Morphological changes in L1210 leukaemic cells induced by hyperthermia

Area of Science:

• Cell Biology
• Cancer Research
• Biophysics

Background:

• Mild hyperthermia is an emerging cancer treatment modality.
• Understanding cellular responses to heat is crucial for optimizing therapeutic strategies.
• L1210 leukaemic cells are a model system for studying cancer cell sensitivity to thermal stress.

Purpose of the Study:

• To investigate the effects of mild hyperthermia on the clonogenic survival of L1210 leukaemic cells.
• To examine the morphological changes in L1210 cells induced by heat treatment using scanning electron microscopy (SEM).
• To correlate cellular morphology with loss of clonogenicity after heat exposure.

Main Methods:

• L1210 leukaemic cells were exposed to 43°C for varying durations (5, 10, 15, 30 minutes).
• Clonogenic survival was assessed using the spleen colony assay.
• Cellular morphology was examined via SEM after fixation within 60 seconds of heating.
• Heated cells were compared to unheated controls stored at different temperatures.

Main Results:

• A 15-minute heat treatment at 43°C reduced the clonogenic fraction to 0.1, with approximately 50% of cells showing no morphological changes.
• Virtually all cells heated for 30 minutes at 43°C exhibited abnormal morphology.
• Progressive membrane changes observed included loss of microvilli, folding, corrugation, and bleb formation.
• Some cells lost clonogenicity before significant morphological changes were evident.

Conclusions:

• Mild hyperthermia induces lethal injury in L1210 cells, likely through damage to enzyme systems.
• Cellular sterilization can occur rapidly, potentially preceding observable morphological alterations.
• The rapid fixation method suggests that lethal injury may manifest before gross structural changes develop.