DSS1 is required for the stability of BRCA2.

DSS1 is an evolutionarily conserved acidic protein that binds to BRCA2. However, study of the function of DSS1 in mammalian cells has been hampered because endogenous DSS1 has not been detectable by Western blotting. Here, we developed a modified Western blotting protocol that detects endogenous DSS1 protein, and used it to study the function of DSS1 and its interaction with BRCA2 in mammalian cells. We found that essentially all BRCA2 in human cell lines is associated with DSS1. Importantly, we found that RNAi knockdown of DSS1 in human cell lines led to dramatic loss of BRCA2 protein, mainly due to its increased degradation. Furthermore, the stability of BRCA2 mutant devoid of the DSS1-binding domain is unaffected by the depletion of DSS1. Most notably, like BRCA2 depletion, DSS1 depletion also led to hypersensitivity to DNA damage. These results demonstrated that the stability of BRCA2 protein in mammalian cells depends on the presence of DSS1. Deletion or mutation of DSS1 or suppression of its expression by other mechanisms are therefore potential causative mechanisms for human breast and ovarian cancer. Such mechanisms may be relevant to sporadic as well as familiar breast cancer where BRCA1 and BRCA2 mutations are not present.

Analysis of normal epithelial cell specific-1 (NES1)/kallikrein 10 mRNA expression by in situ hybridization, a novel marker for breast cancer.

PURPOSE: Normal epithelial cell specific-1 (NES1)/kallikrein 10 gene is expressed in normal mammary and prostate epithelial cells, but the expression of NES1 mRNA and protein is markedly reduced in established breast and prostate cancer cell lines although the NES1 gene is intact. Here, we wished to assess whether NES1 expression is down-regulated in primary breast cancers. EXPERIMENTAL DESIGN: We developed and used an in situ hybridization technique with an antisense NES1 probe to detect NES1 mRNA in sections of normal breast specimens, typical and atypical ductal hyperplasia, ductal carcinoma in situ, and infiltrating ductal carcinoma. RESULTS: All of the 30 normal breast specimens showed high NES1 expression. Notably, 18 (75%) of 24 typical and atypical breast hyperplasia specimens showed high NES1 expression, with weak-to-moderate expression in 6 (25%). Significantly, 13 (46%) of 28 ductal carcinoma in situ specimens lacked NES1 expression, and the remaining 15 (54%) showed weak-to-moderate expression. Finally, 29 of 30 (97%) infiltrating ductal carcinoma grades I-III samples lacked NES1 mRNA, with weak expression in the remaining one sample. CONCLUSIONS: Our results demonstrate that NES1 mRNA is expressed in normal breast tissue and benign lesions, with loss of NES1 expression during tumor progression. We suggest that NES1 expression may serve as a molecular tool in the study of breast cancer progression. Studies with larger series of specimens should help assess whether NES1 expression can be a diagnostic and/or prognostic marker in breast and other cancers.

CpG methylation as a basis for breast tumor-specific loss of NES1/kallikrein 10 expression.

The normal epithelial cell-specific-1 (NES1)/kallikrein 10 gene is expressed in normal mammary epithelial cells, but its expression is dramatically decreased in breast cancer cell lines. Now, we have cloned and characterized the active promoter region of NES1. Using a luciferase reporter system, we demonstrate that most tumor cell lines are able to support full or partial transcription from the NES1 promoter, suggesting a role for promoter-independent cis-acting mechanisms of loss of NES1 expression. We show that hypermethylation of the NES1 gene represents one such mechanism. Using methylation-specific PCR and sequence analysis of sodium bisulfite-treated genomic DNA, we demonstrate a strong correlation between exon 3 hypermethylation and loss of NES1 mRNA expression in a panel of breast cancer cell lines and in primary tumors. Treatment of NES1-nonexpressing cells with a demethylating agent led to reexpression of NES1, suggesting an important role of hypermethylation in the loss of NES1 expression. We suggest that hypermethylation is responsible for tumor-specific loss of NES1 gene expression. Our results also suggest that hypermethylation of the NES1 gene may serve as a potential marker for breast cancer.

