T. Ming Chu

Prostatic‐specific antigen: An immunohistologic marker for prostatic neoplasms

Antiserum to a human prostate‐specific antigen was raised in a rabbit and utilized by immunoperoxidase staining to evaluate its potential value as a diagnostic histologic marker for tumors of prostatic origin. All primary and metastatic prostatic malignancies reacted positively, whereas nonprostatic neoplasms did not stain with this procedure. This is the first immununohistochemical marker for prostate gland epithelium which does not represent prostatic acid phosphatase.

Treatment of newly diagnosed metastatic prostate cancer patients with chemotherapy agents in combination with hormones versus hormones alone

A prospective trial from July 1976 to September 1980 by the National Prostatic Cancer Project randomized newly diagnosed metastatic prostate cancer patients to DES 1 mg orally three times daily or orchiectomy; or DES, 1 mg, three times daily, plus cyclophosphamide at 1 mg/m2 iv every three weeks, or cyclophosphamide 1 g/m2 iv every three weeks plus estramustine phosphate (Estracyt) at 600 mg/m2 orally daily in three divided doses. There were 246 patients evaluated for response of 301 entered. These consisted of 83 on the DES/orchiectomy arm, 77 on DES plus cyclophosphamide, and 86 on Estracyt plus cyclophosphamide. Objective response rates, initially evaluated at 12 weeks, were similar among the treatments. However, chemotherapy as used in this study early in the diagnosis of metastatic disease appears to exhibit an improved effect on overall survival compared to hormone therapy alone. Analysis within groups having pain versus no pain at entry revealed a marked advantage after 80 weeks for chemotherapy when pain was initially present and a slight advantage during treatment (throughout follow‐up) when the pain was absent. Median survival times were 92, 91, and 94 weeks, respectively, for the three treatments. The progression‐free interval for responders showed no difference between initial treatments, although nearly one half of the patients are still in remission; hence, further follow‐up will be essential. Side effects were not excessive for the chemotherapy treatment arms and patient compliance was good. This national multicenter trial provides the basis for further testing of chemotherapy agents at an earlier phase for patients with newly diagnosed metastatic prostate cancer.

CEA as a monitor of gastrointestinal malignancy

Ninety‐four patients with carcinoma of the colon have been followed with serial determinations of plasma CEA (carcinoembryonic antigen) levels over a 3‐year period using the Hansen assay. Nine hundred twelve CEA determinations have been made in these patients. Plasma CEA levels rose in 90% of the instances of clinical progression documented in these patients. In 30% of patients, this rise indicated progression 6 months or more before it was detected by standard clinical methods. Unfortunately, a few patients never developed elevated CEA levels even though disease clearly progressed. False positive results have also been encountered, with significant elevations occurring in patients who have since remained without evidence of disease for several months. Our data indicate that at least two sequential elevated CEA values, the second being higher, must be a minimal criterion for consideration of possible progression of disease. Even with this standard, we have encountered false positive results in 10% of our patients, indicating recurrence or progression where none has occurred clinically. CEA measurement is of limited usefulness for 30 days after curative surgery, because the elevation of CEA levels due to the original amount of tumor present as well as due to surgery per se may persist for this length of time in a significant number of patients. On the other hand, CEA levels have responded to chemotherapy in close correlation with observed clinical course in those patients with metastatic disease treated in this series. Initial pretherapy CEA values have so far proved to be good prognostic indicators of disease course following complete resection. With an initial CEA value of less than 2.5 ng/ml of plasma, recurrent has been rare (1/20). If the pretreatment CEA was greater than 7.0 ng/ml, it has been the rule (7/9).

The proteolytic activity of human prostate-specific antigen

Human prostate-specific antigen has been found to exhibit a mild activity of protease at neutral pH. This finding is based on two observations: a proteolytic activity was always associated with the antigen fractions during purification, and the proteolytic activity and the antigen were precipitated with specific antibody to the antigen. In comparison with physico-chemical and catalytic properties of known proteases, human prostate-specific antigen is a distinct neutral protease.

A comparison of estramustine phosphate and streptozotocin in patients with advanced prostatic carcinoma who have had extensive irradiation.

AbstractIn this second nationally randomized cooperative chemotherapy trial of the National Prostatic Cancer Project 125 patients with histologically confirmed progressing advanced carcinoma of the prostate (clinical stage D) who had had prior pelvic irradiation of at least 2,000R received as initial therapy 1 of 2 non-myelosuppressive agents—estramustine phosphate or streptozotocin—for comparison with patients randomized to receive standard treatment. Patients whose disease was progressive after 12 weeks on chemotherapy were crossed over to receive the alternate therapeutic agent. Response to treatment was evaluated in 105 patients on the basis of previously established and defined criteria.All known prognostic factors were comparable among the 3 treatment arms. The objective response rates to therapy were 19 per cent in the standard arm (stable only), 30 per cent in the estramustine phosphate arm (stable and partial regression) and 32 per cent in the streptozotocin arm (stable arm). Thus far, 4 patients...

