Spontaneous regional lymph node metastases of three variants of the B16 melanoma: relationship to primary tumor size and pulmonary metastases

Malignancy and tumorigenicity of melanoma B16 cells are not affected by silver and gold nanoparticles

Gold (AuNP) and silver (AgNP) nanoparticles have been incorporated into many therapeutic and diagnostic applications. However, previous studies revealed toxic properties as well as the hormesis phenomenon of many nanoparticles in different biological models. To evaluate the effects of low concentrations of AuNP and AgNP on murine melanoma cells B16F1 and B16F10 and relate them with phenotype changes, cells were exposed for 24 and 48 h. No cytotoxicity was observed for B16 cells through neutral red, MTT, trypan blue, and crystal violet assays at concentrations from 0.01 to 10 ng mL^-1. Likewise, the nanoparticles did not interfere with drug-efflux activity, cell migration, cell cycle, and colony formation. Slight toxicity was observed for B16F10 exposed to 100 ng mL^-1, with a decreased number of viable and attached cells, indicating differential sensitivity of B16F1 and B16F10 cells to the nanoparticles. Furthermore, colony size dispersion decreased for both B16 cell sub-lines. Therefore, there is no evidence that the tested concentrations of AuNP and AgNP can render B16 cells more aggressive and malignant, which is important since both nanoparticles are already largely used in nanotechnological products. Considering studies that have showed the hormesis effect of nanoparticles at low concentrations, which could protect cancer cells against chemotherapy, further investigation is advised.

The cholesterol transporter ABCG1 links cholesterol homeostasis and tumour immunity

ATP-binding Cassette Transporter G1 (ABCG1) promotes cholesterol efflux from cells and regulates intracellular cholesterol homeostasis. Here, we demonstrate a role of ABCG1 as a mediator of tumor immunity. Abcg1^−/− mice have dramatically suppressed subcutaneous MB49-bladder carcinoma and B16-melanoma growth and prolonged survival. We show that reduced tumor growth in Abcg1^−/− mice is myeloid cell-intrinsic and is associated with a phenotypic shift of the macrophages from a tumor-promoting M2 to a tumor-fighting M1 within the tumor. Abcg1^−/− macrophages exhibit an intrinsic bias toward M1 polarization with increased NF-κB activation and direct cytotoxicity for tumor cells in vitro. Overall, our study demonstrates that absence of ABCG1 inhibits tumor growth through modulation of macrophage function within the tumor and illustrates a link between cholesterol homeostasis and cancer.

Sentinel lymph node metastases in cancer: causes, detection and their role in disease progression

Malignant tumors of ectodermal or endodermal origin may metastasize to the sentinel lymph node, the first lymph node encountered by tumor cells that enter lymphatics in the organ of origin. This pathway is enabled by the anatomy of the disease and the causes of metastasis are the result of complex interactions that include mechanical forces within the tumor and host tissues, and molecular factors initiated by tumor cell proliferation, elaboration of cytokines and changes in the tumor microenvironment. Mechanical stresses may influence complex biochemical, genetic and other molecular events and enhance the likelihood of metastasis. This paper summarizes our understanding of interacting molecular, anatomical and mechanical processes which facilitate metastasis to SLNs. Our understanding of these interacting events is based on a combination of clinical and basic science research, in vitro and in vivo, including studies in lymphatic embryology, anatomy, micro-anatomy, pathology, physiology, molecular biology and mechanobiology. The presence of metastatic tumor in the SLN is now more accurately identifiable and, based upon prospective clinical trials, paradigm-changing SLN biopsy has become the standard of clinical practice in breast cancer and melanoma.

Effect of the Isoflavone Genistein on Tumor Size, Metastasis Potential and Melanization in a B16 Mouse Model of Murine Melanoma

The isoflavonoid genistein, the aglycone of the heteroside genistin, possesses preventive effect on coronary heart disease and osteoporosis, antioxidant, anthelmintic, antineoplastic and anti-inflammatory properties. Much research has been undertaken regarding the action of genistein on cancer-preventing/treating effects, especially on breast and prostate cancer. The aim of this study was to analyze the effect of this compound in vivo by observing tumor size, metastasis potential and melanization in a mouse model of murine melanoma, employing the B164A5 melanoma cell line and C57BL/6J mice. Genistein decreased the tumor volume and weight by approximately 30%. Non-invasive measurements for both melanin and erythema showed that genistein reduced the quantity of melanin and the degree of erythema in direct proportion to the number of days of treatment. HE analysis diagnosed malignant melanoma in both groups, but no metastasis was recorded in the treated group compared with the liver metastasis in the untreated group after a period of 15 days of experiment at a dose of 15 mg/kg body weight of genistein. Genistein showed beneficial effects regarding tumor size, metastasis potential and melanization in a B16 mouse model of murine melanoma.

