alpha -2b for 4 days prior to enucleation; group 2, intramuscular injections of 100 microl 0.1 microg/microl murine angiostatin every day for 14 days starting on day 1 after enucleation; group 3, treatment of group 1 and group 2 combined; group 4, intraperitoneal and intramuscular injections of equal volumes of phosphate-buffered saline (PBS) (control group).

RESULTS

Results showed decreased micrometastases for groups 1 through 3 compared with group 4, with the greatest reduction in group 3 (p < 0.006).

CONCLUSIONS

This study suggests that combined neoadjuvant interferon alpha -2b and adjuvant low-dose angiostatin therapy act synergistically to decrease hepatic micrometastases in a murine ocular melanoma model.

Prolonged dormancy of human liposarcoma is associated with impaired tumor angiogenesis

The disease state of cancer appears late in tumor development. Before being diagnosed, a tumor can remain for prolonged periods of time in a dormant state. Dormant human cancer is commonly defined as a microscopic tumor that does not expand in size and remains asymptomatic. Dormant tumors represent an early stage in tumor development and may therefore be a potential target for nontoxic, antiangiogenic therapy that could prevent tumor recurrence. Here, we characterize an experimental model that recapitulates the clinical dormancy of human tumors in mice. We demonstrate that these microscopic dormant cancers switch to the angiogenic phenotype at a predictable time. We further show that while angiogenic liposarcomas expand rapidly after inoculation of tumor cells in mice, nonangiogenic dormant liposarcomas remain microscopic up to one-third of the normal severe combined immune deficiency (SCID) mouse life span, although they contain proliferating tumor cells. Nonangiogenic dormant tumors follow a similar growth pattern in subcutaneous (s.c.) and orthotopic environments. Throughout the dormancy period, development of intratumoral vessels is impaired. In nonangogenic dormant tumors, small clusters of endothelial cells without lumens are observed early after tumor cell inoculation, but the nonangiogenic tumor cannot sustain these vessels, and they disappear within weeks. There is a concomitant decrease in microvessel density, and the nonangiogenic dormant tumor remains harmless to the host. In contrast, microvessel density in tumors increases rapidly after the angiogenic switch and correlates with rapid expansion of tumor mass. Both tumor types cultured in vitro contain fully transformed cells, but only cells from the nonangiogenic human liposarcoma secrete relatively high levels of the angiogenesis inhibitors thrombospondin-1 and TIMP-1. This model suggests that as improved blood or urine molecular biomarkers are developed, the microscopic, nonangiogenic, dormant phase of human cancer may be vulnerable to antiangiogenic therapy years before symptoms, or before anatomical location of a tumor can be detected, by conventional methods.

Cancer surgery: risks and opportunities

In the recent past, several papers have pointed to the possibility that tumour removal generates a permissive environment in which tumour growth is potentiated. This phenomenon has been coined "perioperative tumour growth" and whilst it represents a departure in terms of our attitude to the surgical process, this concept was first hinted at by Paget(1) himself. Despite this, the time interval immediately before and after cancer surgery (i.e. the perioperative period) remains an underutilised interval during which chemotherapeutic regimens are rarely implemented. Herein, we present a summarised review of the literature that supports the concept that tumour removal may potentiate the growth of residual neoplastic disease. We also outline current knowledge regarding underlying mechanisms and in this manner highlight potential therapeutic entry points. Finally, we emphasise the urgent need for trials of agents that could protect patients against the harmful host-tumour interactions that may occur during the perioperative period.

Rehabilitation of cancer through oncogene inactivation

The inactivation of the MYC oncogene alone can reverse tumorigenesis. Upon MYC inactivation, tumors stereotypically reverse, undergoing proliferative arrest, cellular differentiation and/or apoptosis. The precise consequences of MYC inactivation appear to depend upon both genetic and epigenetic parameters. In some types of cancer following MYC inactivation, tumor cells become well differentiated and biologically and histologically normal, inducing sustained tumor regression. However, in some cases, these normal-appearing cells are actually dormant tumor cells and upon MYC reactivation they rapidly recover their tumorigenic properties. Future therapies to treat cancer will need to address the possibility that tumor cells can camouflage a normal phenotype following treatment, resting in a dormant, latently cancerous state.

Circulating tumor cells in patients with breast cancer dormancy

PURPOSE

The purpose of this study was to test the hypothesis that circulating tumor cells (CTCs) are present in patients many years after mastectomy without evidence of disease and that these CTCs are shed from persisting tumor in patients with breast cancer dormancy.

