Prostate cancer biomarkers: from early diagnosis to precision treatment

Prostate cancer (PCa) is the second most prevalent cancer in men. In 2020, approximately 1,414,259 new cases were reported that accounted for 3,75,324 deaths (Sung et al. in CA 71:209-249, 2021). PCa is often asymptomatic at early stages; hence, routine screening and monitoring based on reliable biomarkers is crucial for early detection and assessment of cancer progression. Early diagnosis of disease is key step in reducing PCa-induced mortality. Biomarkers such as PSA have played vital role in reducing recent PCa deaths. Recent research has identified many other biomarkers and also refined PSA-based tests for non-invasive diagnosis of PCa in patients. Despite progress in screening methods, an important issue that influences treatment is heterogeneity of the cancer in different individuals, necessitating personalized treatment. Currently, focus is to identify biomarkers that can accurately diagnose PCa at early stage, indicate the stage of the disease, metastatic nature and chances of survival based on individual patient profile (Fig. 1). Fig. 1 Graphical abstract.

Non-canonical androgen signaling pathways and implications in prostate cancer

Androgen signaling is a critical determinant of timely and proper development of all male organs including the prostate. Maturation of prostate and its neoplastic transformation is intricately associated with accurate androgen signaling. Ablation of androgen has therefore been the primary treatment mechanism of Prostate cancer (PCa) patients for several decades. Upon removal, the tumor recedes for a while, yet it reappears soon, in an androgen independent state, untreatable by current therapeutic regimens. Studies reveal that apart from the classical androgen signaling pathway known and targeted for almost a century, there exist several non-canonical pathways, with marked impact on classical androgen signaling and PCa growth. These include non-genomic signaling by androgens via alternate membrane GPCRs, signaling by non-androgens that ultimately impact the androgen signaling pathway, or an integration of non-genomic and genomic response as seen in case of protein kinase A activation. Accurate understanding of these various non-canonical androgen signaling pathways and their influence on the typical androgen signaling pathway can help design important interventions for PCa patients. This review analyses in detail the various non-classical androgen signaling pathways and their impact, if any, on classical mode of androgen action and PCa.

Novel use of coactivators to enhance sensitivity of SEAP-based reporter assay system for visual monitoring and quantitation of androgens and antiandrogens in water

Every year thousands of chemicals get discharged into the waterbodies of the world. These chemicals cause endocrine disruption and induce adverse health effects in human and aquatic life. Global environmental protection agencies emphasise the need to develop rapid and specific tests for identification of these endocrine disruptive chemicals (EDCs) in water. Detection of chemicals that disrupt androgen signaling is especially important because androgen input at specific phases of life is critical for proper male development. Effect-based methods such as reporter assays are suitable tools for identification of EDCs in mixtures of unknown composition. The current study describes a stable, secreted alkaline protease (SEAP)-based reporter assay system, for visual detection of androgenic/antiandrogenic activity present in water samples. A novel feature of this system is the inclusion of coactivators, GRIP1, CARM1, p300 and mZac1b, in addition to an optimal combination of androgen response element (3× HRE), androgen receptor (AR) and the SEAP reporter gene. Incorporation of the coactivators resulted in a transcriptional fold change of 162 folds, enabling visual detection at much lower concentrations of androgen (1 picomolar) within 1 h of addition of test sample. Also, non-androgenic steroids such as estrogen, progesterone and Dexamethasone did not induce significant reporter activity, except at very high concentrations. This reporter assay can be readily converted into a high throughput format for investigation in multiple samples simultaneously, and reflects the changes that can be expected to occur inside a mammalian cell. The androgenic activity in six different water sources was evaluated using this assay. The results reveal significant androgenic activity in rivers and lakes close to Industrial areas, whereas the highest androgenic activity was observed in water containing paper and pulp mill effluents. This bioassay therefore provides a rapid, visual detection tool for effect-directed analysis of androgenic/antiandrogenic compounds in water. IMPACT STATEMENT: The current SEAP-based assay allows visual detection of androgens/antiandrogens in water, at concentrations as low as 1 picomolar, within a 1 h time period, in a high throughput format, providing a very useful technique for field users and regulatory bodies.

Phosphorylation of HSP90 by protein kinase A is essential for the nuclear translocation of androgen receptor

The androgen receptor (AR) is often activated in prostate cancer patients undergoing androgen-ablative therapy because of the activation of cellular pathways that stimulate the AR despite low androgen levels. In many of these tumors, the cAMP-dependent protein kinase A (PKA) pathway is activated. Previous studies have shown that PKA can synergize with low levels of androgen to enhance androgen signaling and consequent cell proliferation, leading to castration-resistant prostate cancer. However, the mechanism by which PKA causes AR stimulation in the presence of low/no androgen is not established yet. Here, using immunofluorescence immunoblotting assays, co-immunoprecipitation, siRNA-mediated gene silencing, and reporter gene assays, we demonstrate that PKA activation is necessary for the phosphorylation of heat shock protein (HSP90) that binds to unliganded AR in the cytoplasm, restricting its entry into the nucleus. We also found that PKA-mediated phosphorylation of the Thr⁸⁹ residue in HSP90 releases AR from HSP90, enabling AR binding to HSP27 and its migration into the nucleus. Substitution of the Thr⁸⁹ in HSP90 prevented its phosphorylation by PKA and significantly reduced AR transactivation and cellular proliferation. We further observed that the transcription of AR target genes, such as prostate-specific antigen (PSA), is also lowered in the HSP90 Thr⁸⁹ variant. These results suggest that using a small-molecule inhibitor against the HSP90 Thr⁸⁹ residue in conjunction with existing androgen-ablative therapy may be more effective than androgen-ablative therapy alone in the treatment of prostate cancer patients.

Complex modulation of androgen responsive gene expression by methoxyacetic acid

BACKGROUND

Optimal androgen signaling is critical for testicular development and spermatogenesis. Methoxyacetic acid (MAA), the primary active metabolite of the industrial chemical ethylene glycol monomethyl ether, disrupts spermatogenesis and causes testicular atrophy. Transcriptional trans-activation studies have indicated that MAA can enhance androgen receptor activity, however, whether MAA actually impacts the expression of androgen-responsive genes in vivo, and which genes might be affected is not known.

METHODS

A mouse TM3 Leydig cell line that stably expresses androgen receptor (TM3-AR) was prepared and analyzed by transcriptional profiling to identify target gene interactions between MAA and testosterone on a global scale.

RESULTS

MAA is shown to have widespread effects on androgen-responsive genes, affecting processes ranging from apoptosis to ion transport, cell adhesion, phosphorylation and transcription, with MAA able to enhance, as well as antagonize, androgenic responses. Moreover, testosterone is shown to exert both positive and negative effects on MAA gene responses. Motif analysis indicated that binding sites for FOX, HOX, LEF/TCF, STAT5 and MEF2 family transcription factors are among the most highly enriched in genes regulated by testosterone and MAA. Notably, 65 FOXO targets were repressed by testosterone or showed repression enhanced by MAA with testosterone; these include 16 genes associated with developmental processes, six of which are Hox genes.

CONCLUSIONS

These findings highlight the complex interactions between testosterone and MAA, and provide insight into the effects of MAA exposure on androgen-dependent processes in a Leydig cell model.

Impact of methoxyacetic acid on mouse Leydig cell gene expression

BACKGROUND

Methoxyacetic acid (MAA) is the active metabolite of the widely used industrial chemical ethylene glycol monomethyl ether, which is associated with various developmental and reproductive toxicities, including neural toxicity, blood and immune disorders, limb degeneration and testicular toxicity. Testicular toxicity is caused by degeneration of germ cells in association with changes in gene expression in both germ cells and Sertoli cells of the testis. This study investigates the impact of MAA on gene expression in testicular Leydig cells, which play a critical role in germ cell survival and male reproductive function.

METHODS

Cultured mouse TM3 Leydig cells were treated with MAA for 3, 8, and 24 h and changes in gene expression were monitored by genome-wide transcriptional profiling.

RESULTS

A total of 3,912 MAA-responsive genes were identified. Ingenuity Pathway analysis identified reproductive system disease, inflammatory disease and connective tissue disorder as the top biological functions affected by MAA. The MAA-responsive genes were classified into 1,366 early responders, 1,387 mid-responders, and 1,138 late responders, based on the time required for MAA to elicit a response. Analysis of enriched functional clusters for each subgroup identified 106 MAA early response genes involved in transcription regulation, including 32 genes associated with developmental processes. 60 DNA-binding proteins responded to MAA rapidly but transiently, and may contribute to the downstream effects of MAA seen for many mid and late response genes. Genes within the phosphatidylinositol/phospholipase C/calcium signaling pathway, whose activity is required for potentiation of nuclear receptor signaling by MAA, were also enriched in the set of early MAA response genes. In contrast, many of the genes responding to MAA at later time points encode membrane proteins that contribute to cell adhesion and membrane signaling.

CONCLUSIONS

These findings on the progressive changes in gene expression induced by MAA in a cultured Leydig cell model may help elucidate signaling pathways that lead to the testicular pathophysiological responses induced by MAA exposure and may identify useful biomarkers of MAA toxicity.

