Mutational profiling of the RAS, PI3K, MET and b-catenin pathways in cancer of unknown primary: a retrospective study of the Hellenic Cooperative Oncology Group.

Cancer of unknown primary origin (CUP) had a poor prognosis, determined by clinico-histological characteristics, partly due to the lack of insights on its biology. We screened tumour DNA from 87 patients with CUP for CTNNB1 (coding exons 2,3,4,5), MET (coding exon 18), PIK3CA (coding exons 9,20), KRAS (coding exons 1,2), BRAF (coding exon 15) gene mutations by using dd-sequencing and evaluated their impact on prognosis. Mutated gene incidences in the 87 CUP cases were: KRAS 11 (12.6 %), BRAF 5 (5.7 %), PIK3CA 8 (9 %), MET 6 (6.7 %) and CTNNB1 18 (20.7 %). Several mutations in the KRAS gene were not the commonly encountered mutations in other solid tumours. Activating mutations were observed in 10.2 % in KRAS, 4.5 % in BRAF, 6.6 % in PIK3CA, 4.5 % in MET, and 19.5 % in CTNNB1. Activating mutations in PIK3CA coding exon 9 were inversely correlated with MET coding exon 18 activating mutations (p = 0.036). MET activating mutations were prognostic for poor Progression-Free Survival (median PFS 5 vs 9 months, p = 0.009) and Overall Survival (median OS 7 vs 20 months, p = 0.005). The complex profile of either CTNNB1 or MET mutations also had an adverse prognostic significance (median OS 11 vs 21 months, p = 0.015). No other gene mutation exhibited prognostic significance. In multivariate analysis, poor performance status, male gender, visceral disease and adenocarcinoma histology, but not gene mutations, were independently associated with poor patient outcome. CTNNB1 gene mutations are frequent, and along with MET mutations have an adverse prognostic effect in patients with CUP.

Vascular endothelial growth factor polymorphisms and clinical outcome in patients with metastatic breast cancer treated with weekly docetaxel.

The aim of the study was to evaluate the association of vascular endothelial growth factor (VEGF) genotypes with treatment efficacy in a phase II trial. This study evaluated weekly docetaxel, as first-line treatment for metastatic breast cancer. Existing data from in vitro and animal model experiments suggest that docetaxel at low doses has anti-angiogenic activity. DNA was extracted from blood samples of 86 patients participating in the trial. Genotyping was performed for selected single-nucleotide polymorphisms (SNPs; VEGF-2578, -1498, -1154, and +936). Moreover, due to the highly polymorphic nature of the studied areas, we were able to analyze additional registered SNPs. All candidate genotypes were evaluated for associations with overall survival (OS), progression-free survival (PFS) and response rate. The VEGF-1154 GG genotype was more frequent in patients not responding to treatment compared with responders (42.9% vs 0.0%, P=0.048). Moreover, the VEGF-2578 AA genotype was associated with longer PFS compared with CC (hazard ratio (HR)=0.40; 95% confidence interval (CI) 0.17-0.98; pairwise P=0.0457). Patients with the VEGF-1190 GG genotype demonstrated shorter PFS compared with those with the alternative genotypes (GA and AA) combined (HR=3.85; 95% CI: 1.20-12.50; P=0.0224). In addition, the VEGF-2551/-2534 homozygous del18bp and VEGF-2430/-2425 homozygous ins1bp genotypes were associated with worse PFS compared with no deletion and no insertion, respectively (HR=2.49; 95% CI: 1.02-6.07; pairwise P=0.0442 and HR=2.57; 95% CI: 1.05-6.27; pairwise P=0.0385, respectively). Furthermore, patients with the VEGF-1498 CC genotype exhibited longer median OS compared with those with the alternatives genotypes (CT and TT) combined (HR=0.27; 95% CI: 0.08-0.89; P=0.0311). In multivariate analysis, the VEGF-2578 AA genotype retained its significance (P=0.0220) for PFS. Our results support the association of specific VEGF genotypes with clinical outcome in patients with metastatic breast cancer treated with a potentially anti-angiogenic regimen, such as weekly docetaxel. However, current results should be validated prospectively in larger cohorts.

Cyclin D1, EGFR, and Akt/mTOR pathway. Potential prognostic markers in localized laryngeal squamous cell carcinoma.

