A phase I study to evaluate the safety, pharmacokinetics, and pharmacodynamics of PF-06939999 (PRMT5 inhibitor) in patients with selected advanced or metastatic tumors with high incidence of splicing factor gene mutations

BACKGROUND

Protein arginine methyltransferase 5 (PRMT5) methylates multiple substrates dysregulated in cancer, including spliceosome machinery components. PF-06939999 is a selective small-molecule PRMT5 inhibitor.

PATIENTS AND METHODS

This phase I dose-escalation and -expansion trial (NCT03854227) enrolled patients with selected solid tumors. PF-06939999 was administered orally once or twice a day (q.d./b.i.d.) in 28-day cycles. The objectives were to evaluate PF-06939999 safety and tolerability to identify maximum tolerated dose (MTD) and recommended part 2 dose (RP2D), and assess pharmacokinetics (PK), pharmacodynamics [changes in plasma symmetric dimethylarginine (SDMA) levels], and antitumor activities.

RESULTS

In part 1 dose escalation, 28 patients received PF-06939999 (0.5 mg q.d. to 6 mg b.i.d.). Four of 24 (17%) patients reported dose-limiting toxicities: thrombocytopenia (n = 2, 6 mg b.i.d.), anemia (n = 1, 8 mg q.d.), and neutropenia (n = 1, 6 mg q.d.). PF-06939999 exposure increased with dose. Steady-state PK was achieved by day 15. Plasma SDMA was reduced at steady state (58%-88%). Modulation of plasma SDMA was dose dependent. No MTD was determined. In part 2 dose expansion, 26 patients received PF-06939999 6 mg q.d. (RP2D). Overall (part 1 + part 2), the most common grade ≥3 treatment-related adverse events included anemia (28%), thrombocytopenia/platelet count decreased (22%), fatigue (6%), and neutropenia (4%). Three patients (6.8%) had confirmed partial response (head and neck squamous cell carcinoma, n = 1; non-small-cell lung cancer, n = 2), and 19 (43.2%) had stable disease. No predictive biomarkers were identified.

CONCLUSIONS

PF-06939999 demonstrated a tolerable safety profile and objective clinical responses in a subset of patients, suggesting that PRMT5 is an interesting cancer target with clinical validation. However, no predictive biomarker was identified. The role of PRMT5 in cancer biology is complex and requires further preclinical, mechanistic investigation to identify predictive biomarkers for patient selection.

Sacituzumab govitecan, a Trop-2-directed antibody-drug conjugate, for patients with epithelial cancer: final safety and efficacy results from the phase I/II IMMU-132-01 basket trial

BACKGROUND

Sacituzumab govitecan (SG), a trophoblast cell surface antigen-2 (Trop-2)-directed antibody-drug conjugate, has demonstrated antitumor efficacy and acceptable tolerability in a phase I/II multicenter trial (NCT01631552) in patients with advanced epithelial cancers. This report summarizes the safety data from the overall safety population (OSP) and efficacy data, including additional disease cohorts not published previously.

PATIENTS AND METHODS

Patients with refractory metastatic epithelial cancers received intravenous SG (8, 10, 12, or 18 mg/kg) on days 1 and 8 of 21-day cycles until disease progression or unacceptable toxicity. Endpoints for the OSP included safety and pharmacokinetic parameters with investigator-evaluated objective response rate (ORR per RECIST 1.1), duration of response, clinical benefit rate, progression-free survival, and overall survival evaluated for cohorts (n > 10 patients) of small-cell lung, colorectal, esophageal, endometrial, pancreatic ductal adenocarcinoma, and castrate-resistant prostate cancer.

RESULTS

In the OSP (n = 495, median age 61 years, 68% female; UGT1A1∗28 homozygous, n = 46; 9.3%), 41 (8.3%) permanently discontinued treatment due to adverse events (AEs). Most common treatment-related AEs were nausea (62.6%), diarrhea (56.2%), fatigue (48.3%), alopecia (40.4%), and neutropenia (57.8%). Most common treatment-related serious AEs (n = 75; 15.2%) were febrile neutropenia (4.0%) and diarrhea (2.8%). Grade ≥3 neutropenia and febrile neutropenia occurred in 42.4% and 5.3% of patients, respectively. Neutropenia (all grades) was numerically more frequent in UGT1A1∗28 homozygotes (28/46; 60.9%) than heterozygotes (69/180; 38.3%) or UGT1A1∗1 wild type (59/177; 33.3%). There was one treatment-related death due to an AE of aspiration pneumonia. Partial responses were seen in endometrial cancer (4/18, 22.2% ORR) and small-cell lung cancer (11/62, 17.7% ORR), and one castrate-resistant prostate cancer patient had a complete response (n = 1/11; 9.1% ORR).