B lymphocytes promote lymphogenous metastasis of lymphoma and melanoma

The prognosis of patients with many types of cancers correlates with the degree of metastasis to regional lymph nodes (LNs) and vital organs. However, the mechanisms and route of cancer cell metastasis are still unclear. Previous studies determined that B-cell accumulation in tumor-draining LNs (TDLNs) induces lymphatic sinus growth (lymphangiogenesis) and increases lymph flow, which could actively promote tumor dissemination through the lymphatic system. Using young Eµ-c-Myc mice that feature LN B-cell expansion as hosts for tumor transplants, we show that subcutaneously implanted lymphomas or melanomas preferentially spread to TDLNs over non-TDLNs, thus demonstrating that these tumors initially metastasize through lymphatic rather than through hematogenous routes. In addition, the rate and amount of tumor dissemination is greater in Eµ-c-Myc mice versus wild-type hosts, which correlates with LN B-cell accumulation and lymphangiogenesis in Eµ-c-Myc hosts. The increased lymphatic dissemination in Eµ-c-Myc hosts is further associated with rapid hematogenous tumor spread of subcutaneously implanted lymphomas, suggesting that TDLN metastasis secondarily drives lymphoma spread to distant organs. In contrast, after intravenous tumor cell injection, spleen metastasis of lymphoma cells or lung metastasis of melanoma cells is similar in Eµ-c-Myc and wild-type hosts. These studies demonstrate that the effect of Eµ-c-Myc hosts to promote metastasis is limited to the lymphatic route of dissemination. TDLN B-cell accumulation, in association with lymphangiogenesis and increased lymph flow, thus significantly contributes to dissemination of lymphomas and solid tumors, providing new targets for therapeutic intervention to block metastasis.

Pregnancy promotes melanoma metastasis through enhanced lymphangiogenesis

The relationships of pregnancy and melanoma have been debatable. Our aim was to assess the influence of gestation on the course of melanoma in a classic murine model of tumor progression and in women. B16 mouse melanoma cells were injected in nonpregnant or pregnant mice on day 5 of gestation. Animals were evaluated for tumor progression, metastases, and survival. Tumor sections were analyzed for lymphatic and blood vessel number and relative surface and expression of angiogenic growth factors. Finally, primary melanomas from pregnant and nonpregnant women, matched for age and tumor thickness, were also considered. Tumor growth, metastasis, and mortality were increased in B16-injected pregnant mice. Tumors displayed an increase in intratumoral lymphangiogenesis during gestation. This increased lymphatic angiogenesis was not observed in normal skin during gestation, showing its specificity to the tumor. An analysis of melanoma from pregnant and matched nonpregnant women showed a similar increase in lymphatic vessels. Tumors from pregnant mice had increased expression of vascular endothelial growth factor A at the RNA and protein levels. The increased vascular endothelial growth factor A production by melanoma cells could be reproduced in culture using pregnant mouse serum. In conclusion, pregnancy results in increased lymphangiogenesis and subsequent metastasis. Caution should be applied in the management of patients with advanced-stage melanoma during gestation.

Animal models and molecular imaging tools to investigate lymph node metastases

Lymph node metastasis is a strong predictor of poor outcome in cancer patients. Animal studies of lymph node metastasis are constrained by difficulties in the establishment of appropriate animal models, limitations in the noninvasive monitoring of lymph node metastasis progression, and challenges in the pathologic confirmation of lymph node metastases. In this comprehensive review, we summarize available preclinical animal cancer models for noninvasive imaging and identification of lymph node metastases of non-hematogenous cancers. Furthermore, we discuss the strengths and weaknesses of common noninvasive imaging modalities used to identify tumor-bearing lymph nodes and provide guidelines for their pathological confirmation.

