Urinary cholesterol. V. Its excretion in men with testicular and prostatic neoplasms

EGFR/FOXO3A/LXR-α Axis Promotes Prostate Cancer Proliferation and Metastasis and Dual-Targeting LXR-α/EGFR Shows Synthetic Lethality

Prostate cancer is the second leading cause of cancer-related death in men. Early prostate cancer has a high 5-year survival rate. However, the five-year survival rate is low in progressive prostate cancer, which manifests as bone metastasis. The EGF receptor overexpression increases during disease progression and in the development of castration-resistant disease, and may be a potential therapeutic target. Liver X receptors (LXRs) are ligand-dependent nuclear receptor transcription factors and consist of two subtypes, LXR-α and LXR-β, which can inhibit tumor growth in various cancer cells. We revealed that LXR-α, but not LXR-β, was reduced in prostate cancer tissues compared with adjacent normal tissues. LXRs' agonist GW3965 enhanced the inhibitory action of LXR-α on the proliferation and metastasis of prostate cancer cells. Furthermore, our results support the notion that LXR-α is regulated by the EGFR/AKT/FOXO3A pathway. As an EGFR inhibitor, Afatinib could weaken AKT activation and increase the expression level of FOXO3A in prostate cancer. In addition, we indicated that the combination of Afatinib and GW3965 simultaneously increased and activated LXR-α, which led to an increase of tumor suppressors, and eventually inhibited tumor progression. Therefore, the combination of EGFR inhibitor and LXRs agonist may become a potential treatment strategy for prostate cancer, especially metastatic prostate cancer.

Role of squalene synthase in prostate cancer risk and the biological aggressiveness of human prostate cancer

BACKGROUND

We previously conducted a genome-wide linkage analysis of Japanese nuclear families affected with prostate cancer and showed that the susceptibility to prostate cancer was closely linked to D8S550 at 8p23. The role of farnesyl diphosphate farnesyltransferase (FDFT1), which is located under the peak marker D8S550 at 8p23, and squalene synthase, the enzyme encoded by FDFT1, in prostate cancer was studied.

METHODS

The association among common variants of FDFT1 with prostate cancer risk, the promoter activities of FDFT1 with different genotypes and the effects of inhibition of squalene synthase were studied, and the FDFT1 transcript levels of human prostate samples were quantified.

RESULTS

The A allele of rs2645429 was significantly associated with prostate cancer risk in a Japanese familial prostate cancer population. Rs2645429 was located in the promoter region of FDFT1, and the AA genotype showed significantly increased promoter activity. The knockdown of FDFT1 mRNA expression or squalene synthase inhibition led to a significant decrease in prostate cancer cell proliferation. Additionally, human prostate cancer specimens expressed significantly higher levels of FDFT1 mRNA compared with noncancerous specimens. Finally, aggressive cancers showed higher transcript levels.

CONCLUSIONS

FDFT1 and its encoded enzyme, squalene synthase, may play an important role in prostate cancer development and its aggressive phenotypes.

High-density lipoprotein induces proliferation and migration of human prostate androgen-independent cancer cells by an ABCA1-dependent mechanism

Androgen deprivation therapy for prostate cancer leads to a significant increase of high-density lipoprotein (HDL), which is generally viewed as beneficial, particularly for cardiovascular disease, but the effect of HDL on prostate cancer is unknown. In this study, we investigated the effect of HDL on prostate cancer cell proliferation, migration, intracellular cholesterol levels, and the role of cholesterol transporters, namely ABCA1, ABCG1, and SR-BI in these processes. HDL induced cell proliferation and migration of the androgen-independent PC-3 and DU145 cells by a mechanism involving extracellular signal-regulated kinase (ERK) 1/2 and Akt, but had no effect on the androgen-dependent LNCaP cell, which did not express ABCA1 unlike the other cell lines. Treatment with HDL did not significantly alter the cholesterol content of the cell lines. Knockdown of ABCA1 but not ABCG1 or SR-BI by small interfering RNA (siRNA) inhibited HDL-induced cell proliferation, migration, and ERK1/2 and Akt signal transduction in PC-3 cells. Moreover, after treatment of LNCaP cells with charcoal-stripped fetal bovine serum, ABCA1 was induced ∼10-fold, enabling HDL to induce ERK1/2 activation, whereas small interfering RNA knockdown of ABCA1 inhibited HDL-induced ERK1/2 activation. Simvastatin, which inhibited ABCA1 expression in PC-3 and DU145 cells, attenuated HDL-induced PC-3 and DU145 cell proliferation, migration, and ERK1/2 and Akt phosphorylation. In human prostate biopsy samples, ABCA1 mRNA expression was ∼2-fold higher in the androgen deprivation therapy group than in subjects with benign prostatic hyperplasia or pretreatment prostate cancer groups. In summary, these results suggest that HDL by an ABCA1-dependent mechanism can mediate signal transduction, leading to increased proliferation and migration of prostate cancer cells.