Clinically evident fat necrosis in women treated with high-dose-rate brachytherapy alone for early-stage breast cancer.

PURPOSE: To investigate the incidence of and variables associated with clinically evident fat necrosis in women treated on a protocol of high-dose-rate (HDR) brachytherapy alone without external-beam whole-breast irradiation for early-stage breast carcinoma. METHODS AND MATERIALS: From 6/1997 until 8/1999, 30 women diagnosed with Stage I or II breast carcinoma underwent surgical excision and postoperative irradiation via HDR brachytherapy implant as part of a multi-institutional clinical Phase I/II protocol. Patients eligible included those with T1, T2, N0, N1 (< or = 3 nodes positive), M0 tumors of nonlobular histology with negative surgical margins, no extracapsular lymph-node extension, and a negative postexcision mammogram. Brachytherapy catheters were placed at the initial excision, re-excision, or at the time of axillary sampling. Direct visualization, surgical clips, ultrasound, or CT scans assisted in delineating the target volume defined as the excision cavity plus 2-cm margin. High activity (192)Ir (3-10 Ci) was used to deliver 340 cGy per fraction, 2 fractions per day, for 5 consecutive days to a total dose of 34 Gy to the target volume. Source position and dwell times were calculated using standard volume optimization techniques. Dosimetric analyses were performed with three-dimensional postimplant dose and volume reconstructions. The median follow-up of all patients was 24 months (range, 12-36 months). RESULTS: Eight patients (crude incidence of 27%) developed clinically evident fat necrosis postimplant in the treated breast. Fat necrosis was determined by clinical presentation including pain and swelling in the treated volume, computed tomography, and/or biopsy. All symptomatic patients (7 of 8 cases) were successfully treated with 3 to 12 months of conservative management. Continuous variables that were found to be associated significantly with fat necrosis included the number of source dwell positions (p = 0.04), and the volume of tissue which received fractional doses of 340 cGy, 510 cGy, and 680 cGy (p = 0.03, p = 0.01, and p = 0.01, respectively). Other continuous variables including patient age, total excised tissue volume, tumor size, number of catheters, number of days the catheters were in place, planar separation, dose homogeneity index (DHI), and uniformity index (UI) were not significant. Discrete variables including the presence/absence of DCIS, sentinel versus full axillary nodal assessment, receptor status, presence/absence of diabetes, and the use of chemotherapy or hormone therapy were not found to have a significant association with the risk of fat necrosis. CONCLUSIONS: In this study of HDR brachytherapy of the breast tumor excision cavity plus margin, treatment was planned and delivered in accordance with the dosimetric parameters of the protocol resulting in a high degree of target volume dose homogeneity. Nonetheless, at a median follow-up of 24 months, a high rate of clinically definable fat necrosis occurred. The overall implant volume as reflected in the number of source dwell positions and the volume of breast tissue receiving fractional doses of 340, 510, and 680 cGy were significantly associated with fat necrosis. Future dosimetric optimization algorithms for HDR breast brachytherapy will need to include these factors to minimize the risk of fat necrosis.

Human papillomavirus type 16 E6-induced degradation of E6TP1 correlates with its ability to immortalize human mammary epithelial cells.

Recent analyses have identified a number of binding partners for E6, including E6AP, ERC55, paxillin, hDlg, p300, interferon regulatory factor 3, hMCM7, Bak, and E6TP1. Notably, association with E6 targets p53, E6TP1, myc, hMCM7, and Bak for degradation. However, the relative importance of the various E6 targets in cellular transformation remains unclear. E6 alone can dominantly immortalize normal human mammary epithelial cells (MECs), permitting an assessment of the importance of various E6 targets in cellular transformation. Studies in this system indicate that E6-induced degradation of p53 and E6 binding to ERC55 or hDlg do not correlate with efficient immortalization. Here, we have examined the role of E6TP1, a Rap GTPase-activating protein, in E6-induced immortalization of MECs. We tested a large set of human papillomavirus type 16 E6 mutants for their ability to bind and target E6TP1 for degradation in vitro and in vivo. We observed a strict correlation between the ability of E6 protein to target E6TP1 for degradation and its ability to immortalize MECs. Recent studies have identified telomerase as a target of E6 protein. Previous analyses of E6 mutants have revealed this trait to closely correlate with MEC immortalization. We examined our entire panel of E6 mutants for rapid induction of telomerase activity and found in general a strong correlation with immortalizing ability. The tight correlation between E6TP1 degradation and MEC immortalization strongly supports a critical role of functional inactivation of E6TP1 in E6-induced cellular immortalization.

