Excess NF-κB induces ectopic odontogenesis in embryonic incisor epithelium

Nuclear factor kappa B (NF-κB) signaling plays critical roles in many physiological and pathological processes, including regulating organogenesis. Down-regulation of NF-κB signaling during development results in hypohidrotic ectodermal dysplasia. The roles of NF-κB signaling in tooth development, however, are not fully understood. We examined mice overexpressing IKKβ, an essential component of the NF-κB pathway, under keratin 5 promoter (K5-Ikkβ). K5-Ikkβ mice showed supernumerary incisors whose formation was accompanied by up-regulation of canonical Wnt signaling. Apoptosis that is normally observed in wild-type incisor epithelium was reduced in K5-Ikkβ mice. The supernumerary incisors in K5-Ikkβ mice were found to phenocopy extra incisors in mice with mutations of Wnt inhibitor, Wise. Excess NF-κB activity thus induces an ectopic odontogenesis program that is usually suppressed under physiological conditions.

Novel signalling mechanisms and targets in renal ischaemia and reperfusion injury

Acute kidney injury (AKI) induced by ischaemia and reperfusion (I/R) injury is a common and severe clinical problem. Vascular dysfunction, immune system activation and tubular epithelial cell injury contribute to functional and structural deterioration. The search for novel therapeutic interventions for I/R-induced AKI is a dynamic area of experimental research. Pharmacological targeting of injury mediators and corresponding intracellular signalling in endothelial cells, inflammatory cells and the injured tubular epithelium could provide new opportunities yet may also pose great translational challenge. Here, we focus on signalling mediators, their receptors and intracellular signalling pathways which bear potential to abrogate cellular processes involved in the pathogenesis of I/R-induced AKI. Sphingosine 1 phosphate (S1P) and its respective receptors, cytochrome P450 (CYP450)-dependent vasoactive eicosanoids, NF-κB- and protein kinase-C (PKC)-related pathways are representatives of such 'druggable' pleiotropic targets. For example, pharmacological agents targeting S1P and PKC isoforms are already in clinical use for treatment for autoimmune diseases and were previously subject of clinical trials in kidney transplantation where I/R-induced AKI occurs as a common complication. We summarize recent in vitro and in vivo experimental studies using pharmacological and genomic targeting and highlight some of the challenges to clinical application of these advances.

Requirement of NF-κB/Rel for the development of hair follicles and other epidermal appendices

NF-κB/Rel transcription factors and IκB kinases (IKK) are essential for inflammation and immune responses, but also for bone-morphogenesis, skin proliferation and differentiation. Determining their other functions has previously been impossible, owing to embryonic lethality of NF-κB/Rel or IKK-deficient animals. Using a gene targeting approach we have ubiquitously expressed an NF-κB super-repressor to investigate NF-κB functions in the adult. Mice with suppressed NF-κB revealed defective early morphogenesis of hair follicles, exocrine glands and teeth, identical to Eda (tabby) and Edar (downless) mutant mice. These affected epithelial appendices normally display high NF-κB activity, suppression of which resulted in increased apoptosis, indicating that NF-κB acts as a survival factor downstream of the tumor necrosis factor receptor family member EDAR. Furthermore, NF-κB is required for peripheral lymph node formation and macrophage function.

Deoxycholic acid (DCA) causes ligand-independent activation of epidermal growth factor receptor (EGFR) and FAS receptor in primary hepatocytes: inhibition of EGFR/mitogen-activated protein kinase-signaling module enhances DCA-induced apoptosis

Previous studies have argued that enhanced activity of the epidermal growth factor receptor (EGFR) and the mitogen-activated protein kinase (MAPK) pathway can promote tumor cell survival in response to cytotoxic insults. In this study, we examined the impact of MAPK signaling on the survival of primary hepatocytes exposed to low concentrations of deoxycholic acid (DCA, 50 microM). Treatment of hepatocytes with DCA caused MAPK activation, which was dependent upon ligand independent activation of EGFR, and downstream signaling through Ras and PI(3) kinase. Neither inhibition of MAPK signaling alone by MEK1/2 inhibitors, nor exposure to DCA alone, enhanced basal hepatocyte apoptosis, whereas inhibition of DCA-induced MAPK activation caused approximately 25% apoptosis within 6 h. Similar data were also obtained when either dominant negative EGFR-CD533 or dominant negative Ras N17 were used to block MAPK activation. DCA-induced apoptosis correlated with sequential cleavage of procaspase 8, BID, procaspase 9, and procaspase 3. Inhibition of MAPK potentiated bile acid-induced apoptosis in hepatocytes with mutant FAS-ligand, but did not enhance in hepatocytes that were null for FAS receptor expression. These data argues that DCA is causing ligand independent activation of the FAS receptor to stimulate an apoptotic response, which is counteracted by enhanced ligand-independent EGFR/MAPK signaling. In agreement with FAS-mediated cell killing, inhibition of caspase function with the use of dominant negative Fas-associated protein with death domain, a caspase 8 inhibitor (Ile-Glu-Thr-Asp-p-nitroanilide [IETD]) or dominant negative procaspase 8 blocked the potentiation of bile acid-induced apoptosis. Inhibition of bile acid-induced MAPK signaling enhanced the cleavage of BID and release of cytochrome c from mitochondria, which were all blocked by IETD. Despite activation of caspase 8, expression of dominant negative procaspase 9 blocked procaspase 3 cleavage and the potentiation of DCA-induced apoptosis. Treatment of hepatocytes with DCA transiently increased expression of the caspase 8 inhibitor proteins c-FLIP-(S) and c-FLIP-(L) that were reduced by inhibition of MAPK or PI(3) kinase. Constitutive overexpression of c-FLIP-(s) abolished the potentiation of bile acid-induced apoptosis. Collectively, our data argue that loss of DCA-induced EGFR/Ras/MAPK pathway function potentiates DCA-stimulated FAS-induced hepatocyte cell death via a reduction in the expression of c-FLIP isoforms.