Androgenic suppression of ATP-binding cassette transporter A1 expression in LNCaP human prostate cancer cells

Alteration of lipid metabolism is commonly observed in sex hormone-dependent cancer cells, yet its mechanistic involvement in cancer cell proliferation and progression is unclear. We have found that the expression of the cholesterol transporter, ATP-binding cassette transporter A1 (ABCA1), was 15- to 20-fold higher in androgen-dependent than in androgen-independent LNCaP human prostate cancer cells, indicating a possible relationship between the expression levels of ABCA1 and prostate cancer progression. On the basis of real-time quantitative PCR and Western blot analysis, expression of ABCA1 in androgen-dependent cells was inhibited by androgen. The antiandrogen Casodex blocked the effect of androgen, implicating the androgen receptor in regulation of ABCA1 expression by androgens. Using an ABCA1 promoter-reporter gene assay, androgenic suppression was observed at the transcriptional level in androgen-dependent but not in androgen-independent prostate cancer cells. ABCA1 appears to have a role in modulating cell proliferation because knockdown of ABCA1 expression by RNA interference in androgen-dependent cells increased their rate of proliferation. Therefore, a suppressive effect of androgen on ABCA1 expression may be one of the mechanisms by which androgens regulate proliferation in prostate cancer cells. Attenuated ABCA1 expression in androgen-independent cells thus may contribute, in part, to prostate cancer progression.

Urinary cholesterol in cancer screening

Cholesterol determinations in morning urine samples were taken in 235 selected patients with a positive test for microscopic hematuria. Values ranged from 0.2 to 76.0 mg (median 5.5) in 23 patients with urologic malignancies and from 0.1 to 33.4 mg (median 1.1) in 38 patients with various benign diseases of the kidney or urogenital tract. In the 28 patients with urinary tract infections and 146 subjects without evidence of disorders of the kidney and the urogenital system, urinary cholesterol excretion was usually normal (0.1 to 1.9 mg; median 0.35). Using 1.0 mg urinary cholesterol per morning urine as a cutoff point, sensitivity for urologic carcinomas is about 80 per cent with a comparable high specificity of 90 per cent. Therefore, subsequent measurements of urinary cholesterol in populations with microscopic hematuria could define two groups, one with high prevalence and one with low prevalence of urologic malignancies. The less complicated colorimetric instead of gas-liquid chromatographic determination of urinary cholesterol can be recommended as a screening test for urologic carcinomas in populations with microscopic hematuria.

Epoxycholesterols in secretions and tissues of normal, benign, and cancerous human prostate glands