INTRODUCTION: EGFR (epidermal growth factor receptor), cyclin D1 and Akt/mTOR pathways are active in head and neck cancer. The aim of this study was to explore biomarker expression, their correlations with clinicopathological parameters and their prognostic utility in a cohort of patients with localized squamous laryngeal carcinoma. PATIENTS AND METHODS: We assessed relative messenger RNA expression of EGFR, Akt1, 2, and 3, mTOR and CCND1, copy number variants of the EGFR and CCND1 genes and immunohistochemical protein expression of EGFR, p-Akt308, p-Akt473, pmTOR, PTEN, p53 and cyclin D1 in paraffin-embedded tissue samples of localized laryngeal carcinomas. RESULTS: In 289 patients with T3-4 (77.8%), node-negative (84.1%) tumors of the larynx, high EGFR and CCND1 mRNA correlated with no or ex-smoking, (p = 0.003 and p = 0.029, respectively), while low Akt3 mRNA correlated with alcohol abuse, N0 stage, total laryngectomy, and absence of neck dissection. At a median follow-up of 74.5 months, high mTOR mRNA expression was marginally associated with shorter disease-free survival (hazard ratio [HR] = 1.54; p = 0.093) and high Akt3 mRNA with shorter overall survival (HR = 1.49; p = 0.0786), in univariate analysis. In multivariate analysis, node-positive status, subglottic-transglottic location, surgery other than total laryngectomy and mTOR/CCND1 mRNA interaction with a hazard ratio of 2.16 (p value for interaction: 0.0010) were independent predictors of relapse, while node-positive status and subglottic-transglottic location were associated with higher risk for death. CONCLUSION: In localized laryngeal cancer, clinicopathological parameters and an interaction of high mTOR and CCND1 mRNA expression were found to be associated with poor patient outcome.

Prognostic utility of angiogenesis and hypoxia effectors in patients with operable squamous cell cancer of the larynx.

Angiogenesis is active in localised laryngeal squamous cell carcinoma. We assessed relative messenger RNA (mRNA) and immunohistochemical (IHC) expression of Vascular Endothelial Growth Factors (VEGF) A, B, C, their receptors VEGFR1, 2, 3, Neuropilins 1, 2 (NRP1, 2) and Hypoxia-Inducible Factor 1A (HIF1A) in paraffin-embedded localised laryngeal carcinomas. In 289 patients with T3-4 (77.8%), node-negative (84.1%) tumours of the larynx, high VEGFA and VEGFR1 mRNA correlated with advanced T stage, while low VEGFB and VEGFC mRNA with alcohol abuse and supraglottic primary, respectively (p<0.05). Age <55 was associated with high IHC expression of VEGFA, C and poor tumour differentiation with high IHC VEGFA. At a median follow-up of 74.5months, patients with VEGFR1-high tumours had significantly poorer disease-free survival (Hazard Ratio [HR] 1.93, p=0.008) and shorter overall survival (OS, HR 1.71, p=0.041). An association with dismal OS was seen for high VEGFR3 tumoural mRNA expression (HR 1.76, p=0.02). IHC expression of VEGF family proteins in the tumour was not prognostic and had poor concordance with mRNA expression (kappa<0.1, p=NS). In multivariate analysis, node-positive status, non-supraglottic localization, high VEGFR1 mRNA and high IHC VEGFA expression were significantly associated with relapse, while node-positive status, high VEGFR1 and VEGFC mRNA expression in the tumour with risk of death. In laryngeal cancer, upregulated mRNA expression of VEGFR1 and VEGFC is associated with poor patient outcome.

Evaluation of the association of PIK3CA mutations and PTEN loss with efficacy of trastuzumab therapy in metastatic breast cancer.

Trastuzumab (T) is effective in metastatic breast cancer (MBC) with HER2 overexpression and/or amplification, but resistance to T develops in a significant number of HER2-positive patients. Understanding the mechanisms of resistance is critical to the care of these patients. Formalin-fixed paraffin-embedded tumor tissue samples were collected from 256 patients with T-treated MBC. Clinical information was collected retrospectively from the patients' medical records. Central review of HER2 status by fluorescent in situ hybridization (FISH) and/or immunohistochemistry (IHC) revealed that of the 227 eligible patients only 139 (61%) were truly HER2-positive. PTEN, ER, PgR, and Ki67 were evaluated by IHC, while PTEN status was evaluated by FISH as well. PIK3CA mutations were identified with single nucleotide polymorphism (SNP) genotyping. Median time to progression (TTP) was 14.4 months for the HER2-positive and 10.3 for the HER2-negative patients (log-rank, P = 0.22). Survival from the initiation of T (survivalT) was 50.4 months for the HER2-positive and 35.3 for the HER2-negative subgroups (P = 0.006). Higher risk of progression was associated with HER2-positive status and the presence of PIK3CA mutations (P = 0.014). PTEN loss, as determined by IHC, was associated with lower survivalT in the whole population (P = 0.029) and in the HER2-positive population (P = 0.017). PIK3CA mutations and/or PTEN loss status were evaluated together as a single parameter, to estimate the impact of activation of the PI3K/AKT molecular pathway, and it was significantly associated with both decreased TTP (P = 0.003 in the total population, P = 0.004 in HER2-positive patients) and survival (survivalT, P = 0.011 in total, P = 0.006 in HER2-positive). In this trastuzumab-treated breast cancer population, PIK3CA activating mutations were associated with shorter TTP and PTEN loss with decreased survival. The activation of the PI3K/AKT pathway from either defect was associated with both TTP and survival, indicating the adverse effect of this pathway's status on trastuzumab efficacy.

