Folate hydrolase-1 (FOLH1) is a novel target for antibody-based brachytherapy in Merkel cell carcinoma

Backgrounds

Folate Hydrolase‐1 (FOLH1; PSMA) is a type II transmembrane protein, luminally expressed by solid tumour neo‐vasculature. Monoclonal antibody (mAb), J591, is a vehicle for mAb‐based brachytherapy in FOLH1+ cancers. Brachytherapy is a form of radiotherapy that involves placing a radioactive material a short distance from the target tissue (e.g., on the skin or internally); brachytherapy is commonly accomplished with the use of catheters, needles, metal seeds and antibody or small peptide conjugates. Herein, FOLH1 expression in primary (p) and metastatic (m) Merkel cell carcinoma (MCC) is characterized to determine its targeting potential for J591‐brachytherapy.

Materials & Methods

Paraffin sections from pMCC and mMCC were evaluated by immunohistochemistry for FOLH1. Monte Carlo simulation was performed using the physical properties of conjugated radioisotope lutetium‐177. Kaplan–Meier survival curves were calculated based on patient outcome data and FOLH1 expression.

Results

Eighty‐one MCC tumours were evaluated. 67% (54/81) of all cases, 77% (24/31) pMCC and 60% (30/50) mMCC tumours were FOLH1+. Monte Carlo simulation showed highly localized ionizing tracks of electrons emitted from the targeted neo‐vessel. 42% (34/81) of patients with FOLH1+/− MCC had available survival data for analysis. No significant differences in our limited data set were detected based on FOLH1 status (p = 0.4718; p = 0.6470), staining intensity score (p = 0.6966; p = 0.9841) or by grouping staining intensity scores (− and + vs. ++, +++, +++) (p = 0.8022; p = 0.8496) for MCC‐specific survival or recurrence free survival, respectively.

Conclusions

We report the first evidence of prevalent FOLH1 expression within MCC‐associated neo‐vessels, in 60‐77% of patients in a large MCC cohort. Given this data, and the need for alternatives to immune therapies it is appropriate to explore the safety and efficacy of FOLH1‐targeted brachytherapy for MCC.

What's already known about this topic?

We report the first evidence of prevalent folate hydrolase‐1 (FOLH1; also known as prostate‐specific membrane antigen) expression within MCC‐associated neovessels.

What does this study add?

Herein, FOLH1 expression in Merkel cell carcinoma neovasculature is validated, and the therapeutic mechanism of specific, systemic targeting of disseminated disease with antibody‐based brachytherapy, is defined.

Capture and analysis of prostate cancer circulating tumor cells (CTCS) using geometrically enhanced differential immunocapture (GEDI)

53

Background: EpCAM-based immunocapture of prostate cancer (PC) CTCs yields relatively low purity and specificity. We developed a geometrically enhanced differential immunocapture (GEDI) microfluidic device that incorporates flow dynamics and utilizes a mAb to prostate-specific membrane antigen (PSMA) to optimize isolation and analysis of CTCs from PC patients.

Methods: GEDI microfluidic silicon chips, fabricated using standard photolithography techniques, were functionalized by chemical cross-linking ending with a neutravidin terminated surface to which anti-PSMA biotinylated-mAb J591 was bound. C4-2 (PSMA+) and PC-3 (PSMA-) cells were used for chip optimization. 1 mL of peripheral blood from PC patients was flowed (1mL/hour) over functionalized chips. Captured cells were washed with PBS × 30 min, fixed with 3.7% formaldehyde, immunofluorescently stained for DAPI, androgen receptor (AR), tubulin and EpCAM and analyzed by high resolution point-scanning confocal microscopy. PSMA+, DAPI+, and CD45- cells were manually scored. RNA was extracted from unfixed captured CTCs using lysis buffer flowed thru the chip.

Results: ∼80% capture efficiency was achieved from 26 PSMA positive C4-2 cells spiked into 1 mL blood flowed through the GEDI chip. RNA extracted from 50 C4-2 cells in 1 mL blood flowed thru the chip detected a known AR point mutation by RT-PCR and Sanger sequencing. Immunofluorescence staining of PSMA+ cells captured on the chip detected changes in AR subcellular localization and microtubule structure following treatment with DHT or paclitaxel, respectively. 10 patients with metastatic PC were analyzed by CellSearch (range 0-201 cells/7.5 mL) and GEDI chip (range 35->1200 cells/mL) yielding a 7->350 fold enrichment using GEDI. Captured PC cells isolated from PC patient incubated in 50 nm paclitaxel (ex vivo) overnight demonstrated microtubule bundling, indicative of drug-target engagement.

Conclusions: PSMA based GEDI microfluidic CTC capture is highly specific and sensitive in capturing PSMA positive PC CTCs; and allows detailed CTC analysis including protein expression and subcellular localization, mutational analysis and drug sensitivity assessment.

[Table: see text]

Antiprostate-specific membrane antigen (PSMA)-based radioimmunotherapy: A combined analysis of radiolabeled-J591 studies

136

Background: J591 is a monoclonal antibody which selectively binds the external domain of PSMA with high affinity. Two phase I trials of radiolabeled-J591 have been published; two additional studies have been completed. 90Y is a beta-emitting particle optimal for tumor lesions 28-42 mm in size; 177Lu is best suited for lesions 1-3 mm in diameter [O'Donoghue J Nuc Med 1995].

Methods: With WCMC IRB approval, long-term follow-up of 4 clinical trials and the ongoing studies was analyzed. Prospectively collected data were supplemented with retrospective additions when necessary. Median survival (OS) was calculated by Kaplan- Meier methodology.

Results: Between 10/00 and 7/10, 132 pts with metastatic CRPC received radiolabeled J591 (103 received 177Lu-J591, 29 90Y-J591) with a median follow-up of 68.5 months (mo). Median age 70.3 yrs; all progressed after multiple lines of hormonal therapy, 41.7% received prior chemo, 48.5% received post-J591 chemo. Median Halabi nomogram score for the group was 146 (range 97- 196). OS for the entire group was 16.7 mo [95% CI 13.8, 19.7]. 26 (19.7%) experienced > 30% PSA decline, with OS of 22.4 mo (vs 13.6 mo for those with any PSA increase, p=0.08; p=0.006 at phase II doses). Pts receiving 177Lu-J591 had more 30% PSA declines than 90Y-J591 (21.3% vs 6.9%, p=0.06). 37.9% had measurable disease; those who received 90Y-J591 were more likely to have measurable response than 177Lu-J591 [p=0.04]. All objective tumor responses also had significant PSA declines. Of 15 pts with baseline and follow-up CTC counts (CellSearch methodology), 12 (80%) became or remained favorable at follow-up; 3 became or remained unfavorable.

Conclusions: Radiolabled J591 is tolerable and efficacious. As predicted based upon their physical properties, 177Lu-J591 appears more effective for lower volume disease, with objective responses in larger volume disease only with 90Y-J591. Current trials utilizing 177Lu-J591 focus on predictive biomarkers, dose fractionation to improve tolerance and efficacy, combination with chemotherapy, and “salvage radioimmunotherapy” to delay the onset of metastases in men with progressive biochemical (micrometastatic) disease best suitable for 177Lu-J591.

[Table: see text]

Bone marrow recovery and subsequent chemotherapy following radiolabeled anti-prostate-specific membrane antigen (PSMA) monoclonal antibody J591 in patients (pts) with metastatic castration-resistant prostate cancer (metCRPC)

e16004

Background: Reversible myelosuppression is the dose-limiting toxicity of radioimmunotherapy (RIT). Cases of marrow damage, including myelodysplasia and acute leukemia have been reported with the RIT most used to date (that targeting CD20 in Non- Hodgkin's lymphoma), though no statistically significant association exists. In addition, post-RIT chemotherapy (chemo) may theoretically be limited. We have treated metCRPC pts with anti-PSMA RIT since 2000 and analyzed post-therapy outcomes. Methods: Follow-up across 4 prospective phase I and II trials utilizing 177Lu-J591 and 90Y-J591 was performed. Quality of hematologic recovery from post-RIT myelosuppression was documented. Administration of pre- and post-RIT chemo was analyzed. Specific searches for subsequent myelodysplasia and/or leukemia were performed. Results: Median age of the 109 treated pts is 70 (range 47–88). Entry criteria for all trials included progressive metCRPC, PS < 2, normal baseline neutrophil and platelet counts, and hemoglobin > 10 g/dL. 80 received 177Lu-J591 at cumulative doses ranging from 10–120 mCi/m2 and 29 received 90Y-J591 at cumulative doses of 5–40 mCi/m2. 43% received at least 1 line of pre-RIT chemo, 53% received at least 1 line of post-RIT chemo, and 20% have never received chemo to date. All pts with adequate performance status received chemo except per pt choice. Excluding re-treated pts, 98% and 87% of assessable pts had full recovery of neutrophils and platelets respectively. Of the remaining, all but 4 recovered to Gr 1 neutropenia and/or thrombocytopenia. The most common reason for lack of complete hematologic recovery was CRPC progression in bone marrow (16 pts with persistent or recurrent myelosuppression underwent bone marrow biopsy). No cases of post-RIT myelodysplasia and/or leukemia were discovered. Conclusions: Anti-PSMA radioimmunotherapy is well-tolerated with efficacy previously reported. While follow-up is ongoing, reports of irreversible bone marrow damage appear unfounded and all patients with intact performance status willing to undergo post-RIT chemotherapy are able to receive it.