Extracts of prostatic secretions taken from 25 control subjects, twenty-three to seventy-five years of age, were analyzed by gas-liquid chromatography (GLC) for cholesterol and possible epoxycholesterol content. Only subjects fifty-three years or older exhibited any signs of prostatic enlargement. Whereas cholesterol (893 +/- 133 micrograms/ml) was found in all prostatic secretions, the carcinogenic epoxycholesterols (22.6 +/- 3.3 micrograms/ml) were detected only in one third of the specimens examined. Prostatic secretion collected from 29 surgical patients prior to primary (20) and secondary (9) prostatectomies revealed cholesterol contents of 1,182 +/- 148 and 1,134 +/- 157 micrograms/ml, respectively. The epoxycholesterols were essentially present at concentrations of 33.7 +/- 7.9 and 24.0 +/- 10.3 micrograms/ml, respectively. Tissue extracts of the different prostatic lobes taken from 40 surgical BPH patients at the time of primary (26) and secondary (14) prostatectomy were examined by capillary GLC. Of these patients 8 had prostatic carcinoma. The cholesterol content of all tissues was essentially double that of normal prostates. The epoxycholesterols were present in all tissues. The mean cholesterol 5 alpha, 6 alpha-epoxide and cholesterol 5 beta, 6 beta-epoxide contents of all tissue were 120 +/- 23.4 and 9.9 +/- 5.2 micrograms/Gm dry tissue, respectively. There were no apparent differences beteeen the lobes nor between BPH and cancers. No epoxycholesterol could be detected in 8 seminal vesicles obtained at autopsy.

Urinary cholesterol in follow-up of patients with urologic carcinomas or benign prostatic hyperplasia

Urinary cholesterol was determined in follow-up in 2 patients with prostatic adenoma, 3 patients with prostatic carcinoma, 3 patients with carcinoma of bladder, and 4 patients with carcinoma of kidney. All patients revealed marked urinary cholesterol hyperexcretion prior to surgery. Except for 1 patient with prostatic carcinoma, excretion of urinary cholesterol normalized at least six weeks after resection. In 1 remarkable case a localized recurrence of a transurethrally resected bladder tumor was associated with a marked increase of urinary cholesterol excretion six weeks prior to cystoscopy. The results point to a possible future value of this method in monitoring patients with bladder tumors, although additional studies are necessary.

Studies on the clinical significance of nonesterified and total cholesterol in urine

Gas-liquid chromatographic determinations of nonesterified and total urinary cholesterol were performed in 137 normals, 264 patients with various internal diseases without evidence of neoplasias or diseases of the kidney or urinary tract, 497 patients with malignancies and 236 patients with diseases of the kidney, urinary tract infections or prostatic adenoma with residual urine. A normal range (mean +/- 2 SD) of 0.2-2.2 mg/24 hours nonesterified cholesterol (NEC) and of 0.3-3.0 mg/24 hours total cholesterol (TC) was calculated. Values of urinary cholesterol excretion were independent of age and sex and did not correlate with cholesterol levels in plasma. Patients with various internal diseases, without evidence of neoplasias nor diseases of the kidney or obstruction of the urinary tract, showed normal urinary cholesterol excretions, as did patients with infections of the urinary tract. However, elevated urinary cholesterol was found in patients with diseases of the kidney or urinary tract obstruction (prostatic adenoma with residual urine), malignant diseases of the urogenital tract and metastasizing carcinoma of the breast. In patients with other malignant diseases urinary cholesterol was usually normal. Lesions of the urothelial cell membranes are considered to be the most likely cause of urinary cholesterol hyperexcretion. The clinical value of urinary cholesterol determinations as a possible screening test for urogenital carcinomas in unselected populations is limited by lacking specificity, expensive methodology and low prevalence of the mentioned carcinomas, although elevated urinary cholesterol excretions have been observed in early clinical stages of urogenital cancers.

