Does PSA Promote Prostate Cancer?
By William Faloon
|LE Magazine Special Edition, Winter 2005/2006|
Does PSA Promote Prostate Cancer?by William Faloon
Reviewed and critiqued by Stephen B. Strum, MD, FACP
The acronym PSA stands for prostate-specific antigen, the most abundant protein synthesized in the prostate gland. Men have their blood tested for PSA in order to detect prostate cancer at an early stage when it is often curable. The PSA test can also help assess the efficacy of various prostate cancer treatments.
Until now, PSA has been viewed only as a blood indicator of prostate cancer, infection, or inflammation. Emerging evidence, however, reveals that PSA may be more than just a marker of prostate health. It appears that PSA itself may play a role in the progression and metastasis of prostate cancer,1-3 thus opening up new therapeutic pathways for preventing and treating this epidemic disease.
A significant amount of published data associates high intake of certain nutrients with reduced incidences of prostate cancer.4-12 A few studies suggest that these same nutrients may even help control advanced stages of the disease.13,14
Scientists are now finding that some of these nutrients function to reduce or interfere with PSA activity in the prostate gland. With new data suggesting that PSA itself may be involved in the progression and spread of prostate cancer, the anti-PSA activity of these nutrients becomes significant and helps explain why men who consume certain nutrients have lower incidences and a slower progression of disease when prostate cancer has been diagnosed.
Staggering Statistics on Prostate Cancer
Cells in the prostate gland are very prone to gene mutation, while other tissues in the same anatomical region, such as the seminal vesicles, develop primary cancers at a significantly lower rate.15
Autopsy evidence indicates that prostate cancer is histologically evident in up to 34% of men aged 40-49 and up to 70% of men aged 80 and older.16,17 Most men, however, never progress to clinically diagnosed disease, indicating the presence of control mechanisms that keep prostate cancer cell colonies small and thus controlled.
It now appears possible to partially regulate some of the genes that ordinarily enable cells to divide out of control and eventually form a prostate tumor, which may then proliferate, invade, and metastasize. These new findings make it more important than ever for men to monitor their blood PSA levels to detect prostate cancer at its earliest stages.
Hidden Dangers of PSA
Because PSA may contribute not only to prostate cancer progression but also to the ability of these cells to escape the prostate and metastasize to distant sites within the body, we can no longer think of PSA as merely a blood marker reflecting prostate health.
In fact, many, if not all, of the biomarkers used in tracking a wide array of cancers may have specific cancer-facilitating properties. Therefore, in men with prostate cancer, and perhaps even in those trying to prevent the emergence of prostate cancer, taking steps to keep PSA levels low may reduce one’s risk of developing this illness or having it progress to a clinically symptomatic condition.
The easiest way to reduce PSA levels by half is to inhibit the enzyme 5-alpha reductase, which transforms testosterone into the more androgenic dihydrotestosterone (DHT). DHT has a growth-promoting effect on prostate cells that is 2.4 to 10 times greater than that of testosterone.18-20
The most effective DHT-lowering prescription drug is Avodart®. Unlike the more popular Proscar® that inhibits only type 2 5-alpha reductase, Avodart® blocks both type 1 and type 2 5-alpha reductase, thus reducing blood DHT levels by 93%. Using a 5-mg dose of Avodart®—10 times that routinely prescribed for benign prostatic hyperplasia (BPH)—Andriole and colleagues demonstrated a 97% reduction of intra-prostatic DHT.21 Lazier and colleagues found that Avodart® inhibited DHT-induced secretion of PSA as well as cancer cell proliferation, and that at higher doses, Avodart® resulted in cancer cell death in both androgen-dependent (LNCaP) and androgen-independent (PC-3) cell lines.22
Such findings are pertinent to human clinical trials of Avodart®. In a study of 4,325 men with benign prostate enlargement who were randomly selected to receive either Avodart® (0.5 mg/day) or placebo, those receiving Avodart® had a cumulative incidence of prostate cancer of 1.2% compared to 2.5% for the placebo group at 27 months of follow-up. This equates with a 52% reduction in prostate cancer in the Avodart® group.23 In another study using Proscar®, 18,882 men aged 55 or older (with normal digital rectal examination results and a PSA level of 3.0 ng/ml or lower) were randomly assigned treatment with Proscar® (5 mg/day) or placebo for seven years. Prostate cancer was detected in 803 of the 4,368 men in the Proscar® group and 1,147 of the 4,692 men in the placebo group, for a 24.8% reduction in prevalence over seven years. High-grade cancers were noted in 6.4% of Proscar®-treated patients compared to 5.1% of men receiving placebo.24 (As noted earlier, Proscar® suppresses only type 2 5-alpha reductase, whereas Avodart® blocks both type 1 and type 2 5-alpha reductase. Avodart® thus appears to be the better drug.)
