Role of the regional lymph node in cancer metastasis

The lymph node pre-metastatic niche

Lymph node metastases occur frequently during the progression of many types of cancer, and their presence often reflects poor prognosis. The drainage of tumor-derived factors such as antigens, growth factors, cytokines, and exosomes through the lymphatic system to the regional lymph nodes plays an important role in the pre-metastatic conditioning of the microenvironment in lymph nodes, making them receptive and supportive metastatic niches for disseminating tumor cells. Modified immunological responses and remodeling of the vasculature are the most studied tumor-induced pre-metastatic changes in the lymph node microenvironment that promote metastasis, although other metastasis-relevant alterations are also starting to be studied. Here, I review our current understanding of the lymph node pre-metastatic niche, how tumors condition this niche, and the relevance of this conditioning for our understanding of the process of metastasis.

The use of chemokine-releasing tissue engineering scaffolds in a model of inflammatory response-mediated melanoma cancer metastasis

Inflammatory responses and associated products have been implicated in cancer metastasis. However, the relationship between these two processes is uncertain due to the lack of a suitable model. Taking advantage of localized and controllable inflammatory responses induced by biomaterial implantation and the capability of tissue scaffolds to release a wide variety of chemokines, we report a novel system for studying the molecular mechanisms of inflammation-mediated cancer metastasis. The animal model is comprised of an initial subcutaneous implantation of biomaterial microspheres which prompt localized inflammatory responses, followed by the transplantation of metastatic cancer cells into the peritoneal cavity or blood circulation. Histological results demonstrated that substantial numbers of B16F10 cells were recruited to the site nearby biomaterial implants. There was a strong correlation between the degree of biomaterial-mediated inflammatory responses and number of recruited cancer cells. Inflammation-mediated cancer cell migration was inhibited by small molecule inhibitors of CXCR4 but not by neutralizing antibody against CCL21. Using chemokine-releasing scaffolds, further studies were carried out to explore the possibility of enhancing cancer cell recruitment. Interestingly, erythropoietin (EPO) releasing scaffolds, but not stromal cell-derived factor-1α-releasing scaffolds, were found to accumulate substantially more melanoma cells than controls. Rather unexpectedly, perhaps by indirectly reducing circulating cancer cells, mice implanted with EPO-releasing scaffolds had ~30% longer life span than other groups. These results suggest that chemokine-releasing scaffolds may potentially function as implantable cancer traps and serve as powerful tools for studying cancer distraction and even selective annihilation of circulating metastatic cancer cells.

Tumor lymphatics

In this article we survey more than three centuries of observation and research into tumor-associated lymphatic vessels, and their role in the metastatic spread of cancer. This historical overview documents how questions regarding tumor lymphatics have been central to concepts about the process of metastasis, and how this has subsequently influenced the clinical treatment of cancer. In turn, we show how analysis of the efficacy of these treatments has challenged long-standing notions regarding the tumor lymphatics. Starting with the discovery of VEGFR-3 and its ligands VEGF-C and VEGF-D, we also review how the rapid developments over the last 15 years in the molecular analysis of the lymphatic system and in particular lymphangiogenesis have contributed to this debate. Finally we speculate on how apparently paradoxical bodies of evidence regarding the role of tumor lymphatics in determining patterns of metastatic spread might be reconciled.

Cutaneous melanoma: therapeutic lymph node and elective lymph node dissections, lymphatic mapping, and sentinel lymph node biopsy

Early clinical observation in cancer patients suggested that tumors spread in a methodical, stepwise fashion from the primary site, to the regional lymphatics, and only then to distant locations. Based on these observations, the regional lymphatics were believed to be mechanical barriers, at least temporarily preventing the widespread dissemination of tumor. Despite evidence now available disputing its validity, this barrier theory has guided the surgical management of the regional lymphatics in cancer patients for more than a century, influencing the use of such surgical modalities as therapeutic lymph node dissection, elective lymph node dissection, and most recently lymphatic mapping and sentinel lymph node biopsy. No published randomized controlled trial exists that demonstrates improved overall patient survival for cancer of any type, including melanoma, after surgical excision of regional lymphatics. This article will review the biology of lymphatics as it relates to regional tumor metastasis, and based on available information, offer practical recommendations for the clinical dermatologist and their patients who have cutaneous melanoma.

