OncotypeDX Recurrence Score Does Not Predict Nodal Burden in Clinically Node Negative Breast Cancer Patients.

BACKGROUND: OncotypeDX recurrence score (RS)® has been found to predict recurrence and disease-free survival in patients with node negative breast cancer. Whether RS is useful in guiding locoregional therapy decisions is unclear. We sought to evaluate the relationship between RS and lymph node burden. METHODS: Patients with invasive breast cancer who underwent sentinel lymph node dissection from 2010 to 2015 were identified from a prospectively maintained database. Patients were excluded if they were clinically node positive or if they received neoadjuvant chemotherapy. RS was classified as low (< 18), intermediate (18-30), or high (> 30). The association between RS, lymph node burden, and disease recurrence was evaluated. Statistical analyses were performed in R version 3.4.0; p < 0.05 was considered significant. RESULTS: A positive SLN was found in 168 (15%) of 1121 patients. Completion axillary lymph node dissection was performed in 84 (50%) of SLN-positive patients. The remaining 84 (50%) patients had one to two positive SLNs and did not undergo further axillary surgery. RS was low in 58.5%, intermediate in 32.6%, and high in 8.9%. RS was not associated with a positive SLN, number of positive nodes, maximum node metastasis size, or extranodal extension. The median follow-up was 23 months. High RS was not associated with locoregional recurrence (p = 0.07) but was significantly associated with distant recurrence (p = 0.0015). CONCLUSIONS: OncotypeDX RS is not associated with nodal burden in women with clinically node-negative breast cancer, suggesting that RS is not useful to guide decisions regarding extent of axillary surgery for these patients.

Baseline factors predicting a response to neoadjuvant chemotherapy with implications for non-surgical management of triple-negative breast cancer.

BACKGROUND: Patients with triple-negative breast cancer (TNBC) and a pathological complete response (pCR) after neoadjuvant chemotherapy may be suitable for non-surgical management. The goal of this study was to identify baseline clinicopathological variables that are associated with residual disease, and to evaluate the effect of neoadjuvant chemotherapy on both the invasive and ductal carcinoma in situ (DCIS) components in TNBC. METHODS: Patients with TNBC treated with neoadjuvant chemotherapy followed by surgical resection were identified. Patients with a pCR were compared with those who had residual disease in the breast and/or lymph nodes. Clinicopathological variables were analysed to determine their association with residual disease. RESULTS: Of the 328 patients, 36·9 per cent had no residual disease and 9·1 per cent had residual DCIS only. Patients with residual disease were more likely to have malignant microcalcifications (P = 0·023) and DCIS on the initial core needle biopsy (CNB) (P = 0·030). Variables independently associated with residual disease included: DCIS on CNB (odds ratio (OR) 2·46; P = 0·022), T2 disease (OR 2·40; P = 0·029), N1 status (OR 2·03; P = 0·030) and low Ki-67 (OR 2·41; P = 0·083). Imaging after neoadjuvant chemotherapy had an accuracy of 71·7 (95 per cent c.i. 66·3 to 76·6) per cent and a negative predictive value of 76·9 (60·7 to 88·9) per cent for identifying residual disease in the breast and lymph nodes. Neoadjuvant chemotherapy did not eradicate the DCIS component in 55 per cent of patients. CONCLUSION: The presence of microcalcifications on imaging and DCIS on initial CNB are associated with residual disease after neoadjuvant chemotherapy in TNBC. These variables can aid in identifying patients with TNBC suitable for inclusion in trials evaluating non-surgical management after neoadjuvant chemotherapy.

Is surviving enough? Coping and impact on activities of daily living among melanoma patients with lymphoedema.

We assessed the impact of lymphoedema (defined as ≥ 10% limb volume change) on quality of life (QOL), ability to perform activities of daily living (ADLs) and coping in 277 melanoma patients. Limb volume was measured prospectively, pre-operatively and every 3-6 months for 18 months post-operatively using a perometer. Three questionnaires were administered to measure QOL, coping and impact on ADLs. Statistical analyses were conducted using longitudinal logistic regression models. At 18 months, the cumulative incidence of lymphoedema was 31% in patients with upper extremity nodal basin treatment and 40% in lower extremity nodal basin treatment patients. Patients with lower extremity lymphoedema reported lower QOL scores than those with upper extremity lymphoedema. Over 18 months, both groups with mild and moderate lymphoedema showed improvement in coping [odds ratio (OR): 6.67, 95% confidence interval (CI): 3.30-13.47] and performance of ADLs (OR: 7.46, CI: 3.38-16.47). Over the course of 18 months, men were found to have poorer coping scores than women (OR: 2.91, CI: 1.35-6.27). Lymphoedema was associated with improvement in coping over time (P = 0.08) and a higher reported interference with ADLs (OR: 2.53, CI: 1.29-4.97). Patient education about lymphoedema at the time of surgical consent may improve self-efficacy and coping ability. Effective management of lymphoedema may improve patient QOL and reduce interference with ADLs.