Constitutive expression of the alpha4 integrin correlates with tumorigenicity and lymph node metastasis of the B16 murine melanoma

The lymphatic system plays a critical role in melanoma metastasis, and yet, virtually no information exists regarding the cellular and molecular mechanisms that take place between melanoma cells and the lymphatic vasculature. Here, we generated B16-F1 melanoma cells that expressed high (B16alpha(4)+) and negligible (B16alpha(4)-) levels of alpha(4) integrin to determine how the expression of alpha(4) integrins affects tumor cell interactions with lymphatic endothelial cells in vitro and how it impacts lymphatic metastasis in vivo. We found a direct correlation between alpha(4) integrin expression on B16-F1 melanoma cells and their ability to form adhesive interactions with monolayers of lymphatic endothelial cells. Adhesion of B16-F1 melanoma cells to lymphatic endothelial cells was mediated by the melanoma cell alpha(4) integrin binding to its counterreceptor, vascular cell adhesion molecule 1 (VCAM-1), that was constitutively expressed on the lymphatic endothelial cells. VCAM-1 was also expressed on the tumor-associated lymphatic vessels of B16-F1 and B16alpha(4)+ tumors growing in the subcutaneous space of C57BL/6J mice. B16-F1 tumors metastasized to lymph nodes in 30% of mice, whereas B16alpha(4)+ tumors generated lymph node metastases in 80% of mice. B16-F1 melanoma cells that were deficient in alpha(4) integrins (B16alpha(4)-) were nontumorigenic. Collectively, these data show that the alpha(4) integrin expressed by melanoma cells contributes to tumorigenesis and may also facilitate metastasis to regional lymph nodes by promoting stable adhesion of melanoma cells to the lymphatic vasculature.

Impact of sentinel lymphadenectomy on survival in a murine model of melanoma

Lymphatic mapping and sentinel lymph node biopsy-also termed sentinel lymphadenectomy (SL)-has become a standard of care for patients with primary invasive cutaneous melanoma. This technique has been shown to provide accurate information about the disease status of the regional lymph node basins at risk for metastasis, provide prognostic information, and provide durable regional lymph node control. The potential survival benefit afforded to patients undergoing SL is controversial. Central to this controversy is whether metastasis to regional lymph nodes occurs independent of or prior to widespread hematogenous dissemination. A related area of uncertainty is whether tumor cells residing within regional lymph nodes have increased metastatic potential. We have used a murine model of primary invasive cutaneous melanoma based on injection of B16-BL6 melanoma cells into the pinna to address two questions: (1) does SL plus wide excision of the primary tumor result in a survival advantage over wide excision alone; and (2) do melanoma cells growing within lymph nodes produce a higher incidence of hematogenous metastases than do cells growing at the primary tumor site? We found that SL significantly improved the survival of mice with small primary tumors. We found no difference in the incidence of lung metastases produced by B16-BL6 melanoma cells growing exclusively within regional lymph nodes and cells growing within the pinna.

Preclinical models of regional lymph node tumor metastasis

Animal models have produced vital information regarding the mechanisms of RLN metastasis. Modern imaging and molecular techniques have made it clear that growing tumors secrete cytokines that induce invasion, angiogenesis, lymphangiogenesis, increased intratumoral IFV and IFP, increased fluid flow from the tumor to the surrounding tissues, increased lymphatic flow, an increase in the rate of entry of tumor cells into lymphatic capillaries, and an increased number of tumor cells reaching the RLN(s). This is important knowledge that will help direct translational research in human patients. We can look forward to continued improvement in the management of human tumors that metastasize to the RLNs.

Insights into the mechanisms of lymph node metastasis

The mechanisms by which malignant tumors leave the primary tumor site, invade lymphatics, and metastasize to regional lymph nodes (RLNs) are complex and interrelated. Although the phenomenon of lymph node metastasis has been recognized for over 200 years, the exact mechanisms have only recently been the subject of intense interest and sophisticated experimentation. Sentinel lymph node biopsy has rapidly entered the clinical mainstream for melanoma and breast carcinoma, and this technique has provided confirmation of the orderly anatomic progression of tumor cells from primary site to the RLNs through lymphatic capillaries and trunks. Exciting studies involving the pathophysiology of interstitial fluid pressure in tumors and the peritumoral extracellular matrix have focused on lymphatic flow and tumor microenvironment and microcirculation. Molecular techniques have led to the definition of unique markers found on lymphatic endothelial cells. These markers have enabled scientists to identify peritumoral and intratumoral lymphatics and to visualize the ingrowth of tumor cells into the lumena of lymphatic capillaries. Tumor-secreted cytokines, such as vascular endothelial growth factors (VEGF)-C and -D, bind to VEGF receptors on lymphatic endothelial cells and induce proliferation and growth of new lymphatic capillaries; this process is similar to the well-known mechanism of angiogenesis, which results from the proliferation of new blood vessel capillaries. Lymphangiogenesis is associated with an increased incidence of RLN metastasis, and it is possible that this step is essential to the metastatic process. Directional movement toward lymphatics and lymph nodes appears to follow a chemokine gradient, and it is likely that some tumor cells that express certain types of chemokine receptors are more likely to metastasize to the RLNs. In contrast, tumor cells that do not express specific receptors that are responsive to lymphatic chemokines may not metastasize. New knowledge regarding the molecules involved in these processes should enable improvements in prognostic and possibly therapeutic approaches to the management of malignant tumors.