[Table: see text]

Phase II trial of the anti-prostate specific membrane antigen (PSMA) monoclonal antibody (mAb) J591 plus low-dose interleukin-2 (IL-2) in patients (pts) with recurrent prostate cancer (PC)

15558

Background: The de-immunized mAb J591 recognizes the extracellular domain of PSMA and was engineered to induce antibody-dependent cellular cytotoxicity (ADCC). Low-dose IL-2 results in the clonal expansion of NK cells and may enhance ADCC. We conducted a phase 2 trial to determine the efficacy and toxicity of mAb J591 plus low-dose subcutaneous (SC) IL-2 in pts with recurrent PC. Methods: 17 pts with recurrent PC (2 groups: 11 with PSA relapse only; and 6 with progressive castrate metastatic disease) received continuous low-dose SC IL-2 (1.2 x 106 IU/m2/day) daily for 8 weeks with mAb J591 (25 mg/m2 IV) weekly on weeks 4, 5 and 6 (1 cycle). Pts could receive a maximum of 3 cycles. Results: 16 evaluable pts received up to 3 cycles of therapy (16 pts, one cycle, 9 two cycles and 2 three cycles). Toxicity was mild and limited to fatigue and injection site reactions. At the end of cycle 1, PSA was stable (-50%<change in PSA<25%) in 9 of 16 patients, with PSA declines up to 34%. No PSA decline >50% was observed. A post-hoc analysis of PSA kinetics showed 5 patients had a reduction in their PSA slope of =25%; 8 of the remaining 11 patients demonstrated PSA stabilization (- 25%<change in PSA slope<25%). PSA response was most commonly observed during weeks 4–6 of the cycle correlating with mAb administration. Flow cytometric analysis of peripheral blood mononuclear cells revealed an average increase in absolute NK cell count of 107% at week 4 and 117% at the end of cycle 1. Conclusions: The combination of mAb J591 with low-dose IL-2 was well tolerated and inhibited PSA kinetics in some patients, however no responses were seen. Repetitive dosed mAb J591 is a viable strategy for use in combination with immune modulatory or other therapies in recurrent prostate cancer.

No significant financial relationships to disclose.

Phase II trial of 177Lutetium radiolabeled anti-prostate-specific membrane antigen (PSMA) monoclonal antibody J591 (177Lu- J591) in patients (pts) with metastatic androgen-independent prostate cancer (AIPC)

15523

Background: A phase 1 trial of 177Lu-J591 in pts with metastatic AIPC demonstrated acceptable toxicity, excellent targeting of metastatic sites and biologic activity. Methods: Pts with progressive, metastatic AIPC receive one dose of 177Lu-J591 in two- cohorts: cohort 1 (65 mCi/m2), 15 pts; cohort 2: (70 mCi/m2), 17 pts. The primary endpoint is PSA and/or measurable disease response; secondary endpoint is toxicity. A 177Lu-J591 imaging study is done to confirm tumor targeting. Results: 21 pts (8 chemo-naive), median age 73, have been treated to date, 15 in cohort 1, 6 in cohort 2. Two pts with bone-only metastases achieved PSA declines of >50%. One had an 87% PSA decline lasting 126 days with resolution of bone pain. A 2nd pt has a PSA decline of 58% that continues without progression at 6 mo post-rx. PSA stabilization (<25% PSA rise above baseline) occurred in an additional 9 pts (43%), 7 through wk 8 (1 of whom is still under follow-up) and 2 pts through wk 12. Of 7 pts with measurable disease, 6 have had post-rx CT scans completed, 3 were stable, 3 progressed. In these pts with measurable disease, PSA was more likely to diagnose progression, with only 1 stable and 5 progressed by PSA criteria. Platelet nadir <20 x 10e9/L occurred in 6 pts, 3 of whom required platelet transfusions (mean = 2). 17/19 evaluable pts recovered normal platelet counts; the remaining 2 pts had rapidly progressive disease, 1 of whom had biopsy confirmed marrow replacement by tumor. Neutropenia </= 0.5 x 10e9/L occurred in 4 pts, 2 of whom received brief rx with growth factors. All 19 evaluable pts had normal neutrophil recovery. No significant drug-related non-hematologic toxicity has occurred. Targeting of known sites of PC metastases has been observed in all pts. Conclusions: Single dose 177Lu-J591 demonstrates anti-tumor activity in pts with progressive, metastatic AIPC with reversible myelosuppression. Accrual is continuing.

[Table: see text]

In vitro and preclinical targeted alpha therapy of human prostate cancer with Bi-213 labeled J591 antibody against the prostate specific membrane antigen

Limited options for the treatment of prostate cancer have spurred the search for new therapies. One innovative approach is the use of targeted alpha therapy (TAT) to inhibit cancer growth, using an alpha particle emitting radioisotope such as (213)Bi. Because of its short range and high linear energy transfer (LET), alpha-particles may be particularly effective in the treatment of cancer, especially in inhibiting the development of metastatic tumors from micro-metastases. Prostate-specific membrane antigen (PSMA) is expressed in prostate cancer cells and the neovasculature of a wide variety of malignant neoplasms including lung, colon, breast and others, but not in normal vascular endothelium. The expression is further increased in higher-grade cancers, metastatic disease and hormone-refractory prostate cancer (PCA). J591 is one of several monoclonal antibodies (mabs) to the extracellular domain of PSMA. Chelation of J591 mab with (213)Bi forms the alpha-radioimmunoconjugate (AIC). The objective of this preclinical study was to design an injectable AIC to treat human prostate tumors growing subcutaneously in mice. The anti-proliferative effects of AIC against prostate cancer were tested in vitro using the MTS assay and in vivo with the nude mice model. Apoptosis was documented using terminal deoxynucleotidyl transferase [TdT]-mediated deoxyuridinetriphosphate [dUTP] nick end-labeling (TUNEL) assay, while proliferative index was assessed using the Ki-67 marker. We show that a very high density of PSMA is expressed in an androgen-dependent human PCA cell line (LNCaP-LN3) and in tumor xenografts from nude mice. We also demonstrate that the AIC extensively inhibits the growth of LN3 cells in vitro in a concentration-dependent fashion, causing the cells to undergo apoptosis. Our in vivo studies showed that a local AIC injection of 50 microCi at 2 days post-cell inoculation gave complete inhibition of tumor growth, whereas results for a non-specific AIC were similar to those for untreated mice. Further, after 1 and 3 weeks post-tumor appearance, a single (100 microCi/100 microl) intra-lesional injection of AIC can inhibit the growth of LN3 tumor xenografts (volume<100 mm(3)) in nude mice. Tumors treated with AIC decreased in volume from a mean 46+/-14 mm(3) in the first week or 71+/-15 mm(3) in the third week to non-palpable, while in control mice treated with a non-specific AIC using the same dose, tumor volume increased from 42 to 590 mm(3). There were no observed side effects of the treatment. Because of its in vitro cytotoxicity and these anti-proliferative properties in vivo, the (213)Bi-J591 conjugate has considerable potential as a new therapeutic agent for the treatment of prostate cancer.

Downregulation of Bcl-2 sensitises interferon-resistant renal cancer cells to Fas

Interferon α (IFNα) is used to treat patients with advanced renal cell carcinoma (RCC) despite limited clinical benefit. IFNα can induce Fas receptor-mediated apoptosis by direct activation of pro-caspase-8 followed by activation of caspase-3. Alternative, indirect activation of caspase-3 via mitochondrial release of cytochrome c can occur and may explain the rescue from Fas-activated cell death by the antiapoptotic members of the Bcl-2 family. In this study, we examined G3139, a novel antisense compound targeting Bcl-2, in combination with IFNα. Human RCC lines (SK-RC-44 and SK-RC-07) were treated with IFNα, G3139 or a combination of the two. Fas-mediated cytotoxicity was induced by anti-Fas mAb, CH11. An analysis of Bcl-2, Fas and the cleavage of PARP was performed. IFNα induced Fas and Bcl-2 in SK-RC-44 and SK-RC-07. IFNα sensitised SK-RC-44 to anti-Fas and induced PARP cleavage confirming that IFNα has a cytotoxic effect on RCC lines by induction of the Fas antigen. Cytotoxicity was not evident in SK-RC-07 cells treated with IFNα. G3139 induced a specific downregulation of Bcl-2 in SK-RC-07 cells, which were then sensitised to anti-Fas after treatment with IFNα. Taken together, these results suggest that Fas-dependent pathways as well as alternative pathways, which can be inhibited by Bcl-2, exist in renal cell carcinoma. G3139 in combination with IFNα is a potential therapy in patients with metastatic renal cell carcinoma.

