Clinical, genetic and functional characteristics of three novel CYP17A1 mutations causing combined 17alpha-hydroxylase/17,20-lyase deficiency

Phenotypic Heterogeneity and Fertility Potential of Patients With 17-Hydroxylase/17,20-lyase Deficiency

CONTEXT

17α-Hydroxylase/17,20-lyase deficiency (17OHD) is caused by a human CYP17A1 gene mutation and has the classical phenotype of hypertension, hypokalemia, sexual infantilism, and primary amenorrhea in females (46,XX) and disorders of sexual development in males (46,XY). To date, few cases of 17OHD have been reported, and the likelihood of pregnancy has rarely been explored.

OBJECTIVE

To study the clinical characteristics, phenotype heterogeneity, genotyping, and the likelihood of pregnancy of patients with 17OHD.

DESIGN

Genotype analysis was performed by direct sequencing of the CYP17A1 gene and next-generation sequencing in nonclassical patients. In vitro enzyme activity assays and 3-dimensional structure observations were used to assess the function of 3 missense mutations of the CYP17A1 gene. Progestin-primed ovarian stimulation (PPOS) was chosen for ovulation induction in 2 patients.

RESULTS

Eight mutations were identified from 13 patients, including the homozygous mutations p. N395D and p. R496C and compound heterozygous mutations p. Y329fs/p. A421A and p. I332T/p. D487_F489del in 4 nonclassical patients. For the 3 missense mutations, an in vitro functional study showed mild impairment of 17α-hydroxylase activities 15.3-25.0% but residual 17,20-lyase activities 6.6%-9.4%. Two 46,XX females succeeded in pregnancy and delivery by combined PPOS, in vitro fertilization embryo transfer (IVF-ET), and the use of low-dose glucocorticoids.

CONCLUSIONS

Partial 17OHD present nonclassical clinical features, without hypertension and hypokalemia. Successful pregnancy in such 46,XX patients could be attained by the appropriate choice of ovulation induction regimen, precise dose of glucocorticoid to reduce progesterone levels, and the use of IVF-ET.

Insights into Interactions of Human Cytochrome P450 17A1: Review

Abstract:

Cytochrome P450s are a widespread and vast superfamily of hemeprotein monooxygenases that metabolize physiologically essential chemicals necessary for most species' survival, from protists to plants to humans. They catalyze the synthesis of steroid hormones, cholesterol, bile acids, and arachidonate metabolites and the degradation of endogenous compounds such as steroids, fatty acids, and other catabolizing compounds as an energy source and detoxifying xenobiotics such as drugs, procarcinogens, and carcinogens. The human CYP17A1 is one of the cytochrome P450 genes located at the 10q chromosome. The gene expression occurs in the adrenals and gonads, with minor amounts in the brain, placenta, and heart. This P450c17 cytochrome gene is a critical steroidogenesis regulator which performs two distinct activities: 17 alpha-hydroxylase activity (converting pregnenolone to 17-hydroxypregnenolone and progesterone to 17-hydroxyprogesterone, these precursors are further processed to provide glucocorticoids and sex hormones) and 17, 20-lyase activity (which converts 17-hydroxypregnenolone to DHEA). Dozens of mutations within CYP17A1 are found to cause 17-alpha-hydroxylase and 17, 20-lyase deficiency. This condition affects the function of certain hormone-producing glands, resulting in high blood pressure levels (hypertension), abnormal sexual development, and other deficiency diseases. This review highlights the changes in CYP17A1 associated with gene-gene interaction, drug-gene interaction, chemical-gene interaction, and its biochemical reactions; they have some insights to correlate with the fascinating functional characteristics of this human steroidogenic gene. The findings of our theoretical results will be helpful to further the design of specific inhibitors of CYP17A1.

17α-hydroxylase/17,20-lyase deficiency in 46, XY: our experience and review of literature

Context

There are more than 100 pathogenic variants in CYP17A1 that have been identified in patients with 17α-hydroxylase/17,20-lyase deficiency (17OHD).