Prolactin overexpression by MDA-MB-435 human breast cancer cells accelerates tumor growth

Prolactin (PRL) is an important hormone in mammary tumorigenesis in rodents but its involvement in human breast cancer has been controversial. A role for locally produced PRL in breast carcinogenesis is suggested by its mitogenic action on breast cancer cells and the expression of both PRL and its receptor (PRL-R) in breast carcinomas. Our objective was to examine whether PRL, overexpressed by breast cancer cells, forms an autocrine/paracrine loop that confers a growth advantage for tumors. MDA-MB-435 breast cancer cells overexpressing 23K human PRL were generated, and PRL production and secretion by the clones were confirmed by RT-PCR, western blotting, and the Nb2 bioassay; control clones contain vector only. In vitro the 23K PRL clones proliferated faster and expressed higher levels of the PRL-R protein than controls only when incubated in charcoal-stripped serum (CSS) devoid of lactogenic hormones. When injected into the mammary fatpad of female nude mice or subcutaneously into males, the PRL-overexpressing clones formed tumors that grew 2-4-fold faster than tumors derived from control clones or wild type MDA-MB-435 cells. Western analysis demonstrated significantly higher PRL, PRL-R, and bcl-2 levels in the tumors overexpressing PRL compared to control tumors. These data support a role for breast PRL as a growth/anti-apoptotic factor and suggest that it may serve as a novel therapeutic target for the treatment of breast cancer.

Pathways of lymphatic drainage from the breast

BACKGROUND

The current standard for obtaining accurate sentinel lymph node (SLN) mapping is intraparenchymal lymphophilic dye/radiocolloid injection close to the breast tumor. We hypothesized that common lymphatic trunks drain both a large volume of breast parenchyma and skin and that intradermal or intraparenchymal routes flow to the same axillary node.

METHODS

99mTc-labeled filtered sulfur colloid was injected intradermally directly over the breast tumor in 119 patients. Blue dye was injected intraparenchymally in the same quadrant as the primary tumor (concordant quadrant) in 66 and in a discordant quadrant in 53 patients. During axillary exploration, both blue and gamma-emitting (hot) nodes were found. End points were SLNs that were hot and blue, either the same node or different nodes.

RESULTS

In 62 (93.9%) of 66 of concordant quadrant and in 49 (92.5%) of 53 of discordant quadrant patients, the same SLN was both hot and blue (P = .99; Fisher's exact test). In eight cases in which two distinct nodes were blue and not hot and hot but not blue, the lymph nodes were very close to each other.

CONCLUSIONS

The dermal and parenchymal lymphatics of the breast seemed to drain to the same axillary lymph nodes. Lymph from the entire breast seemed to drain through a small number of lymphatic trunks to one or two lymph nodes.

Intact vitronectin induces matrix metalloproteinase-2 and tissue inhibitor of metalloproteinases-2 expression and enhanced cellular invasion by melanoma cells