Gene expression profiles of inflammatory breast cancer: correlation with response to neoadjuvant chemotherapy and metastasis-free survival.

BACKGROUND: Inflammatory breast cancer (IBC) is an aggressive disease. To date, no molecular feature reliably predicts either the response to chemotherapy (CT) or the survival. Using DNA microarrays, we searched for multigene predictors. PATIENTS AND METHODS: The World IBC Consortium generated whole-genome expression profiles of 137 IBC and 252 non-IBC (nIBC) samples. We searched for transcriptional profiles associated with pathological complete response (pCR) to neoadjuvant anthracycline-based CT and distant metastasis-free survival (DMFS) in respective subsets of 87 and 106 informative IBC samples. Correlations were investigated with predictive and prognostic gene expression signatures published in nIBC (nIBC-GES). Supervised analyses tested genes and activation signatures of 19 biological pathways and 234 transcription factors. RESULTS: Three of five tested prognostic nIBC-GES and the two tested predictive nIBC-GES discriminated between IBC with and without pCR, as well as two interferon activation signatures. We identified a 107-gene signature enriched for immunity-related genes that distinguished between responders and nonresponders in IBC. Its robustness was demonstrated by external validation in three independent sets including two IBC sets and one nIBC set, with independent significant predictive value in IBC and nIBC validation sets in multivariate analysis. We found no robust signature associated with DMFS in patients with IBC, and neither of the tested prognostic GES, nor the molecular subtypes were informative, whereas they were in our nIBC series (220 stage I-III informative samples). CONCLUSION: Despite the relatively small sample size, we show that response to neoadjuvant CT in IBC is, as in nIBC, associated with immunity-related processes, suggesting that similar mechanisms responsible for pCR exist. Analysis of a larger IBC series is warranted regarding the correlation of gene expression profiles and DMFS.

Clinical relevance of cancer stem cells in bone marrow of early breast cancer patients.

BACKGROUND: Cancer stem cells (CSCs) are epithelial tumor cells that express CD44(+)CD24(-/lo). CSCs can be further divided into those that have aldehyde dehydrogenase (ALDH) activity (Aldefluor(+)) and those that do not. We hypothesized that if CSCs are responsible for tumor dissemination, their presence in bone marrow (BM) would be prognostic in early stages of breast cancer (EBC) patients. PATIENTS AND METHODS: BM aspirates were collected at the time of surgery from 108 patients with EBC. BM was analyzed for CSCs and ALDH activity by flow cytometry. Overall survival and disease-free survival (DFS) were calculated from the date of diagnosis and analyzed with Kaplan-Meier survival plots. Cox multivariate proportional hazards model was also carried out. RESULTS: Patients with CSCs in BM had a hazard ratio (HR) of 8.8 for DFS (P = 0.002); patients with Aldefluor(+) CSCs had a HR of 5.9 (P = 0.052) for DFS. All deceased patients (n = 7) had CSCs in BM. In multivariate analysis, the presence of CSCs in BM was a prognostic factor of DFS (HR = 15.8, P = 0.017). CONCLUSIONS: The presence of BM metastasis is correlated with CSCs and these CSCs irrespective of ALDH activity are an independent adverse prognostic factor in EBC patients.

International expert panel on inflammatory breast cancer: consensus statement for standardized diagnosis and treatment.