Comparison of Estramustine Phosphate and Vincristine Alone or in Combination for Patients with Advanced, Hormone Refractory, Previously Irradiated Carcinoma of the Prostate

There were 121 men with hormonally refractory metastatic cancer of the prostate who were randomized to receive estramustine phosphate or vincristine, or the combination of these 2 agents. All patients had received prior radiation therapy (greater than 2,000 rad). There were 90 patients who could be compared for response. The objective response rates (partial regression or stabilization of disease) for the 3 treatment groups were 26 per cent for estramustine phosphate, 24 per cent for estramustine phosphate plus vincristine and 15 per cent for vincristine. Subjective parameters varied little among the 3 regimens. The median duration of response for those responding to estramustine phosphate was similar (20 weeks) to that for vincristine (22 weeks) and greater than that for the combination (13 weeks). The probability of survival did not differ significantly for patients randomized to each of the 3 regimens. The addition of vincristine to estramustine phosphate did not enhance the response rate achieved by estramustine phosphate alone and vincristine alone produced the lowest response rate. Estramustine phosphate continues to be the most active agent in previously irradiated patients with hormonally refractory metastatic cancer of the prostate.

Expression of prostatic acid phosphatase in human prostate cancer.

By a specific immunochemical measurement, the activity of prostatic acid phosphatase (PAP) in prostate cancer was found to be about 25%, on average, based on micrograms DNA or per cell, of that in normal prostate or benign prostatic hypertrophy (BPH). The reduction of PAP in prostate cancer was further revealed by a decrease in PAP protein. The 125I-labeled anti-PAP IgG specifically bound to nascent peptides on PAP-synthesizing polysomes showed no qualitative differences among cancerous prostate, normal prostate and BPH. However, the quantitative binding of 125I-labeled anti-PAP IgG to polysomes of cancerous prostate was half that of normal prostate of BPH. These data suggest that a significant amount of PAP and its synthesizing polysomes was reduced in prostate cancer as a result of PAP gene suppression.

Immunoaffinity isolation of ductal carcinoma antigen using monoclonal antibody F36/22

Monoclonal antibody (McAb) F36/22, raised against a human breast tumor line, identifies an antigen found in the circulation of cancer patients. Antigen was purified from malignant effusions using McAb-affinity chromatography followed by adsorption-desorption from immobilized wheat germ lectin. Electrophoretic analysis demonstrated the isolation of a single high mol. wt glycoprotein exhibiting an isoionic point near pH 4.2 and a density of approx. 1.45 g/ml. Although highly reactive with wheat germ lectin, a negligible or weak interaction was observed with concanavalin A, lentil and peanut agglutinin. The antigen was immune-precipitable, indicating the occurrence of multiple McAb-binding sites, and was resistant to heat and acid treatments. Antigenicity was not perturbed following protease or neuraminidase treatments, but was affected upon exposure to alkaline conditions. Taken together, these data suggest that McAb F36/22 recognizes a high mol. wt component occurring in circulation as a mucin-like glycoprotein.

IMMUNOCHEMICAL CHARACTERIZATION OF PROSTATIC ACID PHOSPHATASE WITH MONOCLONAL ANTIBODIES

Hybridoma-derived monoclonal antibodies to human PAP have been produced by fusion of mouse myeloma cells [P3 x 63 Ag 8.653] with spleen cells from mice immunized with purified PAP. One hundred fifty-six out of 252 clones were found to produce antibodies against PAP. These monoclonal antibodies were classified into four different subclasses as IgM [3 clones], IgG2a [2 clones], IgG3 [1 clone], and IgG1 (150 clones] with k-chains. Four monoclonal antibodies, IgG1, IgG2 a, IgG3, and IgM, were selected from the 156 hybridoma clones for immunologic characterization. Results from a binding assay suggested that monoclonal anti-PAP antibodies IgG1 and IgM recognized two distinct antigenic determinants of the PAP molecule, while the hybridoma IgG2a and IgG3 antibodies recognized another antigenic determinant. The specificity of these four hybridoma anti-PAP antibodies has been evaluated by the immunohistochemical method and competitive-binding assay. Monoclonal antibodies IgG2a and IgG3 as well as polyclonal xenoantibodies were found to react with PAP as well as with nonprostatic acid phosphatases; and antibodies IgG1 and IgM reacted more specifically with PAP. These results indicated that monoclonal anti-PAP antibodies IgG1 and IgM possessed a higher specificity for human PAP in comparison with monoclonal antibodies IgG2a, IgG3, and xenoantibodies. The monoclonal anti-PAP IgG1 and IgM antibodies may be useful in delineating antigenic structure of the PAP molecule, as well as in the refinement of serologic determination and immunocytochemical study of PAP in human prostate cancer.

Prostate-Specific Antigenic Domain of Human Prostate Specific Antigen Identified with Monoclonal Antibodies

With the use of five murine monoclonal antibodies (1A5, 2A4, 3F1, F5 and 3A12) and an antigen-affinity purified goat polyclonal IgG antibody, the presence of a prostate-specific antigenic domain in human prostate-specific antigen molecule was identified. The results were based upon a series of quantitative competitive inhibition assays of each 125I-labeled monoclonal antibody and polyclonal antibody binding to prostate-specific antigen by unlabeled monoclonal antibodies as inhibitors, and immunohistochemical examination of an extensive panel of human tissue specimens. A cluster of two epitopes that are spatially related or in close topographical proximity and represent a prostate-specific antigenic domain are defined by the monoclonal antibodies 1A5, 2A4, 3F1, and F5, 3A12, respectively.