Effects on gene expression in rat liver after administration of RXR agonists: UAB30, 4-methyl-UAB30, and Targretin (Bexarotene).

Examination of three retinoid X receptor (RXR) agonists [Targretin (TRG), UAB30, and 4-methyl-UAB30 (4-Me-UAB30)] showed that all inhibited mammary cancer in rodents and two (TRG and 4-Me-UAB30) strikingly increased serum triglyceride levels. Agents were administered in diets to female Sprague-Dawley rats. Liver RNA was isolated and microarrayed on the Affymetrix GeneChip Rat Exon 1.0 ST array. Statistical tests identified genes that exhibited differential expression and fell into groups, or modules, with differential expression among agonists. Genes in specific modules were changed by one, two, or all three agonists. An interactome analysis assessed the effects on genes that heterodimerize with known nuclear receptors. For proliferator-activated receptor α/RXR-activated genes, the strongest response was TRG > 4-Me-UAB30 > UAB30. Many liver X receptor/RXR-related genes (e.g., Scd-1 and Srebf1, which are associated with increased triglycerides) were highly expressed in TRG and 4-Me-UAB30- but not UAB30-treated livers. Minimal expression changes were associated with retinoic acid receptor or vitamin D receptor heterodimers by any of the agonists. UAB30 unexpectedly and uniquely activated genes associated with the aryl hydrocarbon hydroxylase (Ah) receptor (Cyp1a1, Cyp1a2, Cyp1b1, and Nqo1). Based on the Ah receptor activation, UAB30 was tested for its ability to prevent dimethylbenzanthracene (DMBA)-induced mammary cancers, presumably by inhibiting DMBA activation, and was highly effective. Gene expression changes were determined by reverse transcriptase-polymerase chain reaction in rat livers treated with Targretin for 2.3, 7, and 21 days. These showed similar gene expression changes at all three time points, arguing some steady-state effect. Different patterns of gene expression among the agonists provided insight into molecular differences and allowed one to predict certain physiologic consequences of agonist treatment.

An in-vivo study of the combined therapeutic effects of pulsed non-thermal focused ultrasound and radiation for prostate cancer.

PURPOSE: The purpose of this study was to investigate the in vivo combined effects of pulsed focused ultrasound (pFUS) and radiation (RT) for prostate cancer treatment. MATERIALS AND METHODS: An animal prostate tumor model was developed by implanting human LNCaP tumor cells in the prostates of nude mice. Tumor-bearing mice were treated with pFUS, RT or both (pFUS + RT) and compared with a control group. Non-thermal pFUS treatment was delivered by keeping the body temperature below 42 °C as measured real-time by MR thermometry and using a pFUS protocol (1 MHz, 25 W focused ultrasound; 1 Hz pulse rate with a 10% duty cycle for 60 sec for each sonication). Each tumor was covered entirely using 4-8 sonication spots. RT treatment with a dose of 2 Gy was delivered using an external beam (6 MV photon energy with dose rate 300MU/min). Following the treatment, mice were scanned weekly with MRI for tumor volume measurement. RESULTS: The results showed that the tumor volume in the control group increased exponentially to 142 ± 6%, 205 ± 12%, 286 ± 22% and 410 ± 33% at 1, 2, 3 and 4 weeks after treatment, respectively. In contrast, the pFUS group was 29% (p < 0.05), 24% (p < 0.05), 8% and 9% smaller, the RT group was 7%, 10%, 12% and 18% smaller, and the pFUS + RT group was 32%, 39%, 41% and 44% (all with p < 0.05) smaller than the control group at 1, 2, 3, and 4 weeks post treatment, respectively. Tumors treated by pFUS showed an early response (i.e. the first 2 weeks), while the RT group showed a late response. The combined pFUS + RT treatment showed consistent response throughout the post-treatment weeks. CONCLUSIONS: These results suggest that RT combined with non-thermal pFUS can significantly delay the tumor growth. The mechanism of tumor cell killing between pFUS and RT may be different. Pulsed FUS shows early tumor growth delay, while RT contributes to the late effect on tumor growth delay. The addition of pFUS to RT significantly enhanced the therapeutic effect for prostate cancer treatment.

Conditional Dependency of LP-184 on Prostaglandin Reductase 1 is Synthetic Lethal in Pancreatic Cancers with DNA Damage Repair Deficiencies.