CONCLUSIONS

SG demonstrated a toxicity profile consistent with previous published reports. Efficacy was seen in several cancer cohorts, which validates Trop-2 as a broad target in solid tumors.

Abstract P4-22-15: Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory, metastatic triple-negative breast cancer (mTNBC): Updated results

Background. mTNBC has an aggressive course with limited effective therapy options and a median progression-free survival (PFS) of 2-4 months (mos) with standard therapy. Sacituzumab govitecan (IMMU-132) is an ADC targeting Trop-2, an antigen present in many epithelial cancers, including TNBC, and delivering SN-38, a topoisomerase I inhibitor as its therapeutic moiety. IMMU-132 was awarded Breakthrough Therapy designation by FDA based on its previously reported activity in relapsed/refractory mTNBC patients. Here we present updated results from the mTNBC cohort of an ongoing phase I/II study (ClinicalTrials.gov, NCT01631552).

Methods. mTNBC patients (pts) received IMMU-132 10 mg/kg on days 1 and 8 every 21 days. Trop-2 expression was not required for enrollment, but available tumor specimens underwent immunohistological (IHC) testing. Efficacy was assessed locally by RECIST 1.1; ORR, PFS and overall survival (OS) were determined for all pts. Pharmacokinetic parameters were estimated in select pts with adequate blood sampling. Immunogenicity to IMMU-132 was examined in all pts.

Results. We previously reported preliminary efficacy results in 51 mTNBC patients. Here we present data on 69 patients with data cutoff June 5, 2016. Median age was 56 years (31-81) and a median of 5 prior therapies (range 1-12), with 66 evaluable for response; ORR was 29% (19/66) 2 confirmed complete (CR) and 17 confirmed partial responses (PR). The median intention-to-treat PFS is 5.6 mos (95% CI, 3.6-7.1 mos) and median OS is 14.3 mos (95% CI, 10.5-18.8 mos). PRs included 2 pts whose tumors did not respond to anti-PD-L1 therapy. The duration of response in the 19 confirmed responders (8 continuing therapy) is 11.5 mos (95% CI = 7.6 to 12.7). The clinical benefit rate (CR+PR+SD>6 mos) for the 66 assessable patients is currently 45.5%. The majority (88%) of archival tumor specimens were moderately (2+) to strongly (3+) positive by IHC for Trop-2, precluding using Trop-2 expression as a selection criterion. Among current adverse events, grade >3 drug-related toxicities included neutropenia (35%), leukopenia (16%), anemia (13%), vomiting (9%), diarrhea (10%), and febrile neutropenia (4%). Clearance kinetics in 8 pts showed IMMU-132 and IgG had a terminal half-life of 15.3 ± 2.7 h and 86.5 ± 40.5 h, respectively, with area under the curve for free SN-38 (unbound) only 3% of the total amount of SN-38 (e.g., IgG bound). Thus, most SN-38 remains bound to the conjugate, and is released at a rate predicted from in vitro serum stability studies. No pt developed anti-IMMU-132 antibodies.

Conclusion The Trop-2-targeting ADC, IMMU-132, delivering cytotoxic doses of SN-38, shows high objective and durable tumor responses with manageable toxicity in heavily-pretreated pts with mTNBC in this updated cohort, supporting further development in this population with an unmet medical need.

Citation Format: Bardia A, Diamond JR, Mayer IA, Isakoff SJ, Abramson V, Starodub AN, O'Shaughnessy J, Kalinsky K, Moroose R, Shah N, Juric D, Shapiro GI, Guarino M, Ocean AJ, Messersmith WA, Berlin JD, Wegener WA, Sharkey RM, Goldenberg DM, Vahdat LT. Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory, metastatic triple-negative breast cancer (mTNBC): Updated results [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-15.

Abstract PD3-06: Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC

Background: Triple-negative breast cancer (TNBC) comprises about 15% of all breast cancer types, and has a particularly aggressive course. Following first-line therapy, the median PFS is <3 months, and OS is <10 months. Therefore, new treatment strategies are needed. Since Trop-2 is expressed in >90% of TNBC, as measured by IHC, we conducted a trial to evaluate the safety and efficacy of a humanized anti-Trop-2 monoclonal antibody conjugated to a high concentration of SN-38, a camptothecin that is a topoisomerase I inhibitor and the active metabolite of the prodrug irinotecan, with 2-3 logs higher potency than the prodrug.

