Gene interaction and single gene effects in colon tumour susceptibility in mice.

To dissect the multigenic control of colon tumour susceptibility in the mouse we used the set of 20 CcS/Dem (CcS) recombinant congenic (RC) strains. Each CcS strain carries a unique, random subset of approximately 12.5% of the genome of strain STS/A (STS) on the genetic background of BALB/cHeA (BALB/c). Previously, applying a protocol of 26 injections of 1,2-dimethylhydrazine (DMH), we detected two susceptibility loci, Scc1 and Scc2, on chromosome 2 (refs 4, 5). Using a shorter tumour-induction procedure, combining DMH and N-ethyl-N-nitrosourea (ENU) treatment, we demonstrate that BALB/c, STS and most CcS strains are relatively resistant. The strain CcS-19, however, is susceptible, probably due to a combination of BALB/c and STS alleles at several loci. Analysis of 192 (BALB/c x CcS-19) F2 mice revealed, in addition to the Scc1/Scc2 region, three new susceptibility loci: Scc3 on chromosome 1, Scc4 on chromosome 17 and Scc5 on chromosome 18. Scc4 and Scc5 have no apparent individual effect, but show a strong reciprocal interaction. Their BALB/c and STS alleles are not a priori susceptible or resistant but the genotype at one locus determines the effect of the allele at the second locus and vice versa. These findings and the accompanying paper on lung tumour susceptibility show that interlocus interactions are likely to be an important component of tumour susceptibility.

Patterns of Care and Outcomes of Rectal Cancer Patients from the Iowa Cancer Registry: Role of Hospital Volume and Tumor Location.

BACKGROUND: Centralization of rectal cancer surgery has been associated with high-quality oncologic care. However, several patient, disease and system-related factors can impact where patients receive care. We hypothesized that patients with low rectal tumors would undergo treatment at high-volume centers and would be more likely to receive guideline-based multidisciplinary treatment. METHODS: Adults who underwent proctectomy for stage II/III rectal cancer were included from the Iowa Cancer Registry and supplemented with tumor location data. Multinomial logistic regression was employed to analyze factors associated with receiving care in high-volume hospital, while logistic regression for those associated with ≥ 12 lymph node yield, pre-operative chemoradiation and sphincter-preserving surgery. RESULTS: Of 414 patients, 38%, 39%, and 22% had low, mid, and high rectal cancers, respectively. Thirty-two percent were > 65 years, 38% female, and 68% had stage III tumors. Older age and rural residence, but not tumor location, were associated with surgical treatment in low-volume hospitals. Higher tumor location, high-volume, and NCI-designated hospitals had higher nodal yield (≥ 12). Hospital-volume was not associated with neoadjuvant chemoradiation rates or circumferential resection margin status. Sphincter-sparing surgery was independently associated with high tumor location, female sex, and stage III cancer, but not hospital volume. CONCLUSIONS: Low tumor location was not associated with care in high-volume hospitals. High-volume and NCI-designated hospitals had higher nodal yields, but not significantly higher neoadjuvant chemoradiation, negative circumferential margin, or sphincter preservation rates. Therefore, providing educational/quality improvement support in lower volume centers may be more pragmatic than attempting to centralize rectal cancer care among high-volume centers.

Validation of 70-gene prognosis signature in node-negative breast cancer.