The greater efficacy of DNA-damaging drugs for pancreatic adenocarcinoma (PDAC) relies on targeting cancer-specific vulnerabilities while sparing normal organs and tissues due to their inherent toxicities. We tested LP-184, a novel acylfulvene analog, for its activity in preclinical models of PDAC carrying mutations in the DNA damage repair (DDR) pathways. Cytotoxicity of LP-184 is solely dependent on prostaglandin reductase 1 (PTGR1), so that PTGR1 expression robustly correlates with LP-184 cytotoxicity in vitro and in vivo. Low-passage patient-derived PDAC xenografts with DDR deficiencies treated ex vivo are more sensitive to LP-184 compared with DDR-proficient tumors. Additional in vivo testing of PDAC xenografts for their sensitivity to LP-184 demonstrates marked tumor growth inhibition in models harboring pathogenic mutations in ATR, BRCA1, and BRCA2. Depletion of PTGR1, however, completely abrogates the antitumor effect of LP-184. Testing combinatorial strategies for LP-184 aimed at deregulation of nucleotide excision repair proteins ERCC3 and ERCC4 established synergy. Our results provide valuable biomarkers for clinical testing of LP-184 in a large subset of genetically defined characterized refractory carcinomas. High PTGR1 expression and deleterious DDR mutations are present in approximately one third of PDAC making these patients ideal candidates for clinical trials of LP-184.

Quantitative study of focused ultrasound enhanced doxorubicin delivery to prostate tumor in vivo with MRI guidance.

PURPOSE: The purpose of this study was to investigate the potential of MR-guided pulsed focused ultrasound (pFUS) for the enhancement of drug uptake in prostate tumors in vivo using doxorubicin (Dox). METHODS: An antitumor drug Dox, an orthotopic animal prostate tumor model using human prostate cancer, LNCaP cell line, and a clinical FUS treatment system (InSightec ExAblate 2000) with a 1.5T GE MR scanner were used in this study. First, experiments on a tissue mimic phantom to determine the optimal acoustic power and exposure durations with a 10% duty cycle and a 1 Hz pulse rate were performed. The temperature variation was monitored using real-time MR thermometry. Second, tumor-bearing animals were treated with pFUS. There were three groups (n = 8/group): group 1 received pFUS + Dox (10 mg/kg i.v. injection immediately after pFUS exposure), group 2 received Dox only (10 mg/kg i.v. injection), and group 3 was a control. Animals were euthanized 2 h after the pFUS treatment. The Dox concentration in the treated tumors was measured by quantifying fluorescent tracers using a fluorometer. Third, the histological changes of tumors with and without pFUS treatments were evaluated. Finally, experiments were performed to study the spatial drug distribution in tumors after the pFUS treatment, in which two animals received pFUS + Dox, two animals received Dox only, and one animal was used as control. Two hours following the treatment, animals were euthanized and processed. The Dox distribution was determined using a fluorescence microscope. RESULTS: Parametric measurements using a tissue phantom showed that the temperature increased with an increasing acoustic power (from 10 to 50 W) or sonication duration (from 10 to 60 s) with a given acoustic frequency of 1 MHz, duty cycle 10%, and pulse rate 1 Hz. A set of ultrasound parameters was identified with which the temperature elevation was less than 5 °C, which was used for nonthermal pFUS sonication. Increased Dox concentration (14.9 ± 2.5 µg/g) was measured in the pFUS-treated group compared to the Dox-only group (9.5 ± 1.6 µg/g), indicating an approximate 60% increase with p = 0.05. The results were consistent with the increased spatial drug distributions by fluorescence imaging. Histological analysis showed increased extravasation in pFUS-treated prostate tumors suggesting increased drug delivery with pFUS. CONCLUSIONS: The results showed that pFUS-enhanced drug uptake in prostate tumors was significant. This increased uptake may be due to increased extravasation by pFUS. Optimal pFUS parameters may exist to maximize the drug uptake, and this study using Dox demonstrated a quantitative method for such systematic parametric studies. In addition, this study may provide useful data for the potential application of pFUS-mediated Dox delivery for prostate tumor therapy.

Therapeutic effects of in-vivo radiodynamic therapy (RDT) for lung cancer treatment: a combination of 15MV photons and 5-aminolevulinic acid (5-ALA).

