Invasion in vitro by explants of Lucke renal carcinoma cocultured with normal tissue is temperature dependent

Chick Heart Invasion Assay for Testing the Invasiveness of Cancer Cells and the Activity of Potentially Anti-invasive Compounds

The goal of the chick heart assay is to offer a relevant organ culture method to study tumor invasion in three dimensions. The assay can distinguish between invasive and non-invasive cells, and enables study of the effects of test compounds on tumor invasion. Cancer cells - either as aggregates or single cells - are confronted with fragments of embryonic chick heart. After organ culture in suspension for a few days or weeks the confronting cultures are fixed and embedded in paraffin for histological analysis. The three-dimensional interaction between the cancer cells and the normal tissue is then reconstructed from serial sections stained with hematoxylin-eosin or after immunohistochemical staining for epitopes in the heart tissue or the confronting cancer cells. The assay is consistent with the recent concept that cancer invasion is the result of molecular interactions between the cancer cells and their neighbouring stromal host elements (myofibroblasts, endothelial cells, extracellular matrix components, etc.). Here, this stromal environment is offered to the cancer cells as a living tissue fragment. Supporting aspects to the relevance of the assay are multiple. Invasion in the assay is in accordance with the criteria of cancer invasion: progressive occupation and replacement in time and space of the host tissue, and invasiveness and non-invasiveness in vivo of the confronting cells generally correlates with the outcome of the assay. Furthermore, the invasion pattern of cells in vivo, as defined by pathologists, is reflected in the histological images in the assay. Quantitative structure-activity relation (QSAR) analysis of the results obtained with numerous potentially anti-invasive organic congener compounds allowed the study of structure-activity relations for flavonoids and chalcones, and known anti-metastatic drugs used in the clinic (e.g., microtubule inhibitors) inhibit invasion in the assay as well. However, the assay does not take into account immunological contributions to cancer invasion.

Chick heart invasion assay

Tumors are microecosystems in which a continuous cross talk between cancer cells and host cells decides on the invasive behavior of the tumor cell population as a whole (Mareel et al., Encyclopedia of cancer, San Diego, CA, Academic Press, 1997). Both compartments secrete activating and inhibitory factors that modulate activities such as cell-extracellular matrix (ECM) interaction, cell-cell adhesion, remodeling of the ECM, and cell motility. For this reason, confrontations of cancer cells with a living normal host tissue in organ culture have been introduced by several groups: Wolff and Schneider in France (Wolff and Schneider, C R S Soc Biol (Paris) 151:1291-1292, 1957), Easty and Easty in the United Kingdom (Easty and Easty, Nature 199:1104-1105, 1963), and Schleich in Germany (Schleich et al., J Natl Cancer Inst 56:221-237, 1976). Embryonic chick heart fragments in organ culture maintain many histological features of their tissue of origin: They are composed of myocytes, fibroblasts, and endothelial cells, and their ECM contains fibronectin, laminin, and several collagen types. Moreover, the fragments remain contractile, and this activity allows the monitoring of their functional integrity during organ culture.

Development, cell differentiation and cancer. Proceedings of a symposium. 9th International Conference. Pisa, Italy, September 28-October 2, 1996

The northern leopard frog, Rana pipiens, is vulnerable to a herpesvirus-induced renal tumor. The Lucké renal adenocarcinoma is metastatic as a function of temperature. The cloning procedure of nuclear transplantation has been used to study the differentiation potential of the tumor genome. This paper summarizes current studies of the pathology, virology, and differentiation competence of the Lucké tumor.

Allografts of tumor nuclear transplantation embryos: differentiation competence

The developmental potential of nuclei can be studied by nuclear transplantation. Although amphibian blastula nuclei and other early embryonic nuclei are totipotent, to our knowledge no nucleus from an adult cell has ever been shown to be totipotent by this procedure. Transfer of Lucké renal carcinoma nuclei into enucleated eggs results in prefeeding swimming tadpoles. Inasmuch as these tadpoles die, rescue of this pluripotential tissue was attempted by grafting fragments of triploid tumor nuclear transplant tadpoles to the tails of normal diploid Rana pipiens hosts. Grafts of tumor nuclear transplant tadpole tissue were histologically indistinguishable from grafts of normally fertilized embryos and developed normal-appearing structures such as complete eyes, well-differentiated neural tissues, kidney tubules, and gut epithelium. Moreover, histological differentiation in tumor nuclear transplant grafts was comparable to that observed in 50-day-old normal larvae. Grafting enhanced the survival of tumor nuclear transplant tissue from no more than 14 days as part of the donor tadpole to 40 days at which time the grafts were harvested as healthy tissue. Thus, both differentiation and survival of tumor nuclear transplant tissue were augmented with the grafting procedure. Cytophotometric analysis of ploidy was used to confirm the tumor origin of the donor tissue.