Ionizing radiation-induced, mitochondria-dependent generation of reactive oxygen/nitrogen

Transient generation of reactive oxygen or nitrogen (ROS/RNS), detected with dihydrodichlorofluoroscein by fluorescence microscopy, occurs within minutes of exposing cells to ionizing radiation. In the 1-10 Gy dose range, the amount of ROS/RNS produced/cell is constant, but the percentage of producing cells increases with dose (20 to 80%). Reversible depolarization of the mitochondrial membrane potential () and decrease in fluorescence of a mitochondria-entrapped dye, calcein, are observed coincidentally. Radiation-induced ROS/RNS, depolarization, and calcein fluorescence decrease are inhibited by the mitochondrial permeability transition inhibitor, cyclosporin A, but not the structural analogue, cyclosporin H. Radiation-stimulated ROS/RNS is also inhibited by overexpressing the Ca(2+)-binding protein, calbindin 28K, or treating cells with an intracellular Ca(2+) chelator. Radiation-induced ROS/RNS is observed in several cell types with the exception of rho(o) cells deficient in mitochondrial electron transport. rho(o) cells show neither radiation-induced ROS/RNS production nor depolarization. We propose that radiation damage in a few mitochondria is transmitted via a reversible, Ca(2+)-dependent mitochondrial permeability transition to adjacent mitochondria with resulting enhanced ROS/RNS generation. Measurements of radiation-induced mitogen-activated protein kinase activity indicate that this sensing/amplification mechanism is necessary for activation of some cytoplasmic signaling pathways by low doses of radiation.

Substantially improved in vivo radiosensitization of rat glioma with mutant HSV-TK and acyclovir

We recently demonstrated in vitro that a mutant HSV-TK (mutant 75) expressed from an adenovirus (AdCMV-TK75) radiosensitized rat RT2 glioma cells significantly better than wild type HSV-TK (AdCMV-TK) in combination with acyclovir (ACV). To examine whether a similar improvement could also be observed in vivo, we tested these viruses in a syngeneic rat glioma tumor model (RT2/Fischer 344). First, we demonstrate that treatment with AdCMV-TK and ACV significantly radiosensitizes implanted gliomas and roughly doubles the mean survival time to 37 days, compared to 20 days for control animals implanted with Adbetagal-transduced cells (P<.02). Second, it was important to first examine the effect of AdCMV-TK75 and ACV on survival without any irradiation. We found that AdCMV-TK75 appeared to sensitize gliomas more efficiently than AdCMV-TK, although this difference was not significant ( P= .19 ). Third, and most importantly, in combined HSV-TK, ACV and irradiation experiments, we demonstrate that AdCMV-TK75 is superior over AdCMV-TK and significantly (P<.005) prolonged the survival of treated animals. Our results suggest that AdCMV-TK75 is far more efficient than AdCMV-TK in radiosensitizing rat glioma when administered in combination with ACV.

Advances in radiotherapy for carcinoma of the head and neck

Increasingly, progress in the radiotherapy of carcinomas of the head and neck is being driven by principles of radiobiology. This article discusses some of the major advances in head and neck radiotherapy, including altered fractionation, concomitant chemotherapy, and intensity-modulated radiotherapy, in the context of radiobiologic rationale, potential impact on tumor control, and normal tissue complications.

Local tumor control and survival: clinical evidence and tumor biologic basis

Clinical and tumor biologic evidence indicates that local tumor recurrence is associated with a higher rate of distant metastases and adverse effects on patient survival. The findings discussed in this article are based on results from breast, prostate, and lung carcinoma, all tumors with high metastatic potential for which local tumor control was thought to be relatively unimportant. The fact that local tumor recurrence is associated with tumor progression and significant increases in distant metastases has important consequences in the relative emphasis on and the sequencing of locoregional and systemic therapies in the future.

In vivo identification of lymphocyte subsets exhibiting transcriptionally active NF-kappaB/Rel complexes

To analyze the NF-kappaB/Rel activity pattern in a living organism, we previously generated transgenic mice carrying a kappaB-dependent lacZ gene. In situ analysis of both primary and secondary lymphoid organs revealed a strong NF-kappaB transcriptional activity in antigen-presenting cells, some endothelial cells and sinus lining cells of the lymph node capsula with very little activity in lymphocytes and thymocytes. Using fluorescein-di-beta-D-galactopyranoside (FDG) as a vital substrate for the beta-galactosidase, we re-examined by flow cytometry the NF-kappaB/Rel transcriptional activity in our mouse model. We report here that such constitutive NF-kappaB/Rel activity was significantly detected in thymocytes at the CD44+CD25(-) stage. This constitutive activity extended with CD25 expression to the majority of the CD44(-)CD25(+) thymocytes and was then restricted to a few mature T cells. In the spleen, constitutive NF-kappaB/Rel activity was found in most B cells, unlike T cells which were largely negative. Virgin IgD(+) B cells expressed higher levels of NF-kappaB transcriptional activity than other B cell types. Altogether, these results suggest that NF-kappaB/Rel complexes are key players in the in vivo differentiation of IgD(+) B lymphocytes and possibly CD25(+) thymocytes.

Radiobiological considerations in the design of fractionation strategies for intensity-modulated radiation therapy of head and neck cancers

PURPOSE

The dose distributions of intensity-modulated radiotherapy (IMRT) treatment plans can be shown to be significantly superior in terms of higher conformality if designed to simultaneously deliver high dose to the primary disease and lower dose to the subclinical disease or electively treated regions. We use the term "simultaneous integrated boost" (SIB) to define such a treatment. The purpose of this paper is to develop suitable fractionation strategies based on radiobiological principles for clinical trials and routine use of IMRT of head and neck (HN) cancers. The fractionation strategies are intended to allow escalation of tumor dose while adequately sparing normal tissues outside the target volume and considering the tolerances of normal tissues embedded within the primary target volume.