BACKGROUND: Inflammatory breast cancer (IBC) represents the most aggressive presentation of breast cancer. Women diagnosed with IBC typically have a poorer prognosis compared with those diagnosed with non-IBC tumors. Recommendations and guidelines published to date on the diagnosis, management, and follow-up of women with breast cancer have focused primarily on non-IBC tumors. Establishing a minimum standard for clinical diagnosis and treatment of IBC is needed. METHODS: Recognizing IBC to be a distinct entity, a group of international experts met in December 2008 at the First International Conference on Inflammatory Breast Cancer to develop guidelines for the management of IBC. RESULTS: The panel of leading IBC experts formed a consensus on the minimum requirements to accurately diagnose IBC, supported by pathological confirmation. In addition, the panel emphasized a multimodality approach of systemic chemotherapy, surgery, and radiation therapy. CONCLUSIONS: The goal of these guidelines, based on an expert consensus after careful review of published data, is to help the clinical diagnosis of this rare disease and to standardize management of IBC among treating physicians in both the academic and community settings.

COX-2 involvement in breast cancer metastasis to bone.

Cyclooxygenase-2 (COX-2) is expressed in 40% of human invasive breast cancers. Bone is the predominant site of metastasis in case of breast cancer. We investigated the role of COX-2 in a suitable mouse model of breast cancer metastasis to bone using the whole-body luciferase imaging of cancer cells. We provide several lines of evidence that COX-2 produced in breast cancer cells is important for bone metastasis in this model including (1) COX-2 transfection enhanced the bone metastasis of MDA-435S cells and (2) breast cancer cells isolated and cultured from the bone metastases produced significantly more prostaglandin E(2) (an important mediator of COX-2) than the parental injected cell populations of breast cancer cells. Next, we found that a COX-2 inhibitor, MF-tricyclic, inhibited bone metastasis caused by a bone-seeking clone both in prevention regimen (in which case mice started receiving MF-tricyclic 1 week before the injection of cancer cells) and in treatment regimen (in which case mice received MF-tricyclic after the development of bone metastasis). These studies indicate that COX-2 produced in breast cancer cells may be vital to the development of osteolytic bone metastases in patients with breast cancer, and that COX-2 inhibitors may be useful in halting this process.

Modification of ceramide metabolism increases cancer cell sensitivity to cytotoxics.

In the preceding report we demonstrated that MCF-7-AdrR cells (adriamycin resistant) were insensitive to ceramide, whereas MCF-7 wild-type cells were sensitive. It was also shown that the drug resistant cells had an increased capacity to convert ceramide to glucosylceramide. Here we demonstrate that blocking the conversion of ceramide to glucosylceramide increases MCF-7-AdrR cell sensitivity to ceramide as well as to antitumor agents. Treatment of MCF-7 cells with adriamycin elicited a 5-fold increase in ceramide, and caused oligonucleosomal fragmentation, characteristic to apoptosis. Under similar treatment conditions, ceramide was not generated in MCF-7-AdrR cells. In MCF-7-AdrR cells neither C6-ceramide nor tamoxifen was cytotoxic; however, the addition of tamoxifen to the C6-ceramide treatment regimen reduced cell viability to 42% and elicited apoptosis. Treatment of MCF-7-AdrR cells with Adriamycin promoted an increase in ceramide only if tamoxifen was present, in which case ceramide increased 7-fold, and cell viability decreased to 50%. The employment of another agent, RU486 (Mifepristone), which blocks ceramide glycosylation, increased MCF-7-AdrR cell sensitivity to adriamycin in a dose-dependent manner. Our data show that agents that block ceramide glycosylation potentiate cellular sensitivity to ceramide and to chemotherapeutic drugs, and suggest that the ceramide metabolic pathway is an important target for anticancer drug development.

Ceramide toxicity and metabolism differ in wild-type and multidrug-resistant cancer cells.

Previously we demonstrated that multidrug-resistant (MDR) cancer cells have elevated levels of a glycosylated form of ceramide, glucosylceramide. Here we compared ceramide metabolism and ceramide toxicity in MCF-7 and in adriamycin-resistant (MCF-7-AdrR) human breast cancer cells. MCF-7-AdrR cells were resistant to C6-ceramide (1-10 microM); however, in MCF-7 cells treated with C6-ceramide, viability dropped sharply. Ceramide, when supplemented, was not metabolized by MCF-7 cells. In contrast, ceramide was efficiently converted to glucosylceramide by MCF-7-AdrR cells. Analysis of extracellular [3H]ceramide in radiolabeled cells showed that MCF-7-AdrR cells do not have an enhanced capacity to efflux ceramide compared with MCF-7 cells. Triphenylethylene anti-estrogens, known modulators of drug resistance, were effective inhibitors of ceramide conversion to glucosylceramide, suggesting that blocking ceramide metabolism plays a role in chemosensitization. The anti-progestine, RU486, also blocked glucosylceramide synthesis in cells; however, LY117018, a raloxifene analog, was without influence. We propose that an enhanced capacity to glycosylate ceramide as evidenced in MCF-7-AdrR cells, is a molecular determinant of drug resistance, particularly as regards resistance to ceramide-enhancing agents such as anthracyclines, ionizing radiation, and tumor necrosis factor-alpha.