The initial site of melanoma cell metastasis is frequently the regional lymph nodes, and the appearance of lymph node metastasis correlates with poor prognosis. Lymph node adhesion is mediated by an interaction between the tumor cell integrin alphavbeta3 and lymph node vitronectin. In this study, we explored the relationship between adhesion and proteolysis by examining the direct effect of vitronectin receptor ligation on matrix metalloproteinase-2 (MMP-2) production by B16F1 and B16F10 melanoma cells. We report a dose-dependent increase in secretion of both MMP-2 and tissue inhibitor of metalloproteinases-2 (TIMP-2) in response to vitronectin. Cellular invasiveness was also enhanced by vitronectin, as shown by the increased ability of vitronectin-treated cells to invade a synthetic basement membrane (Matrigel). Both the vitronectin-induced MMP-2 production and vitronectin-enhanced invasion were blocked by the peptide ligand Arg-Gly-Asp-Ser (RGDS). Furthermore, neither plasmin-degraded vitronectin nor the peptide ligand RGDS stimulated MMP-2 secretion or invasiveness, indicating that a multivalent ligand-receptor interaction rather than simple receptor occupancy was required for MMP-2 induction. MMP-2 and MMP-2/TIMP-2 interaction with the plasma membrane of melanoma cells resulted in enhanced catalytic activity against 14C-labeled gelatin, suggesting that membrane association may function in posttranslational regulation of MMP-2 activity. This is supported by data showing increased cellular invasion by cells containing membrane-bound MMP-2. Binding of proMMP-2 and proMMP-2/TIMP-2 to melanoma cells was not inhibited by RGDS, and melanoma cell adhesion to vitronectin was unaffected by pro- or active MMP-2, indicating that MMP-2 did not interact with the murine vitronectin receptor. Together, these data provide evidence for a functional link between adhesion and proteolysis and suggest a potential mechanism whereby adhesion of an invasive cell to the extracellular matrix regulates subsequent invasive behavior.

Sentinel lymph node metastasis in experimental melanoma: relationships among primary tumor size, lymphatic vessel diameter and 99mTc-labeled human serum albumin clearance

BACKGROUND

This study was designed to investigate the relationships among primary tumor size, lymphatic vessel diameters, the incidence of sentinel lymph node (SLN) metastasis and lymphatic clearance from murine footpad melanomas.

METHODS

Lymphatic clearance (LC) of [99mTc]HSA from the middle of the footpad of syngeneic C57BL/6 mice, with or without primary melanomas (sizes varying from 1 to 5 mm in anteroposterior diameter), was quantitated using a gamma scintillation detection system. Lymphatic vessel diameters (LD) were measured after injection of aniline blue dye into footpad tumors. The incidence of SLN, femoral lymph node (FLN), and lung metastases was recorded.

RESULTS

Metastasis to SLNs increased as tumor growth progressed (r = 0.976, p = 0.001), and there was a correlation between tumor size and both FLN (p = 0.041) and lung (p = 0.055) metastases. There was also a correlation between lymph node metastasis and LC (r = 0.83, p = 0.04) and LD (r = 0.84, p = 0.04).

CONCLUSIONS

These studies support the hypothesis that lymph flow and LD is increased in experimental murine melanomas and this relates to both primary tumor size and to lymphatic and hematogenous metastasis.

Sentinel lymph node uptake of two different technetium-labeled radiocolloids,

BACKGROUND

The study was designed to compare the uptake of technetium-99m-labeled human serum albumin ([99mTc]HSA) and 99mtechnetium-labeled sulfur colloid ([99mTc]SC) in the sentinel lymph nodes (SLNs).

METHODS

Radiocolloid levels in the SLN, femoral lymph node (FLN), ischial lymph node (ILN), spleen (SP), and right rear footpad (RRF) were quantitated over a period of 240 min after injection of [99mTc]SC or [99mTc]HSA into the rear footpad of C57 BL/6 mice.

RESULTS

There was a significantly greater (p < 0.001) radioactive count in SLNs after [99mTc]SC (mean cpm 211,084.8) compared to [99mTc]HSA (mean cpm 115,640.8). In contrast, the counts in the FLNs were higher after [99mTc]HSA (mean cpm 11,333.4) than after [99mTc]SC injection (mean cpm 5,065.5). The percent uptake in the SP was higher after [99mTc]HSA than after [99mTc]SC injection.

CONCLUSIONS

[99mTc]SC is rapidly and efficiently taken up by lymphatics at the primary injection site, is significantly retained in the SLN, and flows slowly to the next echelon node (FLN or ILN) and to the systemic circulation (SP). [99mTc]HSA tends to accumulate less efficiently in the SLN and to disperse more rapidly to the next echelon nodes and to the systemic circulation. By extrapolation, [99mTc]SC is likely to be a better radiocolloid for the intraoperative detection of SLNs.

