Supplemental oxygenation could improve cancer immunotherapy and shrink tumours by unleashing anti-tumour T lymphocytes and natural killer cells the findings showed. In a major breakthrough researchers have found that just breathing in extra oxygen could spurt the growth of tumour-fighting cells thereby improving cancer treatment. Breathing supplemental oxygen opens up the gates of the tumour fortress and wakes up 'sleepy' anti-tumour cells enabling these soldiers to enter the fortress and destroy it explained Michail Sitkovsky immunophysiology expert at the Northeastern University in the US. However he added if anti-tumour immune cells are not present oxygen will have no impact. (Read: