Paradoxical activation of oncogenic signaling as a cancer treatment strategy

Cancer homeostasis depends on a balance between activated oncogenic pathways driving tumorigenesis and engagement of stress-response programs that counteract the inherent toxicity of such aberrant signaling. While inhibition of oncogenic signaling pathways has been explored extensively, there is increasing evidence that overactivation of the same pathways can also disrupt cancer homeostasis and cause lethality. We show here that inhibition of Protein Phosphatase 2A (PP2A) hyperactivates multiple oncogenic pathways and engages stress responses in colon cancer cells. Genetic and compound screens identify combined inhibition of PP2A and WEE1 as synergistic in multiple cancer models by collapsing DNA replication and triggering premature mitosis followed by cell death. This combination also suppressed the growth of patient-derived tumors in vivo. Remarkably, acquired resistance to this drug combination suppressed the ability of colon cancer cells to form tumors in vivo. Our data suggest that paradoxical activation of oncogenic signaling can result in tumor suppressive resistance.

An LC-MS/MS method for simultaneous determination of LB-100 and its active metabolite, endothall, in human plasma

We have developed and validated a novel LC-MS/MS method for the simultaneous quantification of LB-100 and its active metabolite, endothall, in human plasma following solid-phase extraction. LB-105 and endothall-D6 were used as internal standards. Chromatographic separation was achieved on a Hypercarb™ column using 5 mM (NH4)2CO3 and 30:70 (v/v) 100 mM (NH4)2CO3:acetonitrile as mobile phases. Detection was performed via positive electrospray ionization mode with multiple reaction monitoring. The assay exhibited linearity in the concentration range of 2.5-500 ng/ml for both analytes. Intra- and inter-assay precision and accuracy were within ±11%. LB-100 and endothall recoveries were 78.7 and 86.7%, respectively. The validated LC-MS/MS method enabled the accurate measurement of LB-100 and endothall in patient samples from an ongoing clinical trial (NCT04560972).

Protein Phosphatase 2A as a Therapeutic Target in Small Cell Lung Cancer

Protein phosphatase 2A (PP2A), a serine/threonine phosphatase involved in the regulation of apoptosis, proliferation, and DNA-damage response, is overexpressed in many cancers, including small cell lung cancer (SCLC). Here we report that LB100, a small molecule inhibitor of PP2A, when combined with platinum-based chemotherapy, synergistically elicited an antitumor response both in vitro and in vivo with no apparent toxicity. Using inductively coupled plasma mass spectrometry, we determined quantitatively that sensitization via LB100 was mediated by increased uptake of carboplatin in SCLC cells. Treatment with LB100 alone or in combination resulted in inhibition of cell viability in two-dimensional culture and three-dimensional spheroid models of SCLC, reduced glucose uptake, and attenuated mitochondrial and glycolytic ATP production. Combining LB100 with atezolizumab increased the capacity of T cells to infiltrate and kill tumor spheroids, and combining LB100 with carboplatin caused hyperphosphorylation of the DNA repair marker γH2AX and enhanced apoptosis while attenuating MET signaling and invasion through an endothelial cell monolayer. Taken together, these data highlight the translational potential of inhibiting PP2A with LB100 in combination with platinum-based chemotherapy and immunotherapy in SCLC.

Inhibition of protein phosphatase-2A with LB-100 enhances antitumor immunity against glioblastoma

PURPOSE

Glioblastoma (GBM) carries a dismal prognosis despite standard multimodal treatment with surgery, chemotherapy and radiation. Immune checkpoint inhibitors, such as PD1 blockade, for treatment of GBM failed to show clinical benefit. Rational combination strategies to overcome resistance of GBM to checkpoint monotherapy are needed to extend the promise of immunotherapy to GBM management. Emerging evidence suggests that protein phosphatase 2A (PP2A) plays a critical role in the signal transduction pathways of both adaptive and innate immune cells and that inhibition of PP2A could enhance cancer immunity. We investigated the use of a PP2A inhibitor, LB-100, to enhance antitumor efficacy of PD1 blockade in a syngeneic glioma model.

METHODS

C57BL/6 mice were implanted with murine glioma cell line GL261-luc or GL261-WT and randomized into 4 treatment arms: (i) control, (ii) LB-100, (iii) PD1 blockade and (iv) combination. Survival was assessed and detailed profiling of tumor infiltrating leukocytes was performed.

RESULTS

Dual PP2A and PD1 blockade significantly improved survival compared with monotherapy alone. Combination therapy resulted in complete regression of tumors in about 25% of mice. This effect was dependent on CD4 and CD8 T cells and cured mice established antigen-specific secondary protective immunity. Analysis of tumor lymphocytes demonstrated enhanced CD8 infiltration and effector function.

CONCLUSION

This is the first preclinical investigation of the effect of combining PP2A inhibition with PD1 blockade for GBM. This novel combination provided effective tumor immunotherapy and long-term survival in our animal GBM model.

Inhibition of PP2A with LB-100 Enhances Efficacy of CAR-T Cell Therapy Against Glioblastoma

Chimeric antigen receptor (CAR)-engineered T cells represent a promising modality for treating glioblastoma. Recently, we demonstrated that CAR-T cells targeting carbonic anhydrase IX (CAIX), a protein involved in HIF-1a hypoxic signaling, is a promising CAR-T cell target in an intracranial murine glioblastoma model. Anti-CAIX CAR-T cell therapy is limited by its suboptimal activation within the tumor microenvironment. LB-100, a small molecular inhibitor of protein phosphatase 2A (PP2A), has been shown to enhance T cell anti-tumor activity through activation of the mTOR signaling pathway. Herein, we investigated if a treatment strategy consisting of a combination of LB-100 and anti-CAIX CAR-T cell therapy produced a synergistic anti-tumor effect. Our studies demonstrate that LB-100 enhanced anti-CAIX CAR-T cell treatment efficacy in vitro and in vivo. Our findings demonstrate the role of LB-100 in augmenting the cytotoxic activity of anti-CAIX CAR-T cells and underscore the synergistic therapeutic potential of applying combination LB-100 and CAR-T Cell therapy to other solid tumors.