Objective

We aimed to describe 46,XY patients with 17OHD from our center and review the literature.

Methods

We retrospectively analyzed genetically proven index cases of 17OHD from our 46,XY disorders of sex development cohort and reviewed similar cases from the literature (n = 150). Based on the phenotype, 17OHD probands were classified into combined severe deficiency (n = 128) and combined partial deficiency (n = 16). Additionally, patients with the apparent isolated 17,20-lyase deficiency (n = 7, from 6 families) were noted. Residual enzyme activities with the observed mutant enzymes were divided in 2 categories as < 1% and ≥ 1%, each for hydroxylase and lyase.

Results

We present 4 index cases of 46,XY 17OHD with a complete spectrum of undervirilization and 2 novel variants in CYP17A1. In the review, the combined severe deficiency was the most common form, with more frequent female sex of rearing, hypertension, hypokalemia, suppressed renin, higher plasma corticotropin, lower serum cortisol, and androgens. Immunoassay-measured serum aldosterone was frequently (68.2%) unsuppressed (>5 ng/dL). Elevated serum progesterone had high sensitivity for diagnosis of combined 17OHD, even in combined partial deficiency (83.3%). Among patients with clinical phenotype of combined severe deficiency, 11.5% had partial 17α-hydroxylase and complete 17,20-lyase deficiency (>1%/<1%) and had significantly higher serum cortisol than those with < 1%/<1% activity.

Conclusion

We report the first monocentric case series of Asian Indian 46,XY patients with 17OHD. We propose that a phenotype of severe undervirilization with milder cortisol deficiency may represent a distinct subtype of combined severe 17OHD with residual 17α-hydroxylase activity but severe 17,20-lyase deficiency (>1%/<1%), which needs further validation.

Reproductive endocrine characteristics and in vitro fertilization treatment of female patients with partial 17α-hydroxylase deficiency: Two pedigree investigations and a literature review

BACKGROUND

17α-hydroxylase/17, 20-lyase deficiency (17-OHD) is caused by the mutations of the CYP17A1 gene. The classical phenotype of 17-OHD includes hypertension, hypokalemia, and abnormal sexual development, with partial 17-OHD typically less severe than the complete deficiency. Infertility is always one of the main clinical manifestations of partial 17-OHD. However, to date, the pregnancy potentials of partial 17-OHD female patients have rarely been investigated, and few live-birth cases have been reported among them. Moreover, the reproductive endocrine characteristics of partial 17-OHD female patients have not been completely clarified and the treatment skills of in vitro fertilization and embryo transfer (IVF-ET) have not been well summarized yet.

METHODS

Two Chinese infertile female patients clinically diagnosed as partial 17-OHD were enrolled and their pedigree investigations were performed. Hormones were determined to depict the endocrine conditions of partial 17-OHD female patients. The adrenocorticotropic hormone (ACTH) stimulation test was performed to evaluate the functions of the adrenal cortex. Genotype analysis was conducted by next-generation sequencing (NGS) and Sanger sequencing was used to verify the results. IVF-ET was performed for the treatment of their infertility. Specifically, the progestin-primed ovarian stimulation (PPOS) protocol was chosen for the controlled ovarian hyperstimulation (COH) cycles, and the hormone replacement treatment (HRT) protocol was adopted for the endometrial preparation in frozen-thawed embryo transfer (FET) cycles.

RESULTS

Hormone assays revealed a reduced estradiol (E2) and testosterone (T) level, and an elevated progesterone (P4) level. The classic ACTH stimulating test evidenced a suboptimal response of cortisol to ACTH. Genotype analysis demonstrated that the proband1 carried two variants: c.1459_1467del (p.Asp487_Phe489del)^het and c.995T>C (p.lle332Thr)^het. The proband2 was found to be a homozygote with the mutation of c.1358T>A (p.Phe453Ser)^hom. The two female patients both succeeded in pregnancy and delivery of healthy babies through IVF-ET, with the usage of PPOS, HRT, and low-dose glucocorticoids.

CONCLUSIONS

Partial 17-OHD female patients manifested menstrual cycle disorders and infertility clinically; displayed high P4 and low E2 and T; showed sparse pubic hair in physical examinations; and revealed multiple ovarian cysts in ultrasonic visualization. Moreover, the pregnancy potentials of infertile partial 17-OHD women seemed to increase with the adoption of IVF-ET. Considering the sustained elevated P4 level, PPOS is a feasible protocol for them in COH.

A rare enzymatic defect, true isolated 17,20-lyase deficiency leading to endocrine disorders and infertility: case report

The cytochrome P450 17A1 catalyzes the formation of 17-hydroxysteroids and 17-ketosteroid. Most defects in CYP17A1 impair both enzymatic activities and cause a combined 17α-hydroxylase/17,20-lyase deficiency, which impairs hormone production (cortisol and sex steroids), sexual development, and puberty. Isolated 17,20-lyase deficiency is usually defined by evidently normal activity of 17α-hydroxylase with a dramatic decline of 17,20-lyase activity or complete inactivity. The changes in enzyme activity lead to a lack in the production of sex steroids with normal levels of glucocorticoid and mineralocorticoid hormones. A 24-years-old married woman, as a product of a consanguineous marriage, presented with infertility and a background marked by primary amenorrhea. Laboratory data showed low normal serum cortisol levels and low levels of 17-hydroxyprogesterone. Also, her adrenal androgens were low but estradiol was normal. The chromosomal investigation uncovered a male karyotype of 46, XY. These clinical and laboratory evidence confirm the determination of an isolated 17,20-lyase deficiency in a genotypic male.

Comparisons of Prostate Cancer Inhibitors Abiraterone and TOK-001 Binding with CYP17A1 through Molecular Dynamics

Cytochrome P450 17A1 (CYP17A1) is associated in the steroid hormone biosynthesis in human. As cell proliferation of prostate cancer in response to androgen steroid, an inhibition of CYP17A1 becomes an alternative approach to inhibit biosynthesis of androgen and support treatment of prostate cancer. However, biology-driven inhibitor development of prostate cancer is poorly elucidated. The aims of this study are to address structural differences at atomic-level between CYP17A1 and inhibitors i.e., abiraterone and TOK-001, and further investigate the effect of point mutation of CYP17A1 on the active site stability and the local interactions that are hydrophobic interaction and hydrogen bonding throughout molecular dynamics (MD) simulation. After performing multiple comparisons among four different complexes across CYP17A1 and inhibitors, interestingly TOK-001 oriented toward the active pocket and formed larger volume with I-helix of CYP17A1 than abiraterone, whereas abiraterone showed tighter binding and more active site stability. Considering on the effect of hydrophobic interaction and hydrogen bonding between abiraterone and CYP17A1, the key residues of Phe114, Ile371, Val482, and Asn202 were identified. This contributes into tight binding interactions; however abiraterone is effectively weakened along with the global conformation mobility increased in A105L mutation. Surprisingly, overall conformation of the CYP17A1 remained stable when bound to TOK-001. This basic knowledge can guide future experiments on design of efficient inhibitors for CYP17A1, which provides theoretical basis of androgen-dependent disease therapy.

A review of the literature on common CYP17A1 mutations in adults with 17-hydroxylase/17,20-lyase deficiency, a case series of such mutations among Koreans and functional characteristics of a novel mutation

OBJECTIVE

17α-hydroxylase/17,20-lyase deficiency is a rare form of congenital adrenal hyperplasia, characterized by hypertension and sexual infantilism and caused by loss-of-function mutations in CYP17A1. This study investigated the clinical and molecular characteristics of six adults with 17α-hydroxylase/17,20-lyase deficiency and the functional consequences of a novel CYP17A1 mutation.