Objective.Radiodynamic therapy (RDT) uses high-energy photon beams instead of visible/near-infrared light to treat deep-seated tumors that photodynamic therapy cannot achieve due to the low penetration depth of laser beams. The purpose of this study is to investigate the therapeutic effect of RDT with 15 MV photon beams combined with 5-aminolevulinic acid (5-ALA) using a mouse model.Approach.A subcutaneous C57BL/6 mouse model of KP1 small-cell lung cancer cell line was used. The tumors (N = 120) were randomized into four groups to observe individual and synergistic effects of 5-ALA and radiation treatment: control (untreated, N = 42), radiation treatment (RT) only (N = 20), 5-ALA only (N = 20), and RDT (N = 38). For the RT only and RDT groups, 4 Gy in a single fraction was delivered to the tumors using 15 MV photons. For the 5-ALA only and RDT groups, 5-ALA was injected at a dose of 100 mg kg-1by tail-vein 4 h prior to RT. The tumor response was assessed by monitoring tumor growth using 1.5 T MR, maximum standardized uptake value (SUVmax) and total lesion glycolysis (TLG) using [18F]FDG PET/CT, and animal survival.Main results.RDT achieved a statistically significant delay in tumor growth by 52.1%, 48.1%, and 57.9% 7 days post-treatment compared to 5-ALA only, RT only, and control group (P < 0.001), respectively. There were no significant differences in tumor growth between 5-ALA only and RT only groups. An additional 38.5%-40.9% decrease in tumor growth was observed, showing a synergistic effect with RDT. Furthermore, RDT significantly decreased [18F]FDG uptakes in SUVmaxand TLG 7 days post-treatment by 47.4% and 66.5% (P < 0.001), respectively. RDT mice survived the longest of all treatment groups.Significance.RDT with 15 MV photons and 5-ALA resulted in greater tumor control compared to the control and other treatment groups. A significant synergistic effect was also observed with RDT. These preliminary results demonstrate an effective cancer treatment modality.

Radiodynamic therapy using 15-MV radiation combined with 5-aminolevulinic acid and carbamide peroxide for prostate cancer in vivo.

Photodynamic therapy has been clinically proven to be effective, but its effect is limited to relatively shallow tumors because of its use of visible light. Radiodynamic therapy (RDT) has therefore been investigated as a means to treat deep-seated tumors. In this study, the treatment effect of a novel form of RDT consisting of radiation combined with 5-aminolevulinic acid (5-ALA) and carbamide peroxide was investigated using a mouse model. Male nude mice were injected bilaterally and subcutaneously with human prostate cancer (PC-3) cells and randomized into 8 treatment groups, consisting of various combinations of 15-MV radiotherapy (RT), 5-ALA, and carbamide peroxide. The treatment effect of a single fraction of treatment was measured by calculating tumor growth delay, monitored using weekly MR scans. The ability of the drugs to be delivered to the tumors was qualitatively measured using 18 F-FDG PET/CT scans. RDT was shown to significantly delay the tumor growth for the mouse model and tumor cell line investigated in this work. Tumors treated with RDT showed a decrease in tumor growth of 24 ± 9% and 21 ± 8% at one and two weeks post-treatment, respectively. Peroxide and 5-ALA did not contribute significantly to tumor growth delay when administered alone or separately with RT. Blood perfusion was shown to be able to deliver agents to the tumors investigated in this work, although uptake of 18 F-FDG was shown to be non-uniform.

Vitamin A metabolism is impaired in human ovarian cancer.

OBJECTIVES: We have previously reported that loss in expression of a protein considered critical for vitamin A homeostasis, cellular retinol-binding protein 1 (CRBP1), is an early event in ovarian carcinogenesis. The aim of the present study was to determine if loss of vitamin A metabolism also occurs early in ovarian oncogenesis. METHODS: We assessed CRBP1 expression by immunohistochemistry in ovaries prophylactically removed from women with a genetic risk for ovarian cancer. Furthermore, we investigated the ability of normal, immortalized but nontumorigenic, and tumorigenic human ovarian epithelial cells to synthesize retinoic acid and retinaldehyde when challenged with a physiological dose of retinol, and determined expression levels of the retinoid-related genes, RARalpha, RXRalpha, CRABP1, CRABP2, RALDH1 and RALDH2 in these cells. RESULTS: Immunohistochemistry revealed loss of CRBP1 expression in potentially preneoplastic lesions in prophylactic oophorectomies. HPLC analysis of vitamin A metabolism showed production of retinoic acid in four independent, normal human ovarian surface epithelial (HOSE) cell cultures upon exposure to retinol. However, only one of two SV40-immortalized HOSE cell lines made RA, while none of the ovarian carcinoma cell lines produced detectable RA due to complete loss of RALDH2. CONCLUSIONS: The impaired conversion of retinol to RA in ovarian cancer cells and decreased CRBP1 protein expression in prophylactic oophorectomies support our hypothesis that concomitant losses of vitamin A metabolism and CRBP1 expression contribute to ovarian oncogenesis.