Efficacy of in vitro sensitized cells generated by in vivo priming with OK-432 for adoptive immunotherapy of the poorly immunogenic B16-Bl6 melanoma

We investigated the efficacy of the streptococcal preparation OK-432 as an adjuvant for in vivo priming in induction of sensitized cells for adoptive immunotherapy of the poorly immunogenic B16-BL6 (BL6) melanoma. C57BL/6 (B6) mice were immunized subcutaneously (s.c.) with 3 x 10(6) viable BL6 tumor cells admixed with various doses of OK-432 ranging from 1 to 100 micrograms in the foot-pad. Draining popliteal lymph nodes (LNs) were harvested 7 days after immunization and LN cells were further sensitized with irradiated tumor cells in the presence of 60-300 IU/ml of IL-2 for 11 days. These in vitro sensitized (IVS) cells (2 x 10(6)) were transferred intravenously (i.v.) to B6 mice bearing 4-day pulmonary metastases established by i.v. injection of 2-4 x 10(5) viable BL6 cells. The mice were also received intraperitoneally (i.p.) 4 x 10(4) IU/day of IL-2 for 4 days after adoptive transfer. Transfer of IVS cells from mice immunized by s.c. injection of tumor cells admixed with 10 micrograms of OK-432 significantly reduced the numbers of BL6 pulmonary metastases compared with that of control IVS' cells without the administration of OK-432 (P = 0.003). These effective IVS cells also significantly prolonged the survival of treated animals (P = 0.003). Functional IVS cells required in vitro stimulation with tumor cells. However, addition of OK-432 in the vaccine resulted in no enhancement of in vitro cytotoxicity and no characteristic change of phenotype of IVS cells. These results suggest that in vivo priming of OK-432 facilitates the sensitization of tumor-reactive T-cells. The procedure of in vivo priming with OK-432 may be beneficial in the adoptive immunotherapy of melanoma.

Adoptive immunotherapy of poorly immunogenic tumors with in vitro sensitized cells generated by intratumoral administration of biological response modifiers

We investigated the efficacy of intratumoral administration of biological response modifiers (BRM) in induction of in vitro sensitized (IVS) cells for adoptive immunotherapy of the poorly immunogenic MCA 102 sarcoma and B16-BL6(BL6) melanoma. We used the bacterial immunoadjuvant Nocardia rubra cell wall skeleton (N-CWS), and a streptococcal preparation, OK-432, for MCA 102 and BL6, respectively. After C57BL/6(B6) mice were inoculated subcutaneously (s.c.) with viable MCA 102 or BL6 tumor cells in the foot-pad, mice were injected intratumorally (i.t.) with N-CWS ranging from 10 to 400 micrograms or OK-432 ranging from 1 to 100 micrograms. Draining popliteal lymph nodes (LN) were harvested 7 days after i.t. administration of BRM, and LN cells were cultured with irradiated tumor cells in the presence of IL-2 for 11 days. These IVS cells (7.5 x 10(6) or 2 x 10(6)) were transferred intravenously (i.v.) to B6 mice with 4 day pulmonary metastases established by i.v. injection of viable MCA 102 cells (1 x 10(6)) or viable BL6 cells (3 x 10(5)). The mice were also received intraperitoneally 4 x 10(4) IU/day of IL-2 for 4 days after adoptive transfer. The transfer of IVS cells from mice immunized by i.t. injection of 100 micrograms of N-CWS 1 week after inoculation of tumor cells significantly reduced MCA 102 pulmonary metastases, compared with control IVS cells without administration of N-CWS. Moreover, the transfer of IVS cells from mice immunized by i.t. injection of 10 micrograms of OK-432 3 days after inoculation of tumor cells significantly reduced BL6 pulmonary metastases compared with control IVS cells without administration of OK-432. The administration of N-CWS resulted in no enhancement of in vitro cytotoxicity. Although the administration of 10 micrograms of OK-432 augmented in vitro cytotoxicity of IVS cells against BL6, cytotoxic activity was lower than that of IVS cells immunized with N-CWS. The major phenotype was CD8+ cells in IVS cells immunized with N-CWS or OK-432. These results suggest that i.t. administration of N-CWS and OK-432 facilitates the production of sensitized T-cells, and this administration route of BRM may be useful in the adoptive immunotherapy of human cancer.

