The publisher and the Editor-in-Chief, in consultation with former publisher of Tumor Biology, retract a total of 15 articles from the journals' online catalog. The articles were published in different issues of the journal during the period 2014-2016. All articles affected by this retraction notice have problems related to image manipulation or misuse. A detailed explanation is given for each retracted article. The investigations were carried out in accordance with the recommendations of the Committee on Publication Ethics (COPE).