Tumor therapy with targeted atomic nanogenerators

A single, high linear energy transfer alpha particle can kill a target cell. We have developed methods to target molecular-sized generators of alpha-emitting isotope cascades to the inside of cancer cells using actinium-225 coupled to internalizing monoclonal antibodies. In vitro, these constructs specifically killed leukemia, lymphoma, breast, ovarian, neuroblastoma, and prostate cancer cells at becquerel (picocurie) levels. Injection of single doses of the constructs at kilobecquerel (nanocurie) levels into mice bearing solid prostate carcinoma or disseminated human lymphoma induced tumor regression and prolonged survival, without toxicity, in a substantial fraction of animals. Nanogenerators targeting a wide variety of cancers may be possible.

The T cell death knell: immune-mediated tumor death in renal cell carcinoma

The antitumor effect of T cells is executed either through CD95 or Perforin (PFN)/Granzyme B (GrB) pathways. Induction of apoptosis by either mode requires activation of caspase family members. However, recent studies have suggested that cell death can proceed in the absence of caspase induction and apoptotic events. We investigated the contribution of CD95 and PFN/GrB-mediated cytotoxicity to apoptotic and necrotic mechanisms of cell death in human renal cell carcinoma. Although freshly isolated and cultured tumors expressed CD95 on their surface, they were resistant to CD95-mediated apoptosis. CD95 resistance coincided with decreased levels of FADD protein and diminished caspase-3-like activity. In contrast, we demonstrated that tumor cell death mediated by PFN/GrB can be achieved in the absence of functional caspase activity and is accompanied by a dramatic accumulation of nonapoptotic necrotic cells.

Society of Urologic Oncology Biotechnology Forum: new approaches and targets for advanced prostate cancer

PURPOSE

We provide an overview of advances in molecular based therapeutic strategies for prostate cancer and summarize the studies presented at the Society of Urologic Oncology Biotechnology Forum in 2000.

MATERIALS AND METHODS

Three promising new treatment strategies are presented, and a critique of the advantages and limitations of each is offered by a leading expert in the field.

RESULTS

Treatment results and the current state of dendritic cell based immunotherapy, monoclonal antibody therapy and anti-apoptotic treatment approaches are presented.

CONCLUSIONS

Currently patients with advanced prostate carcinoma have expanded therapeutic options available in the form of molecular based phases II and III clinical trials.

Response of LNCaP spheroids after treatment with an alpha-particle emitter (213Bi)-labeled anti-prostate-specific membrane antigen antibody (J591)

A theoretical drawback to alpha-particle therapy with 213Bi is the short range of the particle track coupled with the short half-life of the radionuclide, thereby potentially limiting effective cytotoxicity to rapidly accessible, disseminated individual tumor cells (e.g., as in leukemia). In this work, a prostate carcinoma spheroid model was used to evaluate the feasibility of targeting micrometastatic clusters of tumor cells using 213Bi-labeled anti-prostate-specific membrane antigen (PSMA) antibody, J591. In prostate cancer, vascular dissemination of tumor cells or tumor cell clusters to the marrow constitutes an important step in the progression of this disease to widespread skeletal involvement, an incurable state. Such prevascularized clusters are ideal targets for radiolabeled antibodies because the barriers to antibody penetration that are associated with the capillary basal lamina have not yet formed. Beta- and gamma-emitting radionuclides such as 131I, which are widely used in radioimmunotherapy, are not expected to be effective when targeting single cells or small cell clusters. This is because the range of the emissions is one to two orders of magnitude greater than the target size, and the energy deposited per traversal is insufficient to produce any significant radiobiological effect. Spheroids of the prostate cancer cell line, LNCaP-LN3, were used as a model of prevascularized micrometastases; their response to an anti-PSMA antibody, J591, radiolabeled with the alpha-particle emitter 213Bi (T(1/2), 45.6 min.) has been measured. The time course of spheroid volume reductions was found to be sensitive to the initial spheroid volume. J591 labeled with 0.9 MBq/ml 213Bi resulted in a 3-log reduction in spheroid volume on day 33, relative to control, for spheroids with an initial diameter of 130 microm; 1.8 MBq/ml were required to achieve a similar response for spheroids with an initial diameter of 180 microm. Equivalent spheroid responses were observed after 12 Gy of acute external beam photon irradiation. Monte Carlo-based microdosimetric analyses of the 213Bi decay distribution in individual spheroids of 130-microm diameter yielded an average alpha-particle dose of 3.7 Gy to the spheroids, resulting in a relative biological effectiveness factor of 3.2 over photon irradiation. The activity concentrations used in the experiments were clinically relevant, and this work supports the possibility of using 213Bi-labeled antibodies not only for disseminated single tumor cells, as found in patients with leukemia, but also for micrometastatic tumor deposits up to 180 microm in diameter (1200 cells).

Overview of evolving strategies incorporating prostate-specific membrane antigen as target for therapy

Prostate-specific membrane antigen (PSMA) is a potential target in prostate cancer patients because it is very highly expressed and because it has been reported to be upregulated by androgen deprivation. This overview addresses the expression of the PSMA gene in terms of the promoter and enhancer and how that may play a role in gene therapy. We also review PSMA as a target for antibodies for imaging and treatment and the development of a novel hybrid T-cell receptor that combines the specificity of anti-PSMA antibodies with that of T-cell receptor activation when introduced into primary lymphocytes by retroviral-mediated gene transfer. We also discuss our recent findings on the expression of a PSMA-like gene and how that understanding allows specific targeting of PSMA.

Na,K-ATPase beta-subunit is required for epithelial polarization, suppression of invasion, and cell motility

The cell adhesion molecule E-cadherin has been implicated in maintaining the polarized phenotype of epithelial cells and suppression of invasiveness and motility of carcinoma cells. Na,K-ATPase, consisting of an alpha- and beta-subunit, maintains the sodium gradient across the plasma membrane. A functional relationship between E-cadherin and Na,K-ATPase has not previously been described. We present evidence that the Na,K-ATPase plays a crucial role in E-cadherin-mediated development of epithelial polarity, and suppression of invasiveness and motility of carcinoma cells. Moloney sarcoma virus-transformed Madin-Darby canine kidney cells (MSV-MDCK) have highly reduced levels of E-cadherin and beta(1)-subunit of Na,K-ATPase. Forced expression of E-cadherin in MSV-MDCK cells did not reestablish epithelial polarity or inhibit the invasiveness and motility of these cells. In contrast, expression of E-cadherin and Na,K-ATPase beta(1)-subunit induced epithelial polarization, including the formation of tight junctions and desmosomes, abolished invasiveness, and reduced cell motility in MSV-MDCK cells. Our results suggest that E-cadherin-mediated cell-cell adhesion requires the Na,K-ATPase beta-subunit's function to induce epithelial polarization and suppress invasiveness and motility of carcinoma cells. Involvement of the beta(1)-subunit of Na,K-ATPase in the polarized phenotype of epithelial cells reveals a novel link between the structural organization and vectorial ion transport function of epithelial cells.