Tissue TGF-ß expression following conventional radiotherapy and pulsed low-dose-rate radiation.

The release of inflammatory cytokines has been implicated in the toxicity of conventional radiotherapy (CRT). Transforming growth factor ß (TGF-ß) has been suggested to be a risk marker for pulmonary toxicity following radiotherapy. Pulsed low-dose rate radiotherapy (PLDR) is a technique that involves spreading out a conventional radiotherapy dose into short pulses of dose with breaks in between to reduce toxicities. We hypothesized that the more tolerable toxicity profile of PLDR compared with CRT may be related to differential expression of inflammatory cytokines such as TGF-ß in normal tissues. To address this, we analyzed tissues from mice that had been subjected to lethal doses of CRT and PLDR by histology and immunohistochemistry (IHC). Equivalent physical doses of CRT triggered more cellular atrophy in the bone marrow, intestine, and pancreas when compared with PLDR as indicated by hematoxylin and eosin staining. IHC data indicates that TGF-ß expression is increased in the bone marrow, intestine, and lungs of mice subjected to CRT as compared with tissues from mice subjected to PLDR. Our in vivo data suggest that differential expression of inflammatory cytokines such as TGF-ß may play a role in the more favorable normal tissue late response following treatment with PLDR.

Loss of cellular retinol-binding protein 1 gene expression in microdissected human ovarian cancer.

PURPOSE: We have previously found that cellular retinol-binding protein 1 (CRBP1),involved in retinol transport and metabolism, is down-regulated in an in vitro rat model of ovarian cancer and in several human ovarian cancer cell lines. The aim of this study was to determine the clinical relevance of this change to human ovarian cancer. EXPERIMENTAL DESIGN: A cohort of 48 frozen human serous ovarian carcinomas was evaluated for CRBP1 gene expression. Malignant ovarian epithelial cells were selectively procured by laser capture microdissection, and their CRBP1 expression was determined by real-time PCR. Immunohistochemistry for CRBP1 was performed on paraffin sections of ovarian tumors using polyclonal affinity-purified rabbit anti-CRBP1 antibody. RESULTS: In 35% of ovarian cancer patient samples, there was no detectable CRBP1 expression by real-time PCR. The expression of CRBP1 in microdissected serous ovarian carcinomas was not related to either tumor stage (P = 0.6839) or grade (P = 0.9599). Quantitative PCR results were confirmed by immunohistochemistry using an antibody against CRBP1. CONCLUSIONS: The loss of CRBP1 expression in clinical ovarian tumor specimens is consistent with our previous findings in the rat model and human ovarian cancer cell lines. It appears to be an early event in ovarian carcinogenesis because there was no statistically significant difference in its frequency between tumor stages and grades. Our findings suggest that the loss of CRBP1 expression contributes to the ovarian cancer oncogenesis via altered vitamin A metabolism.

Local Tumor Control and Normal Tissue Toxicity of Pulsed Low-Dose Rate Radiotherapy for Recurrent Lung Cancer: An In Vivo Animal Study.

