The New Trend of Pre-pectoral Breast Reconstruction: An Objective Evaluation of the Quality of Online Information for Patients Undergoing Breast Reconstruction.

The Web has increasingly become the major source of information about health care, and patients who need to undergo breast reconstruction often use the internet to acquire an initial knowledge on the subject. We would like to present our study that investigates the quality of published information on pre-pectoral breast reconstruction. We searched the term "Pre-pectoral breast reconstruction" on Google® and Yahoo®. Forty-two web sites were selected and underwent qualitative and quantitative assessment using the expanded EQIP tool. The analysis of document contents showed a critical lack of information about qualitative risks and side-effects descriptions, treatment of potential complications, alert signs for the patient and precautions that the patient may take. Health professionals should inform patients about the potential difficulties of identifying reliable informational web sites about pre-pectoral breast reconstruction. The quality of available information should be improved, especially the important topics included in the content data section of the modified EQIP tool.Level of Evidence IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

A phase II trial of short course fludarabine, mitoxantrone, rituximab followed by 9°Y-ibritumomab tiuxetan in untreated intermediate/high-risk follicular lymphoma.

BACKGROUND: A prospective, single-arm, open-label, multicenter, nonrandomised phase II trial to evaluate efficacy and safety of short fludarabine, mitoxantrone, and rituximab (FMR) induction followed by radioimmunotherapy, in untreated, intermediate/high-risk follicular non-Hodgkin's lymphoma (NHL) patients. PATIENTS AND METHODS: Fifty-five patients were treated using a sequential treatment schedule of four induction cycles of FMR chemoimmunotherapy, and a subsequent consolidating single administration of (90)Y-ibritumomab tiuxetan ((90)Y-IT), 8-14 weeks later. Patients were eligible for radioimmunotherapy if at least in partial response (PR) after induction, with normal platelet and granulocyte counts and a bone marrow infiltration ≤ 25%. Primary study end points were response rate and hematologic toxic effects; secondary end points were overall survival (OS) and progression-free survival (PFS). RESULTS: All the 55 patients received four induction cycles with an overall response rate of 96% (38 complete responses [CR] and 15 PR). Fifty-one patients (38 in CR and 13 in PR) received (90)Y-IT. By the end of the treatment, 49/55 patients achieved a CR. With a median follow-up of 21 months, the estimated 3-year PFS was 81% and the 3-year OS 100%. CONCLUSIONS: This study has established feasibility, tolerability, and efficacy of a regimen composed by short FMR induction with (90)Y-IT consolidation in untreated intermediate/high-risk follicular NHL patients.

The effects of COVID-19 pandemic on elective post-bariatric surgery waiting list: a single Plastic Surgery Center investigation.

OBJECTIVE: After massive weight loss, patients that meet specific criteria can be inserted in an ad-hoc post-bariatric surgery list in order to be subjected to body contouring procedures. During COVID-19 pandemic, the Italian National Health System has been overwhelmed by the continue load of life-threatening patients that needed medical assistance. Plastic surgery practice enormously scaled back during this period and this fact greatly affected elective procedures waiting lists. The aim of our study is to analyze how the lockdown and its related sanitary policies affected post-bariatric patients' behaviors towards the delay of their procedure. PATIENTS AND METHODS: A 7-item questionnaire was administered to all patients. Change in the desire to be subjected to body contouring procedures was recorded. Smoking status, level of training during quarantine and psychological co-morbidities were also evaluated. RESULTS: 124 patients completed the questionnaire. Data analysis showed that none of them encountered a decrease of the desire to be subjected to post-bariatric plastic surgery procedures. CONCLUSIONS: The present study showed that all the patients in the waiting list did not modify their interest in being subjected to post-bariatric surgery procedures, even though the waiting time increased.

Prepectoral breast reconstruction with TiLoop® Bra Pocket: a single center prospective study.

OBJECTIVE: In the last decades, immediate breast reconstruction (IBR) raised in frequency, and prepectoral positioning of the implant is becoming the trend nowadays. The aim of this paper is to describe our case series in IBR with prepectoral implant placement and complete coverage of it with the TiLoop® Bra titanium-coated polypropylene mesh (TCPM), pre-shaped as a pocket. PATIENTS AND METHODS: Eighteen women with breast tumors were selected and underwent mono- or bilateral mastectomies and prepectoral IBR with tissue expanders or prostheses. After the prepectoral lodge was ready, the implants were inserted into TiLoop® Bra Pocket meshes and positioned over the pectoralis major muscle fascia. The mean surgical time of their positioning was four minutes. RESULTS: This preliminary study showed meaningful results in prepectoral IBR with TiLoop® Bra Pocket covering the implants, for we observed a reduction of implant's exposure time and risk of bacterial contamination. Of the 18 patients that underwent this procedure, only three presented complications that resolved in a maximum of four weeks. CONCLUSIONS: A considering reduction of surgical time in implant positioning was achieved, lowering exposure time and risk of complications as infection.