Cell-mediated immunity and head and neck cancer: with special emphasis on betel quid chewing habit

Betel quid (BQ) chewing is popular in Taiwan, India, and many southeast-Asian countries. BQ chewing has strong association with the risk of oral leukoplakia (OL), oral submucous fibrosis (OSF), and oral cancer (OC). BQ components exhibit genotoxicity and may alter the structure of DNA, proteins and lipids, resulting in production of antigenicity. BQ ingredients are also shown to induce keratinocyte inflammation by stimulating the production of prostaglandins, TNF-alpha, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF) in keratinocytes. These events may provoke tissue inflammation, early cell-mediated immunity (CMI), and immune surveillance in BQ chewers. However, BQ components also directly affect the functional activities of immunocompotent cells, and moreover tumor cells may hypo-respond to the CMI via diverse mechanisms such as induction of apoptosis of lymphocytes, induction of production of suppressor T cells, downregulation of MHC molecules in tumor cells, etc. Clinically, an alteration in lymphocyte subsets, a decrease in total number of lymphocytes, and a reduction in functional activities of CMI have been observed in isolated peripheral blood mononuclear cells (PBMC) and tumor infiltrated lymphocytes (TIL) in patients with OSF, OL or OC. Adaptation of tumor cells to immune system may promote clonal selection of resistant tumor cells, leading to immune tolerance. Future studies on effects of BQ components on CMI and humoral immunity in vitro and in vivo can be helpful for chemoprevention of BQ-related oral mucosal diseases. To elucidate how virus infection, tobacco, alcohol and BQ consumption, and other environmental exposure affect the immune status of patients with oral premalignant lesions or OC will help us to understand the immunopathogenesis of OC and to develop immunotherapeutic strategies for OC.

Lymphatic system changes in diabetes mellitus: role of insulin and hyperglycemia

BACKGROUND

Diabetic alterations of blood vessels have been well studied, but much less is known about the lymphatic system, which plays an important role in the transport of particles and defensive responses. Accordingly, we investigated lymphatic changes in diabetic rats.

METHODS

Ten, 30 or 60 days after alloxan-induced diabetes (40 mg/kg; i.v.), we studied thoracic duct lymph flow and lymphocyte output, thoracic duct lymph transport of radiotracer particles ((99m)Tc-dextran 500), lymph node uptake and scintigraphic visualization of subcutaneously injected radiotracer particles, as well as the effect of insulin administration and food deprivation.

RESULTS

Diabetes significantly increased thoracic duct lymph flow and the transport of dextran from the footpad subcutaneous tissue. Abnormal lymphocyte output from the thoracic duct occurred in the first 10 days. Uptake of dextran into regional lymph nodes was decreased in diabetes. Insulin per se, although not normalizing blood sugar levels, appeared to recover thoracic duct lymphocyte output and lymph node uptake of (99m)Tc-dextran 500 without affecting the thoracic duct lymph flow or the amount of radiotracer recovered therein. Normalization of glycemia (by food deprivation) restored the lymph flow to control levels without modifying the lymphocyte output. On the other hand, under insulin-restored normoglycemic conditions, both the thoracic duct lymph flow and the lymphocyte output were normalized.

CONCLUSIONS

These findings suggest that variables related to defensive mechanisms, such as lymphocyte recirculation and particles uptake into the lymph nodes can benefit from insulin treatment, whereas glycemic control can benefit transport mechanisms in the lymphatic system, such as lymph flow and lymphatic transport of particles.

Does unnecessary elective neck treatment affect the prognosis of N0 laryngeal cancer patients?

OBJECTIVE

Among detractors of elective neck (N0) treatments, most suggest that lymphadenectomy removes a barrier to the spread of disease with deleterious immunologic consequences. To test this hypothesis we performed a retrospective comparison of the survival results of N0 laryngeal cancer patients who received unnecessary elective neck treatments (N0-) and those of N0 patients subjected to close and regular follow-up.

MATERIAL AND METHODS

A retrospective chart review of 749 N0 laryngeal cancer patients treated at the Institute of Otolaryngology-Head and Neck Surgery, University of Florence between January 1980 and January 1993 was performed. Of these, 245 (33%) received elective neck dissection (ED), while the remaining 504 (67%) N0 patients were subjected to close and regular follow-up (wait-and-see policy; WS).

RESULTS

Of the 245 ED patients, 43 (17.5%) showed an occult neck disease, while of the 504 WS subjects, 83 (17%) developed neck metastases during follow-up. Moreover, 15 ED patients subsequently experienced a contralateral occult failure despite a unilateral negative neck specimen (N0-). Thus, ultimately 187 ED (164 of whom were treated unilaterally and 23 bilaterally) and 421 WS patients were used for survival analysis. No differences in terms of postoperative complications, local or distant failure or disease-free or overall actuarial survival were found between the two groups analyzed.