Abstract LB-193: Protein phosphatase 2A inhibition,with a novel small molecule inhibitor, LB-100, achieves durable immune-mediated antitumor activity when combined with PD1 blockade in a preclinical model

LB-100 is a novel, first-in-class, small molecule inhibitor of protein phosphatase 2A (PP2A) recently shown in a Phase I trial to be well-tolerated at doses associated with stabilization of progressive solid tumors (Chung. Clin Cancer Res. 2017). PP2A has been implicated in mediating Akt signaling downstream of CTLA-4 (Parry. MolCell Biol. 2005). An in vivo pooled short hairpin RNA screen identified PP2A as a key regulator in suppressing T-cell proliferation in the tumor microenvironment (Zhou. Nature. 2014) and to be essential for regulatory-T-cell (Treg) function (Apostolidis. Nat Immunol. 2014). We hypothesized that pharmacologic inhibition of PP2A could enhance cancer immunity. We assessed the effect of LB-100 on T-cells in human allogenic mixed lymphocyte reactions, in which CD8+ or CD4+ T cells were co-cultured with monocyte-derived dendritic cells. We found a dose dependent increase in T cell proliferation in CD8+ and CD4+ cells and an increase in IFNγ secretion in CD4+ T cells. We investigated the effect of LB-100 plus anti-PD-1 antibody on CD4+ T cells in the same assay. The combination enhanced proliferation and IFNγ production compared to anti-PD-1 alone. For in vivo syngeneic studies, BALB/c mice were implanted subcutaneously in the right flank with CT26 colon carcinoma cells (5 x10^5 cells). 12 days after implantation, mice with tumors between 30-100 mm3 were randomized into four treatment groups (placebo, LB-100 - 0.16 mg/kg, anti-PD1- 10 mg/kg, and combination). Treatment was given every 2 days up to 28 days. 10 days after treatment, there was a significant decrease in tumor growth in the combination group compared to placebo or anti-PD-1 alone. 7/11 (63.6%) of mice treated with the combination and none in the other treatment groups achieved complete remission (CR). FACS analysis of the tumor infiltrating lymphocytes (TIL) after 10 days of treatment demonstrated enhanced IFNγ production in CD8+ T cells in the combination group compared to either treatment alone. There was also a marked decrease in FoxP3+ Treg cells in LB-100 treated group compared to placebo (3% vs 12% of CD4+ T cells, p<0.05). Furthermore, mice achieving CR were resistant to tumor growth when re-inoculated with CT26 cells. Mice subjected to CD8+ T cell ablation using depleting antibodies, were unable to reject CT26 tumors - 0/8 (0%) despite treatment with combination therapy. This indicates that the anti-tumor effect of LB100 with anti-PD-1 treatment is CD8+ T cell mediated. In conclusion, we have shown in a syngeneic animal model that the PP2A inhibitor, LB-100, has synergistic potential in conjunction with checkpoint blockade supporting investigation of its ability to enhance immunotherapy in the clinic.

Citation Format: Winson S. Ho, Herui Wang, John S. Kovach, Rongze Lu, Zhengping Zhuang. Protein phosphatase 2A inhibition,with a novel small molecule inhibitor, LB-100, achieves durable immune-mediated antitumor activity when combined with PD1 blockade in a preclinical model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-193. doi:10.1158/1538-7445.AM2017-LB-193

Safety, Tolerability, and Preliminary Activity of LB-100, an Inhibitor of Protein Phosphatase 2A, in Patients with Relapsed Solid Tumors: An Open-Label, Dose Escalation, First-in-Human, Phase I Trial

Purpose: To determine the MTD and to assess the safety, tolerability, and potential activity of LB-100, a first-in-class small-molecule inhibitor of protein phosphatase 2A (PP2A) in adult patients with progressive solid tumors.Experimental Design: LB-100 was administered intravenously daily for 3 days in 21-day cycles in a 3 + 3 dose escalation design.Results: There were 29 patient entries over 7 dose escalations. One patient stopped treatment after one dose because of an acute infection and was reenrolled after recovery; each course was analyzed as a separate patient entry. Two patients had dose-limiting toxicity (reversible increases in serum creatinine or calculated serum creatinine clearance) at the 3.1 mg/m² level. Probable or possible study drug-related grade 3 adverse events occurred in 6 (20.7%) patients [anemia (n = 2), decreased creatinine clearance, dyspnea, hyponatremia, and lymphopenia]. Ten (50%) of 20 response-evaluable patients had stable disease for four or more cycles. One patient with pancreatic adenocarcinoma had a partial response noted after 10 cycles, which was maintained for five additional cycles. The other patients achieving stable disease had one of the following: fibrosarcoma, chondrosarcoma, thymoma, atypical carcinoid of lung, or ovarian, testicular, breast (n = 2), and prostate cancer. The recommended phase II dose of LB-100 is 2.33 mg/m² daily for 3 days every 3 weeks.Conclusions: The safety, tolerability, preliminary evidence of antitumor activity, and novel mechanism of action of LB-100 support its continued development alone and in combination with other therapies. Clin Cancer Res; 23(13); 3277-84. ©2016 AACR.

A Community and Academic Partnership to Improve Breast Cancer Outcomes for African Americans on Long Island: A Ministry of Health Dissemination

Communities on Long Island have a widespread interest and a pressing need for approaches to promote early detection and prompt treatment of breast cancer given the overall high rates of morbidity and mortality in the region. African American communities have a special concern given that population's disproportionately high mortality rates from this disease. This article presents a success story for the development of a collaborative network creating a community, government, and academic partnership to address this disparity in African American women on Long Island. The development process utilized focus group and case story methodologies to work with the community to assess needs. Formal educational programs, community events, and a navigational program were then provided to encourage and assist in breast cancer screening and follow-up when needed. Detailed here is a description of the authors’ program development and the far-reaching community impact such a program can have once implemented.

The relationship between body iron stores and blood and urine cadmium concentrations in US never-smoking, non-pregnant women aged 20-49 years

BACKGROUND

Cadmium is a ubiquitous environmental pollutant associated with increased risk of leading causes of mortality and morbidity in women, including breast cancer and osteoporosis. Iron deficiency increases absorption of dietary cadmium, rendering women, who tend to have lower iron stores than men, more susceptible to cadmium uptake. We used body iron, a measure that incorporates both serum ferritin and soluble transferrin receptor, as recommended by the World Health Organization, to evaluate the relationships between iron status and urine and blood cadmium.

METHODS

Serum ferritin, soluble transferrin receptor, urine and blood cadmium values in never-smoking, non-pregnant, non-lactating, non-menopausal women aged 20-49 years (n=599) were obtained from the 2003-2008 National Health and Nutrition Examination Surveys. Body iron was calculated from serum ferritin and soluble transferrin receptor, and iron deficiency defined as body iron <0 mg/kg. Robust linear regression was used to evaluate the relationships between body iron and blood and urine cadmium, adjusted for age, race, poverty, body mass index, and parity.

RESULTS

Per incremental (mg/kg) increase in body iron, urine cadmium decreased by 0.003 μg/g creatinine and blood cadmium decreased by 0.014 μg/L. Iron deficiency was associated with 0.044 μg/g creatinine greater urine cadmium (95% CI=0.020, 0.069) and 0.162 μg/L greater blood cadmium (95% CI=0.132, 0.193).

CONCLUSIONS

Iron deficiency is a risk factor for increased blood and urine cadmium among never-smoking, pre-menopausal, non-pregnant US women, independent of age, race, poverty, body mass index and parity. Expanding programs to detect and correct iron deficiency among non-pregnant women merits consideration as a potential means to reduce the risk of cadmium associated diseases.