Urinary cholesterol. VIII. Its excretion in women with ovarian neoplasms

The urinary excretion of nonesterified cholesterol (NEC) has been investigated in 57 women with ovarian neoplasms and/or related nonneoplastic diseases. Twelve patients had benign tumors or lesions and 45 had malignant neoplasms of their ovaries. All patients with nonmalignant ovarian tumors or lesions had normal NEC excretion irrespective of the type of tumor or lesion or its degree of extension. In contrast, urinary NEC hyperexcretion occurred with the following frequencies in patients with active malignant ovarian neoplasms: 18 of 19 cystadenocarcinomas of the serous and/or mucinous types; one of one endometrioid carcinoma; four of four malignant granulosa cell tumors; two of two mixed malignant germ cell tumors; and one of one malignant mixed müllerian tumor. Single cases of clear cell carcinoma and of rhabdomyosarcoma had a normal NEC excretion. Urinary hyperexcretion of NEC was also found after surgery in two of seven surviving patients with apparently localized resectable disease according to their staging. It is possible that in these two patients NEC hyperexcretion was due to undetected foci of cancer (wrong staging), since neither omental and peritoneal biopsies, nor cytologic examination of peritoneal washings or free fluid were performed. A normal excretion of urinary NEC has been characteristic of 19 of 21 surviving patients treated by surgery and adjunctive therapy in whom we have performed follow-up NEC determinations. They were 16 of 18 cystadenocarcinomas malignant germ cell tumor. The 94% correlation between the presence of proven active ovarian carcinomas and urinary NEC hyperexcretion is significant. The clinical significance of this investigation is even greater when one considers that cystadenocarcinomas constitute more than 75% of all primary malignant ovarian tumors.

Urinary cholesterol. VII. The significance of the excretion of nonesterified cholesterol in patients with uterine carcinomas

The urinary excretion of nonesterified cholesterol (NEC) in 170 women with cervical and endometrial carcinomas has been investigated. Control patients (236) included: 1) women with other types of (benign and/or malignant diseases of the pelvic organs; 2) patients with non-steroid-related neoplasms; 3) patients with benign and/or malignant breast diseases other than carcinoma; and 4) patients with a variety of non-neoplastic diseases. NEC was determined by a gas-liquid chromatographic procedure. The range of NEC excretion for clinically healthy normal women (64) was previously established by this method. NEC hyperexcretion was defined as any NEC value over 1.5 mg/24 hours. The results showed NEC hyperexcretion in 65 of 68 women with active carcinoma of the cervix, including 13 patients with carcinoma in situ, and in 42 of 45 women with active carcinoma of the endometrium. In contrast, a normal excretion of NEC occurred in all the patients (77) of the first and second control groups, in 39 (80%) of the 48 patients of the third control group (high-risk group), and in 101 of the 111 patients of the fourth control group. Sequential studies performed in patients with uterine carcinomas have demonstrated an almost perfect correlation between the NEC excretion and the clinical status of the patient following surgical and/or radiation therapy. Of 57 patients (31 cervix and 26 endometrium) in which the NEC studies were started after treatment was instituted, 53 have normal NEC excretion in the multiple determination performed to date. Presently these patients have no clinical, chemical, or radiologic evidence of cancer. It is concluded that urinary NEC determination can be used as an additional diagnostic biochemical test to detect active carcinoma of the steroid-producing glands and their main target organs, and that in women with uterine carcinomas, the test can be used as an objective laboratory method to monitor the course of the disease and the response of the patient to therapy.

Comparative evaluation of serum acid phosphatase, urinary cholesterol, and androgens in diagnosis of prostatic cancer

Serum acid phosphatase activity, urinary total cholesterol, and ratio of deoxy to oxy urinary 17-ketosteroids were measured in a group of 42 patients with prostatic carcinoma and in a group of 14 age-matched normal healthy individuals. Our purpose was to evaluate whether or not the simultaneous determinations of these tests would increase the rate of detection obtained by the single assay alone. The results of single assay revealed for the following detection rate: 67 per cent (28 of 42 patients) for serum acid phosphatase, 62 per cent for urinary total cholesterol, and 22 per cent for ratio of 17-ketosteroids. A significant increase of detection rate was observed when simultaneous determinations of two assays were performed; 86 per cent for serum acid phosphatase activity and total urinary cholesterol; 74 per cent for serum acid phosphatase and ratio of 17-ketosteroids; and 74 per cent for total urinary cholesterol and ratio of 17-ketosteroids. A detection rate of 88 per cent (37 of 42 patients) was obtained as all three assays were analyzed, though it was not significantly different from a ratio of 86 per cent for simultaneous assays of acid phosphatase and total cholesterol. It was concluded that simultaneous determinations of serum acid phosphatase activity, urinary total cholesterol, and androgens are of values in diagnosis for patients with prostatic neoplasia.