MATERIALS AND METHODS

Six phenotypic females, three with 46,XY and three with 46,XX karyotypes, presented with primary amenorrhea and hypertension. All had elevated levels of plasma adrenocorticotropic hormone, serum gonadotropin, progesterone, and 11-deoxycorticosterone, and reduced testosterone and dehydroepiandrosterone sulfate (DHEA-S). All coding exons and flanking intronic sequences of CYP17A1 were directly sequenced using genomic DNA. Wild-type and mutant CYP17A1 cDNAs were inserted into the pcDNA3.1/V5-His-P450c17 vector, and transiently expressed in COS-7 cells. This was followed by an assessment of 17α-hydroxylase and 17,20-lyase activities by measuring the conversions of progesterone to 17-hydroxyprogesterone and 17-hydroxypregnenolone to DHEA.

RESULTS

The mutation analysis identified one patient with compound heterozygosity for p.H373L and p.W406L, one with compound heterozygosity for p.H373L and p.A174E, three with compound heterozygosity for p.Y329fs and p.H373L, and one with homozygosity for p.H373L. An in vitro functional analysis of the novel p.W406L mutation revealed a complete loss of 17α-hydroxylase/17, 20-lyase activities.

CONCLUSIONS

p.H373L was the most common mutation among these Korean patients, consistent with the high allele frequency of p.H373L in Chinese and Japanese populations, suggesting possible founder effects in Asian countries. The novel p.W406L mutation caused a complete loss of both catalytic activities, indicating that this amino acid is critical for P450c17 function.

Primary amenorrhea in two sisters: description of a Mexican family with 17α hydroxylase-17 lyase deficiency caused by arginine - stop mutation

A rare cause of congental adrenal hyperplasia is 17α-hydroxylase deficiency. It results in sexual infantilism, primary amenorrhea in females, pseudohermaphroditism in males, hypertension, and hypokalemia. We studied two female siblings from a rural community in Mexico. The cause of consultation was primary amenorrhea. The proband had low levels of estrogen, progesterone and cortisol. Deoxycorticosterone and corticosterone levels were elevated. The proband was homozygous for a transversion of cytosine to thymine at exon 4 (CGA→TGA), causing a premature stop codon at position 239 (R239X). Analysis of family members showed the presence of this heterozygous mutation in the mother, father and one healthy sibling. In summary, we describe a Mexican family with 17α-hydroxylase deficiency due to R239X mutation.

Structures of cytochrome P450 17A1 with prostate cancer drugs abiraterone and TOK-001

Cytochrome P450 17A1 (P450c17) catalyzes the biosynthesis of androgens in humans¹. Since prostate cancer cells proliferate in response to androgen steroids^2,3, CYP17A1 inhibition is a new strategy to prevent androgen synthesis and treat lethal metastatic castration-resistant prostate cancer⁴, but drug development has been hampered by the lack of a CYP17A1 structure. Here we report the only known structures of CYP17A1, which contain either abiraterone, a first-in-class steroidal inhibitor recently approved by the FDA for late-stage prostate cancer⁵, or TOK-001, another inhibitor in clinical trials^4,6. Both bind the heme iron forming a 60° angle above the heme plane, packing against the central I helix with the 3β-OH interacting with N202 in the F helix. Importantly, this binding mode differs substantially from those predicted by homology models or from steroids in other cytochrome P450 enzymes with known structures, with some features more similar to steroid receptors. While the overall CYP17A1 structure provides a rationale for understanding many mutations found in patients with steroidogenic diseases, the active site reveals multiple steric and hydrogen bonding features that will facilitate better understanding of the enzyme’s dual hydroxylase and lyase catalytic capabilities and assist in rational drug design. Specifically, structure-based design is expected to aid development of inhibitors that bind only CYP17A1 and solely inhibit its androgen-generating lyase activity to improve treatment of prostate and other hormone-responsive cancers.