Comparison of radiobiologic modeling for one- and two-isocenter dose distributions applied to ellipsoidal radiosurgery targets.

PURPOSE: RTOG protocol 90-05 determined the maximum acutely tolerated dose of single-fraction radiosurgery in patients receiving prior fractionated large volume cranial irradiation. Data from 90-05 have suggested that patients treated with a gamma unit, compared to linac-based therapy, have a tumor control advantage and lower rates of severe complications. This study was performed to investigate the radiobiologic effect of using one vs. two isocenters in single-fraction radiosurgery of ellipsoidal targets. METHODS AND MATERIALS: For a series of ellipsoidal targets that varied by volume and radiosensitivity, single and two-isocenter treatment plans were generated to approximate those typically employed for gamma unit and linac radiosurgery. Tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP) were generated automatically by the treatment planning system based on established parameter values. RESULTS: The modeling data showed that multiple-isocenter plans resulted in improved TCP with equivalent or lesser NTCP, particularly for larger, radioresistant targets. Multiple-isocenter plans reduce the amount of normal tissue that receives high dose. Also, areas within the tumor receive significantly higher doses than the prescription dose, which contributes to increased tumor cell inactivation. CONCLUSION: For ellipsoidal targets, radiobiologic modeling data are consistent with the clinical findings of the RTOG 90-05 trial, as they predict improved outcome with a multiple-isocenter plan relative to a single-isocenter plan. The benefit is most apparent with increasing target volume and decreasing tumor radiosensitivity.

Multiple genetic changes are required for efficient immortalization of different subtypes of normal human mammary epithelial cells.

Multiple Genetic Changes Are Required for Efficient Immortalization of Different Subtypes of Normal Human Mammary Epithelial Cells. Breast cancer is the second leading cause of cancer-related deaths of women in the U.S. About 180,000 new cases of breast cancer are diagnosed each year, a quarter of them fatal. Early detection is the key to the survival of these patients. However, there are no molecular markers to detect breast cancer at very early stages. A hurdle in understanding the early molecular changes in breast cancer has been the difficulty in establishing premalignant lesions and primary breast tumors as in vitro cell cultures. Normal epithelial cells grow for a finite life span and then senesce. Immortalization is defined by continuous growth of otherwise senescing cells and is believed to represent an early stage in tumor progression. To examine these early stages, we and others have developed in vitro models of mammary epithelial cell immortalization. These models have been extremely important in understanding the role of various tumor suppressor pathways that maintain the normal phenotypes of mammary epithelial cells. In this paper, we describe the establishment of these models and their relevance to understanding the molecular changes that occur in early breast cancer. These models have helped to identify molecular changes that occur in early breast cancers and appear to be well suited to identify novel markers for early diagnosis of breast cancer.

Margin width as a determinant of local control with and without radiation therapy for ductal carcinoma in situ (DCIS) of the breast.

In order to assess the utility of margin width in relation to other histopathologic features as a determinant of local control in ductal carcinoma in situ (DCIS) of the breast, we retrospectively examined the treatment of 109 breasts treated with (n = 54) or without adjuvant radiotherapy (n = 55). Median follow-up was 49 and 54 months for patients treated with excision alone (E) or excision plus adjuvant radiotherapy (E+XRT), respectively. Cases treated with E+XRT were significantly larger and had a trend towards closer surgical margins than those treated with E alone. For all cases, margin width < or = 1 mm and lesion diameter >15 mm were significantly associated with increased local recurrence. Lesion size < or = 15 mm was associated with no cases of local failure regardless of treatment arm. For lesions >15 mm in diameter, there was a significant decrease in 5-year local failure with E+XRT compared to E alone (21% vs. 36%, P = 0.03). Tumor margin >1 mm was associated with a low rate of 5-year local failure for either E alone or E+XRT (10.9% vs. 4.6%, P = NS). Tumor margin < = 1 mm had a high rate of local failure that was not significantly decreased by the addition of adjuvant radiotherapy. These results show that large diameter (>15 mm) and close surgical margins (< or = 1 mm) are the dominant risk factors for local recurrence in DCIS. E+XRT significantly decreased local failure risk compared to E alone for large lesions but not for those with close margins.