Abstract 5497: An inhibitor of phosphatase PP2A enhances in vivo anticancer activity of a phospho (ADP-ribosyl) polymerase inhibitor (PARPi) combined with temozolomide (TMZ)

We previously showed that a novel inhibitor of PP2A enhances the in vivo activity of TMZ against human glioblastoma xenografts (Lu et al, PNAS 2009;104:11697-11702). Several mechanisms underlie this effect of PP2A inhibition and include an increased rate of cancer cell entry into DNA synthesis, inhibition of cell cycle arrest at G1 and G2/M, and a marked reduction in p53. Because inhibitors of PARP1 have been shown to enhance the activity of cytotoxic cancer drugs by inhibiting repair of single-strand breaks in cells with impaired mechanisms for double-stranded DNA repair (BrCa mutants, triple negative breast cancer cells), we reasoned that blocking other types of DNA-damage defense mechanisms by PP2A inhibition might further enhance the activity of a PARPi combined with TMZ in cancers, not necessarily already deficient in DNA repair. We treated mice bearing xenografts of human melanoma, line A2058, with single agent LB-100, a novel water soluble PP2A inhibitor (Lixte Biotechnology Holdings, Inc., East Setauket, NY; Lu et al, J Neurosurg 2010; 113: 225-233) at 1.5mg/kg by continuous intraperitoneal (i.p.) infusion for 21 days and TMZ at 80mg/kg i.p. days 3,6,9,12,15,18. LB-100 and TMZ were given alone and in combination with each other and in 2-drug combinations with the PARPi, ABT-888 (Sigma), at 6.25 mg/kg i.p. on days 3,6,9,12,15,18, and all three drugs were given together at the same doses and schedules as when used alone or in 2-drug combinations. (ABT-888 was inactive as a single agent and was not used alone). The combination of LB-100 + TMZ was more inhibitory to the xenografts at 21 days than ABT-888 + TMZ, but the 3-drug regimen was most effective and no more toxic than any of the 2-drug regimens. Histologic analysis of xenografts 24 hours after treatment of animals with each of the single agents, each 2-drug regimen, and the 3-drug regimen showed increased apoptosis and necrosis by the 3-drug combination compared to the two-drug regimens, which in turn were more effective that the single agents. Similar results were found in vitro by flow cytometric analysis of A2058 cells 24 hours after exposure to the single agent and 2- and 3-drug regimens. Inclusion of a PP2A inhibitor may increase and extend the effectiveness of cytotoxic regimens containing a PARPi to cancers without acquired mutations in DNA repair.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5497. doi:10.1158/1538-7445.AM2011-5497

Environmental cadmium and breast cancer risk

Breast cancer is the most prevalent women's cancer, with an age-adjusted incidence of 122.9 per 100,000 US women. Cadmium, a ubiquitous carcinogenic pollutant with multiple biological effects, has been reported to be associated with breast cancer in one US regional case-control study. We examined the association of breast cancer with urinary cadmium (UCd), in a case-control sample of women living on Long Island (LI), NY (100 with breast cancer and 98 without), a region with an especially high rate of breast cancer (142.7 per 100,000 in Suffolk County) and in a representative sample of US women (NHANES 1999-2008, 92 with breast cancer and 2,884 without). In a multivariable logistic model, both samples showed a significant trend for increased odds of breast cancer across increasing UCd quartiles (NHANES, p=0.039 and LI, p=0.023). Compared to those in the lowest quartile, LI women in the highest quartile had increased risk for breast cancer (OR=2.69; 95% CI=1.07, 6.78) and US women in the two highest quartiles had increased risk (OR=2.50; 95% CI=1.11, 5.63 and OR=2.22; 95% CI=.89, 5.52, respectively). Further research is warranted on the impact of environmental cadmium on breast cancer risk in specific populations and on identifying the underlying molecular mechanisms.

Cadmium, follicle-stimulating hormone, and effects on bone in women age 42-60 years, NHANES III

BACKGROUND

Increased body burden of environmental cadmium has been associated with greater risk of decreased bone mineral density (BMD) and osteoporosis in middle-aged and older women, and an inverse relationship has been reported between follicle-stimulating hormone (FSH) and BMD in middle-aged women; however, the relationships between cadmium and FSH are uncertain, and the associations of each with bone loss have not been analyzed in a single population.

OBJECTIVES

The objective of this study was to evaluate the associations between creatinine-adjusted urinary cadmium (UCd) and FSH levels, and the associations between UCd and FSH with BMD and osteoporosis, in postmenopausal and perimenopausal women aged 42-60 years.

METHODS

Data were obtained from the Third National Health Examination and Nutrition Survey, 1988-1994 (NHANES III). Outcomes evaluated were serum FSH levels, femoral bone mineral density measured by dual energy X-ray absorptiometry, and osteoporosis indicated by femoral BMD cutoffs based on the international standard. Urinary cadmium levels were analyzed for association with these outcomes, and FSH levels analyzed for association with bone effects, using multiple regression. Subset analysis was conducted by a dichotomous measure of body mass index (BMI) to proxy higher and lower adipose-synthesized estrogen effects.

RESULTS

UCd was associated with increased serum FSH in perimenopausal women with high BMI (n=642; beta=0.45; p< or =0.05; R(2)=0.35) and low BMI (n=408; beta=0.61; p< or =0.01; R(2)=0.34). Among perimenopausal women with high BMI, BMD was inversely related to UCd (beta=-0.04; p< or =0.05) and FSH (beta=-0.03; p< or =0.05). In postmenopausal women with low BMI, an incremental increase in FSH was associated with 2.78 greater odds for osteoporosis (109 with and 706 without) (OR=2.78; 95% CI=1.43, 5.42; p< or =0.01).

CONCLUSION

Long-term cadmium exposure at environmental levels is associated with increased serum FSH, and both FSH and UCd are associated with bone loss, in US women aged 42-60 years.

Enhancement of cancer chemotherapy by simultaneously altering cell cycle progression and DNA-damage defenses through global modification of the serine/threonine phospho-proteome

Despite improvements in the therapeutic efficacy of rationally designed cancer treatment regimens, most cancers remain incurable once spread beyond their sites of origin. Failure to achieve sustained control or eradication of cancers arises in large part because a subpopulation of quiescent "cancer stem cells" is insensitive to drugs targeting cell growth and replication and because defense mechanisms critical to survival of the normal cell also protect the cancer cell from cytotoxic injury. Global alteration of signal transduction by inhibition of serine/threonine dephosphorylation has recently been shown to markedly potentiate cancer cell killing by the DNA-methylating drug, temozolomide. Inhibition of the multifunctional protein phosphatase 2A appears to drive quiescent cancer cells into cycle and simultaneously inhibits cycle arrest, permitting cancer cell entry into mitosis despite the presence of chemotherapy induced DNA-damage. Absence of toxicity in animal models suggests that multi-site mutations in pathways regulating cell cycle in cancer cells make them more vulnerable than normal cells to large changes in the balance of phosphorylation-regulated signaling. Global modulation of the serine-threonine phospho-proteome may be a general method for enhancing the effectiveness of cytotoxic cancer therapy.