Aqueous extract of Arbutus unedo inhibits STAT1 activation in human breast cancer cell line MDA-MB-231 and human fibroblasts through SHP2 activation.

Arbutus unedo L. has been for a long time employed in traditional and popular medicine as an astringent, diuretic, urinary anti-septic, and more recently, in the therapy of hypertension and diabetes. Signal transducer and activator of transcription 1 (STAT1) is a fascinating and complex protein with multiple yet contrasting transcriptional functions. Although activation of this nuclear factor is finely regulated in order to control the entire inflammatory process, its hyper-activation or time-spatially erroneous activation may lead to exacerbation of inflammation. The modulation of this nuclear factor, therefore, has recently been considered as a new strategy in the treatment of inflammatory diseases. In this study, we present data showing that the aqueous extract of Arbutus unedo's leaves exerts inhibitory action on interferon-gamma (IFN-gamma) elicited activation of STAT1, both in human breast cancer cell line MDA-MB-231 and in human fibroblasts. This down-regulation of STAT1 is shown to result from a reduced tyrosine phosphorylation of STAT1 protein. Evidence is also presented indicating that the inhibitory effect of this extract may be mediated through enhancement of tyrosine phosphorylation of SHP2 tyrosine phosphatase. The modulation of this nuclear factor turns out into the regulation of the expression of a number of genes involved in the inflammatory response such as inducible nitric oxide synthase (iNOS) and intercellular adhesion molecule-1 (ICAM-1). Taken together, our results suggest that the employment of the Arbutus unedo aqueous extract is promising, at least, as an auxiliary anti-inflammatory treatment of diseases in which STAT1 plays a critical role.

Detection of dibenzo[a,l]pyrene-induced H-ras codon 61 mutant genes in preneoplastic SENCAR mouse skin using a new PCR-RFLP method.

One of the key events in tumor initiation in mouse skin is mutational activation of the H-ras gene. Papillomas induced by the most carcinogenic environmental polycyclic aromatic hydrocarbon (PAH), dibenzo[a,l]pyrene (DB[a,l]P), in SENCAR mouse skin contain a specific H-ras codon 61 (CAA-->CTA) mutation. We describe here detection of these mutations in preneoplastic skin by measuring the frequency of an induced XbaI RFLP, created by the mutation. Development of the PCR-XbaI RFLP method, sensitive enough to detect 1 codon 61 mutant allele among 10,000 wild-type genes, is described. The results indicate that codon 61 mutations are induced 1 day (0.1%) after DB[a,l]P treatment on mouse skin, reach a high value (5%) by day 3, rapidly decline between days 7-9 and increase again during the clonal expansion of pre-papillomas into tumors. The detection of codon 61 mutations 1 day after DB[a,l]P exposure suggests that mutations occurred by pre-replication misrepair.

Evidence that a burst of DNA depurination in SENCAR mouse skin induces error-prone repair and forms mutations in the H-ras gene.

Treatment of SENCAR mouse skin with dibenzo[a,l]pyrene results in abundant formation of abasic sites that undergo error-prone excision repair, forming oncogenic H-ras mutations in the early preneoplastic period. To examine whether the abundance of abasic sites causes repair infidelity, we treated SENCAR mouse skin with estradiol-3,4-quinone (E(2)-3,4-Q) and determined adduct levels 1 h after treatment, as well as mutation spectra in the H-ras gene between 6 h and 3 days after treatment. E(2)-3,4-Q formed predominantly (> or =99%) the rapidly-depurinating 4-hydroxy estradiol (4-OHE(2))-1-N3Ade adduct and the slower-depurinating 4-OHE(2)-1-N7Gua adduct. Between 6 h and 3 days, E(2)-3,4-Q induced abundant A to G mutations in H-ras DNA, frequently in the context of a 3'-G residue. Using a T.G-DNA glycosylase (TDG)-PCR assay, we determined that the early A to G mutations (6 and 12 h) were in the form of G.T heteroduplexes, suggesting misrepair at A-specific depurination sites. Since G-specific mutations were infrequent in the spectra, it appears that the slow rate of depurination of the N7Gua adducts during active repair may not generate a threshold level of G-specific abasic sites to affect repair fidelity. These results also suggest that E(2)-3,4-Q, a suspected endogenous carcinogen, is a genotoxic compound and could cause mutations.

