PGR and retinoblastoma: Many strategies have been proposed to identify patients with therapy-resistant tumors, including PCR-based assays, gene-expression profiling, or immunohistochemical detection of biomarkers such as Her2, EGFR, IGF-IR, PR, p27, AIB1, IRS-1, caveolin-1, retinoblastoma tumor suppressor, and nuclear localized and tyrosine phosphorylated Stat5a/b [30,38,51-55].