Inhibition of serine/threonine phosphatase PP2A enhances cancer chemotherapy by blocking DNA damage induced defense mechanisms

A variety of mechanisms maintain the integrity of the genome in the face of cell stress. Cancer cell response to chemotherapeutic and radiation-induced DNA damage is mediated by multiple defense mechanisms including polo-like kinase 1 (Plk-1), protein kinase B (Akt-1), and/or p53 pathways leading to either apoptosis or cell cycle arrest. Subsequently, a subpopulation of arrested viable cancer cells may remain and recur despite aggressive and repetitive therapy. Here, we show that modulation (activation of Akt-1 and Plk-1 and repression of p53) of these pathways simultaneously results in paradoxical enhancement of the effectiveness of cytotoxic chemotherapy. We demonstrate that a small molecule inhibitor, LB-1.2, of protein phosphatase 2A (PP2A) activates Plk-1 and Akt-1 and decreases p53 abundance in tumor cells. Combined with temozolomide (TMZ; a DNA-methylating chemotherapeutic drug), LB-1.2 causes complete regression of glioblastoma multiforme (GBM) xenografts without recurrence in 50% of animals (up to 28 weeks) and complete inhibition of growth of neuroblastoma (NB) xenografts. Treatment with either drug alone results in only short-term inhibition/regression with all xenografts resuming rapid growth. Combined with another widely used anticancer drug, Doxorubicin (DOX, a DNA intercalating agent), LB-1.2 also causes marked GBM xenograft regression, whereas DOX alone only slows growth. Inhibition of PP2A by LB-1.2 blocks cell-cycle arrest and increases progression of cell cycle in the presence of TMZ or DOX. Pharmacologic inhibition of PP2A may be a general method for enhancing the effectiveness of cancer treatments that damage DNA or disrupt components of cell replication.

Urinary cadmium and osteoporosis in U.S. Women >or= 50 years of age: NHANES 1988-1994 and 1999-2004

BACKGROUND

Urinary cadmium (U-Cd) has been associated with decreased peripheral bone mineral density (BMD) and osteoporosis. This association, however, has not been confirmed using femoral BMD, the international standard for diagnosing osteoporosis, at levels < 1.0 microg Cd/g creatinine.

OBJECTIVES

Our goal was to investigate the statistical association between U-Cd, at levels or= 50 years of age.

METHODS

We drew data from the National Health and Nutrition Examination Surveys for 1988-1994 (n = 3,207) and 1999-2004 (n = 1,051). Osteoporosis was indicated by hip BMD cutoffs based on the international standard and self-report of physician diagnosis. We analyzed U-Cd levels for association with osteoporosis using multiple logistic regression.

RESULTS

Women >or= 50 years of age with U-Cd levels between 0.50 and 1.00 microg/g creatinine were at 43% greater risk for hip-BMD-defined osteoporosis, relative to those with levels

CONCLUSIONS

Results suggest that U.S. women are at risk for osteoporosis at U-Cd levels below the U.S. Occupational Safety and Health Administration's 3-microg/g safety standard. Given null findings among smokers, dietary Cd, rather than tobacco, is the likely source of Cd-related osteoporosis risk for the U.S. female population >or= 50 years of age.

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Key Words

• bone mineral density
• cadmium
• femur
• hip
• osteoporosis
• women

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MESH Headings

• Aged
• Aged, 80 and over
• Bone Density
• Cadmium/urine
• Creatinine/urine
• Female
• Humans
• Middle Aged
• Nutrition Surveys
• Osteoporosis/epidemiology
• Osteoporosis/urine
• Regression Analysis
• United States/epidemiology

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Affiliation(s)

Carolyn M Gallagher Graduate Program in Public Health, Stony Brook University Medical Center, Stony Brook, New York 11790, USA.
John S Kovach
Jaymie R Meliker

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Detection of cancer-specific markers amid massive mass spectral data

We propose a comprehensive pattern recognition procedure that will achieve best discrimination between two or more sets of subjects with data in the same coordinate system. Applying the procedure to MS data of proteomic analysis of serum from ovarian cancer patients and serum from cancer-free individuals in the Food and Drug Administration/National Cancer Institute Clinical Proteomics Database, we have achieved perfect discrimination (100% sensitivity, 100% specificity) of patients with ovarian cancer, including early-stage disease, from normal controls for two independent sets of data. Our procedure identifies the best subset of proteomic biomarkers for optimal discrimination between the groups and appears to have higher discriminatory power than other methods reported to date. For large-scale screening for diseases of relatively low prevalence such as ovarian cancer, almost perfect specificity and sensitivity of the detection system is critical to avoid unmanageably high numbers of false-positive cases.

Low frequency of p53 gene mutations in breast cancers of Japanese-American women

Differences in frequencies and patterns of somatic p53 gene mutations among racially and geographically diverse populations presumably reflect exposure to different mutagens or different responses to certain mutagens. On emigration to the United States, Japanese women experience, over several generations, a four- to fivefold increase in the incidence of breast cancer. To determine whether this increased incidence is associated with a change in the frequency and/or type of p53 mutation in their tumors, we examined paraffin-embedded samples of primary breast cancers from Japanese-American women in Los Angeles County, CA. Mutations in exons 5-9 and adjacent intronic regions of the p53 gene were identified and confirmed by direct sequencing. Seven mutations, including 5 missense, were detected in 44 primary breast carcinomas, a frequency of 16%. There were six transitions and one transversion. As expected, overexpression of p53 protein, detected by immunohistochemistry, occurred in tumors with missense mutations; tumors with nonsense or splice junction mutations had no detectable p53 protein. The frequency of p53 gene mutations showed no increase over that previously found in breast cancers of native Japanese women. The increased incidence of breast cancer in Japanese-American women is likely to be multifactorial in nature and warrants further studies.

A prospective trial of midwest breast cancer patients: a p53 gene mutation is the most important predictor of adverse outcome

Several retrospective studies have suggested p53 gene mutation as an adverse prognostic indicator in breast cancer patients, based on a selective growth advantage of p53 mutant cancer cells and their presumed resistance to current adjuvant therapy regimens. A cohort of 90 Caucasian midwestern breast cancer patients was analyzed prospectively (60 months of follow-up) with a rigorous mutation detection methodology. The presence of a p53 gene mutation was the single most adverse prognostic indicator for recurrence (p = 0.0032) and death (p = 0.0001), and was associated with poor response to both adjuvant (p = 0.0001) and palliative (p = 0.006) therapy. Analysis of the p53 gene with appropriate mutation detection methodology markedly improves the prediction of early recurrence, treatment failure, and death in breast cancer patients.