EXPERIMENTAL DESIGN

We searched for CTCs in 36 dormancy candidate patients and 26 age-matched controls using stringent criteria for cytomorphology, immunophenotype, and aneusomy.

RESULTS

Thirteen of 36 dormancy candidates, 7 to 22 years after mastectomy and without evidence of clinical disease, had CTCs, usually on more than one occasion. Only 1 of 26 controls had a possible CTC (no aneusomy). The statistical difference of these two distributions was significant (exact P = 0.0043). The CTCs in patients whose primary breast cancer was just removed had a half-life measured in 1 to 2.4 hours.

CONCLUSIONS

The CTCs that are dying must be replenished every few hours by replicating tumor cells somewhere in the tissues. Hence, there appears to be a balance between tumor replication and cell death for as long as 22 years in dormancy candidates. We conclude that this is one mechanism underlying tumor dormancy.

A cysteine-rich extracellular protein containing a PA14 domain mediates quorum sensing in Dictyostelium discoideum

Much remains to be understood about quorum-sensing factors that allow cells to sense their local density. Dictyostelium discoideum is a simple eukaryote that grows as single-celled amoebae and switches to multicellular development when food becomes limited. As the growing cells reach a high density, they begin expressing discoidin genes. The cells secrete an unknown factor, and at high cell densities the concomitant high levels of the factor induce discoidin expression. We report here the enrichment of discoidin-inducing complex (DIC), an approximately 400-kDa protein complex that induces discoidin expression during growth and development. Two proteins in the DIC preparation, DicA1 and DicB, were identified by sequencing proteolytic digests. DicA1 and DicB were expressed in Escherichia coli and tested for their ability to induce discoidin during growth and development. Recombinant DicB was unable to induce discoidin expression, while recombinant DicA1 was able to induce discoidin expression. This suggests that DicA1 is an active component of DIC and indicates that posttranslational modification is dispensable for activity. DicA1 mRNA is expressed in vegetative and developing cells. The mature secreted form of DicA1 has a molecular mass of 80 kDa and has a 24-amino-acid cysteine-rich repeat that is similar to repeats in Dictyostelium proteins, such as the extracellular matrix protein ecmB/PstA, the prespore cell-inducing factor PSI, and the cyclic AMP phosphodiesterase inhibitor PDI. Together, the data suggest that DicA1 is a component of a secreted quorum-sensing signal regulating discoidin gene expression during Dictyostelium growth and development.

A secreted factor represses cell proliferation in Dictyostelium

Many cells appear to secrete factors called chalones that limit their proliferation, but in most cases the factors have not been identified. We found that growing Dictyostelium cells secrete a 60 kDa protein called AprA for autocrine proliferation repressor. AprA has similarity to putative bacterial proteins of unknown function. Compared with wild-type cells, aprA-null cells proliferate faster, while AprA overexpressing cells proliferate slower. Growing wild-type cells secrete a factor that inhibits the proliferation of wild-type and aprA- cells; this activity is not secreted by aprA- cells. AprA purified by immunoprecipitation also slows the proliferation of wild-type and aprA- cells. Compared with wild type, there is a higher percentage of multinucleate cells in the aprA- population, and when starved, aprA- cells form abnormal structures that contain fewer spores. AprA may thus decrease the number of multinucleate cells and increase spore production. Together, the data suggest that AprA functions as part of a Dictyostelium chalone.

Targeted Destruction of c-Myc by an Engineered Ubiquitin Ligase Suppresses Cell Transformation and Tumor Formation

Given that expression of c-Myc is up-regulated in many human malignancies, targeted inactivation of this oncoprotein is a potentially effective strategy for cancer treatment. The ubiquitin-proteasome pathway of protein degradation is highly specific and can be engineered to achieve the elimination of undesirable proteins such as oncogene products. We have now generated a fusion protein (designated Max-U) that is composed both of Max, which forms a heterodimer with c-Myc, and of CHIP, which is a U box-type ubiquitin ligase (E3). Max-U physically interacted with c-Myc in transfected cells and promoted the ubiquitylation of c-Myc in vitro. It also reduced the stability of c-Myc in vivo, resulting in suppression of transcriptional activity dependent on c-Myc. Expression of Max-U reduced both the abundance of endogenous c-Myc in and the proliferation rate of a Burkitt lymphoma cell line. Furthermore, expression of Max-U but not that of a catalytically inactive mutant thereof markedly inhibited both the anchorage-independent growth in vitro of NIH 3T3 cells that overexpress c-Myc as well as tumor formation by these cells in nude mice. These findings indicate that the targeted destruction of c-Myc by an artificial E3 may represent an effective therapeutic strategy for certain human malignancies.