PURPOSE: The 70-gene prognosis signature (van't Veer et al., Nature 415(6871):530-536, 2002) may improve the selection of lymph node-negative breast cancer patients for adjuvant systemic therapy. Optimal validation of prognostic classifiers is of great importance and we therefore wished to evaluate the prognostic value of the 70-gene prognosis signature in a series of relatively recently diagnosed lymph node negative breast cancer patients. METHODS: We evaluated the 70-gene prognosis signature in an independent representative series of patients with invasive breast cancer (N = 123; <55 years; pT1-2N0; diagnosed between 1996 and 1999; median follow-up 5.8 years) by classifying these patients as having a good or poor prognosis signature. In addition, we updated the follow-up of the node-negative patients of the previously published validation-series (Van de Vijver et al., N Engl J Med 347(25):1999-2009, 2002; N = 151; median follow-up 10.2 years). The prognostic value of the 70-gene prognosis signature was compared with that of four commonly used clinicopathological risk indexes. The endpoints were distant metastasis (as first event) free percentage (DMFP) and overall survival (OS). RESULTS: The 5-year OS was 82 +/- 5% in poor (48%) and 97 +/- 2% in good prognosis signature (52%) patients (HR 3.4; 95% CI 1.2-9.6; P = 0.021). The 5-years DMFP was 78 +/- 6% in poor and 98 +/- 2% in good prognosis signature patients (HR 5.7; 95% CI 1.6-20; P = 0.007). In the updated series (N = 151; 60% poor vs. 40% good), the 10-year OS was 51 +/- 5% and 94 +/- 3% (HR 10.7; 95% CI 3.9-30; P < 0.01), respectively. The DMFP was 50 +/- 6% in poor and 86 +/- 5% in good prognosis signature patients (HR 5.5; 95% CI 2.5-12; P < 0.01). In multivariate analysis, the prognosis signature was a strong independent prognostic factor in both series, outperforming the clinicopathological risk indexes. CONCLUSION: The 70-gene prognosis signature is also an independent prognostic factor in node-negative breast cancer patients for women diagnosed in recent years.

PRAME expression and clinical outcome of breast cancer.

The tumour antigen PReferentially expressed Antigen of MElanoma (PRAME) is expressed in a variety of malignancies, including breast cancer. We have analysed PRAME gene expression in relation to clinical outcome for 295 primary breast cancer patients. Kaplan-Meier survival curves show a correlation of PRAME expression levels with increased rates of distant metastases and decreased overall patient survival. This correlation existed both for the entire patient group (n=295) and for the subgroup of patients (n=185) who did not receive adjuvant chemotherapy. Multivariable analysis indicated that PRAME is an independent marker of shortened metastasis-free interval in patients who did not receive adjuvant chemotherapy. PRAME expression was associated with tumour grade and negative oestrogen receptor status. We conclude that PRAME expression is a prognostic marker for clinical outcome of breast cancer, independent of traditional clinicopathological markers.

Cisplatin-DNA adduct formation in patients treated with cisplatin-based chemoradiation: lack of correlation between normal tissues and primary tumor.

PURPOSE: In this study, the formation of cisplatin-DNA adducts after concurrent cisplatin-radiation and the relationship between adduct-formation in primary tumor tissue and normal tissue were investigated. METHODS: Three intravenous cisplatin-regimens, given concurrently with radiation, were studied: daily low-dose (6 mg/m(2)) cisplatin, weekly 40 mg/m(2), three-weekly 100 mg/m(2). A (32)P-postlabeling technique was used to quantify adducts in normal tissue [white blood cells (WBC) and buccal cells] and tumor. RESULTS: Normal tissue samples for adduct determination were obtained from 63 patients and tumor biopsies from 23 of these patients. Linear relationships and high correlations were observed between the levels of two guanosine- and adenosine-guanosine-adducts in normal and tumor tissue. Adduct levels in tumors were two to five times higher than those in WBC (P<0.001). No significant correlations were found between adduct levels in normal tissues and primary tumor biopsies, nor between WBC and buccal cells. CONCLUSIONS: In concurrent chemoradiotherapy schedules, cisplatin adduct levels in tumors were significantly higher than in normal tissues (WBC). No evidence of a correlation was found between adduct levels in normal tissues and primary tumor biopsies. This lack of correlation may, to some extent, explain the inconsistencies in the literature regarding whether or not cisplatin-DNA adducts can be used as a predictive test in anticancer platinum therapy.

How to assess and compare the accuracy of continuous glucose monitors?

