Collateral damage: the impact on outcomes from cancer surgery of the COVID-19 pandemic.

BACKGROUND: Cancer diagnostics and surgery have been disrupted by the response of health care services to the coronavirus disease 2019 (COVID-19) pandemic. Progression of cancers during delay will impact on patients' long-term survival. PATIENTS AND METHODS: We generated per-day hazard ratios of cancer progression from observational studies and applied these to age-specific, stage-specific cancer survival for England 2013-2017. We modelled per-patient delay of 3 and 6 months and periods of disruption of 1 and 2 years. Using health care resource costing, we contextualise attributable lives saved and life-years gained (LYGs) from cancer surgery to equivalent volumes of COVID-19 hospitalisations. RESULTS: Per year, 94 912 resections for major cancers result in 80 406 long-term survivors and 1 717 051 LYGs. Per-patient delay of 3/6 months would cause attributable death of 4755/10 760 of these individuals with loss of 92 214/208 275 life-years, respectively. For cancer surgery, average LYGs per patient are 18.1 under standard conditions and 17.1/15.9 with a delay of 3/6 months (an average loss of 0.97/2.19 LYGs per patient), respectively. Taking into account health care resource units (HCRUs), surgery results on average per patient in 2.25 resource-adjusted life-years gained (RALYGs) under standard conditions and 2.12/1.97 RALYGs following delay of 3/6 months. For 94 912 hospital COVID-19 admissions, there are 482 022 LYGs requiring 1 052 949 HCRUs. Hospitalisation of community-acquired COVID-19 patients yields on average per patient 5.08 LYG and 0.46 RALYGs. CONCLUSIONS: Modest delays in surgery for cancer incur significant impact on survival. Delay of 3/6 months in surgery for incident cancers would mitigate 19%/43% of LYGs, respectively, by hospitalisation of an equivalent volume of admissions for community-acquired COVID-19. This rises to 26%/59%, respectively, when considering RALYGs. To avoid a downstream public health crisis of avoidable cancer deaths, cancer diagnostic and surgical pathways must be maintained at normal throughput, with rapid attention to any backlog already accrued.

PITX2 and non-canonical Wnt pathway interaction in metastatic prostate cancer.

The non-canonical Wnt pathway, a regulator of cellular motility and morphology, is increasingly implicated in cancer metastasis. In a quantitative PCR array analysis of 84 Wnt pathway associated genes, both non-canonical and canonical pathways were activated in primary and metastatic tumors relative to normal prostate. Expression of the Wnt target gene PITX2 in a prostate cancer (PCa) bone metastasis was strikingly elevated over normal prostate (over 2,000-fold) and primary prostate cancer (over 200-fold). The elevation of PITX2 protein was also evident on tissue microarrays, with strong PITX2 immunostaining in PCa skeletal and, to a lesser degree, soft tissue metastases. PITX2 is associated with cell migration during normal tissue morphogenesis. In our studies, overexpression of individual PITX2A/B/C isoforms stimulated PC-3 PCa cell motility, with the PITX2A isoform imparting a specific motility advantage in the presence of non-canonical Wnt5a stimulation. Furthermore, PITX2 specific shRNA inhibited PC-3 cell migration toward bone cell derived chemoattractant. These experimental results support a pivotal role of PITX2A and non-canonical Wnt signaling in enhancement of PCa cell motility, suggest PITX2 involvement in homing of PCa to the skeleton, and are consistent with a role for PITX2 in PCa metastasis to soft and bone tissues. Our findings, which significantly expand previous evidence that PITX2 is associated with risk of PCa biochemical recurrence, indicate that variation in PITX2 expression accompanies and may promote prostate tumor progression and metastasis.

Kallikrein 4 (hK4) and prostate-specific antigen (PSA) are associated with the loss of E-cadherin and an epithelial-mesenchymal transition (EMT)-like effect in prostate cancer cells.

Prostate-specific antigen (PSA) and the related kallikrein family of serine proteases are current or emerging biomarkers for prostate cancer detection and progression. Kallikrein 4 (KLK4/hK4) is of particular interest, as KLK4 mRNA has been shown to be elevated in prostate cancer. In this study, we now show that the comparative expression of hK4 protein in prostate cancer tissues, compared with benign glands, is greater than that of PSA and kallikrein 2 (KLK2/hK2), suggesting that hK4 may play an important functional role in prostate cancer progression in addition to its biomarker potential. To examine the roles that hK4, as well as PSA and hK2, play in processes associated with progression, these kallikreins were separately transfected into the PC-3 prostate cancer cell line, and the consequence of their stable transfection was investigated. PC-3 cells expressing hK4 had a decreased growth rate, but no changes in cell proliferation were observed in the cells expressing PSA or hK2. hK4 and PSA, but not hK2, induced a 2.4-fold and 1.7-fold respective increase, in cellular migration, but not invasion, through Matrigel, a synthetic extracellular matrix. We hypothesised that this increase in motility displayed by the hK4 and PSA-expressing PC-3 cells may be related to the observed change in structure in these cells from a typical rounded epithelial-like cell to a spindle-shaped, more mesenchymal-like cell, with compromised adhesion to the culture surface. Thus, the expression of E-cadherin and vimentin, both associated with an epithelial-mesenchymal transition (EMT), was investigated. E-cadherin protein was lost and mRNA levels were significantly decreased in PC-3 cells expressing hK4 and PSA (10-fold and 7-fold respectively), suggesting transcriptional repression of E-cadherin, while the expression of vimentin was increased in these cells. The loss of E-cadherin and associated increase in vimentin are indicative of EMT and provides compelling evidence that hK4, in particular, and PSA have a functional role in the progression of prostate cancer through their promotion of tumour cell migration.

Hypermethylation of the 5' CpG island of the gene encoding the serine protease Testisin promotes its loss in testicular tumorigenesis.

The Testisin gene (PRSS21) encodes a glycosylphosphatidylinositol (GPI)-linked serine protease that exhibits testis tissue-specific expression. Loss of Testisin has been implicated in testicular tumorigenesis, but its role in testis biology and tumorigenesis is not known. Here we have investigated the role of CpG methylation in Testisin gene inactivation and tested the hypothesis that Testisin may act as a tumour suppressor for testicular tumorigenesis. Using sequence analysis of bisulphite-treated genomic DNA, we find a strong relationship between hypermethylation of a 385 bp 5' CpG rich island of the Testisin gene, and silencing of the Testisin gene in a range of human tumour cell lines and in 100% (eight/eight) of testicular germ cell tumours. We show that treatment of Testisin-negative cell lines with demethylating agents and/or a histone deacetylase inhibitor results in reactivation of Testisin gene expression, implicating hypermethylation in Testisin gene silencing. Stable expression of Testisin in the Testisin-negative Tera-2 testicular cancer line suppressed tumorigenicity as revealed by inhibition of both anchorage-dependent cell growth and tumour formation in an SCID mouse model of testicular tumorigenesis. Together, these data show that loss of Testisin is caused, at least in part, by DNA hypermethylation and histone deacetylation, and suggest a tumour suppressor role for Testisin in testicular tumorigenesis.

Papillary urothelial neoplasm of low malignant potential: reliability of diagnosis and outcome.

OBJECTIVE: To determine the ability of pathologists to reproducibly diagnose a newly defined lesion, i.e. the papillary urothelial neoplasm of low malignant potential (PUNLMP) using the published criteria, defined by the 1998 World Health Organisation/International Society of Urological Pathology (WHO/ISUP) classification system; in addition, debate remains about the clinical behaviour of these lesions, thus the rates of recurrence and progression of PUNLMP lesions were assessed and compared with low-grade papillary urothelial carcinomas (LG-PUC) and high-grade (HG-PUC) over a 10-year follow-up. PATIENTS AND METHODS: Forty-nine cases of superficial bladder cancer (G1-3 pTa) representing an initial diagnosis of transitional cell carcinoma made in 1990 were identified and re-graded using the 1998 WHO/ISUP classification by two pathologists. Inter-observer agreement was assessed using Cohen weighted kappa statistics. After re-classification the clinical follow-up was reviewed retrospectively, and episodes of recurrence and progression recorded. RESULTS: The inter-observer agreement was moderate, regardless of whether one (kappa 0.45) or two (kappa 0.60) pathologists were used to grade these lesions. Re-classification identified 12 PUNLMP, 28 LG-PUC and nine HG-PUC. PUNLMP lesions recurred in 25% (3/12) of cases; no progression was documented. Recurrence rates were 75% (21/28) and 67% (6/9) for LG- and HG-PUC, respectively, and progression rates were 4% (1/28) and 22% (2/9). CONCLUSION: The 1998 WHO/ISUP classification of urothelial neoplasms can be reproducibly applied by pathologists, with a moderate level of agreement. There is evidence that PUNLMP lesions have a more indolent clinical behaviour than urothelial carcinomas. However, the risk of recurrence and progression remains, and clinical monitoring of these patients is important.