The approach to understanding aromatic hydrocarbon carcinogenesis. The central role of radical cations in metabolic activation.

Polycyclic aromatic hydrocarbons (PAH) are carcinogens requiring metabolic activation to react with cellular macromolecules, the initial event in carcinogenesis. Cytochrome P450 mediates binding of PAH to DNA by two pathways of activation. One-electron oxidation to form radical cations is the major pathway of activation for the most potent carcinogenic PAH, whereas monooxygenation to form bay-region diol epoxides is generally a minor pathway. For benzo[a]pyrene and 7,12-dimethylbenz[a]-anthracene, 80% and 99%, respectively, of the DNA adducts formed by rat liver microsomes or in mouse skin arise via the radical cation. Therefore, studies of PAH activation should begin by considering one-electron oxidation as the primary mechanism.

Estrogens as endogenous genotoxic agents--DNA adducts and mutations.

Estrogens induce tumors in laboratory animals and have been associated with breast and uterine cancers in humans. In relation to the role of estrogens in the induction of cancer, we examine formation of DNA adducts by reactive electrophilic estrogen metabolites, formation of reactive oxygen species by estrogens and the resulting indirect DNA damage by these oxidants, and, finally, genomic and gene mutations induced by estrogens. Quinone intermediates derived by oxidation of the catechol estrogens 4-hydroxyestradiol or 4-hydroxyestrone may react with purine bases of DNA to form depurinating adducts that generate highly mutagenic apurinic sites. In contrast, quinones of 2-hydroxylated estrogens produce less harmful, stable DNA adducts. The catechol estrogen metabolites may also generate potentially mutagenic oxygen radicals by metabolic redox cycling or other mechanisms. Several types of indirect DNA damage are caused by estrogen-induced oxidants, such as oxidized DNA bases, DNA strand breakage, and adduct formation by reactive aldehydes derived from lipid hydroperoxides. Estradiol and the synthetic estrogen diethylstilbestrol also induce numerical and structural chromosomal aberrations and several types of gene mutations in cells in culture and in vivo. In conclusion, estrogens, including the natural hormones estradiol and estrone, must be considered genotoxic carcinogens on the basis of the evidence outlined in this chapter.

Evidence for distinct binding sites in the cumene hydroperoxide-dependent metabolism of benzo[a]pyrene catalyzed by cytochrome P-450.

A few constitutive cytochrome P-450 isozymes in male rat liver microsomes catalyzed the metabolism of benzo[a]pyrene (BP) in cumene hydroperoxide (CHP)-dependent reactions, which produced predominantly 3-hydroxyBP and BP quinones. This process varied with the concentration of CHP. At 0.05 mM CHP, 3-hydroxyBP was the major metabolite. An increase in CHP concentration reduced 3-hydroxyBP formation but increased the level of BP quinones. This change in metabolic profile was reversed by preincubation with pyrene. Pyrene selectively inhibited quinone formation and enhanced 3-hydroxyBP formation. Naphthalene, phenanthrene and benz[a]anthracene nonspecifically inhibited total metabolism. BP binding to microsomal protein correlated with quinone formation, suggesting a common precursor reactive intermediate. BP metabolism by female rat liver microsomes also depended on CHP concentration but was much less effective than that in the male. With females, quinones were the major metabolites at all CHP concentrations, and their formation was again modulated by pyrene. These data indicate that two distinct binding sites are responsible for the formation of 3-hydroxyBP and BP quinones.

Dependence of benzo[a]pyrene metabolic profile on the concentration of cumene hydroperoxide with uninduced and induced rat liver microsomes.