Methods: After establishing the optimal repeated dose in a Phase I trial (ClinicalTrials.gov, NCT01631552) involving many different solid cancer types, an expanded Phase II was undertaken in a number of cancers, including TNBC. Patients received 8 or 10 mg/kg IMMU-132 i.v. on days 1 and 8 of 21-day repeated cycles. Assessments of safety and response by RECIST1.1 were made weekly and bimonthly, respectively. Tumor biopsies (archival, at baseline prior to treatment, and at disease progression) were obtained when safe and feasible.

Results: As of May 10, 2015, 58 patients with TNBC, with a median of 4 prior therapies (range, 1-11), were treated with IMMU-132. Grade 3-4 toxicities included neutropenia (26%), febrile neutropenia (2%), diarrhea (2%), anemia (4%), and fatigue (4%). No patient developed antibodies to SN-38 or the antibody, and no patient discontinued therapy due to toxicity. Tumor responses were defined as ORR (CR+PR) in 31% of 49 evaluated patients, including 2 with CR, and a clinical benefit ratio (CR+PR+SD>6 mo) of 49% (63% with SD>4 mo; 23 patients continuing treatment after 1st assessment). The current median progression-free survival is 7.3 months with 44% maturity in 50 patients treated at the 8 or 10 mg/kg dose level. Overall survival data are still not mature 20 months after enrollment of first patient. Clinical efficacy correlated to biomarker studies, including Trop-2 expression (target of antibody), topoisomerase-1 expression (target of SN-38), and homologous recombinant deficiency (HRD) assay (marker of DNA repair), is being studied. Immunohistochemistry results in archival specimens currently show 97% positivity of Trop-2 among 34 specimens evaluated, with 79% having high intensity (2+/3+) staining.

Conclusions: The Trop-2-targeting IMMU-132, delivering cytotoxic doses of the topoisomerase I inhibitor, SN-38, shows manageable toxicity, and encouraging anti-tumor activity in relapsed/refractory patients with TNBC. This ADC appears to have a high therapeutic index in heavily pretreated patients.

Citation Format: Bardia A, Diamond JR, Mayer IA, Starodub AN, Moroose RL, Isakoff SJ, Ocean AJ, Guarino MJ, Berlin JD, Messersmith WA, Thomas SS, O'Shaughnessy JA, Kalinsky K, Maurer M, Chang JC, Forero A, Traina T, Gucalp A, Wilhelm F, Wegener WA, Maliakal P, Sharkey RM, Goldenberg DM, Vahdat LT. Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD3-06.

The management of hepatocellular carcinoma. Current expert opinion and recommendations derived from the 10th World Congress on Gastrointestinal Cancer, Barcelona, 2008

This article summarizes the expert discussion on the management of hepatocellular carcinoma (HCC), which took place during the 10th World Gastrointestinal Cancer Congress (WGICC) in Barcelona, June 2008. A multidisciplinary approach to a patient with HCC is essential, to guarantee optimal diagnosis and staging, planning of surgical options and selection of embolisation strategies or systemic therapies. In many patients, the underlying cirrhosis represents a challenge and determines therapeutic options. There is now robust evidence in favour of systemic therapy with sorafenib in patients with advanced HCC with preserved liver function. Those involved in the care for patients with HCC should be encouraged to participate in well-designed clinical trials, to increase evidence-based knowledge and to make further progress.

A phase I study of neoadjuvant paclitaxel/radiation in patients with potentially resectable adenocarcinoma of the pancreas

15067

Background: To determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLT) of weekly paclitaxel when given with concurrent radiation in the neoadjuvant setting to patients with potentially resectable adenocarcinoma of the pancreas. A secondary goal was to assess the value of 18-fluoro-deoxy-glucose positron emission tomography (FDG-PET) as an early marker of therapeutic response. Methods: Patients received weekly paclitaxel, given as a 3-hour infusion, during the course of radiation. The starting dose of paclitaxel was 30 mg/m2/week. Doses were escalated in increments of 15 mg/m2 in successive cohorts of 3–6 patients. Radiation therapy consisted of 45Gy in 25 fractions over 5 weeks. CT and PET scans were obtained prior to initiating treatment and one month following completion of chemoradiation. Results: Nine patients with resectable pancreatic cancer were enrolled through two dose levels. DLT was defined as grade 3 or greater. There were no DLTs at the first dose level of 30 mg/m2/ week. DLTs consisted of nausea, neutropenia and hepatic toxicity developed at the second dose level of 45 mg/m2/ week. Pre-treatment PET scans revealed uptake in all nine of the patients whereas pre-treatment CT scans detected disease in only 5 of 9 patients. Post-treatment PET scans correlated with pathologic findings in all 9 patients. Conclusions: The MTD for concurrent paclitaxel/radiation in the neoadjuvant setting was determined to be 30 mg/m2/week. DLTs were nausea, neutropenia and hepatic toxicity. FDG-PET may be superior to CT scans as a radiographic marker of treatment response.