Aging men should consider having their blood tested for DHT. If DHT levels are elevated, Avodart® drug therapy appears to be safe and effective not only for improving urinary flow symptoms, but more importantly, for potentially reducing prostate cancer risk. Avodart® appears to accomplish these effects by reducing the growth-promoting effects of DHT on pros-tatic tissue, while decreasing the cancer-inducing properties of PSA by reducing PSA synthesis in the prostate gland.
Avodart® does have several downsides. At more than $3 per capsule, it is expensive. Moreover, a small percentage of men who use it have sexual dysfunction problems such as decreased libido (4%), impotence (7%), and a decreased volume of ejaculate (2%). The frequency of these side effects reportedly decline after six months of continued use of Avodart®.
Blocking PSA’s Detrimental Effects Naturally
There may be another way to protect the prostate gland against its own PSA. Since consuming green tea has been reported to lower the risk of prostate cancer, scientists investigated the effects of the green tea flavonoid epigallocatechin gallate (EGCG) on the expression and activity of PSA by prostate cancer cells. In addition to restraining PSA expression, EGCG inhibited numerous cancer-promoting properties of PSA in a dose-dependent manner. EGCG inhibited tumor-promoting activities such as degradation of type IV collagen. EGCG’s beneficial effects were at blood levels close to those measured in serum following ingestion of green tea.25 The study authors proposed that green tea extract may be a natural inhibitor of prostate carcinoma aggressiveness.
Effects of Soy on PSA Levels
Another potential way to lower PSA levels is to increase soy consumption. It has long been known that human populations that consume soy products have a lower risk of prostate cancer.9,26
Scientists have evaluated soy’s effects on PSA and other prostate cancer-related blood markers in men who had already developed prostate cancer.27 A group of 29 men scheduled to undergo surgical removal of the prostate were put on a 50-gram soy bread supplement or a 50-gram wheat supplement. The soy group saw a 12.7% reduction in PSA levels, whereas the wheat group experienced a 40% increase in cancer-promoting PSA. The free/total PSA ratio increased by 27.4% in the soy-supplemented group, compared to a decrease of 15.6% in the wheat group. (A higher free/total PSA ratio is a favorable indicator.) The investigators concluded that men who consume diets high in soy might have a reduced risk of prostate cancer development and progression. 27
Treating Advanced Prostate Cancer with Lycopene
Cancer confined to the prostate gland is usually curable.28-33 The medical literature indicates, however, that untreated prostate cancer leads to continued growth of the tumor cell population. This greater tumor burden is associated with genetic mutation that is likely responsible for the development of hormone-insensitive prostate cancer.34-37 Once prostate cells mutate into aggressive hormone-refractory forms that escape into the body, metastatic prostate cancer usually is diagnosed and the patient faces a grueling battle to survive.
In a study of 20 patients with metastatic hormone-refractory pros-tate cancer, each patient received 10 mg a day of lycopene for three months.14 No other treatment was given. One patient achieved a complete response, defined as a reduction of PSA (to under 4 ng/ml) and the absence of any sign of the disease for eight weeks. Six patients (30%) had a partial response, defined as a 50% reduction in PSA and alleviation of other symptoms such as bone pain if present. The disease remained stable in 10 patients (50%) and progressed in three (15%). A remarkable 63% (10 of 16) with bone pain were able to reduce their daily use of pain-suppressing drugs. The study concluded:
“Lycopene therapy appears to be effective and safe in the treatment of hormone-refractory prostate cancer.” 14
In another study of 54 metastatic prostate cancer patients, half (27) were castrated, while the other half were castrated and given 2 mg of lycopene twice daily.13 Castration (removal of the testes) reduces testosterone levels and is a treatment for those with androgen-dependent prostate cancer. After six months, PSA declined significantly in both groups, but more so in the group receiving lycopene. After two years, 40% of the castrated group had a PSA reduction of less than
4 ng/ml, compared to 78% in the lycopene group. Bone scans showed that twice as many patients in the lycopene-plus-castration group at- tained a complete response compared to the castration-only men.13
The author concluded, “Adding lycopene to orchidectomy (castration) produced a more reliable and consistent decrease in serum PSA level; it not only shrinks the primary tumor but also diminishes the secondary tumors, providing better relief from bone pain and lower urinary tract symptoms, and improving survival compared with orchidectomy alone.” What is impressive about these two studies is that only small doses of lycopene (4-10 mg/day) were used. That low doses of lycopene produced such favorable results in these late-stage prostate cancer patients is quite remarkable and worthy of further study.