METHODS AND MATERIALS

IMRT fractionation regimens are specified in terms of "normalized total dose" (NTD), i.e., the biologically equivalent dose given in 2 Gy/fx. A linear-quadratic isoeffect formula is applied to convert NTDs into "nominal" prescription doses. Nominal prescription doses for a high dose to the primary disease, an intermediate dose to regional microscopic disease, and lower dose to electively treated nodes are used for optimizing IMRT plans. The resulting nominal dose distributions are converted back into NTD distributions for the evaluation of treatment plans. Similar calculations for critical normal tissues are also performed. Methods developed were applied for the intercomparison of several HN treatment regimens, including conventional regimens used currently and in the past, as well as SIB strategies. This was accomplished by comparing the biologically equivalent NTD values for the gross tumor and regional disease, and bone, muscle, and mucosa embedded in the gross tumor volume.

RESULTS

(1) A schematic HN example was used to demonstrate that dose distributions for SIB IMRT are more conformal compared to dose distributions when IMRT is divided into a large-field phase and a boost phase. Both were shown to be significantly superior compared to dose distributions obtained using conventional beams for the large-field phase followed by IMRT for the boost phase. (2) The relationship between NTD and nominal dose for HN tumors was found to be quite sensitive to the choice of tumor clonogen doubling time but relatively insensitive to other parameters. (3) For late effect normal tissues embedded in the tumor volume and assumed to receive the same dose as the tumor, the biologically equivalent NTD for the SIB IMRT may be significantly higher. (4) Normal tissues outside the target volume receive lower dose due to the higher conformality of the IMRT plans. The biologically equivalent NTDs are even lower due to the lower dose per fraction in the SIB strategy.

CONCLUSIONS

IMRT dose distributions are most conformal when designed to be delivered as SIB. Using isoeffect radiobiological relationships and published HN data, fractionation strategies can be designed in which the nominal dose levels to the primary, regional disease and electively treated volumes are appropriately adjusted, each receiving different dose/fx. Normal tissues outside the treated volumes are at reduced risk in such strategies since they receive lower total dose as well as lower dose/fx. However, the late effect toxicities of tissues embedded within the primary target volume and assumed to receive the same dose as the primary may pose a problem. The efficacy and safety of the proposed fractionation strategies will need to be evaluated with careful clinical trials.

The potential for sparing of parotids and escalation of biologically effective dose with intensity-modulated radiation treatments of head and neck cancers: a treatment design study

PURPOSE

Conventional radiotherapy for cancers of the head and neck (HN) can yield acceptable locoregional tumor control rates, but toxicity of many normal tissues limits our ability to escalate dose. Xerostomia represents one of the most common complications. The purpose of this study is to investigate the potential of intensity-modulated radiotherapy (IMRT) to achieve adequate sparing of parotids and to escalate nominal and/or biologically-effective dose to achieve higher tumor control without exceeding normal tissue tolerances.

METHODS AND MATERIALS

An IMRT optimization system, developed at our institution for research and clinical purposes, and coupled to a commercial radiation treatment planning system, has been applied to a number of cases of HN carcinomas. IMRT plans were designed using dose- and dose-volume-based criteria for 4 and 6 MV coplanar but non-collinear beams ranging in number from 5 to 15 placed at equi-angular steps. Detailed analysis of one of the cases is presented, while the results of the other cases are summarized. For the first case, the IMRT plans are compared with the standard 3D conformal radiation treatment (3DCRT) plan actually used to treat the patient, and with each other. The aim of the 3DCRT plan for this particular case was to deliver 73 Gy to the tumor volume in 5 fractions of 2 Gy and 28 fractions of 2.25 Gy/fx; and 46 Gy to the nodes in 2 Gy/fx while maintaining critical normal tissues to below specified tolerances. The IMRT plans were designed to be delivered as a "simultaneous integrated boost" (SIB) using the "sweeping window" technique with a dynamic MLC. The simultaneous integrated boost strategy was chosen, partly for reasons of efficiency in planning and delivery of IMRT treatments, and partly with the assumption that dose distributions in such treatments are more conformal and spare normal tissues to a greater extent than those with sequential boost strategy. Biologically equivalent dose normalized to 2 Gy/fx, termed here as normalized total dose (NTD), for this strategy was calculated using published head and neck fractionation data.

RESULTS

IMRT plans were more conformal than the 3DCRT plans. For equivalent coverage of the tumor and the nodes, and for the dose to the spinal cord and the brainstem maintained within tolerance limits, the dose to parotids was greatly reduced. For the detailed example presented, it was shown that the tumor and the nodes in the 3DCRT plan receive NTDs of 78 and 46 Gy, respectively. For the IMRT plan, a nominal dose of 70 Gy could be delivered to the tumor in 28 fractions of 2.5 Gy each, simultaneously with 50.4 Gy to nodes with 1.8 Gy/fx. The two are biologically equivalent to 82 and 46 Gy, respectively, if delivered in 2 Gy/fx. Similar computations were carried out for other cases as well. The quality of IMRT plans was found to improve with increasing number of beams, up to 9 beams. Dose-volume-based criteria led to a modest improvement in IMRT plans and required less trial and error.

CONCLUSION

IMRT has the potential to significantly improve radiotherapy of HN cancers by reducing normal tissue dose and simultaneously allowing escalation of dose. SIB strategy is not only more efficient and yields better dose distributions, but may also be biologically more effective. Dose-volume-based criteria is better than purely dose-based criteria. The quality of plans improves with number of beams, reaching a saturation level for a certain number of beams, which for the plans studied was found to be 9.