CONCLUSIONS

These data indicate that unilateral or bilateral removal of cervical lymphatics in the absence of histologically proven lymph node metastases does not negatively affect the prognosis of N0 laryngeal cancer patients who were overtreated to the neck.

The management of regional lymph nodes in cancer

Early clinical observation in cancer patients suggested that tumours spread in a methodical, stepwise fashion from the primary site to the regional lymphatics, and only then to distant locations. Based on these observations, the regional lymphatics were believed to be mechanical barriers preventing the widespread dissemination of tumour. Despite evidence now available disputing its validity, this barrier theory has guided the surgical management of the regional lymphatics for more than a century, influencing the use of such surgical modalities as therapeutic lymph node dissection, elective lymph node dissection and most recently sentinel lymph node biopsy. No published randomized controlled trial exists that demonstrates improved overall survival for patients with cancer of any type undergoing surgery of the regional lymphatics. We believe the presence of tumour in the regional lymphatics indicates the presence of systemic disease, and therapeutic interventions should be directed accordingly.

Biology and surgical management of breast cancer

The surgical treatment of breast cancer has been a source of controversy. The controversy arises from the differences in physicians' philosophies regarding the biology of breast carcinoma. Traditionally, surgeons have emphasized the potential therapeutic value of regional lymph node dissection, maintaining that adequate loco-regional treatment is of prime concern in patients with localized tumors. On the other hand, medical oncologists have always stressed the systemic nature of cancer. However, breast cancer is a very heterogeneous disease with an enormous range of different biologic characteristics, and new information is continually becoming available on the natural history of breast cancer. Therefore, we should seek a more rational theory based on the clinical evidence which can explain the biologic characteristics of breast cancer. We have proposed a new spectrum hypothesis as follows: (a)tumor cells traverse lymphatics to lymph nodes by direct extension, and there is an orderly pattern in the early stage of lymph node metastases; (b)regional lymph nodes are able to trap tumor cells but are ineffective or incomplete barriers to tumor cell spread; (c)regional lymph nodes have biologic importance, and a positive lymph node is an indicator of a host-tumor relationship that correlates with the subsequent appearance of distant disease; (d)lymphatic and hematogenous dissemination occur not serially, but in a parallel fashion; (e)many palpable invasive breast cancers are a systemic disease, but non-invasive or minimally invasive breast cancers are likely to be a local disease; (f)early detection and treatment of in-breast cancer improves survival, but variations in regional therapy are unlikely to have a major influence on survival.

Signal minus 1: a key factor in immunological tolerance to tissue-specific self antigens?

Recent data suggest that many autoreactive T cells, particularly to tissue-specific self antigens, can escape thymic deletion. The current dogma is that these autoreactive T cells are silenced by the failure of most tissues to provide co-stimulation (signal 2), antigen alone (signal 1) inducing T cell unresponsiveness. However, I propose that activation of autoreactive T cells frequently occurs but autodestruction by effector T cells is tightly regulated. This phenomenon is most evident with lymph node metastasizing tumour cells where the regional lymph node can mount a vigorous response to the invading tumour cells but tumour growth is unimpaired. I suggest that autodestruction is prevented by inhibitory receptors on T cells which recognize class I MHC structures on target cells. These receptors, which I propose deliver 'signal minus 1' to T cells, were recently described on NK cells and a subpopulation of peripheral T cells. They are also strikingly similar to a family of anti-self receptors that my laboratory described on murine T and B cells 15 years ago. In the 'signal minus 1' model, antigen-activated T cells acquire the inhibitory receptors when they become co-stimulation independent and gain the ability to exit lymphoid organs and enter non-lymphoid tissues. Thus, if autoreactive effector T cells encounter autoantigen in tissues they are functionally silenced by inhibitory receptor engagement and signal minus 1 delivery. In contrast, I propose that in response to intracellular infections, cells down-regulate expression of their ligands for inhibitory receptors. Such a model allows infected cells to be selectively eliminated by effector T cells. If correct, the model predicts that effector T cells, whether foreign-antigen- or autoantigen-specific, can selectively respond to infected cells. This apparent 'usefulness' of autoreactive T cells may explain their observed persistence even after an encounter with autoantigen. It is also suggested that signal minus 1 may silence autoreactive B cells specific for tissue-specific cell surface antigens and lack of signal minus 1 may partially explain the vigorous T cell response to allogeneic MHC. Finally, it is hypothesized that, in evolutionary terms, inhibition of autodestruction by the recognition of a 'self marker' and delivery of signal minus 1 is an ancient process which probably emerged in early metazoans.