Further characterization of a clinically relevant model of melanoma metastasis and an effective vaccine

A major problem in evaluating the effectiveness of tumor cell vaccination and other biological therapies is the variability of experimental models. In this study we have further developed and characterized a model for metastatic melanoma that approximates the major clinical stages of metastatic dissemination: stage I--growth of the primary (local) tumor, stage II--dissemination to regional lymph nodes, and stage III--metastasis to distant organs (lungs). C57BL/6 mice were challenged subcutaneously with B16 F10 murine melanoma cells in the midtail, and within 3 weeks 100% of the mice had local tumors growing in their tails. By 5-7 weeks after challenge, most of the mice had developed metastases to the inguinal lymph nodes and subsequently had metastatic colonies in the lungs and in the bone marrow. Preimmunization of mice with a formalinized extracellular antigen vaccine, derived from B16 F10 melanoma cells, provided partial inhibition of the growth of the primary melanoma tumors, as well as reducing the number of metastases to the regional (inguinal) lymph nodes and lungs along with concomitantly increasing survival time. This model for melanoma metastasis provides a reasonable and reproducible test system for the study of anti-melanoma immunity and the different cellular and humoral mechanisms involved.

A spontaneous subcutaneous tumor in C57BL/6 mice that metastasizes to the liver

A malignant tumor that arose spontaneously in the subcutaneous tissue of the back of a C57BL/6 female mouse was found to metastasize spontaneously to the liver. The primary and metastatic tumors, SML (spontaneous metastasis to the liver) 1 and SML 2, were established in vitro in long-term cell suspension culture and were passaged 10 times in vivo for 18 months. When 100,000 cells were injected subcutaneously in the orthotopic position, tumor growth appeared in 60% of the SML 1 mice and 100% of the SML 2 mice. SML 1 did not grow when injected in the footpad, while SML 2 did. The median survival was 47 days for SML 1 and 48.5 days for SML 2 (P = 0.013). The pattern of metastasis was similar for both tumor cell lines, irrespective of intravenous or subcutaneous injection routes. Spontaneous metastasis of the SML 2 line occurred from both the orthotopic and heterotopic sites, while the SML 1 metastasized spontaneously from the orthotopic site only. Liver metastasis appeared in > 90% of the mice for both SML 1 and SML 2. Metastasis to the spleen occurred in about half the mice. Other sites of metastasis were the ovaries (36% and 52%, respectively, for SML 1 and SML 2), the kidneys (approximately 15%) and the small bowel (very rarely). Metastasis to the lungs did not occur except very rarely in the later passages of the SML 2 line. Histologic, immunohistochemical and electron microscopic studies showed a histiocytic tumor with macrophage characteristics. The cells exhibited chemotaxis toward liver extracellular matrix and reduced motility toward collagen IV, laminin and fibronectin compared to the B16-F10 melanoma line. This spontaneously occurring tumor should prove useful for the study of organ-specific metastasis to the liver.

A novel role for autologous tumour cell vaccination in the immunotherapy of the poorly immunogenic B16-BL6 melanoma

The growth of immunogenic tumours stimulates the generation of tumour-sensitized, but not functional, pre-effector T cells in the draining lymph nodes. These pre-effector cells can mature into effector cells upon in-vitro stimulation with anti-CD3 and IL-2. In the current study, using a defined, poorly immunogenic tumour, B16-BL6 melanoma, the pre-effector cell response was not evident during progressive tumour growth but was elicited by vaccination with irradiated tumour cells admixed with Corynebacterium parvum. After anti-CD3/IL-2 activation, these cells were capable of mediating the regression of established pulmonary metastases. The efficacy of the vaccine depended on the doses of both tumour cells and the adjuvant. While higher numbers of tumour cells were more effective, an optimal dose (12.5 micrograms) of C. parvum was required. The dose of irradiation was not a critical factor. After vaccination, kinetic studies revealed that the pre-effector cell response was evident 4 days later and declined after 14 days. These observations illustrate the potential role of active immunization in the cellular therapy of cancer.

Development of lymph node and pulmonary metastases after local irradiation and hyperthermia of footpad melanomas