The effect of cumene hydroperoxide (CHP) in microsomal metabolism of benzo [a]pyrene (BP) was studied using liver microsomes from mature male Wistar rats induced with phenobarbital (PB), 3-methylcholanthrene (MC), Aroclor 1254 or olive oil (uninduced). In contrast to NADPH-supported metabolism, these inducers did not increase the CHP-dependent metabolism. Total BP metabolism was dependent on CHP concentration and was maximal at 0.15 mM, except for PB-induced microsomes, which had a maximum at 0.5 mM CHP. At 0.05 mM CHP, the major metabolites were phenols. However, increasing CHP concentration enhanced the formation of dihydrodiols, quinones and protein-bound BP but reduced phenol production. At and above 0.15 mM CHP, the profile of BP metabolites was essentially constant, with at least 66% quinones but no more than 10% phenols. The effect of CHP on inhibition of phenol formation and enhancement of quinone formation was reversed by preincubation of microsomes with BP or by increasing BP concentration. These results suggest that CHP-dependent metabolism of BP is selectively mediated by constitutive cytochrome P-450 isozyme(s) and that two forms of BP binding sites exist in cytochrome P-450 isozymes and are responsible for the hydroxylation of BP at C-3 and C-6.

Radical cations in the horseradish peroxidase and prostaglandin H synthase mediated metabolism and binding of benzo[a]pyrene to deoxyribonucleic acid.

Metabolism and DNA binding studies are used to investigate mechanisms of activation for carcinogens. In this paper we describe metabolism of benzo[a]pyrene (BP) and 6-fluorobenzo[a]pyrene (6-FBP) by two peroxidases, horseradish peroxidase (HRP) and prostaglandin H synthase (PHS), which are known to catalyze one-electron oxidation. In addition, binding of BP and BP quinones to DNA was compared in the two enzyme systems. The only metabolites formed from BP or 6-FBP by either enzyme were the quinones, BP 1,6-, 3,6- and 6,12-dione. HRP metabolized BP and 6-FBP to the same extent and produced the same proportion of each dione from both compounds, approximately 40% each of BP 1,6- and 3,6-dione and 20% BP 6,12-dione. PHS formed twice as much quinones from BP as from 6-FBP and produced relatively more BP 3,6-dione from 6-FBP (46%) compared to BP (30%) and relatively less BP 6,12-dione from 6-FBP (16%) compared to BP (33%). Removal of the fluoro substituent in the metabolism of 6-FBP is consistent only with an initial one-electron oxidation of the substrate. Since BP quinones were the only products formed in HRP- and PHS-catalyzed activation of BP, their possible binding to DNA was compared to that of BP. No significant binding of BP quinones to DNA occurred with either HRP or PHS. These results, coupled with those from other chemical and biochemical experiments, demonstrate that HRP- and PHS-catalyzed one-electron oxidation of BP to its radical cation is the mechanism of formation of quinones and binding of BP to DNA.

Radical cations as precursors in the metabolic formation of quinones from benzo[a]pyrene and 6-fluorobenzo[a]pyrene. Fluoro substitution as a probe for one-electron oxidation in aromatic substrates.

Three classes of products are formed when benzo[a]pyrene (BP) is metabolized by cytochrome P-450: dihydrodiols, phenols and the quinones, BP 1,6-, 3,6- and 6,12-dione. These products have been thought to arise from attack of a catalytically-activated electrophilic oxygen atom. In this paper we report chemical and biochemical experiments which demonstrate that BP quinones arise from an initial one-electron oxidation of BP to form its radical cation. BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-chlorobenzo[a]pyrene (6-ClBP), and 6-bromobenzo[a]pyrene (6-BrBP) were metabolized by uninduced and 3-methylcholanthrene-induced rat liver microsomes in the presence of NADPH or cumene hydroperoxide (CHP) as cofactor. BP and 6-FBP produced similar metabolic profiles with induced microsomes in the presence of NADPH or 2 mM CHP. With NADPH both compounds produced dihydrodiols, phenols and quinones, whereas with CHP, they yielded only quinones. Metabolism of BP and 6-FBP was also similar with uninduced microsomes and 2 mM CHP, yielding the same BP quinones. With uninduced microsomes in the presence of NADPH, BP produced all three classes of metabolites, whereas 6-FBP afforded only quinones. At a low concentration of CHP (0.10 mM), BP was metabolized to phenols and quinones, whereas 6-FBP gave only quinones. 6-ClBP and 6-BrBP were poor substrates, forming metabolites only with induced microsomes and NADPH. One-electron oxidation of BP by Mn(OAc)3 occurred exclusively at C-6 with predominant formation of 6-acetoxyBP and small amounts of BP quinones. In the one-electron oxidation of 6-FBP by Mn(OAc)3, the major products obtained were 6-acetoxyBP, a mixture of 1,6- and 3,6-diacetoxyBP, and BP quinones. Reaction of BP and 6-FBP radical cation perchlorates with water produced the same BP quinones. Conversely, electrophilic substitution of 6-FBP with bromine or deuterium ion afforded C-1 and/or C-3 derivatives with retention of the fluoro substituent at C-6. These results indicate that metabolic formation of BP quinones from BP and 6-FBP can only derive from their intermediate radical cation.