Continuous glucose monitors may be valuable tools for improving glycemic control and avoiding hypoglycemia in patients with diabetes. To this goal, sensor readings must adequately reflect the actual blood glucose, emphasizing the need for solid accuracy assessment methods for continuous glucose sensor readings. Analysis of continuous glucose data is challenging, and despite many efforts there still is no all-embracing method to overcome the obstacles in the assessment of continuous data. In this review we disclose the weaknesses of currently available methods and propose a guideline for sensor accuracy assessment and comparison. For accuracy assessment it is best to first plot the sensor readings against the reference values and draw a line of identity, visualizing the degree of agreement. Thereafter data pairs should be given in a Bland-Altman plot to detect a possible relationship between the difference and the mean. The next step is to calculate the absolute relative difference over all paired readings together and per glucose range. A possible lag time between the measurements of both methods can be detected by combined curve fitting. Finally, sensitivity and positive predictive value for detecting hypoglycemia are important indicators of the sensors' performance. For comparing the accuracy between different glucose sensors it is best to use indirect comparison against blood glucose, rather than direct comparison methods, since none of the current glucose sensors is accurate enough to be considered the reference value.

Prognostic factors in feline mammary carcinoma.

Feline mammary carcinoma and canine mammary cancer were evaluated as models for future experimental therapy. Those tumor characteristics known to be of special prognostic significance in human mammary cancers were tested for their prognostic significance in the cat and were compared with those in the dog. The statistical analysis presented is based on a prospective follow-up study of 202 cats treated surgically by mastectomy and by block dissection. Thirty-five factors (general, anamnestic, clinical and histologic data, and data on therapy) were analyzed for relationships with survival, with local recurrence, and with each other. Of the 17 significant relationships found between survival and the direct factors, only 7 remained significant after correction. The factors that related to survival independently of each other were age, diameter of the primary tumor, presence of tumor-positive lymph nodes as judged by microscopic examination, number of mitotic figures, necrosis of the primary tumor, and histologic verification of completeness of surgical treatment. The value of statistical analysis for use in prospective studies of human mammary cancer is discussed.

Some prognostic and epidemiologic factors in canine osteosarcoma.

Naturally occurring skeletal osteosarcomas in a series of 144 untreated dogs were found especially to involve the ends of the long bones of the forelimbs and affected predominantly older male dogs of giant and large breeds. Most tumors were large and partially necrotic and had extended into soft tissues. Of 12 host and tumor characteristics tested in the first part of the study, tumor diameter and volume were significantly associated with the presence of pulmonary metastases at autopsy. The second part of the study revealed that extension of the tumor into the soft tissues and localization of the tumor in the hind legs were associated with a poor prognosis, whereas the fibrosarcomatous type of tumor was associated, as in man, with a favorable prognosis. An association between the 12 characteristics tested was found in 11 of 78 combinations at the 5% level and in 5 combinations at the 1% level. Affected giant dogs were generally younger than affected small and medium-sized dogs. Especially in giant dogs, the osteosarcomas involved the long bones and were of relatively large diameters. The sarcomas in female dogs were larger in volume than those in males. Pure osteoblastic osteosarcomas were generally smaller than combined (chondroblastic and fibroblastic) osteosarcomas. Peritumorous lymphocytes and plasma cells were present in 50% of the dogs, especially in small and young dogs. When compared with a reference population, great Danes, rottweilers, German shepherds, and boxers were found to be overrepresented in the osteosarcoma group.

Prognostic factors in canine mammary cancer.

From a follow-up study of dogs surgically treated for mammary cancer, ten characteristics were analyzed statistically with special reference to their association with prognosis (expressed as survival for 2 years). The interrelations among five of the characteristics were also tested. The histologic type (descending range in malignancy: sarcomas greater than simple carcinomas greater than complex carcinomas), mode of growth (highly infiltrating greater than moderately infiltrating greater than expansive), clinical stage of complex carcinomas (large tumors and/or tumors involving the skin or underlying tissue greater than small, well-defined tumors), and size (greater than 15 cm greater than 11-15 cm greater than 5-10 cm greater than 0-5 cm) were of definite prognostic importance. The histologic grade was of possible prognostic importance. Localization, type of surgical therapy (mastectomy, block-dissection), growth in lymph vessels, involvement of regional lymph nodes, and duration of symptoms before treatment were not important to prognosis. A comparison between the factors associated with the prognosis of canine and human mammary cancer showed many similarities. However, the involvement of regional lymph nodes, important in women, was not so in bitches.

Complexity of lung cancer modifiers: mapping of thirty genes and twenty-five interactions in half of the mouse genome.

