Moreover, methylation determines which genes are read and eventually manifested in the cell. Under-methylation (hypo-methylation) switches the pattern of gene expression to one more commonly associated with cancer. For instance, hypo-methylation of the tumor suppressor gene, p53, leads to a two-fold increase in the incidence of bronchial cancer in male smokers; cigarette smoke severely compromises methylation by degrading cellular folate reserves. Folate deficiency predisposes us to cancer and has been associated with the expression of carcinomas of the colon-rectum, lungs, cervix, esophagus pancreas and breast.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine .