Indeed, increased heterochromatin formation induced by HP1a overexpression reduced tumor growth in rasG12V, HP1a; csk−/− in both female and male flies that were fed HDS, with more drastic reduction of tumor size in females, while HP1a knockdown also reduced tumor growth in rasG12V, HP1a-RNAi; csk−/− flies (Fig. 3). The gene discussed is CSK; the disease is neoplasm.