Roles for basal and stimulated p21(Cip-1/WAF1/MDA6) expression and mitogen-activated protein kinase signaling in radiation-induced cell cycle checkpoint control in carcinoma cells

We investigated the role of the cdk inhibitor protein p21(Cip-1/WAF1/MDA6) (p21) in the ability of MAPK pathway inhibition to enhance radiation-induced apoptosis in A431 squamous carcinoma cells. In carcinoma cells, ionizing radiation (2 Gy) caused both primary (0-10 min) and secondary (90-240 min) activations of the MAPK pathway. Radiation induced p21 protein expression in A431 cells within 6 h via secondary activation of the MAPK pathway. Within 6 h, radiation weakly enhanced the proportion of cells in G(1) that were p21 and MAPK dependent, whereas the elevation of cells present in G(2)/M at this time was independent of either p21 expression or MAPK inhibition. Inhibition of the MAPK pathway increased the proportion of irradiated cells in G(2)/M phase 24-48 h after irradiation and enhanced radiation-induced apoptosis. This correlated with elevated Cdc2 tyrosine 15 phosphorylation, decreased Cdc2 activity, and decreased Cdc25C protein levels. Caffeine treatment or removal of MEK1/2 inhibitors from cells 6 h after irradiation reduced the proportion of cells present in G(2)/M phase at 24 h and abolished the ability of MAPK inhibition to potentiate radiation-induced apoptosis. These data argue that MAPK signaling plays an important role in the progression/release of cells through G(2)/M phase after radiation exposure and that an impairment of this progression/release enhances radiation-induced apoptosis. Surprisingly, the ability of irradiation/MAPK inhibition to increase the proportion of cells in G(2)/M at 24 h was found to be dependent on basal p21 expression. Transient inhibition of basal p21 expression increased the control level of apoptosis as well as the abilities of both radiation and MEK1/2 inhibitors to cause apoptosis. In addition, loss of basal p21 expression significantly reduced the capacity of MAPK inhibition to potentiate radiation-induced apoptosis. Collectively, our data argue that MAPK signaling and p21 can regulate cell cycle checkpoint control in carcinoma cells at the G(1)/S transition shortly after exposure to radiation. In contrast, inhibition of MAPK increases the proportion of irradiated cells in G(2)/M, and basal expression of p21 is required to maintain this effect. Our data suggest that basal and radiation-stimulated p21 may play different roles in regulating cell cycle progression that affect cell survival after radiation exposure.

Radiation-induced release of transforming growth factor alpha activates the epidermal growth factor receptor and mitogen-activated protein kinase pathway in carcinoma cells, leading to increased proliferation and protection from radiation-induced cell death

Exposure of A431 squamous and MDA-MB-231 mammary carcinoma cells to ionizing radiation has been associated with short transient increases in epidermal growth factor receptor (EGFR) tyrosine phosphorylation and activation of the mitogen-activated protein kinase (MAPK) and c-Jun NH(2)-terminal kinase (JNK) pathways. Irradiation (2 Gy) of A431 and MDA-MB-231 cells caused immediate primary activations (0-10 min) of the EGFR and the MAPK and JNK pathways, which were surprisingly followed by later prolonged secondary activations (90-240 min). Primary and secondary activation of the EGFR was abolished by molecular inhibition of EGFR function. The primary and secondary activation of the MAPK pathway was abolished by molecular inhibition of either EGFR or Ras function. In contrast, molecular inhibition of EGFR function abolished the secondary but not the primary activation of the JNK pathway. Inhibition of tumor necrosis factor alpha receptor function by use of neutralizing monoclonal antibodies blunted primary activation of the JNK pathway. Addition of a neutralizing monoclonal antibody versus transforming growth factor alpha (TGFalpha) had no effect on the primary activation of either the EGFR or the MAPK and JNK pathways after irradiation but abolished the secondary activation of EGFR, MAPK, and JNK. Irradiation of cells increased pro-TGFalpha cleavage 120-180 min after exposure. In agreement with radiation-induced release of a soluble factor, activation of the EGFR and the MAPK and JNK pathways could be induced in nonirradiated cells by the transfer of media from irradiated cells 120 min after irradiation. The ability of the transferred media to cause MAPK and JNK activation was blocked when media were incubated with a neutralizing antibody to TGFalpha. Thus radiation causes primary and secondary activation of the EGFR and the MAPK and JNK pathways in autocrine-regulated carcinoma cells. Secondary activation of the EGFR and the MAPK and JNK pathways is dependent on radiation-induced cleavage and autocrine action of TGFalpha. Neutralization of TGFalpha function by an anti-TGFalpha antibody or inhibition of MAPK function by MEK1/2 inhibitors (PD98059 and U0126) radiosensitized A431 and MDA-MB-231 cells after irradiation in apoptosis, 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and clonogenic assays. These data demonstrate that disruption of the TGFalpha-EGFR-MAPK signaling module represents a strategy to decrease carcinoma cell growth and survival after irradiation.

Inhibition of the mitogen activated protein (MAP) kinase cascade potentiates cell killing by low dose ionizing radiation in A431 human squamous carcinoma cells

The molecular mechanism(s) by which tumor cells survive after exposure to ionizing radiation are not fully understood. Exposure of A431 cells to low doses of radiation (1 Gy) caused prolonged activations of the mitogen activated protein (MAP) kinase and stress activated protein (SAP) kinase pathways, and induced p21(Cip-1/WAF1) via a MAP kinase dependent mechanism. In contrast, higher doses of radiation (6 Gy) caused a much weaker activation of the MAP kinase cascade, but a similar degree of SAP kinase cascade activation. In the presence of MAP kinase blockade by the specific MEK1 inhibitor (PD98059) the basal activity of the SAP kinase pathway was enhanced twofold, and the ability of a 1 Gy radiation exposure to activate the SAP kinase pathway was increased approximately sixfold 60 min after irradiation. In the presence of MAP kinase blockade by PD98059 the ability of a single 1 Gy exposure to cause double stranded DNA breaks (TUNEL assay) was enhanced at least threefold over the following 24-48 h. The increase in DNA damage within 48 h was also mirrored by a similar decrease in A431 cell growth as judged by MTT assays over the next 4-8 days following radiation exposure. This report demonstrates that the MAP kinase cascade is a key cytoprotective pathway in A431 human squamous carcinoma cells which is activated in response to clinically used doses of ionizing radiation. Inhibition of this pathway potentiates the ability of low dose radiation exposure to induce cell death in vitro.