Tumor dormancy and MYC inactivation: pushing cancer to the brink of normalcy

Upon MYC inactivation, tumors variously undergo proliferative arrest, cellular differentiation, and apoptosis and in some cases, apparently permanently revoking tumorigenesis. In liver tumor cells, we recently showed that MYC inactivation uncovers stem cell properties and triggers differentiation, but in this case, their neoplastic properties are restorable by MYC reactivation. Thus, whereas oncogene inactivation can push cancer to the brink of normalcy, some cells retain the latent capacity to turn cancerous again, arguing that they may exist in a state of tumor dormancy.

From a unique cell to metastasis is a long way to go: clues to stromelysin-3 participation

Stromelysin-3 (ST3) overexpression is associated with poor patient clinical outcome in numerous carcinomas. The ST3 is expressed by peritumoral fibroblast-like cells. Review of the literature shows that ST3 is an active partner of cancer cells along the whole natural cancer history, and is essential for optimal tumor development as it reduces death of cancer cells invading adjacent connective tissues at the primary tumor site. Paradoxically, ST3 lowers metastasis development in vivo in mice. However, this beneficial effect does not counterbalance the deleterious anti-apoptotic function of ST3.

The oligometastatic state in breast cancer: hypothesis or reality

The term 'oligometastasis' was initially used to describe a restricted locoregional tumour load, but the term has now become synonymous with isolated distant metastases. The existence of an oligometastatic state is still not widely recognised in the management of breast cancer patients. However, there are a number of patients who do develop isolated metastases and in whom long term survival can be achieved following appropriately targeted treatment. This review article discusses the possible biological mechanisms behind the development of an oligometastatic state and the findings from different trials which describe results following radical therapy for isolated metastatic disease. Although no large scale trials in this area have yet been undertaken, there is evidence to support the existence of an oligometastatic state in patients with breast cancer and we discuss the appropriate management for this clinical scenario.

[Long-term locally-recurrent melanoma]

Malignant melanoma is a highly malignant skin tumor with a widely variable individual course. Currently, approximately 75% of German patients can be cured of malignant melanoma by early diagnosis and excision, while more than 20% die of distant metastases of the melanoma. In contrast, there are single cases of long-term locally recurrent melanomas with neither complete cure nor development of distant metastases. We report on a female patient with a nevus-associated melanoma who was treated in 1968 with X-ray radiation (Dermopan, 100 Gy) with curative intent. In the following 31 years, the patient developed four phases of in-transit and satellite metastases in a zosteriform pattern as well as ilioinguinal lymph node metastasis. Since 1999, the patient has been free of recurrence. Besides the unusual biological features of this case, this report reflects the changes of paradigms in the therapy of melanoma over the last forty years.

Menopausal status dependence of the timing of breast cancer recurrence after surgical removal of the primary tumour

INTRODUCTION

Information on the metastasis process in breast cancer patients undergoing primary tumour removal may be extracted from an analysis of the timing of clinical recurrence.

METHODS

The hazard rate for local-regional and/or distant recurrence as the first event during the first 4 years after surgery was studied in 1173 patients undergoing mastectomy alone as primary treatment for operable breast cancer. Subset analyses were performed according to tumour size, axillary nodal status and menopausal status.

RESULTS

A sharp two-peaked hazard function was observed for node-positive pre-menopausal patients, whereas results from node-positive post-menopausal women always displayed a single broad peak. The first narrow peak among pre-menopausal women showed a very steep rise to a maximum about 8-10 months after mastectomy. The second peak was considerably broader, reaching its maximum at 28-30 months. Post-menopausal patients displayed a wide, nearly symmetrical peak with maximum risk at about 18-20 months. Peaks displayed increasing height with increasing axillary lymph node involvement. No multi-peaked pattern was evident for either pre-menopausal or post-menopausal node-negative patients; however, this finding should be considered cautiously because of the limited number of events. Tumour size influenced recurrence risk but not its timing. Findings resulting from the different subsets of patients were remarkably coherent and each observed peak maintained the same position on the time axis in all analysed subsets.