An alpha-particle emitting antibody ([213Bi]J591) for radioimmunotherapy of prostate cancer

A novel alpha-particle emitting monoclonal antibody construct targeting the external domain of prostate-specific membrane antigen (PSMA) was prepared and evaluated in vitro and in vivo. The chelating agent, N-[2-amino-3-(p-isothiocyanatophen-yl)propyl]-trans-cyclohexane-1, 2-diamine-N,N',N',N'',N''-pentaacetic acid, was appended to J591 monoclonal antibody to stably bind the 213Bi radiometal ion. Bismuth-213 is a short-lived (t 1/2 = 46 min) radionuclide that emits high energy alpha-particles with an effective range of 0.07-0.10 mm that are ideally suited to treating single-celled neoplasms and micrometastatic carcinomas. The LNCaP prostate cancer cell line had an estimated 180,000 molecules of PSMA per cell; J591 bound to PSMA with a 3-nM affinity. After binding, the radiolabeled construct-antigen complex was rapidly internalized into the cell, carrying the radiometal inside. [213Bi]J591 was specifically cytotoxic to LNCaP. The LD50 value of [213Bi]J591 was 220 nCi/ml at a specific activity of 6.4 Ci/g. The potency and specificity of [213Bi]J591 directed against LNCaP spheroids, an in vitro model for micrometastatic cancer, also was investigated. [213Bi]J591 effectively stopped growth of LNCaP spheroids relative to an equivalent dose of the irrelevant control [213Bi]HuM195 or unlabeled J591. Cytotoxicity experiments in vivo were carried out in an athymic nude mouse model with an i.m. xenograft of LNCaP cells. [213Bi]J591 was able to significantly improve (P < 0.0031) median tumor-free survival (54 days) in these experiments relative to treatment with irrelevant control [213Bi]HuM195 (33 days), or no treatment (31 days). Prostate-specific antigen (PSA) was also specifically reduced in treated animals. At day 51, mean PSA values were 104 ng/ml +/- 54 ng/ml (n = 4, untreated animals), 66 ng/ml +/- 16 ng/ml (n = 6, animals treated with [213Bi]HuM195), and 28 ng/ml +/- 22 ng/ml (n = 6, animals treated with [213Bi]J591). The reduction of PSA levels in mice treated with [213Bi]J591 relative to mice treated with [213Bi]HuM195 and untreated control animals was significant with P < 0.007 and P < 0.0136, respectively. In conclusion, a novel [213Bi]-radiolabeled J591 has been constructed that selectively delivers alpha-particles to prostate cancer cells for potent and specific killing in vitro and in vivo.

In vitro characterization of radiolabeled monoclonal antibodies specific for the extracellular domain of prostate-specific membrane antigen

Prostate-specific membrane antigen (PSMA) is a well-characterized cell surface antigen expressed by virtually all prostate cancers (PCas). PSMA has been successfully targeted in vivo with (111)In-labeled 7E11 monoclonal antibody (mAb; ProstaScint; Cytogen, Princeton, NJ), which binds to an intracellular epitope of PSMA. This work reports the in vitro characterization of three recently developed mAbs that bind the extracellular domain of PSMA (PSMAext). Murine mAbs J415, J533, J591, and 7E11 were radiolabeled with 131I and evaluated in competitive and saturation binding studies with substrates derived from LNCaP cells. J415 and J591 were conjugated to 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid labeled with (111)In. The uptake and cellular processing of these antibodies were evaluated in viable LNCaP cells. All four mAbs could be labeled with 131I up to a specific activity of 350 MBq/mg with no or little apparent loss of immunoreactivity. Competition assays revealed that J415 and J591 compete for binding to PSMAext antigen. J533 bound to a region close to the J591 binding epitope, but J533 did not interfere with J415 binding to PSMA. mAb 7E11 did not inhibit the binding of J415, J533, or J591 (or vice versa), consistent with earlier work that these latter mAbs bind PSMAext whereas 7E11 binds the intracellular domain of PSMA. Saturation binding studies demonstrated that J415 and J591 bound with a similar affinity (Kds 1.76 and 1.83 nM), whereas J533 had a lower affinity (Kd, 18 nM). In parallel studies, all four mAbs bound to a similar number of PSMA sites expressed by permeabilized cells (1,000,000-1,300,000 sites/cell). In parallel studies performed with viable LNCaP cells, J415, J533, and J591 bound to a similar number of PSMA sites (i.e., 600,000-800,000 sites/cell), whereas 7E11 bound only to a subpopulation of the available PSMA sites (95,000 sites/cell). This apparent binding of 7E11 to viable cells can be accounted for by a 5-7% subpopulation of permeabilized cells produced when the cells were trypsinized and suspended. Up to five DOTA chelates could be bound to either J415 or J591 without compromising immunoreactivity. A comparison of the cellular uptake and metabolic processing of the 131I- and (111)In-labeled antibodies showed a rapid elimination of 131I from the cell and a high retention of (111)In. All four mAbs recognized and bound to similar numbers of PSMAs expressed by ruptured LNCaP cells (i.e., the exposed intracellular and extracellular domains of PSMA). By comparison to J415 and J591, J533 had a lower binding affinity. Both J415 and J591 recognized and bound to the same high number of PSMAs expressed by intact LNCaP. By contrast, 7E11 bound to fewer sites expressed by intact LNCaP cells (i.e., the exposed extracellular domain of PSMA). Both J415 and J591 are promising mAbs for the targeting of viable PSMA-expressing tissue with diagnostic and therapeutic metallic radionuclides.

Prostate-specific membrane antigen (PSMA)-specific monoclonal antibodies in the treatment of prostate and other cancers

Prostate-specific membrane antigen (PSMA) is a cell surface glycoprotein that is expressed by prostate epithelial cells. PSMA-specific monoclonal antibodies have been utilized to characterize the biologic function and in vivo biodistribution of PSMA. PSMA is an attractive target protein for monoclonal antibody directed imaging or therapeutics for prostate cancer since its expression is relatively restricted to prostate epithelial cells and is over-expressed in prostate cancer, including in advanced stages. Currently, clinical usage of PSMA specific monoclonal antibodies has been limited to diagnostic immunohistochemistry and imaging of patients with prostate cancer. Novel applications for these antibodies will be discussed.

Antigens recognized by autologous antibody in patients with renal-cell carcinoma

The screening of cDNA expression libraries derived from human tumors with autologous antibody (SEREX) is a powerful method for defining the structure of tumor antigens recognized by the humoral immune system. Sixty-five distinct antigens (NY-REN-1 to NY-REN-65) reactive with autologous IgG were identified by SEREX analysis of 4 renal cancer patients and were characterized in terms of cDNA sequence, mRNA expression pattern, and reactivity with allogeneic sera. REN-9, -10, -19, and -26 have a known association with human cancer. REN-9 (LUCA-15) and REN-10 (gene 21) map to the small cell lung cancer tumor suppressor gene locus on chromosome 3p21.3. REN-19 is equivalent to LKB1/STK11, a gene that is defective in Peutz-Jeghers syndrome and cancer. REN-26 is encoded by the bcr gene involved in the [t(9:22)] bcr/abl translocation. Genes encoding 3 of the antigens in the series showed differential mRNA expression; REN-3 displays a pattern of tissue-specific isoforms, and REN-21 and REN-43 are expressed at a high level in testis in comparison to 15 other normal tissues. The other 62 antigens were broadly expressed in normal tissues. With regard to immunogenicity, 20 of the 65 antigens reacted only with autologous sera. Thirty-three antigens reacted with sera from normal donors, indicating that their immunogenicity is not restricted to cancer. The remaining 12 antigens reacted with sera from 5-25% of the cancer patients but not with sera from normal donors. Seventy percent of the renal cancer patients had antibodies directed against one or more of these 12 antigens. Our results demonstrate the potential of the SEREX approach for the analysis of the humoral immune response against human cancer.

Monoclonal antibodies: will they become an integral part of the evaluation and treatment of prostate cancer--focus on prostate-specific membrane antigen?

Over the past two decades, monoclonal antibody technology has had an increasing impact on clinical diagnostic and therapeutic options, and this is true in the realm of managing prostate cancer. Several targets such as prostate-specific antigen and prostatic acid phosphatase as well as, more recently, angiogenic antigens such as vascular endothelial growth factor have been examined for therapy. Prostate-specific membrane antigen, a type II integral membrane glycoprotein initially characterized by the monoclonal antibody 7E11, has shown promise. Recent evidence suggests that prostate-specific membrane antigen is also expressed in tumor-associated neovasculature of a wide variety of malignant neoplasms. With its expression in prostate secretory-acinar epithelium and the prostate and in the neovasculature associated with tumors, prostate-specific membrane antigen represents an excellent antigenic target for monoclonal antibody diagnostic and therapeutic options. As research continues, the role of monoclonal antibody imaging and therapy will become increasingly important in the management of prostate cancer.

The detection of renal carcinoma cells in the peripheral blood with an enhanced reverse transcriptase-polymerase chain reaction assay for MN/CA9

BACKGROUND

Using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay, the authors previously determined the expression of MN/CA9 mRNA in renal cell carcinoma (RCC) and its absence in benign renal tissue. In the current study, the utility of an enhanced RT-PCR assay in the detection of renal carcinoma cells in the peripheral blood was assessed.

METHODS

An enhanced MN/CA9 RT-PCR assay was applied to peripheral blood samples from a total of 96 patients. Forty-two patients had renal tumors, including 5 with benign renal lesions, 28 with localized RCC, and 9 with metastatic RCC. Fifty-four control patients without renal tumors were similarly tested. Pathologic staging for patients with localized cancer was T1N0M0 for 5, T2N0M0 for 9, and T3N0M0 for 14 patients.