Radiotherapeutic management of bulky cervical lymphadenopathy in squamous cell carcinoma of the head and neck: is postradiotherapy neck dissection necessary?

Although traditional recommendations for the management of bulky cervical lymphadenopathy (AJCC categories N2-3) with definitive radiotherapy call for postradiotherapy neck dissection regardless of treatment response, recent data suggests that this policy can be modified on the basis of tumor regression rate. In a series of 130 patients with stage III-IV squamous cell carcinoma of the head and neck managed with a concomitant boost-accelerated hyperfractionated radiotherapy schedule, 81 cases had cervical lymphadenopathy at the time of referral. Patients were analyzed with respect to regional control outcomes for those having complete and incomplete clinical responses during the initial 3-month follow-up interval. The general management policy has been close observation of patients demonstrating complete clinical responses to radiation rather than postradiotherapy neck dissection. Failure patterns were examined in the 58 patients classified as complete responders. Failure occurred in the primary site in 16 (28%) of these patients, while isolated neck failure occurred in only 3 (5%). Neck recurrence rates for patients with maximum lymph node size < or = 3 cm vs. > 3 cm were not statistically different at 3-year follow-up (94% vs. 86%). Among the 23 incomplete clinical responders, 18 had incomplete neck responses. Five of these patients underwent salvage neck dissection; 4 remain clinically free of recurrence. The remaining 13 patients who either refused or were not eligible for salvage surgery ultimately succumbed with persistent loco-regional disease. The policy of observation after complete response to the radiotherapy schedule employed here was associated with a very low incidence of isolated neck failures and was safe and appropriate in patients who can be followed reliably. The prognosis for patients who failed to respond in the neck was poor except for those who underwent salvage surgery.

Factors determining outcome in patients treated with interstitial implantation as a radiation boost for breast conservation therapy

PURPOSE

To evaluate the relative utility of interstitial implant as a technique for tumor bed dose escalation and assess technical factors related to outcome.

METHODS AND MATERIALS

From 1982-1994, a prospectively applied institutional policy of margin-directed boost dose escalation to the tumor bed was followed whereby interstitial implantation was commonly employed for a final margin status (FMS) < or = 2 mm. There were 509 treated breasts, of which 127 received an implant boost. For purposes of comparison, cases were broadly classed as "implant" (all FMS < or = 2 mm) and "nonimplant" (FMS < or = 2 mm or FMS > 2 mm). The implant target volume was determined at completion of whole breast irradiation by clinical assessment. All implants were constructed in accordance with a preplanning algorithm designed to maximize dose homogeneity within a prescription isodose goal of 0.50 Gy/h for 40 h. Local control and cosmetic outcome were evaluated with respect to extent of tumor, histopathology, FMS, extent of surgery, and systemic adjuvant therapy. Implant quality was assessed using four calculated parameters: strand separation quotient (SSQ), planar separation quotient (PSQ), global separation quotient (GSQ), and dose homogeneity index (DHI). The mean implant volume was 48.3 +/- 20 cc, the mean prescribed dose rate was 0.46 +/- 0.08 Gy/h, and the mean total implant dose was 19.94 +/- 1.52 Gy.

RESULTS

Cosmetic outcome was good/excellent in 90% of implant and 83% of all nonimplant cases, which was not statistically different. Cosmesis was significantly superior with implant when compared to nonimplant cases receiving an external boost of 20 Gy. Logistic regression analyses of implant cases revealed that reexcision volume and decreased DHI were associated with adverse cosmesis. There were 10 local failures in the implanted patients (4 within the prescribed isodose volume, 5 at the periphery, and 1 elsewhere in the breast). The local failure rate at 5 and 7 years in the implanted group was 3.9 and 9.0%, respectively, compared to nonimplant cases with a margin < or = 2 mm of 3.2 and 3.2%, respectively. These differences were not significant. The crude local failure rate in patients with an associated DCIS component was 12% a compared to 3% in patients with pure invasive histology (p = 0.06). A proportional hazards survival model revealed a significant association of local failure with the performance of a reexcision and young age.

CONCLUSION

We conclude that interstitial implant boost for breast conserving irradiation is associated with cosmesis that is superior than the same nominal dose of external beam boost, although this is highly dependent upon the technical quality of the source position and the relative uniformity of dose deposition. Breast implantation results in a rate of local control no better than dose-matched external beam boost in patients with a final margin < or = 2 mm. Local control with implantation might be further enhanced by increasing implant volume and/or improved target localization.

NF-kappaB activity in transgenic mice: developmental regulation and tissue specificity

The transcription factor family NF-kappaB/Rel is responsible for the regulation of a large number of cellular genes and some viruses. Since there is a strong similarity between the NF-kappaB/Rel family members and the Drosophila melanogaster protein DORSAL, which is activated early during embryogenesis, we were interested in determining the pattern of NF-kappaB activity during mouse development. Two lacZ reporter constructs, each driven by promoter elements that are dependent on the presence of nuclear NF-kappaB/Rel activity, were used to produce transgenic mice. The analysis of these mice did not identify nuclear NF-kappaB/Rel activity in early development prior to implantation or during the gastrulation processes. Earliest expression of the lacZ transgene was detected on day E12.5. Before birth lacZ expression was seen in discrete regions of the rhombencephalon of the developing brain, in the spinal medulla, in some of the blood vessels and in the thymus. After birth, the NF-kappaB/Rel activity in the thymus remained but nuclear activity was also found in the bone marrow, in the spleen and in the capsule of the lymph nodes. In the central nervous system, drastic changes in NF-kappaB/Rel activity could be observed in the first 3 weeks after birth, when the cortex and the cerebellum reach functional and morphological maturity. Considering the results of the p50, p65, relB and c-rel knock-out mice and our present findings, we believe that the NF-kappaB/Rel proteins known so far are probably not implicated in processes of early development and differentiation of the different tissues, but rather in maintaining their function once matured.

Heuristically derived tumor burden score as a prognostic factor for stage IIIB carcinoma of the cervix

PURPOSE

A retrospective analysis of radiotherapeutic management of locally advanced carcinoma of the uterine cervix was performed to evaluate the effect of various treatment parameters and disease extent upon treat outcome.