BACKGROUND: Numerous low-penetrance genes control susceptibility to cancer in experimental animals, but the overall genetic information on this group of genes (i.e., number of loci and their mutual interactions) is missing. We performed a systematic search, scanning roughly half of the mouse genome for lung cancer susceptibility (Sluc) genes affecting tumor size or number by using mouse recombinant congenic (RC) strains. In each RC strain (OcB), approximately 12.5% of the genome is derived from the lung cancer-resistant strain B10.O20, whereas the rest is derived from the lung cancer-susceptible strain O20. METHODS: A total of 730 F2 hybrids from five (OcB x O20) crosses were tested. Pregnant mice were treated on day 18 of gestation with a single dose of N-ethyl-N-nitrosourea. When offspring were 16 weeks old, whole lungs were removed and sectioned semiserially, and the size of all lung tumors (n = 2658) was determined. Analysis of variance was used for detection of linkage, and models (including main effect and two-way interactions) were tested with a statistical program. RESULTS: We detected a total of 30 Sluc loci (16 new plus 14 previously reported) and 25 two-way interactions. Some of these interactions are counteracting (e.g., Sluc17 and Sluc20), resulting in the partial or total masking of the individual independent effect (main effect) of each involved locus. Seven loci (Sluc1, Sluc5, Sluc12, Sluc16, Sluc18, Sluc20, and Sluc26) and two interactions (Sluc5 x Sluc12 and Sluc5 x Sluc26) were detected in more than one RC strain. CONCLUSIONS: The extrapolation of our results to the whole genome suggests approximately 60 Sluc loci (90% confidence intervals = 42 to 78). Despite the genetic complexity of lung cancer, use of appropriate mapping strategies can identify a large number of responsible loci and can reveal their interactions. This study provides an insight into the genetic control of lung tumorigenesis and may serve as a paradigm for investigating the genetics of other cancer types.

Glucocorticoid hormone effect on transplacental carcinogenesis and lung differentiation: influence of histocompatibility-2 complex.

In the mouse, the histocompatibility-2 (H-2) haplotype influences induction of lung and intestinal tumors by N-ethyl-N-nitrosourea (ENU) treatment of fetuses or infant mice. The differentiation of lung and intestinal epithelium is known to be regulated by glucocorticoids. We show that glucocorticoid-induced development of alveolar lung volume is H-2 influenced and that glucocorticoid treatment of fetuses also influences prenatal ENU induction of lung and intestinal tumors. These glucocorticoid effects on tumorigenesis are also H-2 influenced. The number of papillary lung tumors increased in B10 (H-2b) and decreased in B10.A (H-2a) mice. In the intestine, the number of tumors increased in H-2b females and decreased in H-2b males. In H-2a mice, the number of intestinal tumors was unchanged but their location was altered. We propose that the H-2 complex influences tumorigenesis in lung and small intestine by affecting the hormonal regulation of differentiation of target epithelial cells.

Determination of benzo[a]pyrene diol epoxide-DNA adducts in white blood cell DNA from coke-oven workers: the impact of smoking.

We have undertaken a study among coke-oven workers to test the feasibility of an enzyme-linked immunosorbent assay with anti-trans-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydro-benzo[a]pyrene- DNA antibodies for monitoring occupational exposure to polycyclic aromatic hydrocarbons (PAH). Coke-oven workers are occupationally exposed to relatively high levels of PAH and are at increased risk for lung cancer. Three blood samples were collected from each of the 56 coke-oven workers exposed to PAH and 44 unexposed workers employed in a steel-rolling factory of the same plant. In addition, PAH levels were measured in ambient air by personal sampling, and the excretion of 1-hydroxypyrene in urine was also measured on 3 consecutive working days. All participants were interviewed regarding working conditions, personal hygiene, and smoking habits. The results showed that the coke-oven workers were exposed to substantial concentrations of atmospheric PAH (1-186 micrograms/m3), including benzo[a]pyrene (0.1-7.8 micrograms/m3) and pyrene (0.6-23.6 micrograms/m3). Both benzo[a]pyrene and pyrene were shown to be representative for the whole group of PAH. Forty-seven percent of the coke-oven workers had detectable levels of PAH-DNA adducts in their white blood cells, compared with 30% of the controls. In both groups, smokers had significantly higher levels of PAH-DNA adducts than did nonsmokers. At one site, we found the correlation positive between DNA adducts and the duration of exposure (r = .47, P = .005). Generally, the correlation was not significant between PAH-DNA adducts in blood and the concentration of PAH in the air and 1-hydroxypyrene in urine.