Repeat urethrotomy and dilation for the treatment of urethral stricture are neither clinically effective nor cost-effective.

PURPOSE: We developed an algorithm for the management of urethral stricture based on cost-effectiveness. MATERIALS AND METHODS: United Kingdom medical and hospital costs associated with the current management of urethral stricture were calculated using private medical insurance schedules of reimbursement and clean intermittent self-catheterization supply costs. These costs were applied to 126 new patients treated endoscopically for urethral stricture in a general urological setting between January 1, 1991 and December 31, 1999. Treatment failure was defined as recurrent symptomatic stricture requiring further operative intervention following initial intervention. Mean followup available was 25 months (range 1 to 132). RESULTS: The costs were urethrotomy/urethral dilation 2,250.00 pounds sterling (3,375.00 dollars, ratio 1.00), simple 1-stage urethroplasty 5,015.00 pounds sterling (7,522.50 dollars, ratio 2.23), complex 1-stage urethroplasty 5,335.00 pounds sterling (8,002.50 dollars, ratio 2.37) and 2-stage urethroplasty 10,370 pounds sterling (15,555.00 dollars, ratio 4.61). Of the 126 patients assessed 60 (47.6%) required more than 1 endoscopic retreatments (mean 3.13 each), 50 performed biweekly clean intermittent self-catheterization and 7 underwent urethroplasty during followup. The total cost per patient for all 126 patients for stricture treatment during followup was 6,113 pounds sterling (9,170 dollars). This cost was calculated by multiplying procedure cost by the number of procedures performed. A strategy of urethrotomy or urethral dilation as first line treatment, followed by urethroplasty for recurrence yielded a total cost per patient of 5,866 pounds sterling (8,799 dollars). CONCLUSIONS: A strategy of initial urethrotomy or urethral dilation followed by urethroplasty in patients with recurrent stricture proves to be the most cost-effective strategy. This financially based strategy concurs with evidence based best practice for urethral stricture management.

Quality of life compared during pharmacological treatments and clinical monitoring for non-localized prostate cancer: a randomized controlled trial.

OBJECTIVES: To investigate the effects of different management strategies for non-localized prostate cancer on men's quality of life and cognitive functioning. PATIENTS, SUBJECTS AND METHODS: Men with prostate cancer were randomly assigned to one of four treatment arms: leuprorelin, goserelin, cyproterone acetate (CPA), or close clinical monitoring. In a repeated-measures design, men were assessed before treatment (baseline) and after 6 and 12 months of treatment. A community comparison group of men of the same age with no prostate cancer participated for the same length of time. The men were recruited from public and private urology departments from university teaching hospitals. All those with prostate cancer who were eligible for hormonal therapy had no symptoms requiring immediate therapy. In all, 82 patients were randomized and 62 completed the 1-year study, and of the 20 community participants, 15 completed the study. The main outcome measures were obtained from questionnaires on emotional distress, existential satisfaction, physical function and symptoms, social and role function, subjective cognitive function, and sexual function, combined with standard neuropsychological tests of memory, attention, and executive functions. RESULTS: Sexual dysfunction increased for patients on androgen-suppressing therapies, and emotional distress increased in those assigned to CPA or close clinical monitoring. Compared with before treatment there was evidence of an adverse effect of leuprorelin, goserelin, and CPA on cognitive function. CONCLUSIONS: In deciding the timing of androgen suppression therapy for prostate cancer, consideration should be given to potential adverse effects on quality of life and cognitive function.

Altered cognitive function in men treated for prostate cancer with luteinizing hormone-releasing hormone analogues and cyproterone acetate: a randomized controlled trial.

OBJECTIVE: To report the first systematic investigation of the cognitive effects of luteinizing hormone-releasing hormone (LHRH) analogues in male patients, as LHRH analogues have been associated with memory impairments in women using these drugs for gynaecological conditions. PATIENTS AND METHODS: Eighty-two men with extraprostatic prostate cancer were randomly assigned to receive either continuous leuprorelin, goserelin (both LHRH analogues), cyproterone acetate (a steroidal antiandrogen) or close clinical monitoring. These patients underwent cognitive assessments at baseline and before starting treatment (77), and then 6 months later (65). RESULTS: Compared with the baseline assessments, men receiving androgen suppression monotherapy performed worse in two of 12 tests of attention and memory; 24 of 50 men randomized to active treatment and assessed 6 months later had a clinically significant decline in one or more cognitive tests but not one patient randomized to close monitoring showed a decline in any test performance. CONCLUSION: Pharmacological androgen suppression monotherapy for prostate cancer may be associated with impaired memory, attention and executive functions.