Contemporary issues in the use of radiation therapy for early invasive breast cancer.

Breast conservation therapy consisting of tumor excision followed by whole breast irradiation is an accepted alternative to mastectomy for many women with early invasive breast cancer. Ongoing research questions include defining the role of the tumor bed irradiation boost, the identification of patients who are at sufficiently low risk of breast cancer recurrence to be treated with excision only, exploring tumor bed brachytherapy as an alternative to whole breast irradiation, and biologic considerations in the future local management of breast cancer.

PKN binds and phosphorylates human papillomavirus E6 oncoprotein.

The high risk human papillomaviruses (HPVs) are associated with carcinomas of cervix and other genital tumors. Previous studies have identified two viral oncoproteins E6 and E7, which are expressed in the majority of HPV-associated carcinomas. The ability of high risk HPV E6 protein to immortalize human mammary epithelial cells has provided a single gene model to study the mechanisms of E6-induced oncogenic transformation. In recent years, it has become clear that in addition to E6-induced degradation of p53 tumor suppressor protein, other targets of E6 are required for mammary epithelial cells immortalization. Using the yeast two-hybrid system, we have identified a novel interaction of HPV16 E6 with protein kinase PKN, a fatty acid- and Rho small G protein-activated serine/threonine kinase with a catalytic domain highly homologous to protein kinase C. We demonstrate direct binding of high risk HPV E6 proteins to PKN in wheat-germ lysate in vitro and in 293T cells in vivo. Importantly, E6 proteins of high risk HPVs but not low risk HPVs were able to bind PKN. Furthermore, all the immortalization-competent and many immortalization-non-competent E6 mutants bind PKN. These data suggest that binding to PKN may be required but not sufficient for immortalizing normal mammary epithelial cells. Finally, we show that PKN phosphorylates E6, demonstrating for the first time that HPV E6 is a phosphoprotein. Our finding suggests a novel link between HPV E6 mediated oncogenesis and regulation of a well known phosphorylation cascade.

Optimal radiotherapy for prostate cancer: predictions for conventional external beam, IMRT, and brachytherapy from radiobiologic models.

PURPOSE: To determine, on the basis of radiobiological models, optimal modalities of radiotherapy for localized prostate cancer, and to provide a rational basis for therapeutic decisions. METHODS AND MATERIALS: An algorithm based on extensions to the linear-quadratic (LQ) cell survival model is constructed for fractionated and protracted irradiation. These radiobiological models include prostate tumor cell line-derived LQ parameters, clonogen repopulation, repair of sublethal damage, hypoxia, and radioisotope decay. In addition, dose inhomogeneities for both IMRT and brachytherapy (125I and 103Pd) from patient-derived Dose Volume Histograms (DVH), as well as dose escalation, are incorporated. Three risk groups are defined in terms of sets of biologic parameters tailored to correspond to clinical risk groups as follows: Favorable-iPSA <10 and bGS < or =6 and stage T2; Intermediate-one parameter increased; and Unfavorable-two or more parameters increased. Tumor control probabilities (TCP) are predicted for conventional external beam radiotherapy (EBRT, including 3D-CRT), intensity modulated radiotherapy (IMRT), and permanent brachytherapy. RESULTS: Brachytherapy is less susceptible to variations in alpha/beta than EBRT and more susceptible to variations in clonogen potential doubling time (Tp). Our models predict TCP consistent with the bNED results from recent dose escalation trials and long-term outcomes from brachytherapy. TCP from IMRT are systematically superior to those from conventional fractionated RT, and suggests its possible use in dose escalation without additional dose to surrounding normal tissues. For potentially rapidly dividing tumors (Tp < 30 days) 103Pd yields superior cell kill compared with 125I, but for very slowly proliferating tumors the converse is suggested. Brachytherapy predicts equivalent or superior TCP to dose escalated EBRT. For unfavorable risk tumors, combined 45 Gy EBRT+brachytherapy boost predicts superior TCP than with either modality alone. CONCLUSIONS: The radiobiological models presented suggest a rational basis for choosing among several radiotherapeutic modalities based on biologic risk factors. In addition, they suggest that IMRT may potentially be superior to 3D-CRT in allowing dose escalation without increased morbidity, and that brachytherapy, as monotherapy or as boost, may achieve superior tumor control compared with dose escalation 3D-CRT. The latter conclusion is supported by clinical data.