The psychological impact of annual chest X-ray follow-up in head and neck cancer.

CONCLUSION: Annual post-treatment screening of head and neck squamous cell carcinoma (HNSCC) patients for second primary lung cancer and metastatic recurrence appeared to form no major burden for head and neck cancer patients. A majority of patients regard the annual chest X-ray as a reassurance. Given these results a more intensive screening program seems psychologically justifiable for this group. OBJECTIVE: To assess the psychological impact of annual post-treatment screening for second primary lung cancer and metastases in HNSCC patients. PATIENTS AND METHODS: In a cohort of 106 patients, 68 men and 38 women, with a mean age of 56, the impact of the yearly chest radiograph was evaluated by means of a nine-item questionnaire. RESULTS: In all, 90% of the patients were in favor of annual post-treatment screening, 2% would not like to receive this screening, and 8% had no preference. A majority (98%) considered the screening as an extra medical check and 76% felt reassured. Although 21% of the patients were very nervous about the outcome of the screening, only 3% wanted to avoid the yearly chest X-ray for this reason.

Differences in estrogen receptor alpha variant messenger RNAs between normal human breast tissue and primary breast carcinomas.

We evaluated the differences in prevalence and functional activity of human estrogen receptor alpha (hER) variant mRNA between 21 normal breast tissues and 41 primary breast carcinomas using a functional assay in yeast for the hER First, we found that the presence of wild-type hER, relative to the total amount of hER, differs markedly (P < 0.0001) between normal breast tissue (median, 85% wild-type hER) and breast tumors (median, 74% wild-type hER). Second, the hER variants with altered function that are present in normal breast tissue are mainly one-exon deleted splicing variants (median, 100%), whereas in breast tumors only half of all variants lack just one single exon (median, 50%; P < 0.0001). Our results suggest that hER-dependent estrogen responsiveness of breast tissue may change during tumor outgrowth, indicating that specific hER variants may play a role in breast cancer development or progression.

Different genetic susceptibility to aberrant crypts and colon adenomas in mice.

Aberrant crypt foci (ACFs) are the earliest identifiable epithelial lesions thought to precede the development of a subset of colon tumors. To assess their predictive value to adenoma development, we have tested in mice whether the development of ACFs and adenomas is controlled by the same genes. Therefore we used the CcS/Dem series of recombinant congenic strains, in which the effect of multiple susceptibility genes might be studied separately. We investigated susceptibility to ACFs in nine CcS/Dem strains and their parental strains, BALB/cHeA and STS/A, 4 weeks after s.c. injection of 1,2-dimethylhydrazine (20 mg/kg body weight). For the strains BALB/cHeA, STS/A, and CcS-19, we also examined the number of ACFs 2, 8, and 12 weeks after treatment. Susceptibility to adenomas was measured as the number of adenomas 6 weeks after 26 weekly s.c. injections of 1,2-dimethylhydrazine (15 mg/kg body weight). The nine CcS/Dem strains, the BALB/ cHeA strain, and the STS/A strain exhibited different patterns of susceptibility to ACFs and adenomas, demonstrating that different subsets of susceptibility genes are involved. Therefore, in evaluating the role of ACFs as a predictive marker for adenoma development, genetic factors must be taken into account.

Differences in breast cancer risk factors to neu (c-erbB-2) protein overexpression of the breast tumor.