A prospective trial of midwest breast cancer patients: a p53 gene mutation is the most important predictor of adverse outcome

Several retrospective studies have suggested p53 gene mutation as an adverse prognostic indicator in breast cancer patients, based on a selective growth advantage of p53 mutant cancer cells and their presumed resistance to current adjuvant therapy regimens. A cohort of 90 Caucasian midwestern breast cancer patients was analyzed prospectively (60 months of follow-up) with a rigorous mutation detection methodology. The presence of a p53 gene mutation was the single most adverse prognostic indicator for recurrence (p = 0.0032) and death (p = 0.0001), and was associated with poor response to both adjuvant (p = 0.0001) and palliative (p = 0.006) therapy. Analysis of the p53 gene with appropriate mutation detection methodology markedly improves the prediction of early recurrence, treatment failure, and death in breast cancer patients.

Clinical and pharmacokinetic studies of high-dose levamisole in combination with 5-fluorouracil in patients with advanced cancer

PURPOSE

To determine the maximum tolerable dose (MTD) and activity of levamisole administered concurrently with 5-fluorouracil (5-FU) in a standard 5-day course. To determine the pharmacokinetics of levamisole during the course of treatment.

PATIENTS AND METHODS

Levamisole was administered to 38 patients orally three times a day for 5 days concurrently with a course of 5-FU administered daily by rapid intravenous injection for 5 days. Toxicity was evaluated in 20 patients who received escalating doses of levamisole. The activity of the combination was evaluated in 18 patients who received levamisole at the MTD with 5-FU. The pharmacokinetics of levamisole were characterized in ten patients at the MTD level.

RESULTS

Intractable vomiting, confusion and vertigo were the major dose-limiting toxicities. The MTD of oral levamisole was 100 mg/m2 administered three times a day concurrently with 450 mg/m2 per day intravenous 5-FU for 5 consecutive days. Partial responses lasting 5 and 11 months were observed in 2/18 patients with measurable disease at the MTD. Peak plasma concentrations of 1 microg/ml (range 0.6-1.3 microg/ml) were achieved 90 min (range 60-360 min) after an oral dose of 100 mg/m2 levamisole with a 3.5-fold accumulation noted following 4 days of administration. Peak plasma concentrations of p-hydroxylevamisole were about 5% of parent drug. Little parent drug (2-5%) was detected in urine.

CONCLUSIONS

Levamisole may be administered safely with 5-FU at doses which are up to four to five times greater than those presently given in conventional regimens. The recommended dose of levamisole combined with 5-FU for future research protocols is 75 mg/m2 t.i.d for 5 days.

Distribution of endogenous tumour necrosis factor alpha in gliomas

AIMS

To determine the distribution and cellular origin of endogenous tumour necrosis factor alpha (TNF alpha) in the cellular components of human gliomas.

METHODS

Frozen sections of 26 gliomas (four astrocytomas (As); two oligoastrocytomas (OA); one ansplastic astrocytoma (AA); one anaplastic oligoastrocytoma (AOA); 18 glioblastomas (GB)) were examined immunohistochemically using antihuman TNF alpha and anti-Leu-M5 (CD11c) antibodies. Additional studies with double immunohistocchemical procedures were performed with anti-glial fibrillary acidic protein and anti-neurofilament antibodies.

RESULTS

Eighty per cent of the AA, AOA, and GB (16 of 20) had a positive reaction for TNF alpha, but only 17% of As and OA (one of six) were positive. Positive cells were seen in both the tumour tissue and adjacent brain tissues. TNF alpha protein was detected not only in the tumour cells but also in the endothelium of tumour vessels as well as reactive astrocytes and neurons.

CONCLUSIONS

Endogenous TNF alpha is present in cells of various origins in glial tumours including tumour vessels; however, the role of TNF alpha may be different in different types of cells or altered microenvironment.

The molecular epidemiology of p53 gene mutations in human breast cancer

The P53 tumor-suppressor gene is an advantageous tool for analyzing the molecular epidemiology of cancer. We describe the utility of the P53 gene as a 'mutagen test' and a prognostic indicator in breast cancer. Aspects of study design and methodology are discussed. Two major conclusions emerge: (1) there is an extraordinary diversity of mutational patterns among cohorts, hinting that the unique biology of mammary cells results in exposure to high doses of a diversity of ingested lipophilic mutagens; and (2) mutations in the P53 gene predict poor outcome in breast cancer.

Molecular epidemiology of breast cancers in northern and southern Japan: the frequency, clustering, and patterns of p53 gene mutations differ among these two low-risk populations

Comparison of acquired mutations in the p53 tumor suppressor gene can illuminate factors contributing to carcinogenesis among cancer cohorts. Japan has an ethnically homogeneous population with a low incidence of breast cancer. Previously we reported an unusual frequency, allelic status, and clustering of mutations in breast cancers from the northern part of the main Japanese island. To extend these findings, exons 2-11 and adjacent intronic sequences were analysed in tumors of women from northern (Hokkaido) and southern (Tokushima) Japan. The frequency of breast cancers with p53 gene mutations in the Hokkaido group is the highest reported (81%) while that in Tokushima (28%) is similar to most other populations. Thirteen of the 19 mutations (68.4%) in the Hokkaido cohort were heterozygous, an unusually high frequency for p53 mutations in any tumor type. There were three missense mutations at codon 175, a known hotspot for alterations in the p53 gene, and three missense mutations at codon 179, a rare site for p53 changes. In addition, the patterns of p53 gene mutation differed between the two Japanese cohorts (P=0.04). The multiple differences in acquired p53 mutations suggest unsuspected biological differences among breast cancers in northern and southern Japan. In addition, the high frequency of p53 mutations in breast cancers from Hokkaido predicted a poorer prognosis for this population which was confirmed on examination of mortality data.

Need for standardization of cancer practice via nationally accepted treatment guidelines

The critical need for a reduction in health-care costs has revolutionized the management of a significant segment of the American health-care system. The competition, at least on the basis of cost, will continue to restrict access to care and may reduce quality. For patients with diseases such as specific cancers that have been demonstrated by reproducible methods in comparative trials to be potentially curable or strikingly ameliorated, assurance of treatment by these methods must be guaranteed. Achievement of a national consensus on cancer treatment guidelines for potentially curable cancers is needed as the benchmark of quality health-care plans for patients and payors alike. Documenting adherence to such guidelines and finding mechanisms for improving treatments for future patients remain unresolved challenges of the managed-care era.