Three novel CYP17A1 gene mutations (A82D, R125X, and C442R) found in combined 17α-hydroxylase/17,20-lyase deficiency

The aim of this study was to analyze the structure and functional consequences of 3 novel mutations (A82D, R125X, and C442R) of the CYP17A1 gene found in 2 patients with combined 17α-hydroxylase/17,20-lyase deficiency (17OHD). Two Chinese 46, XY female patients were diagnosed with 17OHD based on clinical findings and biochemical results. The CYP17A1 gene was analyzed by polymerase chain reaction direct sequencing. An in vitro expression system was performed in HEK293 cells to analyze the mutant P450c17 activity compared with the wild type. Analysis of the CYP17A1 gene sequences in patient 1 showed compound heterozygous mutations A82D (g.417 C > A) in exon 1 and Y329fs (g.4869 T > A, 4871del) in exon 6; DNA sequencing analysis in patient 2 revealed compound heterozygous mutations R125X (g.2045 C > T) in exon 2 and C442R (g.6457 T > C) in exon 8. The mutations A82D, R125X, and C442R have not been reported previously. The functional study demonstrated that the A82D, R125X, and C442R mutations almost completely eliminate enzymatic activity. These results, which indicate that Ala 82 and Cys 442 are crucial for both 17-hydroxylase and 17,20-lyase activities, help define the structure-function relationship of the CYP17A1 gene. The novel mutations A82D, R125X, and C442R further clarify the patients' clinical manifestations of combined 17OHD.

Six new cases confirm the clinical molecular profile of complete combined 17α-hydroxylase/ 17,20-lyase deficiency in Brazil

In 2004, Costa-Santos and cols. reported 24 patients from 19 Brazilian families with 17α-hydroxylase deficiency and showed that p.W406R and p.R362C corresponded to 50% and 32% of CYP17A1 mutant alleles, respectively. The present report describes clinical and molecular data of six patients from three inbred Brazilian families with 17α-hydroxlyse deficiency. All patients had hypogonadism, amenorrhea and hypertension at diagnosis. Two sisters were found to be 46,XY with both gonads palpable in the inguinal region. All patients presented hypergonadotrophic hypogonadism, with high levels of ACTH (> 104 ng/mL), suppressed plasmatic renin activity, low levels of potassium (< 2.8 mEq/L) and elevated progesterone levels (> 4.4 ng/mL). Three of them, including two sisters, were homozygous for p.W406R mutation and the other three (two sisters and one cousin) were homozygous for p.R362C. The finding of p.W406R and p.R362C in the CYP17A1 gene here reported in additional families, confirms them as the most frequent mutations causing complete combined 17α-hydroxylase/17,20-lyase deficiency in Brazilian patients.

Five novel mutations of SRD5A2 found in eight Chinese patients with 46,XY disorders of sex development

Individuals with male karyotype (46,XY) affected by 5α-reductase type 2 deficiency, a rare autosomal recessive inherited disorder, can have an almost female phenotype or partially virilized external genitalia. Mutations in the steroid-5-α-reductase (SRD5A2) gene, leading to functional impairment of 5α-reductase type 2, are responsible for this disorder. Our present study analyzed SRD5A2 gene mutations in eight unrelated 46,XY Chinese patients with disorders of sex development. Direct sequencing of genomic DNA for SRD5A2 gene revealed the presence of one homozygous (p.Q6X) and seven compound heterozygous mutations (p.G203S/R227Q, p.L20P/R227Q, p.Q6X/p.A228V, p.C222Ffs232X/p.R246Q, p.W140X/F219Sfs278X, p.Q71X/L185Tfs192X and p.Q6X/p.N193S) in our patients. Among them, p.C222Ffs232X, p.A228V, p.Q71X, L185Tfs192X and p.W140X mutations have not been previously reported. These novel mutations may provide us new insights into the molecular mechanism of 5α-reductase type 2 deficiency. Seven out of eight patients had at least one variant in exon 4, and 8 of 12 (66.7%) mutations were located in exon 4. The expanded mutation database of the SRD5A2 gene should benefit patients in the diagnosis and treatment of this disease.