Androgens transduce the G alphas-mediated activation of protein kinase A in prostate cells

Androgens regulate the development and function of male reproductive organs and play a crucial role in the onset and progression of prostate cancer. Androgen action is primarily mediated through the nuclear androgen receptor (AR) which acts as a ligand-dependent transcription factor. This mode of androgen action takes hours to manifest and is called the genomic pathway. The androgen-mediated genomic responses require activity of cyclic AMP (cAMP)-dependent protein kinase (PKA). Androgens also act through nongenomic pathways in certain cell types to evoke rapid responses (manifested in minutes) that are mediated through changes in ion currents and second messengers. Here, we show that androgen causes the rapid and cAMP-dependent activation of PKA in prostate cells. The androgen-induced PKA activation is not inhibited by nuclear AR antagonist bicalutamide and can be observed in cells that do not express nuclear AR gene. Reduction of G alphas expression with siRNA attenuates the androgen-mediated activation of PKA, which is required for the androgen-induced prostate cell proliferation. We conclude that androgen actively evokes a nongenomic signaling pathway to activate PKA that is needed for the genomic functioning of nuclear AR. The inhibition of PKA activation, together with standard AR-targeted therapies, may be more efficacious for treatment of patients with prostate cancer.

Interactions of methoxyacetic acid with androgen receptor

Endocrine disruptive compounds (EDC) alter hormone-stimulated, nuclear receptor-dependent physiological and developmental processes by a variety of mechanisms. One recently identified mode of endocrine disruption is through hormone sensitization, where the EDC modulates intracellular signaling pathways that control nuclear receptor function, thereby regulating receptor transcriptional activity indirectly. Methoxyacetic acid (MAA), the primary, active metabolite of the industrial solvent ethylene glycol monomethyl ether and a testicular toxicant, belongs to this EDC class. Modulation of nuclear receptor activity by MAA could contribute to the testicular toxicity associated with MAA exposure. In the present study, we evaluated the impact of MAA on the transcriptional activity of several nuclear receptors including the androgen receptor (AR), which plays a pivotal role in the development and maturation of spermatocytes. AR transcriptional activity is shown to be increased by MAA through a tyrosine kinase signaling pathway that involves PI3-kinase. In a combinatorial setting with AR antagonists, MAA potentiated the AR response without significantly altering the EC(50) for androgen responsiveness, partially alleviating the antagonistic effect of the anti-androgens. Finally, MAA treatment of TM3 mouse testicular Leydig cells markedly increased the expression of Cyp17a1 and Shbg while suppressing Igfbp3 expression by ~90%. Deregulation of these genes may alter androgen synthesis and action in a manner that contributes to MAA-induced testicular toxicity.

Toxicity of ethylene glycol monomethyl ether: impact on testicular gene expression

Methoxyacetic acid (MAA), the active biological oxidation product of the industrial solvent ethylene glycol monomethyl ether (EGME), causes acute toxicity in several species including humans. MAA primarily affects tissues with rapidly dividing cells and high rates of energy metabolism, including testes, thymus and the fetus. Testicular toxicity, one of the most prominent consequences of EGME, and MAA, exposure, results from apoptosis of primary spermatocytes and is associated with changes in the expression of various genes and signalling pathways. This review of EGME metabolism and its organ-specific toxicities emphasizes genes and signalling pathways that are modulated by EGME exposure and their relevance to the molecular mechanisms underlying EGME and MAA toxicity. Of particular importance are the genes that code for oxidative stress response factors, protein kinases, and nuclear hormone receptors. Nuclear receptors and protein kinases regulate multiple cellular processes and are critical for signalling events required for spermatogenesis. De-regulation of their activity by EGME or MAA leads to inappropriate signalling in testicular cells. Oxidative stress in spermatocytes exposed to MAA triggers mitochondrial release of cytochrome C, activation of caspases and ultimately apoptosis. Detailed investigation of the molecular responses to MAA exposure may help elucidate the overall impact and extent of toxicity seen following EGME exposure. Finally, given the effects of EGME on multiple genes and signalling pathways in the testis, mixture studies combining EGME, or MAA, with other testicular toxicants may help identify toxicities that are aggravated by EGME exposure.

