A new metastasizing mammary carcinoma model in mice: model characteristics and applications

Use of a PEG-conjugated bright near-infrared dye for functional imaging of rerouting of tumor lymphatic drainage after sentinel lymph node metastasis

Tumor lymphangiogenesis promotes metastatic cancer spread to lymph nodes and beyond. However, the potential remodeling and functionality of tumor-draining lymphatic vessels has remained unclear. Thus, we aimed to develop non-invasive imaging methods for repeated quantitative imaging of lymphatic drainage and of contractile collecting lymphatic vessel function in mice, with colloidal near-infrared (NIR) tracers and a custom fluorescence stereomicroscope specially adapted for NIR sensitive imaging. Using these tools, we quantitatively determined pulse rates and valvular function of collecting lymphatic vessels with high resolution. Unexpectedly, we found that tumor-draining lymphatic vessels in a melanoma footpad model initially were dilated but remained functional, despite lower pulse rates. In two independent tumor models, impaired lymphatic function was detected once metastases were present in draining lymph nodes. Importantly, we found that lymphatic dysfunction, induced by metastatic tumor spread to sentinel lymph nodes, can lead to a rerouting of lymphatic flow away from the metastatic lymph node, via collateral lymphatic vessels, to alternate lymph nodes. These findings might have important clinical implications for the procedure of sentinel lymph node mapping that represents the standard of care for determining prognosis and treatment of melanoma and breast cancer patients.

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.

Characterization of F3II, a sarcomatoid mammary carcinoma cell line originated from a clonal subpopulation of a mouse adenocarcinoma

We characterized a new mammary tumor cell line, F3II, previously established in vitro from a clonal subpopulation of the BALB/c transplantable mammary adenocarcinoma M3, moderately metastatic to lung. The F3II cell line has been passaged > 50 times. It has grown as elongated cells adherent to the bottom of the flask. Cytogenetic studies showed that F3II cultures were nearly triploid. Tumor cells expressed fibronectin and showed high levels of cell-surface urokinase, a key protease in invasion and metastasis. F3II cells grew as poorly differentiated, spindle-cell carcinoma tumors (sarcomatoid carcinomas) with a prominent local invasiveness, a high angiogenic response, and a 90-100% incidence of lung metastases when inoculated s.c. into syngeneic mice. Ultrastructural and immunocytochemical analysis revealed characteristic features of carcinomas. Our data suggest that F3II is less differentiated and more aggressive than the original tumor line, supporting the notion that mammary carcinomas are heterogeneous neoplasms and contain subpopulations with diverse biologic behavior. The F3II mouse mammary sarcomatoid carcinoma line is a suitable model to examine antiinvasive, antiangiogenic, and antimetastatic agents.

Mechanisms of organ selective tumour growth by bloodborne cancer cells

The sites of tumour development for 6 rat tumours injected into syngeneic rats via different vascular routes was determined. Xenografts of human tumours were also injected intra-arterially (i.a.) into immunosuppressed rats. Following intravenous (i.v.) and intraportal (i.ptl.) injection of cells tumour colonies localized in lung and liver respectively due to tumour cell arrest. Arterially injected radiolabelled cells disseminated and arrested in a similar distribution to cardiac output and did not 'home' to any organs. Following arterial injection of unlabelled tumour cells colonies grew in many organs. While the pattern of growth for a particular tumour varied with the cell dose, the 'arterial patterns' for all of the tumours studied followed a similar pattern. Some organs (eg adrenals, ovaries and periodontal ligament) were consistently preferred, others (eg skin and skeletal muscle) only supported tumour growth following the delivery of large numbers of cells, while in some tissues (eg spleen and intestines) tumour never grew. Viable tumour cells could be demonstrated by bioassay in many organs for up to 24h after i.a. injection. However tumour growth only occurred in certain organs and the pattern of this growth was not related to the number of tumour cells arrested or their rate of autolysis. This site preference could be expressed quantitatively as the probability of an arrested cell developing into a tumour and was considered a 'soil effect'. Site preference was not directly related to organ vascularity. Organ colonisation was promoted by steroid treatment but the mechanism was unclear and was not secondary to T-cell immunosuppression or prostaglandin synthesis suppression. The adrenal glands were preferred sites of tumour growth but pharmacological manipulation of adrenal function did not alter tumour growth to this organ. Sites of injury and healing were preferred sites of tumour colonisation and this could not be accounted for by increased delivery of tumour cells to these regions. The possibility that the macrophage component of the inflammatory response promoted tumour growth was suggested from studies in which the interval between trauma and inoculation of tumour cells was varied as well as by promotion of intraperitoneal (i.p.) tumour growth by a macrophage infiltrate.