[Table: see text]

Phase II study of the clinical and biological activity of cetuximab and celecoxib in patients (pts) with refractory colorectal cancer (CRC)

14516

Background: The epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) pathways play key roles in colon carcinogenesis. EGFR and COX-2 signaling can be mutually reinforcing. Celecoxib, a selective COX-2 inhibitor, inhibits the EGFR pathway through inhibition of PI3/Akt and NF-κB pathways. This study explores the clinical and biological effects of blockade of complementary pathways of the EGFR by combining cetuximab with celecoxib. Methods: Cetuximab-naive pts with refractory CRC were treated with cetuximab (400 mg/m2 loading dose followed by weekly cetuximab at 250 mg/m2) and celecoxib (200 mg orally twice daily). Patients were assessed for response every 8 weeks. Urinary PGE-M, a metabolite of PGE-2 which correlates with in vivo COX-2 activity, and serum TGF-a, a ligand that binds to EGFR, were measured to assess the biological effect of COX-2 and EGFR blockade. Results: Seventeen of a planned 40 pts accrued to this study. Currently, data is available on 12 of these patients. Three pts had to stop treatment on 1st infusion due to a grade 3 cetuximab infusion reaction. One pt had a mild infusion reaction and was successfully rechallenged after pre-medication and a slower infusion rate. By RECIST criteria, 1 pt (8.3%) achieved a partial response (PR) and 4 pts (33%) had a best response of stable disease (SD). The mean time on study for the 9 pts without grade 3 infusion reaction was 95.7 days (range 28- 175). Pts with SD or PR were on study for a mean of 135 days (range 107–175 days) and pts with progressive disease (PD) were on study for a mean of 47 days (range 28–56 days). Baseline urinary PGE-M levels in pts with SD or PR were higher than in pts with PD (30.5+17.6 vs 18.1+9.4 ng/mg Cr). Baseline serum TGF-a levels were similar between the two groups (27.1+9.6 vs 25.4+10.3 pg/ml respectively). Conclusions: In preliminary analysis, this regimen resulted in response rates similar to published response rates for single agent cetuximab. Pts with at least SD had higher baseline urinary PGE-M levels, which may serve as a marker for efficacy of this combined therapy. Data on serial TGF-a and PGE-M levels will be presented. Response data on all 17 pts will be presented. Supported by P50 CA95103 and Bristol-Myers Squibb. Celecoxib provided by Pfizer.

[Table: see text]

Chemotherapy for resectable and advanced pancreatic cancer

This article will review the pertinent data on the use of chemotherapy for all stages of pancreatic cancer. For patients with metastatic disease, fluorouracil (5-FU) was the standard of care for several decades until a single randomized trial established that gemcitabine (Gemzar) produced a greater clinical benefit response, median survival, and 1-year survival. Among the currently available chemotherapy agents, the taxanes, fluoropyrimidines, and camptothecins are being evaluated in clinical trials alone or in combination with gemcitabine. Newer agents that are not classically cytotoxic are also under investigation and hold promise for the future. In patients with locally advanced unresectable disease, chemotherapy is commonly used to sensitize the cancer to radiation. Current investigations focus on trying to improve chemotherapy as a radiation sensitizer, using, for example, infusional 5-FU and gemcitabine. Early-stage, surgically resectable patients may benefit from the combination of chemotherapy and radiation, although more recent trials conducted in Europe raise some doubt. However, flaws in trial design do not allow firm conclusions to be drawn about the benefits of adjuvant therapy. Both chemotherapy and chemoradiation are under further investigation. Significant improvements in the survival of patients with pancreatic cancer will be achieved as more effective systemic therapies are developed, including agents with novel cellular targets.

