Figure 1.
(A) Xenograft diameters versus time in the transition from androgen-deprivation therapy (ADT)-naïve, via androgen-deprived (AD) and long-term AD (ADL), to castration-resistant (CR) disease, after ADT by castration. The time to develop CR disease in patients is ∼2 to 5 years. In our prostate carcinoma xenograft model, the corresponding time was 5.4±0.4 months. The four circles represent the four experimental groups in this study. Blood samples for prostate-specific antigen (PSA) measurements were withdrawn from all of the mice before tumors were excised and snap-frozen for kinase activity profiling. (B) Serum PSA levels reflected the clinical pattern of disease progression. PSA was decreased in AD and ADL tumors, before being restored in CR tumors. Significant differences (p<0.05) compared to ADT-naïve tumors are indicated (*). Each bar represents mean and s.e.m of 3–6 tumors.
Table 1.
Patient characteristics.
Table 2.
Kinase peptide substrates with significantly affected (reduced or increased) phosphorylation levels by samples from androgen-deprived (AD), long-term AD (ADL), or castration-resistant (CR) prostate carcinoma xenografts, versus androgen-deprivation therapy (ADT)-naïve xenografts.
Figure 2.
Kinase activity in xenografts following androgen-deprivation therapy (ADT).
(A) Decreased (blue; negative log2 ratio) and increased (red; positive log2 ratio) phosphorylation levels of kinase peptide substrates by androgen-deprived (AD), long-term AD (ADL), and castration-resistant (CR) prostate carcinoma xenografts compared to ADT-naïve tumors (mean ratio and s.e.m. per substrate). Protein lysates from three biological replicates from each of the four experimental groups (ADT-naïve, AD, ADL, CR) were analyzed to generate the xenograft kinase activity profiles. Listed are the substrates’ corresponding gene names, with start and end positions for the peptide sequence within the protein in brackets. (B) Volcano plots (−log10 p-values versus ratios) visualizing kinase peptide substrates with most significant and/or highest log2 ratios between treated and ADT-naïve tumors’ phosphorylation levels. Color labeling: yellow: p<0.01 and ratio >1.0; green: p<0.01 and ratio = 0.5–1.0; dark pink: p = 0.01–0.05 and ratio >1.0; orange: p = 0.01–0.05 and ratio = 0.5–1.0; blue: p = 0.01–0.05 and ratio <0.5; light pink: p>0.05.
Figure 3.
Kinase activity in androgen-deprivation therapy (ADT)-naïve xenografts versus ADT-naïve patient tumors.
An ADT-naïve kinase activity signature was defined as the 100 kinase peptide substrates with highest phosphorylation levels. For prostate carcinoma xenografts, the signature was represented by the mean of all ADT-naïve substrate phosphorylation levels. For prostate cancer patients, a top 100 signature was produced by calculating the mean of the three ADT-naïve (case 1, 2, and 3; Table 1) tumor phosphorylation levels. (A) Seventy-four of the 100 substrates were shared by the xenograft and the patients’ tumor ADT-naïve signatures. (B) Phosphorylated kinase peptide substrates shared by ADT-naïve prostate carcinoma xenografts (n = 3) and ADT-naïve tumors from prostate cancer patients (mean of case 1, 2, and 3). Listed are the substrates’ corresponding gene names, with start and end positions for the peptide sequence within the protein in brackets. (C) The exclusively phosphorylated kinase peptide substrates (n = 26) in the xenograft signature (left) and in the patient tumor signature (right).
Figure 4.
STAT5A substrate phosphorylation and HIF-1α expression in prostatectomy tumor samples.
(A) For the androgen-deprivation therapy (ADT)-naïve prostate cancer patients, the log2 ratios between the substrate phosphorylation levels generated by the prostatectomy tumor sample versus the respective contralateral lobe normal tissue sample were calculated. For the patient that received long-term ADT before radical prostatectomy, the log2 ratio between the substrate phosphorylation levels from the tumor sample versus the mean substrate phosphorylation levels from the ADT-naïve patients’ normal tissue samples were calculated (since this patient’s normal tissue also was exposed to ADT). (B) Western immunoblot analysis of the prostatectomy tumor samples’ lysates with an antibody against hypoxia-inducible factor-1α (HIF-1α), the main protein known to be activated and stabilized under hypoxic conditions, revealing increased HIF-1α expression in the lysate from the early CR tumor (case 4). No HIF-1α expression was seen in lysates from ADT-naïve tumors.
Figure 5.
Hypoxia-induced increase in STAT5A substrate phosphorylation by prostate carcinoma cells.
(A) 22Rv1 cells were exposed to moderate (1% O2) and severe (<0.02% O2) hypoxia for 24 hours in a hypoxia chamber. Protein lysates from three biological replicates from each of the three experimental groups (normoxia, moderate hypoxia, severe hypoxia) were analyzed to generate the kinase activity profiles. Kinase activity profiling of hypoxic and normoxic cell lysates detected increased STAT5A substrate phosphorylation with increasing hypoxia (blue bars), whereas the mean phosphorylation level for all 22 kinase peptide substrates with significant changes was low (grey bars). *The increase from normoxia to severe hypoxia was significant (p = 0.020). The difference in mean phosphorylation level at moderate versus severe hypoxia was not significant. (B) The proportion of decreased versus increased kinase activity in hypoxic versus normoxic 22Rv1 cell lysates. Listed are the gene names of the affected kinase peptide substrates, with start and end positions for the peptide sequence within the protein in brackets. (C) Western blot of anti-phospho-STAT5A/B and anti-STAT5A expression in normoxic (−) and severely hypoxic (<0.02% O2, 24 h) (+) cell lysates from PC3, DU145 and 22Rv1 cells. Anti-γ-tubulin served as loading control. (D) Western blot of anti-HIF-1α, anti-phospho-STAT5A/B and anti-STAT5A expression of lysates from PC3, DU145 and 22Rv1 cells with (+) or without (−) 4 hours of exposure to 100 µM of the hypoxia-mimetic agent cobalt chloride (CoCl2), a chemical inducer of HIF-1α. Anti-γ-tubulin served as loading control.