Regional lymph node metastasis created by partial excision of carcinomas induced in hamster cheek pouch with 9,10-dimethyl-1,2-benzanthracene

The feasibility of using the hamster cheek pouch/dimethyl-benzanthracene (DMBA) system as an experimental model of lymphatic metastasis was investigated. Forty male Syrian golden hamsters treated with DMBA were divided into two equal groups--one with surgical excision of their tumors and a control group without tumor excision. In the excision group, the animals received three applications/week to the left cheek pouch of 0.3% DMBA in acetone for 14 weeks. Following a three-week observation period, the tumors in the pouch were excised at their base, and the animals were killed after four weeks of further observation. In the control group, the animals were treated for 14 weeks in a manner similar to that used for the excision group, left for seven weeks without treatment, and then killed. Cheek pouches with tumors and cervical lymph nodes were processed for histological examination. All of the animals, both with and without metastasis, had borne squamous cell carcinomas (SCC) in their treated cheek pouches. Histologically, seven out of 16 animals in the excision group showed metastatic deposits of SCC confined to the left cervical lymph nodes, while in the control group, metastasis was not found in any of the 19 animals with SCC in their cheek pouches. The results demonstrate that surgical excision of the hamster cheek pouch carcinoma is efficient in producing unequivocal lymph node metastasis.

Three tumor sensitivity tests evaluated with mouse tumors

The predictive value of three types of tumor sensitivity tests was evaluated using mouse tumors. Sensitivities of osteosarcoma C22LR, Lewis lung and M2661 carcinoma were determined for the following drugs: DNA interacting or alkylating agent (doxorubicin, cisplatin, 1,3-bis(2-chloroethyl)-1-nitrosourea, melphalan), antimetabolite (5-fluorouracil, methotrexate) and microtubule inhibitor (vinblastine, vincristine). Volume measurements of the subcutaneously growing tumors after treatment with the same drugs were considered to be the traditional reference system with which the results of the in vitro clonogenic assay, the labeled precursor incorporation assay and the subrenal capsule assay were compared. Results obtained with the in vitro clonogenic assay were highly reproducible. With the 1-h drug exposure technique the predictive accuracy was 71%. This result is in the same range as those found by others for human tumors. Predictive accuracy after continuous drug exposure was only 25%. Vinblastine, vincristine and cisplatin caused no inhibition of labeled precursor incorporation. However, the assay is too unreliable to use, due to the extreme variability when used with the other drugs. From 31 consecutively performed duplicate tests in the subrenal capsule assay, nine showed opposite results. This degree of disagreement between duplicate test results was considered too high to make reliable predictions of tumor sensitivity with this assay.

The lymphnodal clonogenicity and kinetics of metastatic cells disseminated by a transplanted rat carcinoma

We report data on the transplantation of primary tumour cells and of lymph nodes containing metastatic cells disseminated by a mammary carcinoma (LMC1) implanted s.c. in the Johns' Strain Wistar rat. A new method is described for deriving the TD50 of metastatic cells and for comparing their lymphnodal clonogenicity in the transplanted and the original, i.e. 'primary' tumour host. The TD50 for transplanted primary LMC1 cells was approximately 12 (fiducial limits 8-20 cells), and the latency of the 8-10mm tumours formed (T8-10) after inocula of 10(2) to 10(5) cells decreased linearly with the logarithmic increase in the number of cells injected. From the T8-10 and tumour incidence data for transplanted inguinal, axillary and para-aortic nodes, the TD50 for metastatic cells was calculated to be 1120 cells (fiducial limits 790-1603 cells) indicating that the clonogenicity of naturally disseminated metastatic cells was about a 100 fold lower than that determined for transplanted primary tumour cells. The incidence and T8-10 data for axillary, inguinal and para-aortic lymph node metastases in primary-tumour-excised hosts suggests that, although metastatic cells may continue translymphnodal dissemination in situ, their TD50 is still consistent with that determined by node transplantation.