A phase II study of gemcitabine and 5-fluorouracil in metastatic pancreatic cancer: an Eastern Cooperative Oncology Group Study (E3296)

Gemcitabine has recently been compared favorably to 5-fluorouracil (5-FU) as the standard chemotherapy for advanced pancreas cancer. Based on phase I data that combining gemcitabine with 5-FU is safe and has evidence for clinical activity, a phase II trial was conducted by the Eastern Cooperative Oncology Group (ECOG). Patients with metastatic disease, good performance status and organ function were eligible and enrolled after providing informed consent. Patients were given gemcitabine (1,000 mg/m(2)) followed by 5-FU (600 mg/m(2)) weekly for 3 weeks of every 4. Of 37 patients enrolled over a 3-month period, 36 were eligible. Partial responses were seen in 5 patients (14%). Median survival was 4.4 months with a 1-year survival rate of 8.6%. A randomized trial of the combination of 5-FU and gemcitabine versus gemcitabine alone is currently accruing patients in ECOG.

Warfarin-5-FU interaction--a consecutive case series

Five patients from a single institution received concomitant warfarin and 5-fluorouracil (5-FU) during a 3-year period. The mean weekly warfarin dose before starting chemotherapy was 40.66 mg and during chemotherapy it was 24 mg (p=0.0026). All patients required a warfarin dosage reduction (range 18-74%, mean 44%). Two patients were hospitalized, one with a major retroperitoneal bleed, the other for fresh-frozen plasma administration and observation. Maximum international normalized ratios (INRs) ranged from 3.66-23.7. This series confirms a common, clinically significant interaction between warfarin and 5-FU. An interaction between capecitabine, the orally available prodrug of 5-FU, and warfarin also has been reported. We recommend weekly monitoring of prothrombin time and INR for all patients receiving concomitant warfarin and 5-FU or capecitabine.

A phase I study of gemcitabine, 5-fluorouracil and leucovorin in patients with advanced, recurrent, and/or metastatic solid tumors

INTRODUCTION

This was a dose escalation phase I trial designed to establish the MTD (maximum tolerated dose) and toxicity profile of the combination of gemcitabine, leucovorin and 5-fluorouracil (5-FU).

METHODS

Standard eligibility criteria were required for patients with advanced malignancy to enroll. Gemcitabine was escalated from an initial dose of 800 mg/m2. Gemcitabine was administered prior to leucovorin (25 mg/m2) followed by bolus 5-FU (600 mg/m2) every week for 3 weeks followed by 1 week of rest.

RESULTS

Of 21 patients enrolled, 20 were eligible for MTD determination. Patients received a median of three 4-week cycles of chemotherapy (range: 1 to 8 cycles). Toxicity was predominantly hematologic or gastroenterologic. Four dose levels were studied. At a gemcitabine dose of 1,500 mg/m2 systemic symptoms of fatigue accompanied hematologic toxicity and patients refused further therapy. At 1,250 mg/m2, full dose intensity was not delivered during the first cycle in 7 of 8 patients treated. Therefore, 1,000 mg/m2 was established as the recommended phase II dose for gemcitabine in this study. Antitumor activity was seen at all dose levels.

CONCLUSIONS

The combination of gemcitabine, leucovorin and 5-FU was tolerable at full doses of all 3 drugs with an expected toxicity profile. Recommended phase II dose for gemcitabine was 1,000 mg/m2. Initial evidence of clinical activity was seen in a variety of tumor types.

5-Fluorouracil and leucovorin therapy in patients with hormone refractory prostate cancer: an Eastern Cooperative Oncology Group phase II study (E1889)

This report is a multi-institutional phase II study designed to obtain the response rate, survival, and toxicity profile for patients having hormone-refractory prostate cancer. Patients who had bidimensionally measurable prostate carcinoma in first or second remission after previous hormonal therapy but no history of chemotherapy were eligible. Patients were treated with leucovorin, 20 mg/m2 intravenously, followed by 5-fluorouracil (5-FU), 425 mg/m2 intravenously daily for 5 days, with cycles repeated every 28 days. Of 38 eligible patients, 3 (7.9%) had partial responses to therapy and 20 (52.6%) had stable disease. Median survival was 11.6 months for all 38 patients and median time to progression was 4.4 months. Most of the serious side effects were gastrointestinal or hematologic and overall, 23 of 38 patients (60.5%) experienced at least one grade 3 or 4 treatment-related toxicity of any type, as measured by the National Cancer Institute common toxicity criteria. Five patients (13.2%) withdrew from the study because of adverse reactions from chemotherapy. We conclude that treatment of hormone-refractory prostate cancer patients with 5-FU and leucovorin chemotherapy produced few responses at the cost of significant side effects. Further investigation of this combination is not warranted in this setting.