RESULTS

Cells expressing MN/CA9 were detected in 1 of 54 controls (1.8%) and in 18 of 37 cancer patients (49%). Thirteen of twenty eight patients (46%) with localized RCC and 5 of 9 (56%) with metastatic disease tested positive with the assay. No patient with a benign renal tumor exhibited MN/CA9 expression. All blood test results for patients with clear cell RCC were noted to be positive. No correlation was noted between MN/CA9 results and age, gender, or tumor grade. The differences in MN/CA9 results according to T classification were not statistically significant.

CONCLUSIONS

The enhanced RT-PCR assay for MN/CA9 is a highly specific technique for detecting circulating renal carcinoma cells in the peripheral blood, and it may prove useful in the diagnosis and monitoring of RCC.

Reduced expression of beta-subunit of Na,K-ATPase in human clear-cell renal cell carcinoma

PURPOSE

Multiple subtypes of renal cancer have been identified. Clear-cell renal cell carcinoma (RCC) is the most common subtype of RCC and one of the more aggressive. The goal of this study was to investigate in RCC the levels of Na,K-ATPase, an abundant enzyme in the kidney which is crucial for various kidney functions. Na,K-ATPase is a heterodimer consisting of a catalytic a-subunit and a glycosylated beta-subunit whose function is still not well-defined.

MATERIALS AND METHODS

Fourteen clear-cell RCC specimens were studied. The levels of the Na,K-ATPase alpha and beta-subunits in normal kidney and RCC tissues were determined by immunoblot analysis. The localization of the alpha and beta-subunits was studied by immunofluorescence and laser scanning confocal microscopy. Na,K-ATPase activity was determined using a coupled-enzyme spectrophotometric assay.

RESULTS

In normal kidney, the cells demonstrate an epithelial morphology with distinct basolateral plasma membrane localization of the alpha and beta-subunits. Conversely, the cells of the clear-cell RCC have lost their epithelial phenotype and the alpha and beta-subunits show a diffuse intracellular staining. Clear-cell RCC tumor cell lysates showed a consistent 95.6+/-2.8% (mean +/- SD) reduction in protein levels of beta-subunit relative to the levels in normal kidney. The alpha-subunit level in RCC lysates was generally near or above the levels relative to normal kidney. The reduced beta-subunit expression was accompanied by a significant reduction in the Na,K-ATPase activity in RCC membranes.

CONCLUSIONS

These results suggest that the beta-subunit may regulate the Na,K-ATPase activity in vivo. Diminished Na,K-ATPase activity in conjunction with the reduced beta-subunit level is associated with the clear-cell RCC phenotype.

Five different anti-prostate-specific membrane antigen (PSMA) antibodies confirm PSMA expression in tumor-associated neovasculature

Prostate-specific membrane antigen (PSMA) is a type II integral membrane glycoprotein that was initially characterized by the monoclonal antibody (mAb) 7E11. PSMA is highly expressed in prostate secretory-acinar epithelium and prostate cancer as well as in several extraprostatic tissues. Recent evidence suggests that PSMA is also expressed in tumor-associated neovasculature. We examined the immunohistochemical characteristics of 7E11 and those of four recently developed anti-PSMA mAbs (J591, J415, and Hybritech PEQ226.5 and PM2J004.5), each of which binds a distinct epitope of PSMA. Using the streptavidin-biotin method, we evaluated these mAbs in viable prostate cancer cell lines and various fresh-frozen benign and malignant tissue specimens. In the latter, we compared the localization of the anti-PSMA mAbs to that of the anti-endothelial cell mAb CD34. With rare exceptions, all five anti-PSMA mAbs reacted strongly with the neovasculature of a wide spectrum of malignant neoplasms: conventional (clear cell) renal carcinoma (11 of 11 cases), transitional cell carcinoma of the urinary bladder (6 of 6 cases), testicular embryonal carcinoma (1 of 1 case), colonic adenocarcinoma (5 of 5 cases), neuroendocrine carcinoma (5 of 5 cases), glioblastoma multiforme (1 of 1 cases), malignant melanoma (5 of 5 cases), pancreatic duct carcinoma (4 of 4 cases), non-small cell lung carcinoma (5 of 5 cases), soft tissue sarcoma (5 of 6 cases), breast carcinoma (5 of 6 cases), and prostatic adenocarcinoma (2 of 12 cases). Localization of the anti-PSMA mAbs to tumor-associated neovasculature was confirmed by CD34 immunohistochemistry in sequential tissue sections. Normal vascular endothelium in non-cancer-bearing tissue was consistently PSMA negative. The anti-PSMA mAbs reacted with the neoplastic cells of prostatic adenocarcinoma (12 of 12 cases) but not with the neoplastic cells of any other tumor type, including those of benign and malignant vascular tumors (0 of 3 hemangiomas, 0 of 1 hemangioendothelioma, and 0 of 1 angiosarcoma). The mAbs to the extracellular PSMA domain (J591, J415, and Hybritech PEQ226.5) bound viable prostate cancer cells (LNCaP and PC3-PIP), whereas the mAbs to the intracellular domain (7E11 and Hybritech PM2J004.5) did not. All five anti-PSMA mAbs reacted with fresh-frozen benign prostate secretory-acinar epithelium (28 of 28 cases), duodenal columnar (brush border) epithelium (11 of 11 cases), proximal renal tubular epithelium (5 of 5 cases), colonic ganglion cells (1 of 12 cases), and benign breast epithelium (8 of 8 cases). A subset of skeletal muscle cells was positive with 7E11 (7 of 7 cases) and negative with the other four anti-PSMA mAbs. PSMA was consistently expressed in the neovasculature of a wide variety of malignant neoplasms and may be an effective target for mAb-based antineovasculature therapy.

Dead or dying: necrosis versus apoptosis in caspase-deficient human renal cell carcinoma

The antitumor effect of immuno- and chemotherapeutic agents is executed through stimulation of apoptotic programs in susceptible cells. Apoptosis induced in tumor cells requires activation of members of the caspase family of proteases. Deficient expression or activation of caspases may account in part for the failure of many current anticancer therapies. However, recent studies suggest that cell death can proceed in the absence of caspases. We investigated the susceptibility of human renal cell carcinoma (RCC) lines to two distinct modes of cell death, apoptosis and necrosis. RCC lines displayed almost complete resistance to apoptosis in response to the intracellular zinc chelator, N,N,N'N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), which instead induced dramatic accumulation of nonapoptotic necrotic cells. Conversely, TPEN was a potent inducer of apoptosis in caspase-competent normal kidney cells (NK-72) and Jurkat T lymphocytes. Resistance to apoptosis in RCC lines correlated with almost complete loss of caspase-3 expression and variable down-regulation of caspase-7, caspase-8, and caspase-10. These data may explain the resistance of RCC to drugs inducing apoptosis and have important consequences for further attempts to manipulate tumor cell death.

Mechanisms of apoptosis in T cells from patients with renal cell carcinoma

Tumors may escape immune recognition and destruction through the induction of apoptosis in activated T lymphocytes. Results from several laboratories suggest that FasL (L/CD95L) expression in tumors may be responsible for this process. In this study of patients with renal cell carcinoma (RCC), we provide evidence for two mechanisms of T-cell apoptosis. One mechanism involves the induction of apoptosis via FasL expression in tumor cells. This is supported by several observations, including the fact that tumor cells in situ as well as cultured cell lines expressed FasL mRNA and protein by a variety of techniques. The FasL in RCC is functional because in coculture experiments, FasL+ tumors induced apoptosis in Fas-sensitive Jurkat T cells and in activated peripheral blood T cells but not in resting peripheral blood T cells. Most importantly, antibody to FasL partially blocked apoptosis of the activated T cells. Moreover, Fas was expressed by T cells derived from the peripheral blood (53% median) and tumor (44.3% median) of RCC patients. Finally, in situ staining for DNA breaks demonstrated apoptosis in a subset of T cells infiltrating renal tumors. These studies also identified a second mechanism of apoptosis in RCC patient peripheral T cells. Whereas these cells did not display DNA breaks when freshly isolated or after culture for 24 h in medium, peripheral blood T cells from RCC patients underwent activation-induced cell death after stimulation with either phorbol 12-myristate 13-acetate/ionomycin or anti-CD3/CD28 antibodies. Apoptosis mediated by exposure to FasL in tumor cells or through T-cell activation may contribute to the failure of RCC patients to develop an effective T-cell-mediated antitumor response.