The pattern and timing of lymphatic metastasis of the rat carcinoma LMC

The distribution pattern and latency of lymphatic metastases naturally disseminated by the Leeds Mammary Carcinoma (LMC1) when transplanted subcutaneously in isogeneic Johns' Strain Wistar rats has been determined. After the curative local irradiation and excision of the primary tumour in 210 rats, 55 +/- 3 per cent developed either local (26 +/- 3 per cent), and/or regional (28 +/- 3 per cent) and/or distant (37 +/- 3 per cent) lymph node metastases. Analysis of their pattern of distribution suggests that metastasis to local (inguinal and lumbar) and distant (axillary and mediastinal) nodes results mainly from the radial dissemination, trapping and nodal proliferation of cells released by the primary tumour. Although direct metastasis to the para-aortic node may have occurred, in the main seeding of this site and thence to other, regional, i.e. iliac and/or adrenal nodes, resulted from the dissemination of tumour cells from the local nodes. The latency of metastases appearing at different sites after primary tumour ablation, although highly variable, was site dependent and for local, regional and distant nodes was 30 +/- 14, 48 +/- 16, 56 +/- 17 days respectively. In addition, the latency of metastases at regional and distant nodes was directly correlated with the latency of local metastases. The latency of adrenal and iliac metastases also correlated with para-aortic node metastasis, as did mediastinal with axillary lymph node metastasis. From the data, a semi-quantitative model of lymphatic metastasis has been developed for further evaluation and adjuvant chemotherapy testing.

Investigation of a new murine model of regional lymph node metastasis: characteristics of the model and applications

The RC tumor, originally a renal adenocarcinoma very sensitive to different classes of chemotherapeutic agents, maintained in CDF 1 mice, was examined for its ability to metastasize. When inoculated into the foot (with 10(7) tumor cells), bulky metastases developed in the popliteal and para-aortic lymph nodes, in a constant and reproducible pattern, producing a massive microscopic invasion of the liver, the lungs and the spleen. The antigenicity tests demonstrated a low immunogenicity of the tumor. Chemotherapy assays showed that adriamycin and vincristine were effective against metastatic dissemination when administered early after tumor cell inoculation and principally when combined with excision of the tumor-bearing leg. The RC model appears to be suitable for the study of lymph node metastasis and could be used in chemotherapy trials of new drugs potentially effective against metastases of the lymphatic system.

Morphologic studies on a murine reticulum cell sarcoma (histiocytic sarcoma) of histiocytic origin and its metastases

The M5076 tumor, a reticulum cell sarcoma of histiocytic origin that arose spontaneously in the ovary of a C57BL/6 mouse, is highly invasive and metastatic. Regardless of the site of the primary tumor, this neoplasm rapidly and preferentially metastasizes to the liver and spleen, killing the host. Numerous other organs also are involved, including the lungs and bone marrow. This tendency to metastasize to osseous tissues appears to be a characteristic of the M5076 tumor that rarely is found with other rodent neoplasms. However, these extrahepatic foci are evident only microscopically and are seen relatively late in the progression of tumor growth. We describe the sequential gross and microscopic lesions that develop in syngeneic mice during the metastatic spread of the M5076 tumor. Since viable tumor cells form small tumor colonies in most organs, we suggest that the gross pattern of metastasis, with the apparent predilection for hepatic tissue, is caused by variations in tumor cell proliferation rather than by distinctive patterns of neoplastic cell spread and entrapment.

Lymphatic metastasis; lymphangiochemotherapy of mammary cancer: ascitic form of rat mammary adenocarcinoma 13762

When 5 million cells of the ascitic form of the RMT 13762 are injected into syngeneic F344 rat footpads there is consistent metastasis to the popliteal node more rapidly than when the solid form is used. A greater number of tumor cells escapes from the footpad to the draining node via the afferent lymph than with the solid tumor. Local intralymphatic injection of 5FU produces cure or retardation of nodal metastasis in a significant number of animals (p less than 0.002).