Capitate hairs on cotton textile wastes

Bract and leaf samples from growing cotton plants and from cotton textile wastes were examined by scanning electron microscopy to determine if intact capitate hairs are important components fo raw cotton wastes. The density of capitate hairs on bract and leaf fragments in raw cotton was similar to that found on bracts and leaves from greenhouse and field collections. A bale of strict low middling raw cotton contains between 1.23 an 2.54 X 10(8) capitate hairs of bract origin alone. Capitate hairs could be important components of cotton textile wastes because of their abundance and because they contain chemicals that may be involved in the cause of respiratory disease in textile workers.

Cytoplasmic annulate lamellae in human spermatogenesis

Electron microscopic examination of normal human testicular tissue revealed annulate lamellae (AL) in the cytoplasm of primary spermatocytes and spermatids. AL of primary spermatocytes are encountered in the perinuclear region, parallel to the nuclear envelope and form single or multiple membranous profiles containing numerous annuli (500-600 A in diameter) frequently associated with a fibrillar electron dense material. Spermatids contain numerous layers of AL either continuous with the nuclear envelope and caudal to the acrosome or peripherally positioned in the cytoplasm. Individual lamellae possess terminal dilations and display continuities with the endoplasmic reticulum. The interlamellar space in spertmatid AL is entirely filled with a fine granular electron dense material. Additionally, the breakdown of AL in spermatozoan residual bodies is indicated by a dilation of AL cisternae to form vacuoles following the dissolution of pore complexes.

Morphologic and immunologic studies of a human colon tumor cell line (SW-48)

A permanent human tissue culture cell line (SW-48) has been established from an adenocarcinoma of the transverse colon. Cells in the center of early colonies were cuboidal and loosely bound; cells on the periphery of the same colonies were more columnar, the nuclei were displaced toward the basal region, and the free surface formed stunted microvilli. These columnar cells ofter aligned themselves to resemble normal absorptive tissue. Carcinoembryonic antigen (CEA) was identified by immunofluorescent microscopy on the surface membrane of the tumor cells. Significantly more CEA could be isolated from the culture medium than from the whole cells. On agar gel diffusion analysis with a monospecific anti-CEA serum (G.P. 32), SW-48 CEA and CEA preparations from solid tumors demonstrated complete identity.

The fine structural localization of testicular phosphatases in man: the control testis

Electron microscopic cytochemistry was used to determine the localization of five phosphatase enzymes-glucose-6-phosphatase, inosine diphosphatase, thiamine pyrophosphatase, acid phosphatase, and adenosine triphosphatase-in control human testes. Glucose-6-phosphatase occurred in the endoplasmic reticulum and nuclear envelope of Sertoli cells, Leydig cells and primitive spermatogonia, but was not observed in more advanced spermatogenic cells. The presence of glucose-6-phosphatase activity paralleled the presence of glycogen in spermatogenic cells, i.e., both occurred in type AL and AD spermatogonia but not in type AP or B spermatogonia or in more advanced spermatogenic cells. Inosine diphosphatase activity was found in the endoplasmic reticulum, nuclear envelope, and Golgi complex of Sertoli cells and all spermatogenic cells except late spermatids. Additionally, inosine diphosphatase activity was localized at the junctions between Sertoli cells and late spermatids, but was not associated with any other plasma membrane. Thiamine pyrophosphatase reaction product was found in the Golgi bodies of Sertoli cells and in spermatogenic cells through immature spermatids. Neither inosine diphosphatase nor thiamine pyrophosphatase was observed in the Golgi bodies of spermatids during acrosomal formation. Acid phosphatase activity was found in lysosomes of spermatogonia, spermatocytes, and spermatids, in lysosomes of Leydig cells, and in lysosomes, lipofuscin bodies, and Golgi cisternae of Sertoli cells. It is thought that Sertoli lysosomes play a role in the phagocytosis of degenerating germ cells; however, the role of spermatogenic or Leydig lysosomes is unknown. Adenosine triphosphatase activity occurred at the interfaces between two spermatogonia, and between Sertoli cells and spermatogonia, but was not observed in the spaces between two Sertoli cells, two spermatocytes, two spermatids, or between Sertoli cells and spermatocytes, or between Sertoli cells and spermatids.