METHODS AND MATERIALS

Between 1976 and 1989, 89 patients with Stage IIIB disease were treated with external beam radiotherapy and brachytherapy. Treatment outcomes were evaluated by dose to Point A, the proportion of Point A dose delivered by brachytherapy, clinical response at 3 months, and a newly developed tumor burden scoring system that quantifies the anatomical extent of disease. Kaplan-Meier estimates of tumor control and survival parameters were determined.

RESULTS

Loco-regional control (LRC), disease-free survival (DFS), and overall survival (OVS) at 5 years were 52.9%, 45.5%, and 50.3%, respectively. Clinical response at 3 months was highly predictive of local and distant tumor control. There was no correlation between proportion of brachytherapy dose and treatment outcome. The tumor burden scoring system demonstrates that FIGO Stage IIIB disease can be clinically divided into two prognostic groups of low and high tumor burden. Five year LRC was 62.9% and 40.2% for the low and high tumor burden groups, respectively (p = 0.024). Within the high tumor burden group the LRC was 53.0% and 22.5% when the point A dose given was > 78 Gy and < or = 78 Gy, respectively (p = 0.047). This correlated with improved DFS and OVS.

CONCLUSION

The tumor burden scoring system subdivides FIGO Stage IIIB cervical carcinoma into two prognostic groups, predicting for overall survival and demonstrating a dose response in the high tumor burden group. This system may serve to improve future comparison of treatment outcome and to guide selection of patients who may benefit from a more aggressive treatment approach.

Dose uniformity in a planar interstitial implant system

PURPOSE

This work makes use of a volume-ratio technique to examine dose uniformity in a planar interstitial implant system based entirely on geometrical constraints. The rationale for determining an upper limit for acceptable dose variation is examined and discussed. Variation of ribbon spacing and interplanar separation is evaluated in terms of its effect on dose homogeneity.

METHODS AND MATERIALS

Volume-dose curves were generated for a range of planar implant dimensions. The volume inside the target region and enclosed between the reference isodose and a higher isodose surface was calculated as a measure of dose uniformity. Studies of homogeneity, target coverage, and external tissue irradiation were carried out to evaluate the importance of flexible interplanar spacing in optimizing implants. New dose tables were generated to accommodate the frequent clinical need to minimize the number of catheter insertions.

RESULTS

Implants carried out in accordance with specified geometric constraints were found also to provide optimal dose homogeneity as determined using the volume ratio method with a flexible high dose limit. For two-plane implants, the interplanar spacing should be determined specifically in each case to ensure accurate target coverage. Calculations for specific cases showed that the tissue volume treated to unnecessarily high dose levels can be reduced by a large factor by careful positioning of the implant planes. A smaller ribbon and seed spacing will, in general, lead to better dose uniformity when this is evaluated in terms of the volumes treated to very high dose levels.

CONCLUSIONS

Our studies showed that implants carried out using simple and useful geometric guidelines will also provide an acceptably uniform dose distribution. For double plane implants, the separation of the implant planes should be optimized for each target thickness.

Effects of the protein kinase C stimulant bryostatin 1 on the proliferation and colony formation of irradiated human T-lymphocytes

The protein kinase C stimulant bryostatin 1 (Bryo) was used in examining human peripheral blood T-lymphocyte radiosensitivities in proliferation assays. Bryo was similar to PMA in inducing T-cell proliferation by the CD3, CD28 and CD69 pathways. No difference in radiosensitivities was observed in T-cells stimulated by the three independent surface antigen-mediated activation pathways. CD3 was chosen as the second signal for comparing the potencies of the three different first signals Bryo, phorbol 12-myristate, 13-acetate (PMA), and interleukin 2 (IL-2) in stimulating T-cell proliferation and in maintaining this response after radiation. Though there were radioresponse differences among various individuals, the irradiated lymphocytes consistently showed significantly greater proliferation when treated with Bryo or PMA than with IL-2 (p < 0.05- < 0.005). No difference in proliferative responses was observed in T-cells irradiated between 4 h before and 15 h after the addition of stimulants. Colony forming assays showed higher colony survival for irradiated T-cells stimulated with Bryo than with PMA. These results support the important role of protein kinase C in T-cell radiation responses, and suggest a potential role for Bryo in enhancing T-lymphocyte survival during radiation therapy.

Breast conservation in elderly women for clinically negative axillary lymph nodes without axillary dissection

BACKGROUND

A prospective study was initiated to explore an approach of limited therapy in elderly patients with early clinical stage breast cancer.

METHODS

Between 1982 and 1989, 73 women with American Joint Committee on Cancer Stage I/II, clinically negative axillary lymph nodes aged 65 years or older (median age, 74 years) were enrolled in a treatment program consisting of tumor excision, breast and regional lymph node irradiation, and, in 66 patients, tamoxifen. Patients were assessed for disease outcome and complications.

RESULTS

At a median follow-up of 54 months, 8-year rates of local and regional lymph node control were 92.5% and 100%, respectively. Eight-year probabilities of disease free, overall, and breast cancer specific survival were 84%, 52.5%, and 93.8%, respectively. There was minimal morbidity associated with either regional irradiation or tamoxifen.

CONCLUSIONS

An approach to early breast cancer in the elderly that seeks to limit the aggressiveness of local and systemic therapies appears to result in a satisfactory disease outcome with few complications.

