Hemoglobin also carries the important regulatory molecule nitric oxide bound to a globin protein thiol group, releasing it at the same time as oxygen. Haemoglobin is also found outside red blood cells and their progenitor lines. Other cells that contain haemoglobin include the A9 dopaminergic neurons in the substantia nigra, macrophages, alveolar cells, lungs, retinal pigment epithelium, hepatocytes, mesangial cells in the kidney, endometrial cells, cervical cells and vaginal epithelial cells. In these tissues, haemoglobin has a non-oxygen-carrying function as an antioxidant and a regulator of iron metabolism. Haemoglobin and haemoglobin-like molecules are also found in many invertebrates, fungi, and plants.
The Hallmarks of Cancer apoptosis, karyotypic disarray, and the occasional (10) emergence of an immortalized cell that can double without limit. Most tumor cells are immortalized. The counting device for cell doublings is the telomere, which decreases in size (loses nucleotides at the ends of chromosomes) during each cell cycle. About 85% of cancers upregulate telomerase to extend their telomeres and the remaining 15% use a method called the Alternative Lengthening of Telomeres. Normal tissues of the body have blood vessels running through them that deliver oxygen from the lungs. Cells must be close to the blood vessels to get enough oxygen for them