Mouse-human chimeric anti-epidermal growth factor receptor antibody C225 inhibits the growth of human renal cell carcinoma xenografts in nude mice

The epidermal growth factor (EGF) receptor and its ligand transforming growth factor-alpha (TGF-alpha) are overexpressed in human renal cell carcinoma (RCC). The chimeric anti-EGF receptor monoclonal antibody C225 was used to determine the effects of blocking the EGF receptor on RCC growth both in vitro and in vivo. A panel of RCC cell lines all tested positive at various levels for EGF receptor cell surface expression. C225 inhibited DNA synthesis of cultured A498, Caki-1, SK-RC-4, SK-RC-29, and SW839 cells in a dose-dependent manner, ranging from 20 to 45% inhibition compared with untreated controls. C225 also inhibited exogenous ligand-stimulated tyrosine phosphorylation of EGF receptor on RCC cells. The antitumor effects of C225 on RCC tumor growth were evaluated in ascites, s.c., and orthotopic RCC xenograft models. Mice treated with C225 in a Caki-1 ascites xenograft model showed a significant increase in survival (P = 0.002). All control mice died with ascites tumors by week 9, whereas >70% of C225-treated mice survived beyond 12 weeks. C225 also inhibited the growth of s.c. SK-RC-29 tumors in a dose-dependent manner. Mice treated with C225 (1 mg/dose) displayed a significant decrease in tumor volume compared with mice treated with control antibody (P < 0.05) or vehicle alone (P < 0.01). Lastly, C225 inhibited the growth and metastasis of RCC tumors growing orthotopically in the renal subcapsule of nude mice. Histological examination of RCC tumors from mice treated with C225 showed a substantial decrease in proliferating cell nuclear antigen staining and an increase in tumor cell apoptosis. These data suggest that C225 affects growth of RCC tumors by inhibiting EGF receptor-dependent proliferation and demonstrate the potential for therapeutic application of C225 in the treatment of human renal cancer.

Phase I/II radioimmunotherapy trial with iodine-131-labeled monoclonal antibody G250 in metastatic renal cell carcinoma

This Phase I/II radioimmunotherapy study was carried out to determine the maximum tolerated dose (MTD) and therapeutic potential of 131I-G250. Thirty-three patients with measurable metastatic renal cell carcinoma were treated. Groups of at least three patients received escalating amounts of 1311I (30, 45, 60, 75, and 90 mCi/m2) labeled to 10 mg of mouse monoclonal antibody G250, administered as a single i.v. infusion. Fifteen patients were studied at the MTD of activity. No patient had received prior significant radiotherapy; one had received prior G250. Whole-body scintigrams and single-photon emission computed tomography images were obtained in all patients. There was targeting of radioactivity to all known tumor sites that were > or =2 cm. Reversible liver function test abnormalities were observed in the majority of patients (27 of 33 patients). There was no correlation between the amount of 131I administered or hepatic absorbed radiation dose (median, 0.073 Gy/mCi) and the extent or nature of hepatic toxicity. Two of the first six patients at 90 mCi/m2 had grade > or =3 thrombocytopenia; the MTD was determined to be 90 mCi/m2 131I. Hematological toxicity was correlated with whole-body absorbed radiation dose. All patients developed human antimouse antibodies within 4 weeks posttherapy; retreatment was, therefore, not possible. Seventeen of 33 evaluable patients had stable disease. There were no major responses. On the basis of external imaging, 131I-labeled mouse monoclonal antibody G250 showed excellent localization to all tumors that were > or =2 cm. Seventeen of 33 patients had stable disease, with tumor shrinkage observed in two patients. Antibody immunogenicity restricted therapy to a single infusion. Studies with a nonimmunogenic G250 antibody are warranted.

Constitutive and antibody-induced internalization of prostate-specific membrane antigen

Prostate-specific membrane antigen (PSMA) is a cell surface glycoprotein expressed predominantly by prostate cancer cells. We have characterized four monoclonal antibodies that bind to the extracellular domain of PSMA (Liu et al., Cancer Res., 57: 3629-3634, 1997). Here we report that viable LNCaP cells internalize these antibodies. Laser scanning confocal microscopy reveals that the internalized antibodies accumulate in endosomes, and immunoelectron microscopy reveals that endocytosis of the PSMA-antibody complex occurs via clathrin-coated pits. In addition, a quantitative cell surface biotinylation assay demonstrates that PSMA is constitutively endocytosed in LNCaP cells and that anti-PSMA antibodies increase the rate of internalization of PSMA. These studies suggest that PSMA might function as a receptor mediating the internalization of a putative ligand. The availability of prostate-specific internalizing antibodies should aid the development of novel therapeutic methods to target the delivery of toxins, drugs, or short-range isotopes specifically to the interior of prostate cancer cells.

Aminopeptidase A expression and enzymatic activity in primary human renal cancers

The gp160 human kidney differentiation antigen is identical to human aminopeptidase A (APA), a zinc-dependent cell-surface metallopeptidase which hydrolyzes peptides with N-terminal acidic residues. GP160/APA is constitutively expressed by proximal tubule cells, the normal cellular counterpart of most renal cancers (RCs). Immunohistochemical analysis of gp160/APA protein expression in 62 primary renal tumor specimens using monoclonal antibody S4 revealed heterogeneous or homogeneous expression of gp160/APA in 46/51 (90%) of clear cell carcinomas in contrast with 1/8 (13%) papillary renal tumors and 0/3 oncocytomas (p<0.001). Analysis of five primary clear cell carcinomas for gp160 protein expression immunohistochemically and associated APA catalytic activity revealed one tumor which expressed gp160/APA protein which was enzymatically inactive. Direct sequence analysis of DNA derived from this specimen could not detect mutations within the zinc-binding domain which would eliminate gp160/APA catalytic activity. These data indicate that the gp160/APA protein is expressed by primary clear cell but not papillary RCs or oncocytomas, and that alterations in gp160/APA protein including loss of protein expression or enzymatic activity occur in 20% of primary clear cell RCs.

MHC class I and II expression in prostate carcinoma and modulation by interferon-alpha and -gamma

BACKGROUND

Expression of Major Histocompatibility Complex (MHC) class I and II antigens are critical for the cellular immune response. Loss of MHC expression represents one mechanism by which cancer cells escape immune recognition.

PURPOSE

To define MHC class I and II expression by prostate cancer (PCa) in vivo and in vitro and the ability to modulate MHC expression in vitro with IFN-alpha and -gamma.

METHODS

Frozen tissue sections of 25 benign prostatic hyperplasia (BPH) and 18 PCa specimens were studied by immunohistochemistry. PCa cell lines LNCaP, PC-3, and DU-145 were studied by FACS, ELISA, and cytospin. Class I was detected by monoclonal antibody (mAb) W6/32, and class II by mAb 13.17. The effects of IFN-alpha and -gamma were assessed by testing the three cell lines in the presence or absence of varying concentrations of the cytokine for varying incubation times.

RESULTS

Class I was strongly expressed by 24/25 BPH specimens; 4/18 (22%) PCa were homogeneously class I-positive, while 5/18 (28%) were heterogeneously positive and 9/18 (50%) were class I-negative. PC-3 and DU-145 expressed normal levels of class I, while LNCaP expressed only low levels. All line except LNCaP demonstrated significant up-regulation of class I with either IFN-alpha or -gamma. Class II expression was not seen in BPH epithelium nor in 17/18 PCa. Class II could be only weakly induced in the three PCa lines.

CONCLUSIONS

These findings confirm prior studies demonstrating that class I expression is commonly lost or diminished in PCa. In addition, class II up-regulation by IFN-gamma appears very limited in relation to other normal or neoplastic epithelium.

IMPLICATIONS

The present findings, taken together with previous studies, are most consistent with the expression of neoantigens by PCa, which are recognized and appropriately eliminated by the cellular immune system. This selective pressure favors outgrowth of cells which down-regulate or lose class I and/or class II expression. Understanding PCa immunobiology will help in the development of effective immunotherapy for this disease.

A multicenter trial evaluation of the fibrin/fibrinogen degradation products test for detection and monitoring of bladder cancer

PURPOSE

Presently there is a lack of effective, noninvasive tests for the detection and monitoring of bladder cancer. Measurement of fibrin/fibrinogen degradation products in urine has been shown to be a useful indicator of bladder carcinoma. The objective of this study was to evaluate the AuraTek FDP rapid immunoassay device for the detection of urinary fibrin/ fibrinogen degradation products associated with bladder cancer.

MATERIALS AND METHODS

A prospective multicenter study was conducted to compare AuraTek FDP with urinary cytology and hemoglobin dipstick for the detection of bladder cancer in 192 patients with a history of bladder cancer.