Isomer differentiation in 7, 12-dimethylbenz[a]anthracene-pyridine adducts by fast atom bombardment tandem mass spectrometry.

Three isomeric 7,12-dL-nethylbenz[α]anthracene-pyridine adduct salts, namely.. the 5-N-pyridinium-7,12-dimethylbenz[α]anthracene perchlorate, the 7-N-pyridiniummethylene-12methylbenz[ α]anthracene picrate, and the 7-methyl-12-N-pyridiniummethylenebenz[ α]anthracene picrate, were studied by fast atom bombardment tandem mass spectrometry using high energy collisional-activated dissociation (CAD). The CAD mass spectra of the molecular cations and the (M - pyridine)(+) ions allow one to distinguish positional isomers on the basis of daughter ion peak height ratios. The differences in the CAD mass spectra of the (M - pyridine)(+) ions are probably due in part to formation of isomer-specific fused-ring tropyliumions.

Mass spectrometric methods for distinguishing structural isomers of glutathione conjugates of estrone and estradiol.

Collisionally activated decompositions (CAD) of [M + H]+ ions from two sets (estrone and estradiol) of three isomeric glutathione (GSH) conjugates were studied by using five tandem mass spectrometric methods: (1) low energy (LE) CAD in an ion trap, (2) LE CAD in a triple quadrupole, (3) electrospray ionization (ESI)-source CAD in a tandem four sector, (4) high energy (HE) CAD of both ESI-produced and fast-atom bombardment (FAB)-produced ions in a tandem four-sector mass spectrometer, and (5) metastable-ion decompositions of FAB-produced ions. Four types of fragment ions are produced. The first type, formed from cleavage of the peptide backbone, gives rise to modified b2, modified y2, y2, and b1 ions. These fragments are observed with all the methods and show that the catechol estrogen attachment is at the cysteine moiety of the GSH. Internal fragment ions are the second type, and they also support that the modification is at cysteine. The third type involves fragmentation of the C-S bond to give an ion containing the steroid bonded to the sulfur. The fourth type of fragment ion is similar to the third but involves oxidation of the steroid ring and reduction of the GSH moiety; it is the most isomer specific of the four. The isomer-specific ions are of relatively low abundance in the product-ion spectra taken on the triple quadrupole and ion trap, but their abundances can be improved by increasing the collision energy. ESI source-CAD and the HE-CAD spectra of the isomers are the most distinctive because abundant product ions of all four types are seen in a single spectrum.

Matrix design for matrix-assisted laser desorption ionization: Sensitive determination of PAH-DNA adducts.

Two matrices, 4-phenyl-α-eyanocinnamic acid (PCC) and 4-benzyloxy-α-eyanocinnamic acid (BCC), were identified for the determination of polycyclic aromatic hydrocarbon (PAH) adducts of DNA bases by matrix-assisted laser desorption ionization. These matrices were designed based on the concept that the matrix and the analyte should have structural similarities. PCC is a good matrix for the desorption of not only PAH-modified DNA bases, but also PAHs themselves and their metabolites. Detections can be made at the femtomolar level.

Role of radical cations in aromatic hydrocarbon carcinogenesis.

Carcinogenic activation of polycyclic aromatic hydrocarbons (PAH) involves two main pathways: one-electron oxidation and monooxygenation. One-electron oxidation produces PAH radical cations, which can react with cellular nucleophiles. Results from biochemical and biological experiments indicate that only PAH with ionization potentials below ca. 7.35 eV can be metabolically activated by one-electron oxidation. In addition, the radical cations of carcinogenic PAH must have relatively high charge localization to react effectively with macromolecules in target cells. Metabolic formation of PAH quinones proceeds through radical cation intermediates. Binding of benzo[a]pyrene (BP) to mouse skin DNA occurs predominantly at C-6, the position of highest charge localization in the BP radical cation, and binding of 6-methyl BP to DNA in mouse skin yields a major adduct with the 6-methyl group bound to the 2-amino group of deoxyguanosine. Studies of carcinogenicity by direct application of PAH to rat mammary gland indicate that only PAH with ionization potentials low enough for activation by one-electron oxidation produce tumors in this target tissue. These constitute some of the results which provide evidence for the involvement of one-electron oxidation in PAH carcinogenesis.

