Model of micro-metastases of breast cancer cells in ovarian tissue: Cryopreservation of ZR-75-1 and MDA-MB-231 cells with increased speed of warming increases malignancy

Abstract

In medicine, ovarian tissue cryopreservation exists for fertility preservation of cancer patients. In fact, ovarian tissue frozen for subsequent thawing and re-transplantation can be contaminated with cancer cells. Therefore, investigations on the effect of cryopreservation on the post-thawed viability of such cells are relevant. Speed of warming is a key parameter of cell cryopreservation. However, the data about comparative viability of cancer cells cryopreserved with different parameters of warming are limited. The aim of our investigations was to assess the malignancy of cryopreserved cancer cells after conventional cooling followed by relatively slow and quick speed of warming. In vitro cultured breast cancer cells of lines ZR-75-1 and MD0MD-231 in form of compacted fragments (as a model of solid tumors) were frozen following a protocol usually used for freezing of ovarian tissue (6 % ethylene glycol+6 % glycerol+0.15 M sucrose, −0.3 °C/min). Cells were warmed by two routine regimes of warming: at 37 °C (“slow” warming) and 100 °C (“quick” warming). Biological properties of cells were investigated: viability, proliferation rate, 2D- and 3D-migration, transmembrane movement and invasion. Quick warming at 100 °C in comparison with slow warming at 37 °C exhibited significantly higher cell survival for MDA-MB-231 cells: 70.1 % vs. 63.2 % and for ZR-75-1 86.8 % vs. 82.9 %, respectively. The cell motility including 2D movement and 3D transmembrane migration were higher after quick thawing at 100 °C. Invasive abilities of cells after cryopreservation were higher than that of fresh (non-treated cells). Both thawing regimes showed a similar rate of cell proliferation. Cryopreservation procedures, and especially this one with quick thawing, increase malignancy of ZR-75-1 and MDA-MB-231 breast cancer cells and risk of metastasis.