Culture of PNKT-4B cells at invasion permissive and restrictive temperatures. I. Chromosomal analysis

PNKT-4B is an aneuploid cell line derived from a herpesvirus-induced renal adenocarcinoma of Rana pipiens that displays restricted invasion at 21 degrees C or cooler and invasion at 23 degrees C through 28 degrees C. Metaphase chromosomes obtained from subcultures (passages 297; 345-347) grown at 18 degrees C or 28 degrees C were Giemsa stained or N-banded with acidic silver nitrate. Cells grown at 18 degrees C displayed a modal chromosome number of 41, while 28 degrees C cultures displayed a modal number of 40. The distribution of the chromosomes suggests that the two temperatures may be allowing growth of different subclonal populations. N-banding of chromosomes at both temperatures revealed an increase of active nucleolar organizer regions (NORs) over normal frog tissues, 2/2N. Analysis of 200 N-banded spreads from cells grown at each temperature revealed modal numbers of 9 NORs/cell and modal numbers of 6 NOR-containing chromosomes/cell. Nine specific NOR-containing chromosomes were identified and scored. Similar distributions were observed at 18 degrees C and 28 degrees C. The data imply that the modal number of PNKT-4B has shifted since it was first described, 39, and differs at invasion-permissive and -restrictive temperatures. Increased numbers of active NORs and alterations of NOR-containing chromosomes imply an amplification of rDNA over the amount in normal frog.

Adhesion of frog pronephric tumor cells to normal cells cultivated on microcarrier beads

The processes of cell adhesion and active spreading were assessed between frog normal pronephric, pronephric tumor and heterologous liver cells. Confluent monolayers were developed on collagen-coated microcarrier beads, then exposed to homologous or heterologous cells and cultivated with a rotary (orbital) flask culture technique at 23 degrees C. All three cell lines attach and actively spread on the collagen-coated microcarrier beads. Secondary attachment of normal (non-transformed) proliferating cells to their confluent monolayers occurs but cell spreading is restrained. Dissociated pronephric tumor cells adhere and actively spread on the surfaces of normal pronephric cells, and eventually encapsulate them. Normal pronephric cells do not adhere readily to the cell surfaces of pronephric tumor cells grown on microcarrier beads. Tumor cells also attach, actively spread and overgrow heterologous liver cells attached to microcarrier beads. Suboptimal temperatures (17 degrees C) slow tumor cell attachment and spreading on normal cells. Colder temperature (8 degrees C) permits tumor cell attachment and adhesion to normal cell-coated beads but active cell spreading is prohibited. The same temperature retards cell spreading directly on the collagen-coated beads.

Quantitative evaluation of melanoma cell invasion in three-dimensional confrontation cultures in vitro using automated image analysis

Tumor invasion is a crucial feature of tumor growth in vivo. Confrontation cultures of multicellular melanoma spheroids and embryonic chick heart fragments provide a model for invasive growth in vitro. We have developed an image analysis method, which facilitates the objective measurement of tumor cell invasion in this model. Cryostat sections of confrontation cultures were immunohistochemically stained with an antiserum directed against the stromal component for automated recognition of the stroma tissue. The slides were automatically processed by a grey level based computerized image analysis system. On Spearman's rank correlation test, 25 out of 39 parameters correlated with the reference value of invasion, which was derived from the subjective evaluation of five independent observers. Two parameters combining the stroma margin and the total amount of stroma tissue completely reproduced the judgement of the morphologists in our test set. The quantitative evaluation of tumor invasion in vitro by automated image analysis may be helpful in pharmacologic and pathogenetic studies of tumor growth.

Restored invasion of mouse MO4 cells into chick heart in vitro through mutual conditioning at reduced temperature

Invasion of malignant mouse MO4 cells into embryonic chick heart fragments in confronting organ cultures was arrested for 7 days when the temperature of incubation was lowered to 28 degrees C. Afterwards invasion resumed and progression between days 10 and 17 at 28 degrees C was comparable to that between days 0 and 7 at 37 degrees C. This pattern of progression of MO4 cell invasion at 28 degrees C was unaltered when either MO4 cells or heart fragments or both were preincubated separately at 28 degrees C for 14 days before confrontation with each other. Invasion at 28 degrees C resumed only when MO4 cells and heart tissue had been in immediate contact for at least 7 days. Metabolic labelling with [3H]fucose showed a correlation in time between transient suppression of invasion and transient inhibition of incorporation of fucosylation-precursor molecules into glycoproteins by MO4 cells. The latter activity was far less temperature-sensitive in heart cells. Our observations suggest that metabolic cooperation between invading MO4 cells and heart tissue is essential for progression of invasion in vitro.

Temperature-dependent malignant invasion in vitro by frog renal carcinoma-derived PNKT-4B cells

The northern leopard frog, Rana pipiens, may be afflicted with a herpesvirus-transmitted renal carcinoma which has the interesting property that its metastatic behavior is temperature-related. PNKT-4B is a cell line derived from a pronephric carcinoma arising in a tadpole. We sought to ascertain if invasion of normal tissue by PNKT-4B cells in three-dimensional confrontation culture in vitro is similarly temperature-dependent. Normal fragments of tadpole and frog organs are invaded by PNKT-4B cells at 28 degrees C but not at 20 degrees C or 21 degrees C. PNKT-4B cells failed to invade tadpole tissues at 7 degrees C. A temperature critical for invasion was sought. Temperatures of 21 degrees C and cooler are invasion-restrictive and 23 degrees C and warmer are invasion-permissive under the conditions of this study. Identification of a critical permissive temperature allows for the characterization of biochemical events which may be activated at the same temperature. The biochemical changes, which are selectively activated and subsequently repressed as tumor cells are cycled through invasion-permissive and invasion-restrictive temperatures, become compelling candidates as reactions involved in, or causal for, malignant invasion.