Carbon dye as an adjunct to isosulfan blue dye for sentinel lymph node dissection.

BACKGROUND: The success of intraoperative lymphatic mapping depends on accurate identification of the sentinel node. We hypothesized that a carbon particle suspension would allow histopathologic confirmation of the sentinel lymph node through deposition of carbon within that node. METHODS: An animal model was used to compare the lymphatic mapping accuracy of carbon dye with that of isosulfan blue dye, the standard agent for intraoperative visualization of the sentinel lymph node. Twenty-two rats underwent lymphatic mapping in each distal lower extremity with various combinations of carbon dye and isosulfan blue dye. All stained (blue or black) nodes in the inguinal drainage basin were removed for pathologic analysis, including carbon particle analysis. A meticulous search identified all nonstained (nonsentinel) nodes in the same basin. These nonsentinel nodes were examined for carbon particles by light microscopy. Dermal diffusion of mapping agents at the injection site was also recorded. Animals were then observed for 28 days to assess the toxicity of mapping agents. RESULTS: Although isosulfan blue dye and full-strength carbon dye each stained all sentinel nodes, the latter obscured histologic detail. The combination of 2.5% carbon dye, 7.5% saline solution, and 90% isosulfan blue dye also stained all sentinel nodes; carbon particles were seen on light microscopy in all 13 stained nodes and did not interfere with histologic evaluation. No unstained node contained carbon particles, although the number of nonsentinel nodes was small. Carbon dye exhibited significantly less intradermal diffusion than isosulfan blue dye, but the carbon left a permanent mark on the skin. No toxicity or side effect associated with the use of carbon dye was observed. CONCLUSION: Carbon dye allows histopathologic confirmation of sentinel lymph nodes identified by isosulfan blue dye.

National practice patterns of sentinel lymph node dissection for breast carcinoma.

BACKGROUND: The sentinel node is the first regional lymph node to receive tumor cells that metastasize through the lymphatic channel from a primary tumor. The tumor status of the sentinel node should reflect the tumor status of the entire regional node basin. Sentinel lymph node dissection (SLND) has recently been investigated for use in patients with early breast carcinoma to avoid the sequelae of complete axillary lymph node dissection (ALND). Published studies of SLND in breast cancer patients identify marked variations in technique, and there are few guidelines for credentialing surgeons to perform SLND. STUDY DESIGN: The purpose of this study was to assess the current practice of SLND for breast cancer in the United States. A 27-item questionnaire was mailed to 1,000 randomly selected Fellows of the American College of Surgeons. Responses were anonymous. Statistical analysis was performed using SAS software (SAS Institute, Cary, NC). RESULTS: Response rate was 41% (n = 410), and 77% of those who responded performed SLND for breast cancer. The majority (60%) of surgeons responding routinely ordered preoperative lymphoscintigraphy. Of those who did lymphoscintigraphy, 28% removed internal mammary lymph nodes when lymphoscintigraphy showed drainage to these nodes. Ninety percent of surgeons used both blue dye and radiocolloid. Eighty percent of centers responding performed routine immunohistochemistry on sentinel lymph nodes, and 15% performed reverse transcription polymerase chain reaction. Ninety-six percent of surgeons performed SLND for primary tumors 5 cm or smaller, and 95% performed SLND for an excisional cavity 6 cm and smaller. Twenty-eight percent performed SLND for high-grade ductal carcinoma in situ, and 28% of respondents performed 10 or fewer SLND procedures with subsequent ALND before performing SLND alone. Surgeons learned SLND through courses (35%), oncology fellowships (26%), observation of other surgeons (31%), or were self-taught (26%). CONCLUSIONS: The majority of surgeons in the United States use similar technique for SLND breast cancer. But, there was marked variation in the number of SLND cases validated by an ALND before performing SLND only.

Glucosylceramide: a marker for multiple-drug resistant cancers.

