Efficacy of combination therapy varies by PTEN levels, type of endocrine therapy, and combined kinase inhibitors. MCF7-shPTEN cells were pre-treated in PRF medium with 5% CS-FBS and -/+Dox for three days. Bar charts presented the % of cell growth of MCF7L-shPTEN cells treated for five days with single or two-agent combination kinase inhibitors (mTORi, 0.2 μm; AKTi, 1 μm; MEKi, 1 μm), under E2 (A), ED (B), or Tam (C) condition, all -/+Dox (gray/red color). Cell growth in five days of the E2 (-/+Dox) groups was used as the normalization control. The Bonferroni post hoc test was performed for paired comparisons between single-kinase inhibitors and DMSO (drug carrier control) (#P <0.05), or between a two-agent kinase inhibitor combination and either agent alone (*P <0.05, **P <0.01, ***P <0.001). Heat maps were used for all calculated % of growth inhibition (scaled so as to not exceed 100% by dividing by the maximum growth inhibition within each matrix) in two-agent combinations of kinase inhibitors: mTORi plus AKTi (D and G), mTORi plus MEKi (E and H), or AKTi plus MEKi (F and I), all under ED or Tam. Cell growth under ED or Tam without kinase inhibitor was set as 100% (0% of growth inhibition) for the normalization control. Percentages of combinations among each matrix with enhanced (P ≤0.05) or attenuated (P ≥0.95) effect compared to single drug alone (tested by the Min test) were summarized in (J) (under ED) and (K) (under Tam). AKT, protein kinase B; CS-FBS, charcoal-stripped-FBS; Dox, doxycycline; E2, β-estradiol; ED, estrogen deprivation; Ful, fulvestrant; MEK, mitogen-activated protein kinase kinase; mTOR, mammalian target of rapamycin; PRF, phenol-red free; PTEN, phosphatase and tensin homolog; Tam, tamoxifen.