Promoter analysis of the gene encoding the I kappa B-alpha/MAD3 inhibitor of NF-kappa B: positive regulation by members of the rel/NF-kappa B family

In order to characterize the regulation of the gene encoding the I kappa B-alpha/MAD3 inhibitor of the transcription factor NF-kappa B, we have isolated a human genomic clone and sequenced the promoter of this gene. The MAD3 promoter exhibits a potential TATA element upstream of one of the two major transcription sites, and contains several potential NF-kappa B binding sequences, suggesting that the gene is positively regulated by members of this family. Transfection experiments demonstrate that the MAD3 promoter can be activated by various combinations of members of the rel/NF-kappa B family, as well as by phorbol esters and tumor necrosis factor. Specific deletion of one of the kappa B motifs, located 37 bp upstream of the TATA box, abolishes responses to PMA and TNF. This kappa B motif binds NF-kappa B (p50/relA), p50/c-rel and relA/c-rel heterodimers as well as KBF1 (p50 homodimer). These results help to explain the previously observed transient nature of the NF-kappa B response: following NF-kappa B activation, the expression of the inhibitor is increased, therefore the extent of nuclear translocation of the active complex is reduced, resulting in a decreased activation of its target genes.

Enhanced oxygenation in vivo by allosteric inhibitors of hemoglobin saturation

The in vivo effects on hemoglobin (Hb)-O2 affinity and tissue PO2 were investigated after intraperitoneal administration of 2-[4-(((dichloroanilino)-carbonyl)methyl)phenoxyl]-2-methyl propionic acid (RSR4; 150 mg/kg) or its 3,5-dimethyl derivative (RSR13; 300 mg/kg) in C3Hf/Sed mice. The Hb-O2 dissociation curve was plotted from tail vein blood samples using an O2 dissociation analyzer before and up to 160 min after compound administration. Twenty to 40 min after injection, the PO2 at 50% saturation of hemoglobin (Hb P50) increased by a mean of 25% (range 18-31%) after RSR4 and 53% (range 36-76%) after RSR13. Tissue PO2 was continuously measured using an O2 microelectrode in thigh muscle before and up to 40 min after RSR4 or RSR13 injection. Twenty to 40 min after administration, tissue PO2 increased by a mean of 78% (range 30-127%) after RSR4 and 66% (range 39-97%) after RSR13 administration in anesthetized mice. No change in tissue PO2 was seen in anesthetized controls.

Reirradiation of head and neck neoplasms using twice-a-day scheduling

Between 1985 and 1988, we have explored the value of twice-a-day (BID) irradiation for the retreatment of head and neck neoplasms. In this pilot study of ten patients we used a schedule of BID irradiation at fraction sizes between 1.4 and 1.6 Gy separated by at least 6 h. Of the four patients were treated with curative intent, three patients received 30 Gy in 20 fractions over twelve days followed within ten days by an interstitial/intracavitary Ir-192 implant boost to doses of 30 to 40 Gy and one patient was treated with a 32 Gy BID boost. Four patients were reirradiated with aggressive palliation and received 45 Gy in 30 fractions over 26 days including a break in the third week. The remaining two patients were treated with palliative intent to 30 Gy in 20 fractions over twelve days. Eight patients were treated for recurrent/persistent or second carcinomas, one for a recurrent glomus jugulare tumor. At a median follow-up of 36 months, ranging from six to 61 months, nine of ten patients experienced excellent symptomatic relief. Five patients are alive and free of tumor, one patient is alive with distant metastases, and two each are dead from local or systemic tumor progression. All four patients retreated for cure are alive with no evidence of local disease. The tolerance and tumor control rate of the BID reirradiation schedule were good with severe late sequelae in only one patient.

Human monoclonal antibodies against Plasmodium falciparum: production, stabilization and characterization

Nine human monoclonal antibodies (MoAbs) recognizing 7 different antigenic structures of blood-stages of the human malarial parasite P. falciparum (Pf) were produced by Epstein-Barr virus transformed B-cell lines (EBV-TCL) with or without fusion to the lymphoblastoid cell line KR4. The peripheral blood B-lymphocytes were obtained from 8 Gambian donors immune to Pf malaria. Two of the EBV-TCL could be expanded and maintained for more than 6 months but neither one could be cloned. Six additional EBV-TCL were stabilized after fusion with the KR4 lymphoblastoid cell line. All resulting hybridomas permitted easy cloning. Some of the MoAbs produced distinct fluorescent staining patterns of asexual Pf blood-stage parasites when using high-resolution digitized video-intensified fluorescence microscopy. Antigens on 195 kD and 155 kD proteins were recognized by 3 and 1 MoAb, respectively, using Western blotting and immunoprecipitation techniques.

Factors influencing cosmetic outcome and complication risk after conservative surgery and radiotherapy for early-stage breast carcinoma

PURPOSE

The study was undertaken to assess the relationship among cosmesis and complications to factors related to disease presentation, surgical and radiotherapeutic technique, and adjuvant systemic therapy in conservative treatment for early-stage breast carcinoma.

PATIENTS AND METHODS

Between 1982 and 1988, 234 women with stage I/II breast carcinoma were treated with conservation therapy by a highly standardized protocol of limited excision and radiotherapy. Radiation boost and/or reexcision were determined by careful quantitation of the normal tissue margin around the primary tumor. Boosts to 20 Gy were preferentially performed with interstitial iridium-192 (192Ir) implants. Axillary node dissections were performed in all patients aged less than 70 years. Adjuvant therapy consisted of cyclophosphamide, methotrexate, (doxorubicin), and fluorouracil (CM[A]F) six to eight times for node-positive premenopausal women and tamoxifen for node-positive or -negative postmenopausal women. Median follow-up was 50 months (range, 20 to 80 months). Cosmesis was graded by defined criteria, and complications were individually scored.

RESULTS

Factors found to impact cosmesis adversely were palpable tumors (P = .046), volume of breast tissue resected (P = .027), reexcision of the tumor bed (P = .01), number of radiation fields (P = .03), radiation boost (P = .01), and chest wall separation (P = .01). There was a trend toward worse cosmesis (P = .062) in patients receiving tamoxifen. Cosmesis was not adversely affected by interstitial implant in spite of a higher prescribed dose. Factors influencing complication risk were axillary node dissection (P = .02), number of lymph nodes harvested (P = .05), and chemotherapy (P = .03).

CONCLUSIONS

Optimal cosmesis and minimal complication risk require careful attention to the technical details of surgery and radiotherapy. The impact of systemic therapies needs to be more thoroughly examined.