BACKGROUND: Multiple-drug resistance (MDR) is a major reason for chemotherapy failure. Herein we describe glucosylceramide, a new marker for MDR. METHODS: Cellular lipids were analyzed in three human MDR cancer cell lines and their drug-sensitive counterparts. Analysis of glucosylceramide was also performed in six melanoma specimens and one breast tumor specimen obtained from patients who had undergone chemotherapy. Glucosylceramide, analyzed by mass and by cellular utilization of radiolabeled precursor ([3Hpalmitic acid), was isolated by lipid extraction techniques and resolved from other components by thin-layer chromatography. RESULTS: Glucosylceramide was present consistently in all MDR cell lines and was absent, or present only at very low levels, in the corresponding drug-sensitive cells. Examination of human tumor specimens documented presence of the marker in all patients who had failed chemotherapy, and absence of the marker in each of the patients with known clinical response to chemotherapy. The response to chemotherapy was followed for a median of 8 months in melanoma patients and for 22 months in the breast cancer patient. CONCLUSION: These findings suggest that glucosylceramide may hold clinical significance for the early identification of drug-resistant tumors.

A caution regarding lymphatic mapping in patients with colon cancer.

BACKGROUND: The value of lymphatic mapping and sentinel lymph node biopsy in the treatment of colon cancer is controversial. The purpose of this study was to determine the accuracy of lymphatic mapping in patients with colon cancer. METHODS: Forty-eight patients with colon cancer underwent lymphatic mapping and sentinel lymph node biopsy using isosulfan blue dye followed by standard surgical resection. The sentinel lymph nodes underwent thin sectioning as will as immunohistochemical staining for cytokeratin, in addition to standard hematoxylin and eosin staining. RESULTS: In 47 (98%) patients, a sentinel lymph node was identified. Sixteen patients had lymph nodes containing metastatic disease, and in 6 patients the sentinel lymph node was positive for disease. In no patient was the sentinel lymph node the only site of metastatic disease. In 10 patients the sentinel lymph node was negative for disease, whereas the nonsentinel lymph nodes contained metastatic disease (false negative rate = 38%). CONCLUSIONS: The role of lymphatic mapping and sentinel lymph node biopsy in colon cancer is not as clear as its role in other tumors. Further large prospective studies are needed to evaluate the accuracy and potential benefit of this procedure in patients with colon cancer.

Placental examination can help determine cause of brain damage in neonates.

Intrapartum asphyxia rarely causes cerebral palsy. More than 90% of cases of cerebral palsy are now believed to result from an antecedent intrauterine developmental abnormality. It is now also known that there is an association between subacute and chronic intrauterine hypoxia (decreased uteroplacental blood flow) and brain damage. We present an evaluation protocol that includes clinical findings of the mother and infant combined with pathologic examination of the placenta. The purpose of this protocol is to better identify and separate cases of acute from chronic perinatal asphyxia. We believe that improved screening and identification of perinatal asphyxia will reduce the number of malpractice suits for infants with brain damage. The objective is to eliminate from litigation those cases due to antecedent developmental abnormality over which the clinician has no responsibility and should not be held medically liable.

A microbiological test for the diagnosis of death by drowning.

The present study was aimed at demonstrating the diffusion of sea water or freshwater into the bloodstream as a consequence of water aspiration due to drowning. The study was carried out on 42 study group subjects who died by drowning in salt water (20 cases) and freshwater (22 cases) and 30 control group subjects who died from causes other than drowning. For 25 cases we obtained water samples from the aquatic locations where the victims were found. The blood samples of study and control groups were analyzed to search for faecal coliforms (FC) and faecal streptococci (FS) bacteria. The presence of FC and FS was showed by the development of blue and red colonies, respectively. From left ventricular (LV) and right ventricular (RV) blood cultures of the 20 sea drowning victims we always isolated FS and FC, whereas 19 (95%) femoral arterial (FA) and 18 (90%) femoral venous (FV) blood cultures were positive for both faecal bacteria. Related to freshwater victims, LV blood cultures showed FS presence for all the 22 cases studied (100%) and FC presence for 20 cases (90.91%). Blood cultures from RV, FV, and FA showed various patterns of faecal bacteria presence. The analysis of 25 water samples from the aquatic locations where the victims were found showed the presence of FC and FS bacteria. Blood cultures from the 30 control subjects uniformly proved the absence of faecal bacteria.

Silent cholinesterase gene: three homozygotes in a small Caucasian population.