Cosmetic outcome in patients receiving an interstitial implant as part of breast-conservation therapy.

PURPOSE: To study factors related to breast cosmetic outcome in patients treated with an interstitial implant as part of breast-conservation therapy. MATERIALS AND METHODS: One hundred fifty-six patients with stage I or II breast carcinoma who received 50 Gy of external-beam irradiation followed by a 20-Gy interstitial boost were examined. The dose homogeneity index (DHI) was calculated for each evaluable implant and was examined in light of other patient-, treatment-, and tumor-related variables previously demonstrated to affect cosmesis. RESULTS: Of the variables examined, both the DHI (P = .021) and the total excision volume (P = .019) were significantly related to cosmetic outcome (excellent vs less than excellent) in a univariate model. In the multivariate analysis, only the total excision volume remained significant (P = .032). The mean total excision volume +/- SD in patients with excellent cosmetic outcome (81.8 cm3 +/- 84.0) was significantly less than that in patients with less than excellent cosmetic outcome (120 cm3 +/- 84). The probability of excellent cosmetic outcome linearly increased with an increase in DHI. The mean DHI was 0.74 +/- 0.12 for the cases with excellent cosmetic outcome and 0.68 +/- 0.10 for those with less than excellent cosmetic outcome. CONCLUSION: To achieve optimal cosmesis, DHI should be maximized. The volume of tissue removed, however, remains the most significant determinant.

The influence of age and extensive intraductal component histology upon breast lumpectomy margin assessment as a predictor of residual tumor.

PURPOSE: Young age and extensive intraductal component (EIC) histology have been shown to be associated with increased local recurrence in women treated with breast conservation therapy. This study was conducted to determine if the status of the lumpectomy specimen margin consistently predicted for residual tumor burden risk irrespective of these variables. METHODS AND MATERIALS: As part of an institutional prospective approach for breast conservation therapy (BCT), 265 cases with AJCC Stage I/II carcinoma with an initial excision margin that was < or =2 mm or indeterminate were subjected to reexcision. The probability of residual tumor (+RE) was evaluated with respect to tumor size, histopathologic subtype (invasive ductal carcinoma, invasive ductal carcinoma with an EIC, and invasive lobular carcinoma), relative closeness of the measured margin, and the extent of margin positivity graded as focal, minimal, moderate, or extensive. The amount of residual tumor was graded as microscopic, small, medium, or large. All variables were analyzed for patient age < or =45 or >45 years. RESULTS: There was no significant difference in the incidence of a +RE according to age < or =45 versus >45 years when the margin was >0 < or =2 mm. Of the patients aged < or =45 years, the incidence of a +RE with a margin that was positive as compared to >0 < or =2 mm was 71% vs. 23%, respectively (p = 0.002). For women >45 years old, the difference in the incidence of +RE comparing margins that were positive or >0 < or =2 mm was not significant at 50% vs. 40%, respectively (p = 0.23). For all cases in aggregate, age < or =45 years was associated with a greater incidence of +RE as compared to patients aged >45 years with the discrepant incidence of a +RE by age strata most pronounced for focally positive margins (60% vs. 18%;p< or =0.05). In a logistic regression analysis, age (per year, as a continuous variable) and an EIC histology were significantly associated with the probability of a +RE (odds ratio [OR] = 0.80, p = 0.05 and OR = 1.9, p = 0.01, respectively). Tumor size was not significant (p = 0.23). In patients with an EIC histology, margin status is generally less predictive for differences in the incidence of a +RE. Further, the overall magnitude of difference in the incidence of a +RE related to age appears to be minimized when an EIC histology is present. In contrast, for cases classified as having non-EIC histology, there is a near-linear relationship for both age strata with respect to margin status and the incidence of a +RE. When histology is classified as non-EIC, age < or =45 years is consistently associated with a greater risk of residual tumor for all margin status categories. When the extent of margin positivity was graded as focal or minimal, residual tumor was semiquantitatively estimated as a medium/large amount in 33% versus 26% of cases aged < or =45 or >45 years, respectively (p = 0.62). CONCLUSION: For positive lumpectomy specimen margins, younger age is associated with an increased residual tumor risk. An EIC histology appears to be associated with an elevated risk of residual tumor irrespective of age and may undermine the predictive utility of margin status. Therefore, age and an EIC histology should be factored into risk assessments for residual tumor that rely upon margin assessment.