Renal cell carcinoma may adapt to and overcome anti-angiogenic intervention with thalidomide.

OBJECTIVE: To report on the failure of thalidomide to inhibit tumour growth in an animal model of human renal cell carcinoma (RCC). MATERIALS AND METHODS: An orthotopic xenograft model of human RCC was used in which tumour cells were implanted in the left kidney of male 'severe combined immunodeficient' mice. Thalidomide was administered by intraperitoneal injection and after 34 days the mice were killed. The extent of tumour growth was compared in treated and untreated mice. Total RNA was extracted from both tumour-affected and contralateral kidneys, and analysed by reverse transcription-polymerase chain reaction for various genes implicated in angiogenesis and metastasis in RCC. RESULTS: Thalidomide failed to inhibit the growth of xenograft tumours. The expression of angiogenic genes, e.g. vascular endothelial growth factor and fibroblast growth factor type 2 (FGF-2) within normal and tumour-affected kidney tissue was not reduced by thalidomide. Intratumoral transcription of beta3-integrin, a critical component of angiogenesis, was significantly increased in response to thalidomide treatment (P < 0.01). There was also a trend to increased expression of FGF-2 and tumour necrosis factor-alpha in thalidomide-treated tumours. CONCLUSIONS: These findings suggest that RCC is capable of adapting to the inhibitory effects of thalidomide. The current uncertainty surrounding the action of thalidomide in vivo warrants caution about its use in humans. Further studies of thalidomide should be carried out in animal models, particularly to establish its safety and effectiveness as part of a combined therapeutic strategy.

TTYH2, a human homologue of the Drosophila melanogaster gene tweety, is located on 17q24 and upregulated in renal cell carcinoma.

Using differential display PCR, we identified a novel gene upregulated in renal cell carcinoma. Characterization of the full-length cDNA and gene revealed that the encoded protein is a human homologue of the Drosophila melanogaster Tweety protein, and so we have termed the novel protein TTYH2. The orthologous mouse cDNA was also identified and the predicted mouse protein is 81% identical to the human protein. The encoded human TTYH2 protein is 534 amino acids and, like the other members of the tweety-related protein family, is a putative cell surface protein with five transmembrane regions. TTYH2 is located at 17q24; it is expressed most highly in brain and testis and at lower levels in heart, ovary, spleen, and peripheral blood leukocytes. Expression of this gene is upregulated in 13 of 16 (81%) renal cell carcinoma samples examined. In addition to a putative role in brain and testis, the over-expression of TTYH2 in renal cell carcinoma suggests that it may have an important role in kidney tumorigenesis.

Characterization of a novel gene, STAG1/PMEPA1, upregulated in renal cell carcinoma and other solid tumors.

Using differential display-polymerase chain reaction, we identified a novel gene sequence, designated solid tumor-associated gene 1 (STAG1), that is upregulated in renal cell carcinoma (RCC). The full-length cDNA (4839 bp) encompassed the recently reported androgen-regulated prostatic cDNA PMEPA1, and so we refer to this gene as STAG1/PMEPA1. Two STAG1/PMEPA1 mRNA transcripts of approximately 2.7 and 5 kb, with identical coding regions but variant 3' untranslated regions, were predominantly expressed in normal prostate tissue and at lower levels in the ovary. The expression of this gene was upregulated in 87% of RCC samples and also was upregulated in stomach and rectal adenocarcinomas. In contrast, STAG1/PMEPA1 expression was barely detectable in leukemia and lymphoma samples. Analysis of expressed sequence tag databases showed that STAG1/PMEPA1 also was expressed in pancreatic, endometrial, and prostatic adenocarcinomas. The STAG1/PMEPA1 cDNA encodes a 287-amino-acid protein containing a putative transmembrane domain and motifs that suggest that it may bind src homology 3- and tryptophan tryptophan domain-containing proteins. This protein shows 67% identity to the protein encoded by the chromosome 18 open reading frame 1 gene. Translation of STAG1/PMEPA1 mRNA in vitro showed two products of 36 and 39 kDa, respectively, suggesting that translation may initiate at more than one site. Comparison to genomic clones showed that STAG1/PMEPA1 was located on chromosome 20q13 between microsatellite markers D20S183 and D20S173 and spanned four exons and three introns. The upregulation of this gene in several solid tumors indicated that it may play an important role in tumorigenesis.