Three sera, showing only a 2-3% of the usual cholinesterase activity and belonging to two families of 800 Caucasian inhabitants of the same small town, were classified as type II silent cholinesterase genes by polyacrylamide slab gel electrophoresis, dibucaine and fluoride number and by their specific activity with acetyl- butyryl- or propionyl-thiocholine.

Assessment of knowledge of melanoma risk factors, prevention, and detection principles in Texas teenagers.

INTRODUCTION: The incidence of melanoma has increased in the past 10 years more rapidly than any other cancer. Exposure to intense solar radiation in youth significantly increases the lifetime risk of developing melanoma. We postulate that teenagers have little awareness of melanoma prevention or detection principles. The purpose of this study was to assess the knowledge of teenagers about melanoma and to identify which age groups are most receptive to altering their sun exposure behaviors. METHODS: Two hundred and ten examinations testing general knowledge of sun exposure and melanoma were completed and returned by junior high and high school students ages 12 to 18 in Dallas and Houston, Texas. All students completing and returning the examination were provided with the correct answers to the test and a detailed explanation of each of the test items as part of an educational exercise. A second questionnaire was then administered to determine the effect of the educational exercise on future sun exposure practices. Students were divided into two age groups (12 to 15 and >or=16 years old) for comparison of scores on the knowledge examination and responses to behavioral items. Comparison of response rates between age groups was performed using chi(2) analysis. RESULTS: The return rate was 100%, with 109 students age 12-15 years, and 101 students >or=16 years. Seventy-six percent of all respondents sunbathed outdoors, and 18% had used a tanning bed in the past 6 months. Thirty-three percent of students admitted to at least three blistering sunburns in the past. The average score on the knowledge assessment examination was 65% correct for students >or=16 years old and 54% correct for those 12-15 years old. Students 12 to 15 years old were significantly more likely to indicate they planned to change future behaviors regarding performance of skin self-examinations and limiting sun exposure as compared to the older students. CONCLUSION: A significant number of teenagers have already enhanced their risk for future melanoma by suffering severe sunburns. Students younger than 16 years of age were significantly more likely to indicate they planned to change future behaviors after receiving information about melanoma. The data from this pilot study support education aimed at younger age groups to most effectively achieve risk reduction and prevent future melanomas.

Multidrug resistance modulators and doxorubicin synergize to elevate ceramide levels and elicit apoptosis in drug-resistant cancer cells.

BACKGROUND: To provide insight for the development of more effective clinical agents, the authors attempted to elucidate the mechanisms of action of multidrug resistance (MDR) modulators. Previously, the authors found that MDR modulators blocked the conversion of ceramide to glucosylceramide in MDR cells, thereby enhancing cytotoxicity. Because ceramide is a critical component of the apoptosis signaling cascade, the current study examined the impact of therapy using agents that elicit ceramide formation combined with agents that block ceramide glycosylation. METHODS: Doxorubicin-resistant human breast carcinoma cells (MCF-7-AdrR) were treated with either doxorubicin, tamoxifen, cyclosporine A, or the cyclosporine A analog SDZ PSC 833 (PSC 833) or with combinations thereof, and ceramide and glucosylceramide metabolisms were measured by cell radiolabeling. Cell viability was quantitated spectrophotometrically and apoptosis was evaluated analyzing DNA integrity by gel electrophoresis. RESULTS: Whereas cyclosporine A blocked the generation of glucosylceramide in MCF-7-AdrR cells, a chemical cousin, PSC 833, elicited a 3-fold increase in glucosylceramide and a 5-fold increase in ceramide levels at 24 hours. The PSC 833 response was time-dependent(as early as 30 minutes) and dose-dependent (as low as 0.1 microM). The appearance of ceramide foreran the generation of glucosylceramide. Sphingomyelin levels were not decreased in response to PSC 833; however, Fumonisin B1, a ceramide synthase inhibitor, blocked PSC 833-induced ceramide generation. Adding tamoxifen, which blocks ceramide glycosylation, to the PSC 833 regimen boosted ceramide levels 11-fold over controls and caused DNA fragmentation. A 3-component regimen comprised of tamoxifen, doxorubicin, and PSC 833 increased ceramide levels 26-fold and brought cell viability to zero. CONCLUSIONS: These results demonstrate that MDR modulators can be used separately, in combination, or in conjunction with chemotherapy at clinically relevant concentrations to manipulate cellular ceramide levels and restore sensitivity in the drug resistant setting. As such, this represents a new direction in the treatment of cancer.