Role of splenic irradiation in patients with chronic myeloid leukemia undergoing allogeneic bone marrow transplantation.

Allogeneic bone marrow transplantation (BMT) has become the treatment of choice for patients of appropriate age with chronic myeloid leukemia (CML). In an attempt to enhance tumor cytoreduction, splenic radiation therapy (RT) has been done before the allogeneic transplant, but the role of splenic RT in this setting remains controversial. The purpose of this study is to evaluate the role of splenic RT before allogeneic BMT in patients with CML. Thirty-seven patients with chronic (n=33) or accelerated (n=4) phase CML underwent BMT from April 1990 to January 1998. All patients received splenic RT consisting of 500 cGy in five daily fractions (n=36) or 250 cGy in five daily fractions (n=1) completed within 10 days before BMT. The conditioning regimen included total-body irradiation and cyclophosphamide; etoposide was added to the regimen of patients in the accelerated phase. Continuous-infusion cyclosporine and pulse methotrexate were administered to all patients for prophylaxis of graft-vs.-host disease (GVHD). All patients achieved hematologic and cytogenetic remission. At a median follow-up of 37 months, the freedom from progression (FFP) and overall survival (OS) were 90 and 82%, respectively. None of the patients in accelerated phase have relapsed. Five patients have died of late transplant-related complications while in complete remission. Acute GVHD of grade > or = II was observed in 20% (14% grade II, 6% grade III). Fifty-one percent of patients developed limited chronic GVHD. The median posttransplant creatinine level was 1.2 mg/dL (range 0.6-4.2). Renal dysfunction, manifested as a persistent elevation in serum creatinine level (> 1.2 mg/dL), was observed in 40% of the patients. Only 8.5% had a creatinine level > 2.0 mg/dL, and no patient required dialysis as a result of renal dysfunction. Seven patients (18.9%) developed pulmonary complications, which included idiopathic interstitial pneumonitis (two), biopsy-proven interstitial fibrosis (four), and alveolar hemorrhage (one). The low relapse rate observed in this study may reflect the use of splenic RT as a part of the cytoreductive regimen before BMT. The fractionation schedule of 500 cGy in five daily fractions was well tolerated and did not appear to increase the toxicity of the preparative regimen. These favorable results indicate that splenic RT deserves further investigation and may be of benefit as a part of the conditioning regimen for patients receiving allogeneic BMT for CML.

Extent of margin positivity as a predictor for local recurrence after breast conserving irradiation.