OBJECTIVES: This study investigates (1) local tumor control and (2) normal tissue toxicity of pulsed low-dose rate radiotherapy (PLDR) for recurrent lung cancer. METHODS: For study 1, nude mice were implanted with A549 tumors and divided into the following 3 groups: (1) control (n = 10), (2) conventional radiotherapy (RT; n = 10), and (3) PLDR (n = 10). Tumor-bearing mice received 2 Gy daily dose for 2 consecutive days. Weekly magnetic resonance imaging was used for tumor growth monitoring. For study 2, 20 mice received 8 Gy total body irradiation either continuously (n = 10) or 40 × 0.2 Gy pulses with 3-minute intervals (n = 10). RESULTS: For study 1, both conventional RT and PLDR significantly inhibited the growth of A549 xenografts compared with the control group (>35% difference in the mean tumor volume; P < .05). The PLDR results were slightly better than conventional RT (8% difference in the mean tumor volume; P > .05). For study 2, the average weight was 20.94 ± 1.68 g and 25.69 ± 1.27 g and the survival time was 8 days and 12 days for mice treated with conventional RT and PLDR (P < .05), respectively. CONCLUSION: This study showed that PLDR could control A549 tumors as effectively as conventional RT, and PLDR induced much less normal tissue toxicity than conventional RT. Thus, PLDR would be a good modality for recurrent lung cancers. ADVANCES IN KNOWLEDGE: This article reports our results of an in vivo animal investigation of PLDR for the treatment of recurrent cancers, which may not be eligible for treatment because of the dose limitations on nearby healthy organs that have been irradiated in previous treatments. This was the first in vivo study to quantify the tumor control and normal tissue toxicities of PLDR using mice with implanted tumors, and our findings provided evidence to support the clinical trials that employ PLDR treatment techniques.

Early events in ovarian oncogenesis.

Ovarian cancer represents the most lethal of the gynecological neoplasms. The molecular and genetic events associated with early ovarian oncogenesis are still largely unknown, thus contributing to the lack of reliable biomarkers for disease detection. Since the majority of ovarian tumors are diagnosed at an advanced stage, the availability of early ovarian cancer tissue samples for molecular analyses is very limited. In this review, problems encountered in the study of early ovarian cancer are presented, along with the controversies concerning precursor lesions and stepwise progression towards ovarian malignancy. Experimental modeling in the development of ovarian cancer is also described, as well as genetic and epigenetic alterations associated with early ovarian cancer. Lastly, examples of technological advances in the study of early ovarian cancer are discussed. Hopefully, the increasing knowledge about molecular and genetic events involved in the early stages of ovarian tumorigenesis will provide the basis for management of ovarian cancer in the future.

Decreased expression of retinol-binding proteins is associated with malignant transformation of the ovarian surface epithelium.

We have developed a modified form of suppression subtractive hybridization (SSH) that allows multiple specimens of distinct phenotypic groups to be compared for consistent differences in gene expression. We applied this system to identify genes that were expressed in normal rat ovarian surface epithelial (ROSE) cells but whose expression was lost/downregulated in four independently transformed rat ovarian cancer cell lines. Northern blot analysis using 14 of 28 nonredundant cDNA fragments from this difference library showed that the mRNA transcripts were present in normal ROSE cells but lost or markedly downregulated in four related transformed cell lines. Of particular interest, cellular retinol-binding protein 1 (CRBP1) and retinol-binding protein (RBP), two genes whose products are involved in retinol transport and metabolism, were found to be downregulated in this ovarian cancer model system. To determine if this change had relevance to human ovarian cancer, we evaluated a series of human ovarian cancer cell lines and a limited number of frozen human ovarian tumors and found lost or decreased expression of CRBP1 and RBP relative to expression in human ovarian surface epithelial (HOSE) cells. We hypothesize that the loss of CRBP1 and RBP expression disrupts retinol metabolism and retinoic acid production, which may facilitate the occurrence of genetic damage leading to the malignant transformation of the ovarian surface epithelium, the cells from which ovarian cancer arises.

An in-vivo investigation of the therapeutic effect of pulsed focused ultrasound on tumor growth.

PURPOSE: High-intensity focused ultrasound (HIFU) has been investigated for ablative therapy and drug enhancement for gene therapy and chemotherapy. The aim of this work is to explore the feasibility of pulsed focused ultrasound (pFUS) for cancer therapy using an in vivo animal model. METHODS: A clinical HIFU system (InSightec ExAblate 2000) integrated with a 1.5 T GE MR scanner was used in this study. Suitable ultrasound parameters were investigated to perform nonthermal sonications, keeping the temperature elevation below 4 °C as measured in real time by MR thermometry. LNCaP cells (10(6)) were injected into the prostates of male mice (n = 20). When tumors reached a diameter of about 5 mm in 3D as measured on magnetic resonance imaging (MRI), the tumor-bearing mice (n = 8) were treated with pFUS (1 MHz frequency; 25 W acoustic power; 0.1 duty cycle; 60 s duration). A total of 4-6 sonications were used to cover the entire tumor volume under MR image guidance. The animals were allowed to survive for 4 weeks after the treatment. The tumor growth was monitored on high-resolution (0.2 mm) MRI weekly post treatment and was compared with that of the control group (n = 12). RESULTS: Significant tumor growth delay was observed in the tumor-bearing mice treated with pFUS. The mean tumor volume for the pFUS treated mice remained the same 1 week after the treatment while the mean tumor volume of the control mice grew 42% over the same time. Two weeks after the pFUS treatment, the control group had a mean tumor volume 40% greater than that of the treated group. There was a greater variation in tumor volume at 4 weeks post treatment for both treated and control mice and a slightly faster tumor growth for the pFUS treated mice. CONCLUSIONS: The authors' results demonstrated that pFUS may have a great potential for cancer therapy. Further experiments are warranted to understand the predominantly nonthermal cell killing mechanisms of pFUS and to derive optimal ultrasound parameters and fractionation schemes to maximize the therapeutic effect of pFUS.

