## 3 Results
(**D**) Graphical representation and (**E**) heatmap of the association between HSD17B2, HSD17B3, SHBG,  
Distinct Interaction between the Testosterone Tetrad Elicits Androgenic Signals That Drive Cell Cycle Progression, Enhanced Motility, Cancer Stemness, and Resistance to Therapy in Patients with PCa  
To determine the molecular linkage between SRD5A1/SHBG/HSD17B2/HSD17B3 androgenic signaling and therapy response, we performed molecular connectivity and functional enrichment analyses using the STRING software version 11.0 ([[https://string-db.org/](https://string-db.org/)]([https://string-db.org/](https://string-db.org/)), accessed on 11 February 2021). Our bioinformatics-aided visualization shows a significantly high protein-protein interaction (PPI) enrichment between the tetrad (\(p=6.43\times 10^{-9}\)), and suggests an active role for SRD5A1 in the transcriptional regulation of SHBG, the HSD17B2/HSD17B3 complex (Figure 4A), and cytochrome P450 family 17 subfamily A member 1 (CYP17A1) (Figure 4B). This indicates, at least in part, a critical role for the testosterone tetrad in drug metabolism, coupled with steroids, cholesterol, and lipid biosynthesis--a dyad that modulates cancerization, disease progression, and treatment  
Figure 3: The differential but concerted expression of HSD17B2, HSD17B3, SHBG, and SRD5A1 is associated with the metastatic and recurrent phenotype of patients with PCa. Graphical representation of the association between HSD17B2, HSD17B3, SHBG, or SRD5A1 mRNA expression level and (**A**) clinical M stage, (**B**) biochemical recurrence status, (**C**) number of days to biochemical recurrence, and (**D**) treatment success, in the GDC TCGA PRAD cohort. (**E**) Representative photo-images and histograms of SRD5A1, HSD17B3, SHBG, or HSD17B2 protein expression level in adjacent nontumor prostate, primary, or metastatic samples from the SHH PCa cohort. M, metastasis; exp, expression; CI, confidence interval; GDC, genomic data commons; SHH, Shuang Ho Hospital; *, \(p<0.05\); **, \(p<0.01\); ***, \(p<0.001\). success. Furthermore, molecular docking shows that the HSD17B2/HSD17B3 complex (docking score = \(-\)359.46; ligand root-mean-square deviation, RMSD = 49.54 A) directly interacts with the SRD5A1/SHBG complex (docking score = \(-\)296.02; ligand RMSD = 69.47 A) to form a HSD17B2/HSD17B3/SHBG/SRD5A1 macro-complex (docking score = \(-\)355.07; ligand RMSD = 114.28 A), posited herein to drive the androgenic cum recurrent phenotype of patients with PCa (Figure 4C). Furthermore, AFFY_HG_U133_PLUS_2 expression profiling array analysis of the stromal molecular signatures of prostate and breast cancer using the GSE26910 dataset (n = 24) showed that, compared to downregulated SHBG, HSD17B2 and HSD17B3 expression, upregulated expression of SRD5A1 in tumor samples positively correlated with upregulation of ATP-binding cassette subfamily C member 1/multidrug resistance-associated protein 1 (ABCC1/MRP1), multidrug resistance protein 1 (ABCB1/MDR1) (Figure 4D), NANOG, SOX2, and POU Class 5 Home-obox 1 (POU5F1/OCT4) (Figure 4E). Reanalysis of the GSE33455 expression data from docetaxel-resistant PCa cell lines (n = 12) showed that, compared to the WT cells, SRD5A1, ALDH1A1, ABCC1, and ABCB1 expression were concomitantly upregulated in docetaxel-resistant DU-145 cells, while SHBG, HSD17B2, HSD17B3, and ABCB1 were enhanced in docetaxel-resistant PC3 cells (Figure 4F). More so, using the GSE3325 dataset (n = 19), we observed markedly upregulated SRD5A1, HSD17B2, POU5F1, SOX2, and NANOG in the metastatic PCa, and HSD17B3, CD44, POU5F1, ABCB1, prominin 1 (PROM1/CD133), ABCC1, NANOG, and Kruppel-like factor 4 (KLF4) in primary PCa (Figure 4G).