RESULTS

AuraTek FDP was significantly more sensitive (68%) than conventional urinary cytology (34%, p < 0.001) or hemoglobin dipstick (41%, p < 0.001) in the detection of bladder tumors, particularly for low stage low grade disease. In subjects with invasive disease (T2-T4) the AuraTek FDP test had a sensitivity of 100%. Specificity of AuraTek FDP was 96% for healthy subjects, 86% in patients with urological disease other than bladder cancer and 80% for patients under surveillance for bladder cancer but with a negative cystoscopic finding at the time of assay.

CONCLUSIONS

This simple, rapid (less than 7 minutes) point of care test is superior to conventional urine cytology and hemoglobin dipstick as an aid in the detection of bladder cancer.

Monoclonal antibodies to the extracellular domain of prostate-specific membrane antigen also react with tumor vascular endothelium

Prostate-specific membrane antigen (PSMA), initially defined by monoclonal antibody (mAb) 7E11, is a now well-characterized type 2 integral membrane glycoprotein expressed in a highly restricted manner by prostate epithelial cells. 7E11 has been shown to bind an intracellular epitope of PSMA that, in viable cells, is not available for binding. Herein, we report the initial characterization of the first four reported IgG mAbs that bind the external domain of PSMA. Competitive binding studies indicate these antibodies define two distinct, noncompeting epitopes on the extracellular domain of PSMA. In contrast to 7E11, these mAbs bind to viable LNCaP cells in vitro. In addition, they show strong immunohistochemical reactivity to tissue sections of prostate epithelia, including prostate cancer. These mAbs were also strongly reactive with vascular endothelium within a wide variety of carcinomas (including lung, colon, breast, and others) but not with normal vascular endothelium. These antibodies should prove useful for in vivo targeting to prostate cancer, as well as to the vascular compartment of a wide variety of carcinomas.

Expression of the tumor-associated gene MN: a potential biomarker for human renal cell carcinoma

MN is a novel cell surface antigen originally detected in human HeLa cells. Although it is also expressed in normal gastric mucosa, this antigen was previously found to be expressed in cells with a malignant phenotype in certain tissues of the female genital tract (cervix and ovary). Using an oligonucleotide primer set specific for MN-complimentary DNA, we performed reverse transcription-PCR assays on RNAs extracted from human cell lines and tissues to evaluate whether this marker might be expressed at other sites. RNA libraries extracted from normal human heart, lung, kidney, prostate, peripheral blood, brain, placenta, and muscle were negative for MN expression. RNAs extracted from liver and pancreatic tissue were positive for MN expression. Three of six renal cancer cell lines tested revealed MN expression. In addition, 12 of 17 samples of human renal cell carcinoma tissue tested positive for MN, all 12 of which were clear cell adenocarcinomas. This survey identified a unique association of MN expression with renal cell cancers, especially those of the clear cell variety, suggesting that MN is a potential marker for the diagnosis, staging, and therapeutic monitoring of renal cell carcinoma in humans.

Major histocompatibility complex class I and class II expression in renal cell carcinoma and modulation by interferon gamma

PURPOSE

To determine the expression of MHC class I and II in human renal cancer.

MATERIALS AND METHODS

We analyzed tissue sections from 22 primary and 28 metastatic renal cell carcinomas (RCC), as well as 31 established RCC cell lines. Tissue specimens from normal kidney and cell cultures of normal kidney epithelium were also studied. In addition, MHC antigen expression on RCC cell lines was assessed both before and after incubation with human recombinant interferon gamma (IFN-gamma). Antigen expression was determined by mixed hemadsorption, indirect immunofluorescence, fluorescence activated cell sorting (FACS) or immunoperoxidase staining using the monoclonal antibodies (mAbs) W6/32 (anti-MHC class I), mAbs NAMB-1 and BBM.1 (anti-beta-2 microglobulin), and mAbs L243 and 13-17 (anti-MHC class II) antibodies. Soluble beta-2 microglobulin in conditioned medium was measured by ELISA.

RESULTS

Normal renal epithelial cells, both in vivo and in vitro, showed low level expression of class I antigens. Immunohistochemical staining for MHC class II was limited to some proximal tubular cells, while cultured renal tubular cells were uniformly class II negative. The tumor cell populations in all 22 primary and in 26 of 28 (93%) metastatic RC specimens consisted predominantly of class I positive cells. Half of the samples from primary and metastatic tumors were class II negative. Incubation of RCC cell lines with IFN-gamma enhanced the expression of MHC class I, beta-2 microglobulin and class II. The upregulation of MHC expression was time and dose dependent and associated with increased release of soluble beta-2 microglobulin.

CONCLUSIONS

(i) Like normal kidney, virtually all primary human renal cell carcinomas express MHC class I antigens and retain this phenotype even during tumor progression and metastasis; (ii) class II expression on normal and RCC cells appears more limited but occurs frequently in both primary and metastatic lesions; and (iii) in most continuous RCC cell lines expression of MHC class I and II can effectively be stimulated by IFN-gamma. Since expression of MHC molecules might determine the immunogenicity of human RCC, its constitutive expression and augmentation could play an important role for the immunotherapy and prognosis of human renal cancer.

Cytotoxicity of gallium nitrate in vitro using bladder cancer cells

BACKGROUND

Gallium nitrate has been used systemically for some malignancies in clinical trials. Because bladder cancer has many transferrin (Tf) receptors and gallium has been reported to bind avidly with Tf receptors, gallium cytotoxicity and the possibility of intravesical instillation therapy with gallium nitrate were studied in vitro.

METHODS

The bladder cancer cell lines J82, 639V, VMCuB1, SCaBER, and 5637 were used. The amount of Tf receptor was checked by a rosette assay. As a cytotoxicity assay, two experimental models were tested using two or 72 hours of exposure to gallium solution. A gallium release study using 67Ga was done to investigate the movement of incorporated gallium.

RESULTS

J82 had the most and SCaBER had the least Tf receptors. For 72 hours of exposure at gallium concentrations above 250 mumol/L, the inhibitory effect was a function of gallium concentration, and 100% cytotoxicity occurred at 2 mmol/L. At lower concentrations of gallium, the effect was related to the amount of Tf and the level of Tf receptor expression of the cells. With two hours of exposure, which was assumed to be a model of intravesical therapy, the inhibitory effect increased in proportion to gallium concentration and the frequency of treatment. Twenty mmol/L gallium effectively inhibited the growth in two hours of exposure.

CONCLUSIONS

Intravesically administered gallium might be an effective therapy for bladder cancer, because its cytotoxicity is determined not by the amount of Tf receptor but by the gallium concentration and the duration of gallium exposure.

Reactivities of mouse monoclonal antibody K2.7 to renal cancers in complement dependent cytotoxicity and antibody dependent cell-mediated cytotoxicity

Immunohistochemical analysis by indirect immunoperoxidase staining demonstrated that monoclonal antibody (mAb) K2.7, derived from a mouse immunized with a renal cell carcinoma (RCC) cell line OS-RC-2, reacted with 89 of 95 renal cancer tissues (94%). Only 1 gastric and uterine cancer tissue showed positive staining among 87 cancer specimens from 9 different organs. Among normal human tissues, the renal tubule, testis, epithelium of the uterine endometrial gland and Fallopian tube, grey matter of cerebrum and cerebellum, and foreskin showed positive staining. Serological analysis by protein A mixed hemadsorption (PA) assay demonstrated that mAb K2.7 reacted with 25 of 31 RCC cell lines (81%), but with only 2 of 50 other cell lines from different organs. The specific antitumor activities of mAb K2.7 against RCC cell lines were investigated in vitro by complement dependent cytotoxicity (CDC) and antibody dependent cell-mediated cytotoxicity (ADCC) assays. In the CDC assay, all of the 9 RCC cell lines reactive serologically with mAb K2.7 were killed by mAb K2.7 with normal human serum, and the killing activity of mAb K2.7 correlated well with the reactivity of mAb K2.7 in the PA assay. mAb K2.7 showed the same killing activity against each of 3 RCC cell lines with sera from 9 patients with low and high stage renal cancers, as well as with normal human serum. In the ADCC assay, mAb K2.7 with peripheral blood leukocytes (PBLs) from 4 healthy donors showed cytotoxic activity against RCC cell lines. Peripheral blood leukocytes from the same 9 renal cancer patients also showed significant killing activity against the 3 RCC cell lines. These findings suggest the potential utility of mAb K2.7 for specific immunotherapy of renal cancer.

Current status of monoclonal antibodies for imaging and therapy of prostate cancer

It is clear that there is significant need for improved staging and therapy of prostate cancer. The attributes and strengths of MoAbs seem particularly well-suited to the setting of prostate cancer. Recent progress in the application of MoAbs to in vivo imaging and therapy is encouraging. Clearly, further such efforts in prostate cancer are warranted.