CONCLUSIONS

The risk of early recurrence for node positive patients is dependent on menopausal status. The amount of axillary nodal involvement and the tumour size modulate the risk value at any given time. For pre-menopausal node-positive patients, the abrupt increase of the first narrow peak of the recurrence risk suggests a triggering event that synchronises early risk. We suggest that this event is the surgical removal of the primary tumour. The later, broader, more symmetrical risk peaks indicate that some features of the corresponding metastatic development may present stochastic traits. A metastasis development model incorporating tumour dormancy in specific micro-metastatic phases, stochastic transitions between them and sudden acceleration of the metastatic process by surgery can explain these risk dynamics.

MYC inactivation uncovers pluripotent differentiation and tumour dormancy in hepatocellular cancer

Hepatocellular carcinoma is generally refractory to clinical treatment. Here, we report that inactivation of the MYC oncogene is sufficient to induce sustained regression of invasive liver cancers. MYC inactivation resulted en masse in tumour cells differentiating into hepatocytes and biliary cells forming bile duct structures, and this was associated with rapid loss of expression of the tumour marker alpha-fetoprotein, the increase in expression of liver cell markers cytokeratin 8 and carcinoembryonic antigen, and in some cells the liver stem cell marker cytokeratin 19. Using in vivo bioluminescence imaging we found that many of these tumour cells remained dormant as long as MYC remain inactivated; however, MYC reactivation immediately restored their neoplastic features. Using array comparative genomic hybridization we confirmed that these dormant liver cells and the restored tumour retained the identical molecular signature and hence were clonally derived from the tumour cells. Our results show how oncogene inactivation may reverse tumorigenesis in the most clinically difficult cancers. Oncogene inactivation uncovers the pluripotent capacity of tumours to differentiate into normal cellular lineages and tissue structures, while retaining their latent potential to become cancerous, and hence existing in a state of tumour dormancy.

In a model of tumor dormancy, long-term persistent leukemic cells have increased B7-H1 and B7.1 expression and resist CTL-mediated lysis

In tumor dormancy, tumor cells persist in the host over a long period of time but do not grow. We investigated in the DA1-3b mouse model of acute myeloid leukemia how leukemic cells could persist for months in spite of an effective antileukemic immune response. Mice were immunized with irradiated interleukin 12 (IL12)- or CD154-transduced DA1-3b cells, challenged with wild-type DA1-3b cells, and randomly killed during 1-year follow-up. Quantification of residual disease 1 year after challenge showed that persistent leukemic cells represented less than 0.02% of spleen cells in most animals. These residual cells were still able to kill naive hosts, even when isolated after 1 year of persistence. Persistent leukemic cells were more resistant to specific cytotoxic T-cell (CTL)-mediated killing and had enhanced B7-H1 and B7.1 expression proportional to the time they had persisted in the host. Blocking B7-H1 or B7.1/cytotoxic T-lymphocyte-associated antigen (CTLA-4) interaction enhanced CTL-mediated killing of the persistent cells, and blocking B7-H1, B7.1, or CTLA-4 in vivo prolonged survival of naive mice injected with persistent leukemic cells. Thus, escape of leukemic cells from tumor immunity via overexpression of B7-H1 or B7.1 might represent a new mechanism of tumor dormancy in acute leukemia.

Ineffectiveness of doxorubicin treatment on solitary dormant mammary carcinoma cells or late-developing metastases

Breast cancer is noted for long periods of tumor dormancy and metastases can occur many years after treatment. Adjuvant chemotherapy is used to prevent metastatic recurrence but is not always successful. As a model for studying mechanisms of dormancy, we have used two murine mammary carcinoma cell lines: D2.0R/R cells, which are poorly metastatic but form metastases in some mice after long latency times, and D2A1/R cells, which form more numerous metastases much earlier. Previously we identified a surprisingly large population of dormant but viable solitary cells, which persisted in an undivided state for up to 11 weeks after injection of D2.0R/R cells. Dormant cells were also detected for D2A1/R cells, in a background of growing metastases. Here we used this model to test the hypothesis that dormant tumor cells would not be killed by cytotoxic chemotherapy that targets actively dividing cells, and that the late development of metastases from D2.0R/R cells would not be inhibited by chemotherapy that effectively inhibited D2A1/R metastases. We injected mice with D2A1/R or D2.0R/R cells via a mesenteric vein to target liver. We developed a doxorubicin (DXR) treatment protocol that effectively reduced the metastatic tumor burden from D2A1/R cells at 3 weeks. However, this treatment did not reduce the numbers of solitary dormant cells in mice injected with either D2A1/R or D2.0R/R cells. Furthermore, DXR did not reduce the metastatic tumor burden after an 11-week latency period in mice injected with D2.0R/R cells. Thus, apparently effective chemotherapy may spare non-dividing cancer cells, and these cells may give rise to metastases at a later date. This study has important clinical implications for patients being treated with cytotoxic chemotherapy.