The extent of positivity of the final excision margin in relationship to other relevant factors was evaluated as a predictor for local recurrence after breast conservation therapy (BCT). As part of an institutional practice policy for BCT in 509 stage I/II breast carcinomas, 105 cases had a final excision margin, which was positive. The median age for this cohort was 58 years and the median follow-up was 86 months. All positive margin patients received whole breast irradiation to 50 Gy-50.4 Gy followed by a boost to the tumor bed for an additional 20 Gy. The extent of positivity (EOP) of the excision margin was graded according to a four-point scale: focal, minimal, moderate, extensive. Cases were then analyzed for local failure according to EOP grade, histology, age, tumor size, total excision volume, re-excision, tamoxifen therapy, and chemotherapy. A focal or minimal EOP grade was found in 70% of specimens while an additional 26% were moderate or extensive. The incidence of invasive carcinoma with prominently associated DCIS was significantly greater in cases with an EOP grade of moderate/extensive. There were nine ipsilateral breast recurrences, eight of which could be evaluated for EOP grade. All recurrences were in or near the previous biopsy cavity. A Kaplan-Meier plot of freedom from local failure showed a significant (P = 0.008) difference between cases grouped by EOP grade of focal/minimal as compared to moderate/extensive. A Cox proportional hazards regression model found that the only variable significantly related at the P < or = 0.05 level to local failure was an EOP grade of moderate/extensive. For breast excision specimens with a positive final margin, an EOP grade of moderate/extensive is a predictor for local recurrence after BCT, which may be independent of other variables such as age or histology.

Local excision of rectal carcinoma: a safe alternative for more advanced tumors?

BACKGROUND AND OBJECTIVES: Local excision of rectal carcinoma has primarily been limited to patients with small (< or =3 cm), early rectal carcinoma. We wanted to determine whether local excision (transanal or transacral), when combined with selective chemoradiation therapy, would be adequate treatment for patients with larger (>3 cm) and more advanced T3 and N1 tumors. METHODS: A prospective study of 20 patients with clinical T1-T3, N0-N1 rectal carcinoma was initiated in 1990. Local excision (transanal or transacral) was performed on all patients. Sixteen patients were treated with postoperative 5-fluorouracil (5-FU) and leucovorin (LV) combined with radiation therapy; six high-risk patients (T3 or N1) received an additional 6 months of 5-FU and LV. All patients were followed for a minimum of 4 years. RESULTS: Tumor size ranged from 2 to 5.5 cm (mean, 3.6 cm). Histology revealed well or moderate differentiation (19/20), gross or microscopic ulceration (14/20), and vessel invasion (5/20). Mucosal margins were 3-12 mm (mean, 8.3 mm); radial margins were clear in all patients except one (microscopically positive). Five patients had T3 tumors; two had node positive tumors (N1). With a median follow-up of 56 months (48-71), there have been no local or regional failures and two patients have died from metastatic disease. CONCLUSIONS: Local excision, when combined with selective chemoradiation therapy, can be safely applied to patients with large (>3 cm) and more advanced T3 and N1 rectal carcinomas.

A non-invasive immobilization system and related quality assurance for dynamic intensity modulated radiation therapy of intracranial and head and neck disease.

PURPOSE: To develop and implement a non-invasive immobilization system guided by a dedicated quality assurance (QA) program for dynamic intensity-modulated radiotherapy (IMRT) of intracranial and head and neck disease, with IMRT delivered using the NOMOS Corporation's Peacock System and MIMiC collimator. METHODS AND MATERIALS: Thermoplastic face masks are combined with cradle-shaped polyurethane foaming agents and a dedicated quality assurance program to create a customized headholder system (CHS). Plastic shrinkage was studied to understand its effect on immobilization. Fiducial points for computerized tomography (CT) are obtained by placing multiple dabs of barium paste on mask surfaces at intersections of laser projections used for patient positioning. Fiducial lines are drawn on the cradle along laser projections aligned with nasal surfaces. Lateral CT topograms are annotated with a crosshair indicating the origin of the treatment planning and delivery coordinate system, and with lines delineating the projections of superior-inferior field borders of the linear accelerator's secondary collimators, or with those of the fully open MIMiC. Port films exposed with and without the MIMIC are compared to annotated topograms to measure positional variance (PV) in superior-inferior (SI), right-left (RL), and anterior posterior (AP) directions. MIMiC vane patterns superposed on port films are applied to verify planned patterns. A 12-patient study of PV was performed by analyzing positions of 10 anatomic points on repeat CT topograms, plotting histograms of PV, and determining average PV. RESULTS AND DISCUSSION: A 1.5+/-0.3 mm SD shrinkage per 70 cm of thermoplastic was observed over 24 h. Average PV of 1.0+/-0.8, 1.2+/-1.1, and 1.3+/-0.8 mm were measured in SI, AP, and RL directions, respectively. Lateral port films exposed with and without the MIMiC showed PV of 0.2+/-1.3 and 0.8+/-2.2 mm in AP and SI directions. Vane patterns superimposed on port films consistently verified the planned patterns. CONCLUSION: The CHS provided adequately reproducible immobilization for dynamic IMRT, and may be applicable to decrease PV for other cranial and head and neck external beam radiation therapy.