Region-specific methylation of the parathyroid hormone-related peptide gene determines its expression in human renal carcinoma cell lines

Tumor production of a parathyroid hormone-related peptide (PTHrP) is a common cause of the syndrome of humoral hypercalcemia of malignancy, which is frequently associated with renal cell carcinomas. Why certain renal cell carcinomas produce PTHrP while others do not is unknown. Using a system of 12 human renal carcinoma cell lines which either do (n = 6) or do not (n = 6) produce PTHrP, we found that the expression of the PTHrP gene in these cell lines is controlled at the transcriptional level. Transfection studies failed to demonstrate variation in PTHrP promoter activity in these cell lines sufficient to account for the differential PTHrP expression, implicating a cis-acting mechanism. Transcription of the PTHrP gene in these cell lines was found to correlate with the methylation state of specific CpG dinucleotides located within the promoter region but outside a CpG island. The functional importance of this mechanism of control was confirmed by the ability of the demethylating agent, 5-azacytidine, to induce PTHrP mRNA expression in previously nonexpressing cell lines.

Interleukin-10 production by human carcinoma cell lines and its relationship to interleukin-6 expression

Recent data indicate a major role for IL-10 in suppressing immune and inflammatory reactions. To date, expression of human IL-10 has been attributed primarily to helper T lymphocytes, activated monocytes, and neoplastic B cells, and was often found to be associated with IL-6 expression. In this study we sought to determine whether non-hematopoietic human tumor cell lines produce IL-10 and, if so, what is the relationship between IL-10 and IL-6. Using ELISA, we determined IL-10 and IL-6 levels in culture supernatants of 48 cell lines established from carcinomas of the kidney, colon, breast and pancreas, malignant melanomas and neuroblastomas. IL-6 protein was secreted by 28 of the tumor cell lines; IL-10 was measurable in 15 cell lines. IL-6 secretion was maximal and most frequent in renal-cancer cell lines, while IL-10 production was found to be highest and most common among cell lines derived from colon carcinomas. IL-10 in conditioned medium of one of the colon carcinoma cell lines (CCL222) was bio-active, as demonstrated in the mouse MC/9 mast-cell-line assay and in human mixed-lymphocyte reactions. In both assays, IL-10 bio-activity was neutralized by an anti-IL-10 monoclonal antibody. Expression of IL-6 and IL-10 was confirmed by RNA analysis using message amplification by PCR and sequencing of amplified cDNA. LPS, IL-1 alpha, and TNF-alpha strongly enhanced the release of IL-6 by RCC cells, but only marginally affected IL-10 production in colon-carcinoma cells. IL-10 secretion by colon-carcinoma cells was moderately stimulated by IFN-gamma and IL-4. Dexamethasone suppressed the release of IL-6, but had no inhibitory effect on IL-10 secretion. Our results demonstrate that tumor cell lines established from certain types of human carcinomas are capable of expressing and releasing IL-6 and/or IL-10, suggesting a role of these cytokines in solid-tumor development and anti-tumor immunity.

Molecular cloning of the human kidney differentiation antigen gp160: human aminopeptidase A

gp160 is a cell surface differentiation-related glycoprotein of 160 kDa expressed by epithelial cells of the glomerulus and proximal tubule cells of the human nephron but only by a subset of renal cell carcinomas (RCCs). We have reported that gp160 expression correlates with the resistance of cultured RCCs to the antiproliferative effects of alpha interferon, while lack of expression correlates with sensitivity to alpha interferon. In this study, we have purified gp160 protein, obtained partial sequences of random peptides, and isolated a full-length cDNA. The gp160 cDNA possesses 78% homology to the murine BP-1/6C3 antigen, a B-lymphocyte differentiation protein that exhibits aminopeptidase A (APA; EC 3.4.11.7) activity. Enzymatic assays on human RCC cell lines indicated a 100% concordance between APA activity and gp160 expression. APA activity of gp160-expressing RCC cells was increased or decreased by a panel of APA activators or inhibitors, respectively. Furthermore, anti-gp160 monoclonal antibodies immunoprecipitate APA activity from RCC cell lysates and selectively deplete APA activity from RCC cell extracts. These data indicate that the gp160 human kidney/RCC glycoprotein is human APA.

Antibody localization in human renal cell carcinoma: a phase I study of monoclonal antibody G250

PURPOSE

To define the imaging and biodistribution characteristics of iodine 131-labeled monoclonal antibody (mAb) G250 (131I-mAbG250), which recognizes a cell-surface antigen expressed by human renal cell carcinoma (RCC).

PATIENTS AND METHODS

G250 is a cell-surface antigen recognized by mAbG250 expressed by RCC but not detected in normal kidney. Clear-cell RCC, the most frequent form of RCC, shows homogeneous expression of G250, whereas non-clear-cell RCC and cancers derived from other organs generally do not express G250. Expression in normal tissues is highly restricted and limited to large bile ducts and gastric epithelium. 131I-mAbG250 was administered intravenously (IV) to 16 patients with RCC 7 to 8 days before surgery at five dose levels, with at least three patients entered at each dose level.

RESULTS

Clear tumor images were observed in 12 patients with G250-positive tumors and in one of three patients with G250-negative tumors. Imaged lesions in the peritoneal cavity were confirmed at surgery. The smallest lesion visualized was 8 mm in diameter. The specificity of 131I-mAbG250 localization to tumor tissue was established by radioactivity measurements, autoradiography, and immunohistochemistry of biopsied tissues, and technetium 99-human serum albumin blood-flow studies. The fraction of the injected 131I-mAbG250 dose per gram tumor (%ID/g tumor) localized in G250-positive tumors showed a broad range, but reached levels as high as 0.02% to 0.12%.

CONCLUSION

131I-mAbG250 localized specifically to G250 antigen-positive RCC and seems to have considerable potential as an imaging agent in RCC patients. 131I-mAbG250 uptake in the tumors, relative as well as absolute, are among the highest reported for tumor biopsies obtained 8 days after IV mAb administration. Based on the specific localization and high accumulation, mAb G250 may have therapeutic potential.

High IL-6 levels in ascitic fluid correlate with reactive thrombocytosis in patients with epithelial ovarian cancer

Non-haematopoietic malignancies are commonly associated with thrombocytosis. The aetiology of tumour-associated thrombocytosis is still unclear but may be related to tumour-derived thrombopoietin-like factors. Epithelial ovarian tumour cells have been shown to release IL-6 in vitro and high IL-6 levels have been identified in ascites of patients with ovarian cancer. Since IL-6 is a potent stimulator of megakaryocytopoiesis we examined IL-6 production at the tumour site and its relationship to serum IL-6 levels and circulating platelet counts in patients with ovarian cancer. Forty patients undergoing exploratory laparotomy for epithelial ovarian cancer [stage I+II: 6 (15%); stage III: 25 (62.5%); stage IV: 9 (22.5%)] and 24 women with benign ovarian conditions were evaluated. Sera were available from 39 cases with ovarian cancer and from 19 cases with benign ovarian tumours. Ascites was obtained from 35 patients with ovarian cancer. IL-6 activity in serum and ascitic fluid was determined by the standard B9 proliferation assay (detection level: 1 pg/ml). IL-6 bioactivity was detectable in 22 (56%) sera from patients with ovarian cancer, but in only five (26%) of the serum samples obtained from benign cases (P < 0.001). Serum IL-6 levels in patients with ovarian cancer were significantly higher (median 3 pg/ml; range < 1 to 1221 pg/ml) than in patients with benign ovarian conditions (median 0 pg/ml; range < 1 to 4 pg/ml) (P < 0.001). However, much higher concentrations of IL-6 were measured in malignant ascites specimens (median 22,100 pg/ml; range < 1 to 182,600 pg/ml). IL-6 bioactivity in serum and ascites samples was completely inhibited by a neutralizing goat anti-human IL-6 antiserum. Thrombocytosis (platelet counts > 400 x 10(9)/l) occurred in 25 (62.5%) of the 40 patients with ovarian cancer, but in only two (8%) of the 24 cases with benign ovarian tumours. In eight (20%) cases with malignant disease platelet counts ranged between 600 x 10(9)/l and 1060 x 10(9)/l. IL-6 bioactivity in ascitic fluid correlated significantly with circulating platelet counts (r = 0.5916; P < 0.001). Maximum IL-6 bioactivity in ascites and highest platelet counts occurred in patients with undifferentiated ovarian adenocarcinoma or advanced disease. In conclusion, these observations strongly suggest a role for IL-6 in the development of tumour-associated thrombocytosis.