Transcription and autoregulation of the Rv3134c-devR-devS operon of Mycobacterium tuberculosis

DevR is a transcriptional regulator that mediates the genetic response of Mycobacterium tuberculosis to oxygen limitation and nitric oxide exposure. devR is co-transcribed along with devS, which encodes its cognate sensor kinase, and an upstream gene, Rv3134c. The transcriptional activity of this operon was characterized by primer extension, transcriptional fusion and electrophoretic mobility shift assays (EMSAs) under aerobic conditions. Transcription start points (Tsps) were detected upstream of both Rv3134c and devR, and the major transcript was derived from upstream of Rv3134c. Sequences with similarity to sigma factor consensus elements and to DevR-binding motifs were detected in the vicinity of the Tsps by in silico analysis. EMSAs with promoter regions and DevR protein showed that DevR binds to its own promoters in a sequence-specific manner with differing affinities. Consistent with the primer extension and EMSA data, Rv3134c promoters, and not devR promoters, were determined to be the principal promoters of this operon using reporter assays performed in Mycobacterium smegmatis and Escherichia coli. Furthermore, DevR modulated the activity of both devR and Rv3134c promoters. From these findings it is inferred that the Rv3134c-devR-devS operon is transcribed from multiple promoters and is autoregulated.

Androgen receptor activation by G(s) signaling in prostate cancer cells

The androgen receptor (AR) is activated in prostate cancer patients undergoing androgen ablative therapy and mediates growth of androgen-insensitive prostate cancer cells, suggesting it is activated by nonandrogenic factors. We demonstrate that activated alpha subunit of heterotrimeric guanine nucleotide-binding G(s) protein activates the AR in prostate cancer cells and also synergizes with low concentration of androgen to more fully activate the AR. The G alpha(s) activates protein kinase A, which is required for the nuclear partition and activation of AR. These data suggest a role for G alpha(s) and PKA in the transactivation of AR in prostate cancer cells under the environment of reduced androgen levels.

Molecular analysis of the dormancy response in Mycobacterium smegmatis: expression analysis of genes encoding the DevR-DevS two-component system, Rv3134c and chaperone alpha-crystallin homologues

Mycobacteria adapt to a decrease in oxygen tension by entry into a non-replicative persistent phase. It was shown earlier that the two-component system, DevR-DevS, was induced in Mycobacterium tuberculosis and Mycobacterium bovis BCG cultures during hypoxia, suggesting that it may play a regulatory role in their adaptation to oxygen limitation. The presence of a homologous genetic system in Mycobacterium smegmatis was predicted by scanning its unfinished genome sequence with devR and devS genes of M. tuberculosis. Rv3134c, which is cotranscribed with devR-devS in M. tuberculosis, was also present in M. smegmatis at a similar location upstream from devR. The expression of all three genes was induced at the RNA and protein levels in M. smegmatis cultures grown under microaerobic and anaerobic conditions. The M. smegmatis genome also contained the hspX gene, encoding chaperone alpha-crystallin, Acr, that was induced during hypoxia. The similarity in sequences and hypoxia-responsive behaviour of devR-devS, Rv3134c and hspX genes in M. smegmatis and M. tuberculosis suggests that the molecular mechanisms involved in the dormancy response are likely conserved in these two species. M. smegmatis could therefore serve as a useful model for the delineation of the hypoxia response in general and DevR-DevS regulated pathways in particular.

Hematological changes produced in mice by ochratoxin A and citrinin

The effect of 6 weekly injections of ochratoxin A (5 mg/kg) and citrinin (20 mg/kg) on the following hematological indices of mice was studied: erythrocyte sedimentation rate, hematocrit percentage, mean corpuscular values, red cell indices, platelet count, total count of bone marrow cells, differential count of bone marrow cells, total count of splenic cells, spleen weight, and serum calcium. These mycotoxins resulted in a significant decrease in platelet count and hematocrit values. On the other hand, they increased erythrocyte sedimentation rate, mean corpuscular values and red cell indices. Weight of the spleen and the splenic cell count decreased significantly in ochratoxin A and citrinin treated mice. Total count of bone marrow cells, erythrocyte precursors, leucocyte precursors and megakaryocyte precursors of femoral bone marrow decreased significantly in toxin treated mice. Calcium concentration in the serum of toxin treated mice also was decreased significantly.

Hematological changes produced in mice by Nuvacron or Furadan

The effects of multiple intraperitoneal doses of Nuvacron (0.8 mg/kg) or Furadan (0.25 mg/kg) on hematological values in mice were studied. The following were measured: clotting time, hemoglobin content, total count of red blood cells and white blood cells, differential count of white blood cells, platelet count, erythrocyte sedimentation rate, hematocrit value, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration, bone marrow and splenic measurements. These pesticides caused a significant decrease in hemoglobin content, total count of red blood cells, platelet count, erythrocyte sedimentation rate and hematocrit value. The administration of Nuvacron or Furadan prolonged the clotting time and caused an increase in total count of white blood cells. Among white blood cells, there was an increase in neutrophils and basophils and a fall in the count of lymphocytes in treated animals. Bone marrow depression and splenic hyperplasia were observed in mice after administration of the pesticides.