Clinical management of the regional lymph node

Appropriate clinical management of the regional lymph node remains controversial. This article briefly reviews the anatomy and physiology of the lymphatic system, pathophysiology of lymphatic metastases, and some guidelines and rationale for clinical management.

Development of a new in vivo model for head and neck cancer

We have developed an improved model for studying in vivo nonsurgical treatment of head and neck cancer. In situ oral cavity implantation has been documented, but its natural history is not defined. In light of this, an improved model is described. Forty-two nude mice had tumor cells from one of two established laryngeal squamous cell carcinoma cell lines implanted into the floor of the mouth. The tumor mass was measured and followed. When the tumor burden was great enough to cause cachexia, the animals were killed and submitted for microscopic examination. Pulmonary metastases were noted in 44%, bone invasion in 80%, angioinvasion in 76%, and soft tissue invasion in 96% of the animals. Growth characteristics in the head and neck have not been documented in previous models. Our model not only exhibits the locally invasive activity typically associated with malignant neoplasms, but also closely parallels the results of clinical studies examining the percent of end stage patients and autopsies with pulmonary metastases. Therefore, this model should open the way for more meaningful in vivo studies of nonsurgical treatment modalities for both local and metastatic tumor foci in head and neck cancer.

Cyclophosphamide-dependent lymph node modification in lymph node metastasis of MM48 tumor cells in syngeneic mice

We investigated the role of immunosuppressive activity induced in the regional lymph nodes (RLN, popliteal lymph nodes) in the establishment of lymph node metastasis by cyclophosphamide (CY) administration. The CY treatment led to the elimination of suppressive activity with the appearance of positive immune responses, and the inhibition of lymph node metastasis of MM48 tumor cells. In CY-treated mice, the removal of RLN together with the primary tumor lowered the survival rate compared with the mice in which the RLN remained intact. During 4 days after primary tumor resection, the proliferation of tumor cells in the RLN was significantly decreased in CY-treated mice. These results suggested that the induction of suppressive activity in the lymph node is closely associated with the establishment of lymph node metastasis.

Lymphokine-activated killer-cell function of lymphocytes from peripheral blood, regional lymph nodes and tumor tissues of patients with oral cancer

Lymphokine-activated killer (LAK) cells, generated from peripheral blood lymphocytes (PBL) from patients with oral cancer or oral leukoplakia and from healthy donors showed comparable lysis of 6 target tumor cell lines, including 3 derived from head and neck and oral cancers. The tumor burden of the host did not appear to influence the systemic LAK activity. LAK activity of lymphocytes infiltrating the tumor tissues (TIL) was also comparable to that of the PBL. Both TIL and PBL showed a parallel increase in proportion of HNK-I+ and CD-25+ cells upon activation with IL-2. The lymph-node lymphocytes (LNL) from metastatic (met) and non-metastatic (non-met) draining lymph nodes, however, showed reduced LAK activity and an increase in CD8+ cells, in addition to CD25+ and HNK-I+ cells, when cultured with IL-2. When IL-2-activated LNL were co-cultured with autologous PBL during IL-2 activation of the latter, a strong suppressive effect was exerted by LNL. In contrast, IL-2-activated PBL did not suppress autologous LAK generation in spite of an increase in CD8+ cells seen after activation with IL-2. Frequency distribution of LAK precursors was significantly lower in LNL than in PBL from oral cancer patients. LAK precursor frequency in TIL was comparable to that of PBL. The results show that, in oral cancer, regional lymph nodes may not have adequate IL-2-inducible cytotoxic potential, due to a reduced number of LAK progenitors and possible activation of suppressor cells. Alternatively, TIL can be a potential source for LAK cell function.

The nature of tumor presentation in the animal changes the effects of levamisole treatment on metastasis

We have investigated the ability of levamisole (LMS) to modulate growth and metastasis of a rat hepatocarcinoma. LMS treatment decreased spontaneous metastasis to the lungs and lymph nodes, while it increased tumor lung colonization following intravenous tumor cell inoculation. Both serum immunoglobulin (Ig) and circulating immune complex (CIC) levels were higher than normal in tumor-bearing rats. LMS treatment did not alter these parameters in the lung colony assay, while a small decrease of serum IgG was noted for LMS treated animals in the spontaneous metastasis assay. We found no convincing evidence for CIC levels, immunoglobulin isotype shifts or induced changes in natural killer (NK) cell reactivity being involved in the observed LMS modulation of tumor metastasis. The nature of the presentation of the tumor in the animal, however, appeared to be critical in determining the metastatic response to LMS therapy.