Postoperative radiotherapy in head and neck carcinoma with extracapsular lymph node extension and/or positive resection margins: a comparative study

In head and neck carcinoma, the finding of extracapsular lymph node extension and/or positive resection margins portends poor locoregional control and survival. The effectiveness of postoperative radiotherapy in these patients has been controversial due to insufficient studies comparing resected patients with those also receiving radiation. Between 1982 and 1988, 441 radical head and neck resections were performed at the Medical College of Virginia. Pathologic review of these cases identified 125 with extracapsular lymph node extension and/or positive resection margins. Of these, 43 had extracapsular lymph node extension only, 24 had both positive resection margins and extracapsular lymph node extension, and 58 demonstrated positive resection margins only. Surgery alone was performed in 71 of these patients while 54 cases received surgery and postoperative radiotherapy, (combined modality treatment) CMT. Radiotherapy doses ranged from 50 to 70 Gy. The surgery alone and combined modality treatment groups were comparable with respect to the distribution of positive resection margins and extracapsular lymph node extension. Slightly more CMT patients had clinical T4 disease compared with the surgery alone group (22% vs 14%). Slightly fewer combined modality treatment patients had clinical N0 necks than the surgery alone group (20% vs 29%). Multivariate analysis was performed with the variables T, N stages, radiotherapy, margin status, primary tumor sites, microscopic and macroscopic extracapsular lymph node extension, number of positive lymph nodes, number of nodes with extracapsular lymph node extension. Locoregional control was maintained at 5 years in 59% of the combined modality treatment group and 31% of the surgery alone group (p.0001). Subgroup analysis likewise reveals significant differences favoring the combined modality treatment group for positive resection margins only (49% vs 41%; p = .04), extracapsular lymph node extension only (66% vs 31%; p = .03) and extracapsular lymph node extension+positive resection margins (68% vs 0%; p = .001). Adjusted survival also shows a significant benefit of combined modality treatment vs surgery alone for the entire group (72% vs 41%; p = .001). Multivariate analysis revealed that the use of radiotherapy is a strongly favorable variable for local control and adjusted survival. Macroscopic extracapsular lymph node penetration and positive resection margins are unfavorable independent variables for local control. T-stage is the only variable predicting local control in the combined modality group. Extracapsular extension remains an important negative prognostic variable for survival in both treatment groups. In conclusion, this study demonstrates a locoregional control and survival benefit for postoperative radiotherapy in patients with the high risk pathologic findings of extracapsular lymph node extension and positive resection margins.

Proliferative inhibition of human breast carcinoma cells by high concentration estradiol does not alter radiosensitivity

The proliferation of ER+ malignant mammary epithelial cells (MMEC), MCF-7 and T-47D, was markedly inhibited by 10 microM 17 beta-estradiol (E2), while the ER- line, MDA-MB-231, was minimally affected. This concentration of E2 did not alter the proportion of non-viable cells or the plating efficiency. The decrease in proliferation was not associated with any consistent alteration in the cell kinetic profile between lines, though there was clearly no dominant cell cycle re-assortment after a two day incubation. Colony forming ability after exposure to ionizing irradiation was compared for proliferating and confluent MMEC to cells incubated in 10 microM E2 for two days. The presence of E2 resulted in no significant differences for any of the linear quadratic curve fitting parameters or for mean inactivation doses for both subconfluent and confluent cultures. Further, 10 microM E2 had no effect on the ability of cells to recover from split radiation fractions. There were no differences in the amount of DNA single strand break induction with E2, but there was a significant shortening in the repair halftime with E2 for the ER- MDA-MB-231 cells. Though high concentrations of E2 can markedly inhibit the proliferation of ER+ MMEC, this does not alter sensitivity to ionizing irradiation.

Interstitial IR-192 implants of the oral cavity: the planning and construction of volume implants

The success of radioactive implant therapy for head and neck carcinomas depends critically on careful planning and execution of the implant procedure. In this paper we discuss our experience with oral tongue and floor of mouth implants, and some innovations introduced to facilitate these procedures. Implants were carried out using standard angiocatheters modified with magnetic caps at the open end and terminated with Teflon spacers and lead shot at the closed end. The importance of accurate source placement and careful determination of the target dose rate is discussed with numerical examples. Differential hot-loading of sources is clearly indicated in cases of extension of the lesion to the dorsal or lateral tongue surface. For dorsal surface extension the use of Teflon spacers at the closed ends of the catheters helps to ensure adequate coverage of the target volume with the higher dose region enclosing the demonstrable tumor. All 10 patients implanted with this technique are controlled without recurrence at a median follow-up of 38 months. The two complications observed appeared to be associated with excessive hot-loading of edge plane sources.

Effects of tamoxifen and protein kinase C inhibitors on hyperthermic cell killing

The effects of the anti-estrogen, tamoxifen, and the protein kinase C inhibitor, 1-(5-isoquinolinylsulfonyl)2-methylpiperazine (H7), on hyperthermic cytotoxicity were studied. Three cell lines were used, a human colon cancer cell line (HT-29), a human mammary carcinoma cell line (MCF-7), and Chinese hamster V79 lung fibroblasts. With all three cell lines, tamoxifen at concentrations greater than 7.5 microM during heating or with a 3-hr exposure prior to heating significantly sensitized cells to heat. When cells were preincubated with 10-20 microM tamoxifen for 1-2 hr at 37 degrees C prior to heat treatment, washed free of extracellular tamoxifen, heated to generate thermoresistance, and examined 18 hr later for thermoresistance, tamoxifen treated HT-29 and MCF-7 cells were significantly more heat sensitive than thermotolerant controls not previously exposed to tamoxifen. In contrast, the degree of induced thermoresistance of V79 cells was unchanged after tamoxifen treatment. H7, but not its structural analogue and low affinity protein kinase C inhibitor, HA1004, also sensitized cells to heat. Neither H7 nor HA1004 had any apparent effect on the degree of heat-induced thermoresistance in the three cell lines tested.