Carcinogenicity of aromatic hydrocarbons directly applied to rat mammary gland.

To obtain some initial evidence on the mechanism(s) of activation of PAH in rat mammary gland, we studied the carcinogenicity of a series of PAH directly applied to this tissue. A series of PAH which are or are not expected to be activated by one-electron oxidation because of their low or high ionization potential (IP), respectively, were tested. The compounds were dispersed as fine powders on an exposed mammary gland of female Sprague-Dawley rats. 5-Methylchrysene, dibenz[a,h]anthracene and benz[a]anthracene, which have relatively high IP, were inactive. In contrast, three PAH with relatively low IP, 7,12-dimethylbenz[a]anthracene, benzo[a]pyrene (BP), and 3-methylcholanthrene (MC), were potent carcinogens, 6-MethylBP, with low IP, and 7-methyl-benz[a]anthracene, with borderline IP, elicited only mesenchymal tumors, whereas BP 7,8-dihydrodiol and cyclopenta[cd]pyrene were inactive. A series of MC derivatives substituted at C-1 or C-2 was tested. Substituents at C-1, the position of activation in the one-electron oxidation pathway, generally suppressed carcinogenic activity. Substitution at C-2 did not eliminate carcinogenic activity, with the exception of MC2-one. These results provide initial information suggesting that one-electron oxidation may be a mechanism of activation for PAH in the mammary gland.

Tumorigenicity of 6-halogenated derivatives of benzo[a]pyrene in mouse skin and rat mammary gland.

Studies of the tumorigenicity of 6-halogenated derivatives of benzo[a]pyrene (BP) can provide evidence about the role of the 6 position in the carcinogenic activation of BP. Female Swiss and A-strain mice were treated on the skin with BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-chlorobenzo[a]pyrene (6-C1BP), 6-bromobenzo[a]pyrene (6-BrBP) and 6-iodobenzo[a]pyrene (6-IBP) by repeated application, and in some cases by initiation-promotion. While BP was more potent than 6-FBP, only these two compounds exhibits tumor-initiating and carcinogenic activity in mouse skin. Female Sprague-Dawley rats were treated with BP, 6-FBP, 6-ClBP, and 6-BrBP by intramammillary injection. BP and 6-FBP induced high levels of mammary epithelial tumors and fibrosarcomas. 6-ClBP elicited only a high percentage of fibrosarcomas, whereas 6-BrBP induced a few adenocarcinomas. These results indicate that chloro or bromo substitution at C-6 in BP reduces or eliminates carcinogenic activity. Conversely, 6-FBP, from which the fluoro substituent has been chemically and metabolically removed by one-electron oxidation, displays a moderate carcinogenic activity which is consistent with activation by either one-electron oxidation or monooxygenation.

Tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland of fluorinated derivatives of benzo[a]pyrene and 3-methylcholanthrene.

Comparative studies of tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland were conducted with benzo[a]pyrene (BP) and 3-methylcholanthrene (MC) derivatives. SENCAR mice were initiated with BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-methylBP, 7-FBP, 8-FBP, 9-FBP, 10-FBP, or 10-azaBP and promoted with tetradecanoyl phorbol acetate. The same compounds plus BP 7,8-dihydrodiol were tested by intramammillary injection in female Sprague-Dawley rats. Tumor-initiating activity in mice and/or carcinogenicity in rats were observed for BP, 6-methylBP, 6-, 7-, 8-, and 10-FBP, whereas 9-FBP was inactive in both experiments and 10-azaBP was only marginally active in the mammary gland. BP 7,8-dihydrodiol was carcinogenic in rat mammary gland, although it was less potent than BP. MC, 8-FMC, 10-FMC, and 3-methylcholanthrylene were also tested in Sprague-Dawley rats by intramammillary injection. All compounds were carcinogenic, with MC displaying the most potent activity. The less potent carcinogenic activity of BP 7,8-dihydrodiol in the mammary gland, compared with BP, and the moderate-to-weak tumor-initiating and/or carcinogenic activity of 7-, 8-, and 10-FBP suggest that the bay-region diol-epoxide pathway does not play a significant role in the activation of BP in these two target tissues. Similarly, the carcinogenic activity of 8-FMC and 10-FMC, in which the bay-region diol-epoxide pathway is blocked, suggests that this mechanism of activation is not important in the carcinogenicity of MC in rat mammary gland.