MR-guided pulsed high intensity focused ultrasound enhancement of docetaxel combined with radiotherapy for prostate cancer treatment.

The purpose of this study is to evaluate the efficacy of the enhancement of docetaxel by pulsed focused ultrasound (pFUS) in combination with radiotherapy (RT) for treatment of prostate cancer in vivo. LNCaP cells were grown in the prostates of male nude mice. When the tumors reached a designated volume by MRI, tumor bearing mice were randomly divided into seven groups (n = 5): (1) pFUS alone; (2) RT alone; (3) docetaxel alone; (4) docetaxel + pFUS; (5) docetaxel + RT; (6) docetaxel + pFUS + RT, and (7) control. MR-guided pFUS treatment was performed using a focused ultrasound treatment system (InSightec ExAblate 2000) with a 1.5T GE MR scanner. Animals were treated once with pFUS, docetaxel, RT or their combinations. Docetaxel was given by i.v. injection at 5 mg kg(-1) before pFUS. RT was given 2 Gy after pFUS. Animals were euthanized 4 weeks after treatment. Tumor volumes were measured on MRI at 1 and 4 weeks post-treatment. Results showed that triple combination therapies of docetaxel, pFUS and RT provided the most significant tumor growth inhibition among all groups, which may have potential for the treatment of prostate cancer due to an improved therapeutic ratio.

Altered expression and loss of heterozygosity of the LOT1 gene in ovarian cancer.

OBJECTIVES: Previously, we demonstrated that the LOT1 (PLAGL1/ZAC1) gene encodes a zinc-finger transcription factor and has growth suppressive effects in carcinoma cell lines. The gene is localized on chromosome 6q24-25, a common site for loss of heterozygosity (LOH) in many solid tumors including ovarian cancer. In this study, we evaluated the LOT1 gene expression and allelic deletion in the tumor tissues in order to provide additional evidence to support the gene's potential role in cancer. METHODS: The LOT1 gene expression was analyzed in malignant ovarian epithelium obtained from frozen human ovarian tumor tissues using laser capture microdissection (LCM) and real-time PCR techniques. Highly frequent single nucleotide polymorphic (SNP) sites within the LOT1 gene were identified and used for PCR and direct sequencing to determine the occurrence of allelic imbalance in a series of surgically resected ovarian and breast carcinomas. RESULTS: The analysis revealed that LOT1 mRNA expression was not detectable in 12 of 31 (39%) cases of ovarian cancer and was variable between the remaining 19 tumor specimens. These findings are consistent with the previous data that showed altered expression of LOT1 in different human ovarian carcinoma cell lines. In addition, we analyzed the occurrence of LOT1 allelic deletion in different ovarian tumor genomic DNA samples that included papillary serous (majority), mucinous, and primary peritoneal adenocarcinomas of low- to high-grade and the corresponding normal lymphocytes. The informative samples showed 12 out of 33 or about 36.4% LOH of this gene based on allelic loss of one or more polymorphic sites within the LOT1 genomic sequences. Similarly, primary breast carcinomas, which included invasive ductal (majority), spindle cell, mucinous, giant cell, and atypical medullary carcinomas, were examined on genomic DNA from patients for the allelic loss of LOT1. The informative cases showed 4 out of 10 samples or 40% LOH of this candidate tumor suppressor gene locus in breast cancer. CONCLUSIONS: The altered expression and LOH of the LOT1 locus support the gene's potential role, at least in part, in the pathogenesis of ovarian cancer and possibly in other types of cancer.