Temperature-dependent dissociation of Lucké renal adenocarcinoma cells

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.

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.

Cytoplasmic microtubules of normal and tumor cells of the leopard frog. Temperature effects

The cytoplasmic microtubule complex (CMTC) was examined in monolayer cultures of normal tadpole mesonephros, primary renal adenocarcinoma, and an established cell line derived from a pronephric renal adenocarcinoma (PNKT-4B) of the leopard frog, Rana pipiens. Immunocytochemistry revealed typical arrays of microtubules extending from the cytocentrum to the cell periphery in all three cell types when cultured at 28 degrees C; similar results were obtained at 20 degrees C. However, the CMTC was disorganized in both tumor types, in contrast to the retention of a typical CMTC in normal tissue cultured at 7 degrees C. The response of PNKT-4B cells differed from that of normal tadpole mesonephros when treated with the microtubule inhibitor drug nocodazole. At 28 degrees C, PNKT-4B and tadpole mesonephros cells lost their CMTC with nocodazole treatment, and both were able to reconstitute CMTC when nocodazole was removed. Similarly, both lost CMTC organization with nocodazole and culture at 70 degrees C. However, while normal cells could effect a recovery at 7 degrees C after the removal of nocodazole, PONKT-4B cells were unable to restructure CMTC under the same conditions. Metastasis in the frog renal adenocarcinoma is temperature-dependent, with an elevated prevalence of metastasis in tumor-bearing frogs maintained at 28 degrees C. Few metastatic colonies are detected in tumor-bearing frogs maintained at a low temperature (7 degrees C). Other studies have indicated that microtubules, which are essential for cell motility, play an important role in the invasion by tumor cells of normal tissue fragments in vitro. The effects of temperature on metastasis of the Lucke renal adenocarcinoma are consistent with temperature-mediated changes in tumor-cell CMTC.

Temperature-dependent metastasis of the Lucke renal carcinoma and its significance for studies on mechanisms of metastasis

Metastasis is temperature dependent in the renal adenocarcinoma of the North American leopard frog, Rana pipiens. Widespread, multiple, metastatic colonies occur in tumor-bearing frogs kept at 28 degrees C for 50 days while tumor-bearing frogs kept at 7 degrees C for 98 days or more have either no secondary deposits or they have only an occasional small metastatic nodule. An attractive aspect of the frog tumor is that invasion and metastasis can be permitted or inhibited by the manipulation of temperature alone-no exogenous chemicals or drugs are required for the effect. Because of this, biological variables which reproducibly and specifically associate with metastasis permissive conditions when ambient temperature is cycled between permissive and inhibitory values are strong candidates for being causal elements in the multistep process leading to metastasis. Intravascularly injected labelled renal tumor cells reached all organs studied in as little as 15 minutes at both metastasis restrictive and permissive temperature. The results with tumor cell inoculation dispose of the possibility that failure of metastasis in chilled animals is due to cold-induced changes in blood flow. Histologically typical metastatic colonies developed in frogs, kept at the permissive temperature, after injection with disaggregated tumor cells which were previously cryopreserved. Frog tumors elaborate type I collagenase in a temperature dependent manner. Type IV collagenase has been demonstrated as well. Tumor cell detachment in vitro, assembly and disassembly of tumor cell cytoplasmic microtubules, and invasion in vitro, are all temperature dependent.