Overexpression and mutations of p53 in metastatic malignant melanomas

Alterations of the p53 tumor suppressor gene are the most frequent genetic abnormalities in human malignancies, but the role of p53 in the etiology of malignant melanomas is unclear. Fifty unselected malignant melanomas were analyzed for p53 overexpression by immunohistochemistry using 3 monoclonal antibodies (MAbs). Fifteen tumors (29.4%) showed positive staining with at least 2 different antibodies. In the first 20 consecutive tumors exons 5-9 and adjacent splice sites of the p53 gene were analyzed by genomic sequencing. There were 4 mutations in 20 metastatic melanomas. Three of 4 mutations were C:G-->T:A transitions. A search of our database of p53 mutations revealed that out of 8 p53 mutations reported by others, 4 are C:G-->T:A transitions at dipyrimidine sites, and one is a tandem CC-->TT mutation. This mutational pattern is comparable with the pattern of p53 mutations in squamous cell and basal cell carcinomas of the skin and is related to exposure to ultraviolet B (UV-B) wavelength radiation. Taken together with a predominance of UV-induced mutations in the CDKN2/ p16 gene demonstrated in melanoma cell lines, our data support a role of sunlight exposure in the etiology of malignant melanoma. The low frequency of p53 mutants in melanomas compared with other types of skin cancers suggests that although mutations in this gene are likely to be involved in the development of some malignant melanomas, they do not play as large a role as in squamous and basal cell carcinomas of the skin.

High frequency of p53 gene mutations in primary breast cancers in Japanese women, a low-incidence population

The pattern of acquired mutations in the p53 tumour-suppressor gene is potentially useful for determining factors contributing to carcinogenesis in diverse populations differing in incidence and/or mortality from the disease. We previously reported differences in mutational patterns of the p53 gene in primary breast cancers from Midwest US Caucasian, African-American and Austrian women. Herein, we report 16 mutations in 27 primary breast cancers from Japanese women from Hirosaki, a population with a low incidence of breast cancer. The frequency of 59.3% of p53 mutations is the highest reported in breast cancers from a particular ethnic group thus far. A relatively high number of mutations (7/16) were heterozygous in at least some tumour cell clusters. Intergroup comparisons of the mutational pattern between this population and several other US, European and Japanese populations do not show any statistically significant differences. There were recurrent mutations at two sites, codon 273 (R --> H; three mutations), a common hotspot of mutations in breast and other cancers, and codon 183 (S --> Stop; two mutations), a very rare location for p53 mutations. These mutations were shown to be independent and presumably not in the germ line. The highest frequency of p53 mutations raises the possibility that p53 mutagenesis is a predominant factor for breast cancer development in this low-risk Japanese group, whereas in other cohorts different mechanisms are likely to account for the higher proportion of breast cancer. Further studies are needed to confirm the present observations.

A polymorphism but no mutations in the GADD45 gene in breast cancers

The p53 gene product is part of a pathway regulating growth arrest at the G1 checkpoint of the cell cycle. Mutation of other components of this pathway, including the products of the ataxia telangiectasia (AT), GADD45, mdm2, and p21WAF1/CIP1 genes may have effects comparable to mutations in the p53 gene. The GADD45 gene is induced by ionizing radiation and several DNA-damaging xenobiotics. Induction requires the binding of wild-type p53 to an evoulutionarily highly conserved putative intronic p53 binding site in intron 3 of GADD45. We recently analyzed the entire coding region of the p53 gene in primary breast cancers of Midwestern white women and found 21 mutations among 53 tumors (39.6%). We now have shown by direct sequencing that there are no mutations in the intronic p53 binding site of the GADD45 gene in any of the 53 primary breast cancers and no mutations in the entire coding region of the GADD45 gene in a subset of 26 consecutive tumors (12 with p53 mutation and 14 without p53 mutation). The only sequence variation detected was a common polymorphism in intron 3. The absence of mutations in the GADD45 gene, including the putative p53-binding intronic site, suggests that this gene is not a frequent target of mutations in breast cancer. Although mutations of the p53 gene have been studied in a wide spectrum of human cancers, GADD45 has not been examined in any tumor or cell line to the best of our knowledge. Our results raise the possibility that mutation of the GADD45 gene alone is not functionally equivalent to loss of wild-type p53 activity.

Mutation detection by highly sensitive methods indicates that p53 gene mutations in breast cancer can have important prognostic value

Human cancer cells with a mutated p53 tumor-suppressor gene have a selective growth advantage and may exhibit resistance to ionizing radiation and certain chemotherapeutic agents. To examine the prognostic value of mutations in the p53 gene, a cohort of 90 Midwestern Caucasian breast cancer patients were analyzed with methodology that detects virtually 100% of all mutations. The presence of a p53 gene mutation was by far the single most predictive indicator for recurrence and death (relative risks of 4.7 and 23.2, respectively). Direct detection of p53 mutations had substantially greater prognostic value than immunohistochemical detection of p53 overexpression. Analysis of p53 gene mutations may permit identification of a subset of breast cancer patients who, despite lack of conventional indicators of poor prognosis, are at high risk of early recurrence and death.

Database of mutations in the p53 and APC tumor suppressor genes designed to facilitate molecular epidemiological analyses

Germline and somatic mutations in the p53 and APC genes contribute to neoplasia. The patterns of these and other acquired mutations in cancers reflect environmental mutagens and endogenous factors that contribute to carcinogenesis. Herein, we describe a database of almost 2,300 mutations in the p53 and APC genes published until September 1, 1993. In addition to cataloging the mutations, multiple fields of information have been added to facilitate future molecular epidemiological analyses of human cancer. The accuracy of the database has been checked by the present authors and, by soliciting feedback from the original corresponding authors. The strengths and limitations of the primary literature are discussed.

p53 gene mutations inside and outside of exons 5-8: the patterns differ in breast and other cancers

Most studies of mutations in the p53 tumor suppressor gene in tumors have examined only exons 5-8. Our laboratory previously found 64 mutations in exons 5-8 of the p53 gene in 194 primary breast cancers. Herein, we report 18 additional mutations found outside of exons 5-8. Mutations are present in exons 4, 9 and 10, and flanking splice junctions, but not in the promotor region or in exons 1, 2, 3 and 11. No missense mutations are found outside of exons 5-8. Instead, there is a predominance of frameshift mutations with lesser numbers of nonsense and splice site mutations. In contrast, the majority of mutations in exons 5-8 in this sample are missense changes and all of these are at amino acids that are identical in the 11 known p53 sequences that represent about 1.6 billion years of evolutionary divergence. The difference in mutational pattern between these two regions of the p53 gene is due to a lack of missense mutations and inframe microdeletions outside of exons 5-8. A review of our database of p53 mutations (De Vries et al., in preparation) shows that the patterns of mutation inside and outside of exons 5-8 differ in other types of cancers as well. The paucity of missense mutations in exons 2-4 and 9-11 in breast and other cancers (even at amino acids identical throughout p53 gene evolution) suggest that at least some missense mutations result in a phenotype other than malignant transformation. These data also illustrate the importance of examining identical exons when comparing the pattern of p53 gene mutations in different populations.

