The present invention concerns the use of a ribonuclease of the T2 family for the preparation of a medicament for preventing, inhibiting and/or reversing proliferation, colonization, differentiation and/or development of abnormally proliferating cells in a subject, wherein the RNAse T2 has the following characteristics: (i) 5 cysteine-cysteine disulphide bonds； (ii) a molecular weight of between 24-36 kDa； (iii) binds actin in either its active or non-active ribonucleolytic form； and (iv) in the ribonucleolytic form has an optimum temperature range of 50-60 °C and a pH optimum in the acidic range of between 3.5-5.
