CTSD and neoplasm: investigated protein expression profiles of breast cancer MDA- MB-231 BC cell treated with single or fractionated radiotherapy and found that several tumor-derived factors including CTSD (Cathepsin D), Gelsolin (GSN), and Mannose Receptor C Type 2 (MRC2) were upregulated, the results also suggested that these factors were involved in regulating the immune response during radiotherapy (65).