Rapid and efficient screening for p53 gene mutations by dideoxy fingerprinting

Dideoxy fingerprinting (ddF) is an efficient method for detecting single base and other sequence changes in PCR-amplified DNA segments. This screening method is a hybrid between single-strand conformation polymorphism analysis (SSCP) and Sanger dideoxy sequencing. It involves a Sanger sequencing reaction with one dideoxynucleotide followed by non-denaturing gel electrophoresis. We are using ddF to screen for mutations in the p53 tumor suppressor gene in primary breast cancers. ddF detected more than 100 mutations in different regions of the gene, including all types of single-base mutations and microdeletions/microinsertions of various sizes. Furthermore, ddF reliably detected heterozygous mutations, if the region of interest was screened in both directions. In a blinded, prospective study, ddF detected all 25 mutations within exons 4-10 and adjacent flanking intronic regions previously found by direct sequencing. ddF was also useful in scoring two common polymorphisms within the p53 gene. Guidelines for preventing false-positive and false-negative results are summarized.

Novel pattern of P53 mutation in breast cancers from Austrian women

Since mutagens produce an extraordinary diversity of mutational patterns, differential mutational exposures among populations are expected to produce different patterns of mutation. Classical epidemiological methods have been successful in implicating specific mutagens in cancers such as those of lung and skin in which one mutagen predominates. In breast cancer, however, no mutagens have been implicated in an unequivocal manner. In an attempt to facilitate epidemiological studies, we have been studying the pattern of p53 gene mutations in breast cancers from multiple populations with high and low breast cancer incidences. We previously reported that breast cancers from Midwest United States, predominantly rural Caucasian women, have a different pattern of p53 gene mutation from populations of Western European women. Herein, we analyze patterns of p53 mutations from Graz, Austria, another population with a high incidence of breast cancer. Among the 60 Austrian breast cancers analyzed, 14 (23%) have a p53 gene mutation in exons 5-9 or in adjacent splice junctions. Analysis of the patterns of mutation shows differences between the "Western European" profile and the Austrian and Midwest United States groups (P = 0.027 and 0.024, respectively). The Austrian pattern is characterized by a high frequency of A:T-->T:A transversions (P = 0.006). The presence of distinct patterns of mutation among the limited number of analyzed populations of Western European origin supports the idea that differential mutagenic exposure and/or genetic differences contribute to breast cancer mutagenesis among geographically distinct Caucasians of Western European origin.

Novel pattern of p53 gene mutations in an American black cohort with high mortality from breast cancer

The pattern of acquired mutations in the p53 gene can be used to study differences in factors contributing to carcinogenesis. We investigated mutations in exons 5-9 and adjacent intronic regions in 47 breast cancers of black women from Michigan, a population with the highest breast-cancer mortality in the US. The 16 mutations detected differed from those of other populations. In particular, the black women had an excess of A:T-->G:C transitions compared with rural white US midwest women. While the causes of the different pattern of acquired mutation remain to be determined, this molecular epidemiological approach detects the consequences of mutagenic processes in specific populations. Mutation patterns will constrain hypotheses to mechanisms consistent with the observed biochemical alterations.

Detection of p53 antigen expression in cytologic preparations of ovarian carcinomas

We explored the value of p53 immunostaining in detection of malignant cells in cytologic analyses in ovarian cancer patients. Ninety-six percent of 23 tumor touch preparations had nuclear staining with PAb240: 44% had nuclear only, 26% had both nuclear and cytoplasmic staining, and 26% had cytoplasmic staining alone. Eight of 20 cytospins of peritoneal washings from ovarian cancer patients were PAb240 positive, 6 had cytoplasmic, and two had nuclear staining. Cytospins of fluid from 3/15 patients with no malignancy revealed cytoplasmic staining of mesothelial cells. The lack of concordance between staining of primary tumors and cytospins of peritoneal washings and the apparent reactivity in some benign samples may limit the utility of immunohistochemical detection of malignant cells in the peritoneal fluid of ovarian cancer patients.

Distribution of transforming growth factor-beta 1 in human astrocytomas

We used immunohistochemical techniques to study the distribution of transforming growth factor-beta 1 (TGF-beta 1) and infiltrating lymphocytes and macrophages in human astrocytomas. Thirteen of 15 grade 4 astrocytomas (glioblastomas) showed staining with anti-TGF-beta 1 antibody, predominantly in proliferating endothelial complexes and surrounding small and medium-sized blood vessels. Brain tissue microscopically free of tumor cells (n = 8) and more differentiated astrocytomas of varying grade (1 to 3; n = 6) devoid of endothelial proliferation did not stain with anti-TGF-beta 1. Normal brain contained only rare lymphoreticular cells. The majority of astrocytomas studied, however, contained T lymphocytes and macrophages with smaller numbers of B lymphocytes. The lymphoreticular infiltrates were concentrated primarily in close proximity to blood vessels. Within an individual tumor perivascular regions staining for TGF-beta 1 never contained more than occasional T lymphocytes. Perivascular regions not staining for TGF-beta 1 frequently contained low to high numbers of T lymphocytes. The inverse relationship in the distribution of TGF-beta 1 and lymphocyte infiltrates is compatible with a functional relationship between this cytokine and an immune effector cell response to glioblastomas.

Current status of adjuvant chemotherapy for colorectal cancer. Can molecular markers play a role in predicting prognosis?

BACKGROUND

Recent clinical trials establish a beneficial effect for adjuvant chemotherapy after surgical resection of the primary tumor (1) as single treatment for patients with colonic cancer and (2) combined with radiation therapy for patients with rectal cancer. Because adjuvant chemotherapy is not universally effective and is associated with toxicity and some degree of risk, it would be desirable to supplement standard pathologic staging criteria to define more precisely the subset of patients at high risk for tumor recurrence who would benefit most from adjuvant therapy. Tumor cell DNA content and cell proliferation measured by flow cytometry were identified as important and independent prognostic factors for patients undergoing curative resection of colorectal cancer. Basic laboratory investigations show a series of more specific molecular and genetic abnormalities that might provide better prognostic discrimination. Recent molecular studies suggest that the process of tumorigenesis in colorectal cancer proceeds through a series of genetic alterations that include both dominant and recessive protooncogenes. Characterization of these molecular genetic abnormalities may provide valuable prognostic information for use in patient management.

METHODS

Allelic loss was studied for chromosomes 5, 17, and 18, and immunohistochemical analysis was done of the p53 protein product in tumors from 91 patients with colorectal cancer.

RESULTS

Preliminary analysis of disease-free survival after surgical resection in 60 patients with Dukes' B or C tumors suggests a poorer prognosis associated with allelic loss on chromosome 18q (P = 0.08).