C57BL/6 mice with syngeneic B16-F10 melanomas were treated 7 days after tumor inoculation into the footpad with local hyperthermia (HT) of 43.5 degrees C for 90 min. A combination of local 30 Gy X-irradiation (XRT) given 2, 4 or 12 h after HT cured the primary tumor in 34/35 mice, with irreversible damage to normal foot tissues in most of the animals. When 7.5, 10 or 15 Gy XRT were delivered 4, 18 or 24 h after HT, there were only a small number of cures and also a much smaller incidence of irreversible normal tissue damage. HT alone resulted in a significant (P less than 0.001) increase in metastases to regional lymph nodes (RLN) and the lungs. The 'curative' doses of combined XRT and HT resulted in a significant (P less than 0.001) decrease in metastasis to RLN and to the lungs. Conversely, subcurative doses of combined therapy resulted in an increase in RLN and lung metastasis (P less than 0.001). Abdominal lymph node metastasis, not usually seen in control mice, is markedly increased after HT alone or in combination with subcurative XRT (P less than 0.001). The overall survival of mice treated with HT alone is decreased (P less than 0.0028). The survival of mice treated with HT followed 4, 18 or 24 h later with 10 Gy XRT is further decreased (P less than 0.0025). These data show that subcurative HT, or XRT plus HT, increases the incidence of spontaneous metastasis in this syngeneic mouse melanoma model. Curative doses prevent this effect on metastasis, but there is an unacceptable incidence of irreversible damage to the tumor-bearing foot. The cause(s) of this phenomenon are not known.

Lung metastases after curative or noncurative irradiation of microscopic primary melanomas

Melanomas growing in the feet of syngeneic C57BL/6 mice were treated with a single dose of X-irradiation. After doses of 0, 3.75, 7.5, 10, 20, or 30 Gy the tumor-bearing limb was amputated at tumor sizes 1, 2, 3, 4, or 5 mm. After doses of 40, 50, 62.5, or 72.5 Gy, progressive tumor growth did not occur, and amputation of tumor-bearing limbs was done when controls were 1, 2, 3, 4, or 5 mm in size. Eighteen days after amputation the mice were killed, and pulmonary metastases were documented at autopsy. None of the mice developed pulmonary metastases after curative irradiation of the primary foot tumor. After subcurative irradiation there was a significant increase (P less than .003) in pulmonary metastases. The size of the primary melanoma is important in the prediction of these metastases. In this model melanomas can be cured by an adequate dose of irradiation, but in those not cured the incidence of lung metastases is increased. The impact of this biologic phenomenon on survival is unclear.

Regional lymph node and pulmonary metastases after local hyperthermia of melanomas in C57BL/6 mice

The effects of local tumor hyperthermia on regional lymph node metastases are inconclusive. We studied the effects of hyperthermia on the incidence of popliteal, femoral, and abdominal lymph node metastases in C57BL/6 mice with primary B16 melanomas (F10 variant) growing subcutaneously in the left foot. Tumors were heated to 42.3, 43.5, and 44.2 degrees C for 90 minutes either 7 days after inoculation of 5 X 10(4) viable cells (microscopic tumor = mic) or when the tumors were approximately 3 mm in diameter (macroscopic tumor = mac). Femoral lymph node metastases occurred in 0/21 control animals and in 8/22 (36%), 11/19 (58%), and 11/17 (65%) animals whose primary tumors were heated to 42.3, 43.5, and 44.2 degrees C, respectively. For all three treatments, the increase in metastases as compared to controls was statistically significant (p less than 0.004, Fisher's exact test). The incidence of abdominal lymph node metastasis was slightly higher in the treated groups than controls. Twenty of 21 (95%) control mice developed popliteal lymph node metastases and hyperthermia-induced increases could not be demonstrated. Fifteen of 21 control mice killed 3 weeks after amputation of tumor-containing leg had pulmonary metastases with an average of 6 +/- 4 (standard deviation) lesions per affected mouse. Pulmonary metastases occurred in 22/22 (100%), 17/19 (89%), and 13/17 (76%) of mice whose tumors were heated to 42.3, 43.5, and 44.2 degrees C, respectively. The numbers of metastases for affected mice were significantly increased compared to controls for tumors heated to 43.5 and 44.2 degrees C (28 +/- 43, 43 +/- 52, 119 +/- 121, p greater than 0.02, p less than 0.006, p less than 0.002, for two sample T-test). While 0/8 mic tumors were cured 5/9 mac tumors heated to 44.2 degrees C disappeared (p less than 0.03, Fisher's exact test) and there was a growth delay in the remaining mice. Mic tumors, heated to 43.5 degrees C, had an accelerated onset of growth while mac tumors heated to this temperature had a slight growth delay. Growth of both mic and mac primary tumors heated to 42.3 degrees C was similar to controls. These results show that therapeutic and subtherapeutic local hyperthermia increases metastases to regional lymph nodes and to lungs even when primary tumor growth rate is partially or totally controlled.