Excisional surgery for cancer cure: therapy at a cost

Excisional surgery is one of the primary treatment modalities for cancer. Minimal residual disease (MRD) is the occult neoplastic disease that remains in situ after curative surgery. There is increasing evidence that tumour removal alters the growth of MRD, leading to perioperative tumour growth. Because neoplasia is a systemic disease, this phenomenon may be relevant to all patients undergoing surgery for cancer. In this review we discuss the published work that addresses the effects of tumour removal on subsequent tumour growth and the mechanisms by which tumour excision may alter residual tumour growth. In addition, we describe therapeutic approaches that may protect patients against any oncologically adverse effects of tumour removal. On the basis of the evidence presented, we propose a novel therapeutic paradigm; that the postoperative period represents a window of opportunity during which the patient may be further protected against the oncological effects of tumour removal.

Axis of evil: molecular mechanisms of cancer metastasis

Although the genetic basis of tumorigenesis may vary greatly between different cancer types, the cellular and molecular steps required for metastasis are similar for all cancer cells. Not surprisingly, the molecular mechanisms that propel invasive growth and metastasis are also found in embryonic development, and to a less perpetual extent, in adult tissue repair processes. It is increasingly apparent that the stromal microenvironment, in which neoplastic cells develop, profoundly influences many steps of cancer progression, including the ability of tumor cells to metastasize. In carcinomas, the influences of the microenvironment are mediated, in large part, by bidirectional interactions (adhesion, survival, proteolysis, migration, immune escape mechanisms lymph-/angiogenesis, and homing on target organs) between epithelial tumor cells and neighboring stromal cells, such as fibroblasts as well as endothelial and immune cells. In this review, we summarize recent advances in understanding the molecular mechanisms that govern this frequently lethal metastatic progression along an axis from primary tumor to regional lymph nodes to distant organ sites. Affected proteins include growth factor signaling molecules, chemokines, cell-cell adhesion molecules (cadherins, integrins) as well as extracellular proteases (matrix metalloproteinases). We then discuss promising new therapeutic approaches targeting the microenvironment. We note, however, that there is still too little knowledge of how the many events are coordinated and integrated by the cancer cell, with conspiratorial help by the stromal component of the host. Before drug development can proceed with a legitimate chance of success, significant gaps in basic knowledge need to be filled.

Immediate local and regional recurrence after the excision of a polypoid melanoma: tumor dormancy or tumor activation?

Recurrent melanoma occurs in approximately one third of the patients who are treated for cutaneous melanoma. Although the majority of recurrences occur within the first few years of primary therapy, a significant number remain at risk beyond 10 years. Tumor dormancy provides the conceptual framework to explain a prolonged quiescent state in which tumor cells are present, but tumor progression is not clinically apparent. Surgery, or other perturbing factors, might modulate the transition of dormant cancer cells to rapidly growing ones. These may be due to a perturbation of the mechanisms of tumor regulation such as local immunity or angiogenesis. Here, the case of a woman is discussed in whom the surgical removal of a polypoid melanoma was followed, in less than a month, by local recurrence and locoregional lymph nodal metastases, which were previously clinically absent.

Cancer immunoprevention: tracking down persistent tumor antigens

The immune response can effectively hamper the progression of preclinical stages of tumor growth. Medicine in the postgenomic era offers an increasing possibility of detecting healthy individuals at risk of developing cancer who could benefit from tumor-preventive vaccines. The identification of novel tumor antigens that fulfill two conditions will be crucial for the development of cancer immunoprevention. First, an ideal antigen should have a crucial pathogenetic role in tumor growth to avoid the selection of antigen-loss variants. Second, the antigen should be recognizable by the immune system even in MHC-loss variants and should therefore be recognized both by antibodies and T cells. Identifying such antigens will also provide new targets for cancer immunotherapy.