To investigate whether overexpression of the neu protein in breast tumors differentiates risk factor patterns for breast cancer, neu protein overexpression was determined in 296 breast carcinomas of patients participating in an ongoing population-based case-control study. Risk factor information on these patients and 737 controls was obtained during home interviews. Most breast cancer risk factors showed similar associations with neu-positive and neu-negative tumors, but remarkable differences were found for breast-feeding and age at first full-term pregnancy. In contrast to the slightly protective effect of breast-feeding in the neu-negative group, the risk of neu-positive breast cancer was 4.2-fold increased in women who ever breast-fed. Increasing age at first full-term pregnancy was positively associated with both neu-positive and neu-negative breast cancer, but the association was about 2 times stronger for neu-positive tumors. We conclude that neu oncogene overexpression of the breast tumor seems to be associated with a distinct risk factor pattern.

Influence of mouse major histocompatibility complex (H-2) on N-ethyl-N-nitrosourea-induced tumor formation in various organs.

The influence of the major histocompatibility complex (MHC) of the mouse (H-2) on carcinogen-induced tumorigenesis was investigated. Mice of five H-2 congenic strains on the C57BL/10 background were treated with the direct-acting carcinogen N-ethyl-N-nitrosourea at the age of 15 days, and examined for tumors when moribund. Significant differences between strains in susceptibility to N-ethyl-N-nitrosourea-induced tumors in lung, small intestine, and liver were found. For lung tumors the strains B10.A and 2R were most susceptible, the strains 4R and B10 were relatively resistant. The strain 5R was intermediate. Susceptibility to small intestine tumors was highest in the strain 2R, intermediate in the strain B10.A, the strains 4R, 5R, and B10 were relatively resistant. The location of the tumors in the intestine was also affected by H-2. In the strain 2R most tumors are located in the proximal part, in 4R in the distal part. Tumorigenesis in the liver was highest in the strain 2R, intermediate in the strains B10.A, 4R, and B10, and lowest in the strain 5R. We conclude that susceptibility to carcinogen-induced tumors in the lung, small intestine, and liver in congenic strains on the C57BL/10 background is H-2 haplotype dependent. Susceptibility to tumors in the lung and intestine has a similar strain distribution, but differs from that for liver tumors. Males were more susceptible than females in the strain B10 (lung tumors) and 4R (small intestine and liver tumors). This indicates haplotype- and organ-specific, sex-related influences on tumor development. The possible mechanism(s) of H-2 effects on chemically induced tumorigenesis are discussed. Apart from the well-known immunological functions of the MHC, the involvement of hormonally related effects of the MHC is considered as well.

Drug-induced DNA modification in buccal cells of cancer patients receiving carboplatin and cisplatin combination chemotherapy, as determined by an immunocytochemical method: interindividual variation and correlation with disease response.

Twenty-six patients with a variety of tumor types were treated according to a phase 1 experimental treatment protocol consisting of repetitive cycles of cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II) (carboplatin, 200-480 mg/m2) at day 1 and cis-diamminedichloroplatinum(II) (cisplatin, 50-100 mg/m2) at day 3. Buccal cells were collected in one or two treatment cycles prior to carboplatin, 24 h after carboplatin, just prior to cisplatin, and approximately 24 h after cisplatin administration. Drug-induced DNA modification was visualized at the single cell level by anti-serum NKI-A59 and quantitated by microdensitometry. All (39 of 39) treatments with carboplatin, and almost all (33 of 35) treatments with cisplatin resulted in an increase in nuclear stain. Interindividual variation in drug-induced, adduct-specific nuclear stain amounted to a factor of 5-8 for carboplatin and 5-12 for cisplatin. This drug-induced increase was, however, not related to the dose of either carboplatin or cisplatin, suggesting that large interindividual differences in DNA adduct formation and/or repair obscured the effects of dose variation within the relatively small range used for the drugs (2.4 for carboplatin and 2.0 for cisplatin). This explanation was strengthened by the good reproducibility of the immunocytochemical assay and by the reasonable correlation between carboplatin-induced nuclear stain in cycles 1 and 2 (correlation coefficient, 0.69; P = 0.009). Mean carboplatin-induced nuclear stain was significantly higher in the first cycle than in the second cycle (P = 0.0001) but this difference was no longer significant when drug-induced nuclear stain was corrected for carboplatin dose. Differences in cisplatin-induced nuclear stain between cycle 1 and cycle 2 were small and not significant. Carboplatin-induced nuclear stain was significantly higher in the partial responders than in the nonresponders (P < 0.0001, two cycles combined); the level of statistical significance remained the same after dose correction. Cisplatin-induced nuclear stain did not differ significantly between partial responders and nonresponders; this result might, however, be confounded to some extent by remaining carboplatin-induced nuclear stain at the moment of cisplatin administration. It is concluded that determination of the extent of platinum-induced DNA modification might be helpful in predicting the tumor response in cancer patients.