Influence of implantation site on formation of metastases

It has been suggested that local factors at the site of growth of a primary tumor might influence the outcome of the metastatic process. Compilation of the data from the literature revealed that growth of tumor cells in the selective medium of the intraperitoneal cavity, of the lymph node and/or of the spleen leads to progression towards a population of cells with a higher metastatic capacity. In search for an experimental model with transplantable rodent tumors that could be used to study the influence of the anatomic site of an implant on the formation of spontaneous metastases, we have considered heterogeneity of microenvironmental conditions in the subcutaneous milieu. For the MO4 mouse fibrosarcoma, a primary tumor growing subcutaneously in the tail was highly metastatic to lymph nodes and lungs while it failed to produce metastases when growing in the pinna. Implantation of a spheroidal aggregate of MO4 tumor cells, alternatively in the tail and in the pinna of syngeneic C3H/He mice, might be an appropriate model, which is discussed in this review.

Host resistance to metastasis from mouse mammary carcinomas

Although undisturbed primary mouse mammary tumors may give rise to overt metastases, these have generally been observed near the terminal stage of progressive tumor growth. Unlike malignant breast disease in women, metastases are seldom the cause of death in mice, and in some strains as few as 2% of mammary tumor hosts may be affected (1). Highly metastatic tumors may, of course, be found, and hosts of the mammary carcinoma WHT all develop metastases (2). Evidence from animal models suggests that host defense reactions against immunogenic tumors may affect the incidence of metastatic spread (3-5). But nonimmunogenic and weakly immunogenic tumors probably represent the majority of mammary carcinomas (2, 6, 7), and this class was once considered outside control by the host. However, natural protective factors are also known which may prevent metastasis independently of specific antitumor immunity (8-10). There are therefore most likely several different biological factors and mechanisms which prevent circulating, viable cancer cells from developing into metastases. But one can not yet generalize whether natural resistance factors or induced resistance factors are the most important, or whether any resistance factors are as important in preventing metastases as is the basic unacceptability of cells in heterotopic locations. This review will not attempt to present a comprehensive analysis of cell-mediated and humoral immunity to mouse mammary tumors because this topic has recently been exhaustively treated in the reviews by Stutman (11) and Blair (12). We will focus primarily on information from in vivo investigations of the role of host resistance in the control of mammary tumor cells progressing through successive levels of metastasis from the primary tumor, through lymphatic or hematogenous dissemination, to colonization of distant organs.

Comparison of metastatic disease after local tumour treatment with radiotherapy or surgery in various tumour models

Spontaneous metastases in lymph nodes and/or the lung were obtained after tumour cell inoculation of four mouse tumours and one rat tumour into the foot-pads of syngeneic animals or their F1 hybrids. Following local radiotherapy with doses of 45-80 Gy, significantly more mice died with metastases than following local amputation of the tumour-bearing foot when the 2661 carcinoma was involved. No significant difference was observed after these treatments for the other tumours. The enhancement of metastastic growth after local radiotherapy in the 2661 carcinoma seems not to be due to incomplete killing of tumour cells in the foot. The presence of irradiated normal structures and tumour tissue after radiotherapy promoted the outgrowth of 261 carcinoma cells which were outside the radiation field at the time of treatment. Evidently, even under similar experimental conditions, radiotherapy may enhance the growth of metastases from some tumours and not from others.

'Seed and soil' revisited: mechanisms of site-specific metastasis

Clinical studies have shown that malignant tumors frequently show definite metastatic patterns. This tendency for neoplasms of a particular histologic type to metastasize to a specific organ is also a characteristic of experimental animal tumor systems. Mechanical entrapment, arrest determined by specific recognition between neoplastic cells and capillaries and organ-determined modulation of tumor growth have all been suggested as mechanisms that regulate this specificity. Experimental evidence for the role that each of these mechanisms plays in the regulation of metastatic patterns of transplantable rodent tumors is discussed in this review.

Lymph node metastases of EMT6 tumour in nude mice

Metastatic axillary lymph nodes following the injection of EMT6 tumour cells were observed in athymic nude mice, more often in female animals, and had a rapid growth rate. These metastases did not develop in syngeneic hosts. The latency of their appearance was inversely related to the number of injected cells.

Adjuvant chemotherapy: theoretical considerations and model studies

Comparison of response of experimental tumors to adjuvant chemotherapy for minimal disease with the response of solid large tumors to similar drug regimens has indicated that for many tumors the small microscopic foci are more responsive. There are, however, a number of model tumors that respond far less to chemotherapy when applied to minimal disease than when applied to large tumors. The response of these tumors to adjuvant treatment shows similarities with the clinically observed response. The data do not support the hypothesis that the success of a drug combination given as adjuvant chemotherapy may be predicted from the success of the same treatment when applied for manifest disease.