The role of angiogenesis, vascular maturation, regression and stroma infiltration in dormancy and growth of implanted MLS ovarian carcinoma spheroids

MLS ovarian epithelial carcinoma multicellular spheroids xenografted subcutaneously in CD-1 nude mice displayed growth delay, or dormancy, of up to 52 days. In the study reported here, implanted MLS spheroids were used for testing the role of angiogenesis and vascular maturation in triggering the initiation of tumor progression. The kinetics and impact of neovascular maturation and functionality, in dormancy, and growth of MLS spheroid xenografts were studied noninvasively by BOLD contrast MRI. MR data were supported by histologic staining for biotinylated albumin as a blood pool marker and alpha-smooth muscle actin (alpha-SMA) as marker for perivascular mural cells. Although the tumor periphery showed higher levels of total and mature vasculature than normal skin, the fraction of mature out of the total vessels as detected by MRI vascular maturation index (VMI(MRI)) was significantly lower in the tumor both before and after tumor exit from dormancy. The neovasculature induced by the implanted spheroid was unstable and showed cycles of vessel growth and regression. Surprisingly, this instability was not restricted to the immature vessels, but rather included also regression of mature vessels. During dormancy, neovasculature was predominantly peripheral with no infiltration into the implanted spheroid. Infiltration of alpha-SMA positive stroma cells into the spheroid was associated with functional vascularization and tumor growth. Thus, stroma infiltration and vascular maturation are an important checkpoint linking the angiogenic switch with initiation of tumor progression.

Cancer spread and micrometastasis development: quantitative approaches for in vivo models

Death from cancer is usually due to metastasis. Fortunately, most cells that escape from a primary tumor fail to form metastases. Identifying reasons for this failure will help development of anti-metastatic therapies. Intravital videomicroscopy (IVVM) can be used to observe cancer cells injected into live animals. Co-injected microspheres can be used to assess cell survival. These techniques have been used to show that circulating tumor cells generally arrest in the microcirculation and may extravasate with high efficiency. While many tumor cells may survive in a secondary site, only a small subset form micrometastases and only a subset of these micrometastases persist to form vascularized macrometastases. Furthermore, solitary tumor cells may remain dormant for long periods of time in secondary sites. These findings suggest that metastatic growth and angiogenesis are prime targets for anti-metastatic therapy.

Dissemination and growth of cancer cells in metastatic sites

Metastases, rather than primary tumours, are responsible for most cancer deaths. To prevent these deaths, improved ways to treat metastatic disease are needed. Blood flow and other mechanical factors influence the delivery of cancer cells to specific organs, whereas molecular interactions between the cancer cells and the new organ influence the probability that the cells will grow there. Inhibition of the growth of metastases in secondary sites offers a promising approach for cancer therapy.

Mechanisms of tumour invasion and metastasis: emerging targets for therapy

The progression of a tumour from one of benign and delimited growth to one that is invasive and metastatic is the major cause of poor clinical outcome in cancer patients. The invasion and metastasis of tumours is a highly complex and multistep process that requires a tumour cell to modulate its ability to adhere, degrade the surrounding extracellular matrix, migrate, proliferate at a secondary site and stimulate angiogenesis. Knowledge of the process has greatly increased and this has resulted in the identification of a number of molecules that are fundamental to the process. The involvement of these molecules has been shown to relate not only to the survival and proliferation of the tumour cell but, also to the processes of tumour cell adhesion, migration, and the tumour cells ability to degrade and escape the primary site as well as play a role in angiogenesis. These molecules may provide important therapeutic targets that represent the ability to target specific steps in the process of invasion and metastasis and provide additional therapies. The review focuses on representative key targets in each of these processes and summarises the state of play in each case.

T cell memory, anergy and immunotherapy in breast cancer

T cell immunity in breast cancer is suggested to play a role in tumor dormancy, a period of stability which can correspond to the time interval between primary treatment and tumor recurrence. Bone marrow in breast cancer patients seems to be particularly important because it is highly enriched with cancer specific memory T cells. Similar cells can be found in peripheral blood, but these appear to be functionally anergic. The immune system of primary operated breast cancer patients does not seem to be completely anergized. Bone marrow derived memory T cells can be reactivated ex vivo and show functional reactivity, including tumor rejection in NOD/SCID mice. Promising results were obtained from a postoperative phase-II active specific immunotherapy study. In this study, 32 patients treated with an optimal formulation of a virus-modified autologous tumor vaccine (ATV-NDV) appeared to have a significant 5-year survival benefit. Our results suggest that cancer reactive memory T cells which are enriched in the bone marrow of breast cancer patients, can be activated ex vivo via autologous dendritic cells pulsed with breast cancer tumor antigens, or they can be activated in situ via a tumor vaccine, which combines tumor antigens with virus infection. The findings should encourage further studies in breast cancer on active specific immunotherapy with tumor vaccines or adoptive immunotherapy with activated memory T cells.