CONCLUSIONS

Additional studies involving a much larger population of patients with Dukes' B and C colorectal cancer are needed to define the true prognostic significance of these molecular markers.

Expression of p53 and 17p allelic loss in colorectal carcinoma

Mutations in the p53 gene are the most common genetic changes in cancer thus far. Many p53 mutations result in a protein product having a prolonged half-life compared to wild-type p53. The mutant protein is frequently detectable immunohistochemically, whereas the wild-type p53 present in normal cells is not. We examined 90 colorectal carcinomas for increased expression of p53 using 3 p53 specific monoclonal antibodies, PAb1801, PAb421, and PAb240. Overall, 70% of the colorectal carcinomas stained for p53. Each tumor's DNA was also assessed for loss of heterozygosity on chromosome 17p, the location of the p53 gene. Of those tumors that reacted with the anti-p53 antibodies, 76% showed loss on chromosome 17p. Tumors with loss of heterozygosity on 17p generally stained with all 3 antibodies, whereas those without loss tended to stain with just one antibody, typically PAb240. Fifteen tumors were examined for the presence of specific p53 mutations. A total of 10 mutations were found, 6 were missense and 2 were deletions, and all but one of the tumors with missense mutations stained for p53.

Levamisole potentiation of fluorouracil antiproliferative activity mimicked by orthovanadate, an inhibitor of tyrosine phosphatase

BACKGROUND

Levamisole is an effective antihelminthic drug with immunomodulatory and anticancer activities in model systems. Combined with fluorouracil (5-FU) as adjuvant treatment following resection of Dukes' stage C colon carcinomas, levamisole significantly reduces mortality. However, neither 5-FU nor levamisole alone has a significant effect on survival in this patient group. Previously, we noted that in vitro levamisole potentiated the antiproliferative activity of 5-FU.

PURPOSE

Because levamisole is known to inhibit alkaline phosphatases and has been reported to inhibit dephosphorylation of some membrane phosphoproteins, we studied the effects of levamisole analogues and of chemically unrelated inhibitors of phosphatases for their ability to potentiate 5-FU inhibition of tumor cell line proliferation in vitro.

METHODS

Human cancer cell lines were exposed to drugs alone or in combination with 5-FU. Antiproliferative activity was measured by determining the extent of reduction of colony formation by the cell lines in test plates compared with control plates.

RESULTS

We found that potentiation of 5-FU cytotoxicity by levamisole and by p-hydroxytetramisole, a metabolite of levamisole, is mimicked by orthovanadate, an inhibitor of tyrosine phosphatases, but not by okadaic acid, an inhibitor of serine and threonine phosphatases, Furthermore, l-p-bromotetramisole, a synthetic analogue of levamisole that is 10-fold more potent in inhibition of alkaline phosphatase than levamisole, potentiates the antiproliferative activity of 5-FU to a greater extent than d-p-bromotetramisole, a stereoisomer of l-p-bromotetramisole with little antiphosphatase activity.

CONCLUSION

Inhibition of tyrosine phosphatases may be responsible for the potentiation by levamisole of the inhibitory activity of 5-FU in vitro.

IMPLICATIONS

Inhibition of dephosphorylation of regulatory phosphoproteins may be related to the therapeutic efficacy of the combination of levamisole and 5-FU in the adjuvant treatment of colon carcinoma and may underlie at least some of the multiple effects of levamisole on immune parameters.

Pattern of p53 gene mutations in breast cancers of women of the midwestern United States

BACKGROUND

Mutation in the p53 gene is the most common genetic lesion in human cancers. The pattern of mutation in the p53 gene differs among cancers and may be a useful epidemiological tool for identification of factors contributing to carcinogenesis.

PURPOSE

Our purpose was to determine if the pattern of p53 mutation in breast carcinomas in our population of women residing in the midwestern region of the United States is similar to the pattern of p53 mutation in breast cancers in patients from other regions of the United States and Europe and in other epithelial tumors.

METHODS

With a technique we recently developed for the analysis of p53 mutations in genomic DNA from tumor cell clusters in touch preparations of solid tumors, we sequenced exons 5-9 and adjacent splice junctions of the gene in 44 breast cancers. Cells from each tumor were also stained with three monoclonal antibodies which recognize different epitopes of the p53 protein.

RESULTS

We detected p53 mutations in 14 (32.6%) of 44 breast carcinomas. Only half of the mutations were missense changes. The other half included five microdeletions (three producing frame-shifts), one single-base substitution generating a stop codon, and one single-base substitution generating a splice junction abnormality. Nuclear expression of p53 antigen was present in eight of 44 cancers, including six with hemizygous missense mutations in the p53 gene.

CONCLUSIONS

The pattern of p53 mutations in our breast cancer population differs from that reported in breast cancer populations by other investigators in which most p53 mutations were missense. Among 14 mutations in our population, at least five drastically altered the structure of p53, suggesting that a recessive mechanism of inactivation of the p53 gene may be more common than in other populations.

IMPLICATIONS

Differences in the pattern of p53 mutation in breast cancers in Midwestern women and in breast cancers in other populations may reflect selection bias or small sample sizes currently available. However, our data are compatible with the possibility that an endogenous or exogenous factor influences p53 carcinogenesis in some women with breast cancer in the Midwest to a greater extent than in other regions of the United States and Europe.

Administration of interleukin-2 (IL-2) results in increased plasma concentrations of IL-5 and eosinophilia in patients with cancer

Peripheral eosinophilia is almost invariably observed during the course of interleukin-2 (IL-2) therapy and is frequently accompanied by the development of a capillary leak syndrome characterized by edema, weight gain, and oliguria. We studied five patients with advanced malignancy treated with IL-2. Eosinophilia was not present initially but developed in all patients late in the course of therapy, with counts ranging from 2,328/mm3 to 15,958/mm3. In all patients, there was a temporal relationship between the infusion of IL-2 and the appearance of elevated plasma concentrations of IL-5, a growth factor for eosinophils. Granulocyte-macrophage colony-stimulating factor was not detectable in plasma. IL-4 and gamma-interferon plasma levels were variably elevated. Plasma concentrations of major basic protein, a toxic eosinophil granule protein, began increasing before eosinophil counts increased. By the time of the third IL-2 infusion, high concentrations of major basic protein were present in all five patients (up to 5,600 ng/mL) and skin biopsies showed major basic protein deposition in the dermis. Four patients developed significant capillary leak syndrome and all of these patients showed markedly elevated major basic protein levels. The lowest peak plasma concentration of major basic protein (1,751 ng/mL) was observed in the one patient who did not develop edema and weight gain. These results suggest that IL-2 induces IL-5 leading to marked peripheral eosinophilia and extravascular eosinophil degranulation. The release of toxic eosinophil products at extravascular sites and in the circulation may contribute to the pathogenesis of the capillary leak syndrome complicating IL-2 therapy.