Molecular and anatomic considerations in the pathogenesis of breast cancer.

In spite of the recent recognition of specific genes associated with an elevated lifetime incidence risk of breast cancer, the molecular mechanisms of breast tumor formation remain largely unknown. Tumorigenesis is thought to be highly complex, likely involving the accumulation of 5-10 genetic and epigenetic events. Recent investigations have begun to identify some of these events, and in vitro model systems for breast tumorigenesis, including radiation-induced breast cancer, are expected to provide further insight. Normal human breast epithelial cells exhibit a finite life span, both in vivo and in vitro. A critical event in oncogenic transformation is the ability of cells to multiply indefinitely, a phenomenon referred to as "immortalization." Using human papillomavirus (HPV) oncogenes, multiple normal breast epithelial subtypes have been shown to have distinct susceptibilities to immortalization by the HPV E6 and E7 oncogenes. Because HPV E6 and E7 inactivate two well-known tumor suppressor proteins, p53 and Rb, respectively, this suggests that a cell-type-specific predominance exists with respect to these tumor suppressor pathways. Additional evidence for variability to oncogenic stimuli among normal breast epithelial cells is provided by findings of locally confined loss of heterozygosity. An in vitro model of radiation-induced breast cancer is associated with early abrogation of p53 function. The resultant pair of normal and radiation-transformed breast epithelial cells serves as a useful system to identify other genes critically relevant to breast tumorigenesis. These and other models should help further define the molecular mechanisms underlying the early steps of breast cancer formation.

The E6 oncoproteins of high-risk papillomaviruses bind to a novel putative GAP protein, E6TP1, and target it for degradation.

The high-risk human papillomaviruses (HPVs) are associated with carcinomas of the cervix and other genital tumors. Previous studies have identified two viral oncoproteins, E6 and E7, which are expressed in the majority of HPV-associated carcinomas. The ability of high-risk HPV E6 protein to immortalize human mammary epithelial cells (MECs) has provided a single-gene model to study the mechanisms of E6-induced oncogenic transformation. In this system, the E6 protein targets the p53 tumor suppressor protein for degradation, and mutational analyses have shown that E6-induced degradation of p53 protein is required for MEC immortalization. However, the inability of most dominant-negative p53 mutants to induce efficient immortalization of MECs suggests the existence of additional targets of the HPV E6 oncoprotein. Using the yeast two-hybrid system, we have isolated a novel E6-binding protein. This polypeptide, designated E6TP1 (E6-targeted protein 1), exhibits high homology to GTPase-activating proteins for Rap, including SPA-1, tuberin, and Rap1GAP. The mRNA for E6TP1 is widely expressed in tissues and in vitro-cultured cell lines. The gene for E6TP1 localizes to chromosome 14q23.2-14q24.3 within a locus that has been shown to undergo loss of heterozygosity in malignant meningiomas. Importantly, E6TP1 is targeted for degradation by the high-risk but not the low-risk HPV E6 proteins both in vitro and in vivo. Furthermore, the immortalization-competent but not the immortalization-incompetent HPV16 E6 mutants target the E6TP1 protein for degradation. Our results identify a novel target for the E6 oncoprotein and provide a potential link between HPV E6 oncogenesis and alteration of a small G protein signaling pathway.