An orthotopic xenograft model of human nonseminomatous germ cell tumour.

We have established the first example of an orthotopic xenograft model of human nonseminomatous germ cell tumour (NSGCT). This reproducible model exhibits many clinically relevant features including metastases to the retroperitoneal lymph nodes and lungs, making it an ideal tool for research into the development and progression of testicular germ cell tumours.

Novel association of a diverse range of genes with renal cell carcinoma as identified by differential display.

We have used differential-display PCR (DD-PCR) to compare renal-cell carcinoma (RCC) and normal kidney gene expression with the aim of identifying genes specifically associated with RCC. Using a modified DD-PCR approach, which was non-radioactive, quicker and simpler than the conventional method, 24 cDNA samples were clearly up- or down-regulated in RCC tissue from 4 patients. Fourteen of these showed high similarity to a number of known genes. Eight of these cDNA clones were chosen for further analysis. These were a regulator of G-protein signalling (RGS-5), Notch-3, Na,K-ATPase alpha subunit, HLA class II antigen, ETS-like protein, transforming growth factor beta-stimulated clone (TSC-22), bladder cancer-related protein (BC10) and adipophilin. Semi-quantitative RT-PCR using specific primers to each of these genes confirmed differential expression in 67% to 83% of a further 12 RCC and normal kidney paired samples from 7 of the 8 cDNA clones. Northern analysis further confirmed the up-regulation in expression of RGS-5 and Notch-3 in RCC. Further characterisation of these differentially expressed genes should lead to a better understanding of the changes that occur at the molecular level during RCC development and progression.

Novel surveillance and cure of a donor-transmitted lymphoma in a renal allograft recipient.

BACKGROUND: In this report we describe a malignant lymphoma of donor origin inadvertently transplanted into two renal allograft recipients, despite standard comprehensive donor screening. The successful clearance of the tumor from both patients and a novel method of surveillance are detailed. METHODS: Initial management consisted of withdrawal of immunosuppression to promote rejection of the allograft and the transplanted tumor in both patients, followed by graft removal. Peripheral blood microchimerism was assessed in both recipients using nested polymerase chain reaction to detect the DYZ3 gene on the Y chromosome (donor male, recipients female). RESULTS: Although microchimerism was detected on day 6 after transplantation and day 1 after explantation, repeat peripheral blood examination at 1, 3, and 6 months after explantation demonstrated no microchimerism. Both patients remain well at 12 months and have been relisted for transplantation. CONCLUSION: Despite inadvertent transplantation of a previously undiagnosed malignancy of donor origin, the recipients' immune response was able to eliminate donor tumor cells after the withdrawal of immunosuppression. Repeated surveillance of peripheral blood from both recipients, using a novel application of the technique of nested polymerase chain reaction to amplify donor DNA, demonstrated no persistence of donor cells, supporting effective eradication of the donor malignancy.

Is obesity a favorable prognostic factor in peritoneal dialysis patients?

OBJECTIVE: To determine the influence of an elevated body mass index (BMI) on cardiovascular outcomes and survival in peritoneal dialysis (PD) patients. DESIGN: Prospective, observational study of a prevalent PD cohort at a single center. SETTING: Tertiary care institutional dialysis center. PATIENTS: The study included all patients with a BMI of at least 20 who had been receiving PD for at least 1 month as of 31 January 1996 (n = 43). Patients were classified as overweight [BMI > 27.5; mean +/- standard error of mean (SEM): 32.1 +/- 1.1; n = 14] or normal weight (BMI 20-27.5; mean +/- SEM: 23.8 +/- 0.4; n = 29). OUTCOME MEASURES: Patient survival and adverse cardiovascular events (myocardial infarction, congestive cardiac failure, cerebrovascular accident, and symptomatic peripheral vascular disease) were recorded over a 3-year period. RESULTS: At baseline, no significant differences were seen between the groups in clinical, biochemical, nutritional, or echocardiographic parameters, except for a lower dietary protein intake (0.97 +/- 0.10 g/kg/day vs 1.44 +/- 0.10 g/kg/day, p = 0.004) and a higher proportion of well-nourished patients by subjective global assessment (100% vs 72%, p < 0.05) in the overweight group. After 3 years of follow-up, 29% of overweight patients and 69% of normal-weight patients had died (p < 0.05). Using a Cox proportional hazards model, a BMI greater than 27.5 was shown to be an independent positive predictor of patient survival, with an adjusted hazard ratio (HR) of 0.09 [95% confidence interval (CI): 0.01-0.85; p < 0.05]. However, being overweight did not significantly influence myocardial infarction-free survival (adjusted HR: 0.33; 95% CI: 0.07-1.48; p = 0.15) or combined adverse cardiovascular event-free survival (adjusted HR: 0.67; 95% CI: 0.23-1.93; p = 0.46). CONCLUSIONS: Obesity conferred a significant survival advantage in our PD population. Obese patients should therefore not be discouraged from receiving PD purely on the basis of BMI. Moreover, maintaining a higher-than-average BMI to preserve "nutritional reserve" may help to reduce the mortality and morbidity rates associated with PD.