Eradication of large human B cell tumors in nude mice with unconjugated CD20 monoclonal antibodies and interleukin 2.

Since antibody-dependent cellular cytotoxicity is considered an important mechanism by which mAbs may exert their antitumor effects, it seems likely that these antitumor effects can be enhanced by the activation of the appropriate effector cell populations. We have used nude mice xenografted with human Daudi tumor cells as a model to compare the antilymphoma effects of unconjugated CD19 (CLB-CD19) and CD20 (BCA-B20) mAbs (IgG2a subclass) alone or in combination with recombinant human interleukin 2 (rhIL-2) or recombinant mouse granulocyte-macrophage-colony-stimulating factor (rmGM-CSF). Treatment of established tumors with BCA-B20 or rhIL-2 or rmGM-CSF as a single agent, all resulted in highly significant decreases of tumor growth rates, but did not increase the number of complete regressions. The combination of CLB-CD19 or BCA-B20 mAbs with rhIL-2 or rmGM-CSF resulted in larger decreases of growth rates than either of the agents alone. Complete eradication of large Daudi tumors could be achieved when treatment with BCA-B20 mAbs was combined with rhIL-2, but not with the combination of CLB-CD19 mAbs and rhIL-2 nor with the combination of BCA-B20 mAbs and rmGM-CSF. Cured animals kept for 2-3 months after complete regression of the tumors were still tumor free. Regression of tumors was correlated with the infiltration of lymphocytes as well as macrophages into the tumor. This is the first report to show that unconjugated CD20 mAbs are to be preferred over unconjugated CD19 mAbs, and interleukin 2 over GM-CSF in the combinational treatment of large B cell tumors.

Enhanced antitumor effects of CD20 over CD19 monoclonal antibodies in a nude mouse xenograft model.

We used a nude mouse xenograft tumor model to compare the efficacy of unconjugated CD19 and CD20 mAbs (IgG2a subclass) in mediating antilymphoma effects. Treatment with the CD20 mAbs NKI-B20 and BCA-B20 resulted in a drastic decrease in tumor take rate (P < 0.0001) in comparison to controls, whereas the CD19 mAb CLB-CD19 was ineffective. Tumor growth rates were reduced by both CD19 and CD20 (P < 0.0001). The decrease in growth rate induced by NKI-B20 or BCA-B20 was larger than that induced by CLB-CD19 (P = 0.0022). In vitro experiments showed that NKI-B20 or BCA-B20 are more powerful than CLB-CD19 in mediating lysis by interleukin 2-activated natural killer cells. No difference was observed between different isotypes (IgG1, IgG2a, IgG2b) of the switch variants of NKI-B20 or CLB-CD19. A positive correlation between antigen density and the sensitivity to antibody-dependent cellular cytotoxicity was demonstrated with human lymphoblastoid B cells, JY, transfected with cDNA encoding the human CD19 antigen that expressed high levels of this antigen. These cells are more efficiently killed by natural killer cells when coated with CLB-CD19 mAbs than JY wildtype cells that express 1 log lower levels of the CD19 antigen. Antibody-dependent cellular cytotoxicity experiments with thioglycolate-activated macrophages show a more complex relationship between antigen density, isotype of the mAb, and cytotoxicity. BCA-B20 (IgG2a) and CLB-CD19 (IgG2a) and all isotypes of NKI-B20 mediated strong cytotoxicity, whereas CLB-CD19 isotypes IgG1 and IgG2b were associated with limited cytotoxicity. Proliferation of Daudi cells was inhibited with high concentrations of all isotypes of CLB-CD19, but not with any of the CD20 mAbs. To our knowledge this is the first report showing that the antitumor effects in vivo of unconjugated CD20 mAbs are far superior to those of CD19 mAbs.