Indeed, analysis of TfR expression revealed approximately 105 or more receptors per cell in several breast cancer cell lines (including MDA-MB-231) [30], HeLa (human cervical carcinoma) [31], HT-29 (human colon carcinoma cells) [32], K562 (human erythroleukemia cells) [31,33] and pancreatic tumor cells [34] compared to a few or often undetectable TfR levels in normal cells [35]. Here, TFRC is linked to breast carcinoma.