A comparison of the effects of dialysis and renal transplantation on the survival of older uremic patients.

BACKGROUND: Patients over age 60 constitute half of all new patients accepted into the renal replacement therapy programs in Australia. However, the optimal treatment of their end-stage renal disease remains controversial. The aim of the present study was to compare survival for dialysis and renal transplantation in older patients who were rigorously screened and considered eligible for transplantation. METHODS: The study cohort consisted of 174 consecutive patients over 60 who were accepted on to the Queensland cadaveric renal transplant waiting list between January 1, 1993 and December 31, 1997. Follow-up was terminated on October 1, 1998. Data were analyzed on an intention-to-transplant basis using a Cox regression model with time-varying explanatory variables. An alternative survival analysis was also performed, in which patients no longer considered suitable for transplantation were censored at the time of their removal from the waiting list. RESULTS: There were 67 patients receiving a renal transplant, whereas the other 107 continued to undergo dialysis. These two groups were well matched at baseline with respect to age, gender, body mass index, renal disease etiology, comorbid illnesses, and dialysis duration and modality. The overall mortality rate was 0.096 per patient-year (0.131 for dialysis and 0.029 for transplant, P<0.001). Respective 1-, 3- and 5-year survivals were 92%, 62%, and 27% for the dialysis group and 98%, 95%, and 90% (P<0.01) for the transplant group. Patients in the transplant group had an adjusted hazard ratio 0.16 times that of the dialysis group (95% confidence interval 0.06-0.42). If patients were censored at the time of their withdrawal from the transplant waiting list, the adjusted hazard ratio was 0.24 (95% confidence interval 0.09-0.69). CONCLUSIONS: Renal transplantation seems to confer a substantial survival advantage over dialysis in patients with end-stage renal failure who are rigorously screened and considered suitable for renal transplantation.

Testisin, a new human serine proteinase expressed by premeiotic testicular germ cells and lost in testicular germ cell tumors.

We have cloned and characterized a cDNA encoding a new human serine proteinase, testisin, that is abundantly expressed only in the testis and is lost in testicular tumors. The testisin cDNA was identified by homology cloning using degenerate primers directed at conserved sequence motifs within the catalytic regions of serine proteinases. It is 1073 nucleotides long, including 942 nucleotides of open reading frame and a 113-nucleotide 3' untranslated sequence. Northern and dot blot analyses of RNA from a range of normal human tissues revealed a 1.4-kb mRNA species that was present only in testis, which was not detected in eight of eight testicular tumors. Testisin cDNA is predicted to encode a protein of 314 amino acids, which consists of a 19-amino acid (aa) signal peptide, a 22-aa proregion, and a 273-aa catalytic domain, including a unique 17-aa COOH-terminal hydrophobic extension that is predicted to function as a membrane anchor. The deduced amino acid sequence of testisin shows 44% identity to prostasin and contains features that are typical of serine proteinases with trypsin-like substrate specificity. Antipeptide antibodies directed against the testisin polypeptide detected an immunoreactive testisin protein of Mr 35,000-39,000 in cell lysates from COS-7 cells that were transiently transfected with testisin cDNA. Immunostaining of normal testicular tissue showed that testisin was expressed in the cytoplasm and on the plasma membrane of premeiotic germ cells. No staining was detected in eight of eight germ cell-derived testicular tumors. In addition, the testisin gene was localized by fluorescence in situ hybridization to the short arm of human chromosome 16 (16p13.3), a region that has been associated with allellic imbalance and loss of heterozygosity in sporadic testicular tumors. These findings demonstrate a new cell surface serine proteinase, loss of which may have a direct or indirect role in the progression of testicular tumors of germ cell origin.