EGFR expression and activation are common in HER2 positive and triple-negative breast tumours.

EGFR has been associated with unfavourable prognosis in patients with triple-negative breast carcinomas, although little is known about EGFR activation in these tumours. In a series of breast carcinomas (archived formalin fixed tumours, n=100), we investigated EGFR phosphorylation status at Tyr992 (pEGFR-Y992) and Tyr1068 (pEGFR-Y1068) by immunohistochemistry, along with EGFR protein expression (extracellular domain), gene amplification status (fluorescent in situ hybridization) and conventional clinicopathologic parameters. EGFR protein was present in 21.9%, while phosphorylation at Y1068 and Y992 was observed in 27.8% and 50.5% of tumours, respectively. None of the tumours showed EGFR gene amplification, whereas 21.1% exhibited chromosome 7 polysomy. The above EGFR parameters were usually not simultaneously detected and were not associated with each other. High grade (p=0.003), lymph node positive (p=0.045), estrogen receptor (ER) negative (p<0.001) tumours often expressed EGFR protein. EGFR-Y992 and Y1068 phosphorylation was inversely associated with ER presence (p=0.023 and p=0.029, respectively) but positively with HER2 expression status (p<0.001 and p=0.002, respectively). The global positivity for any EGFR parameter did not significantly differ between triple-negative and HER2 positive tumours. In conclusion, EGFR phosphorylation is commonly encountered in breast carcinomas, although unrelated to EGFR protein presence and gene amplification. EGFR may appear activated even in cases where the extracellular domain of this protein is not observed with immunohistochemistry. These findings may be useful for further studies aiming at the assessment of EGFR parameters on this type of material.

Coexistence of B-cell non-Hodgkin lymphoma and cutaneous T-cell lymphoma in a patient with chronic hepatitis C and cryoglobulinaemia.

The coexistence of chronic active hepatitis C with cryoglobulinemia and B-cell lymphoma has been presented in numerous case reports. However, the combination of these conditions with T-cell lymphoma has never been described before. We present the case of a patient who suffered chronic active hepatitis C, cryoglobulinaemia and B-cell lymphoma and was later complicated by cutaneous T-cell lymphoma (CTCL).

Significance of increased expression of decoy receptor 3 in chronic liver disease.

BACKGROUND/AIMS: Considerable evidence has indicated that apoptosis plays an important role in hepatocyte death in chronic liver disease. However, the cellular and molecular mechanisms underlying liver regeneration in these diseases are largely unknown. Plausibly, certain molecules expressed to counteract apoptosis might provide survival advantage of certain liver cells. Therefore, we investigated a possible expression of decoy receptor 3 of the tumour necrosis factor receptor family in chronic liver diseases since decoy receptor 3 is known to inhibit apoptosis mediated by pro-apoptotic tumour necrosis factor family ligands including Fas ligand. METHODS: A series of liver biopsies from patients with different stages of fibrosis were subjected to immunohistochemistry and in situ hybridization. RESULTS: Both decoy receptor 3 protein and mRNA were mainly expressed in biliary epithelial cells and infiltrating lymphocytes in the diseased livers. Most noticeably, intense decoy receptor 3 expression was observed in newly developing biliary ductules in regenerative nodules as well as dysplastic nodules of cirrhotic livers. In addition, decoy receptor 3 secretion in hepatocellular carcinoma cells in culture was via the activation of mitogen-activated protein kinases. CONCLUSION: Decoy receptor 3 was specifically expressed in chronic liver diseases and hepatocellular carcinoma cells, and decoy receptor 3 might facilitate the survival of liver cells by exerting its anti-apoptotic activity during the progression of liver cirrhosis and hepatocarcinogenesis.

Relative expression of human telomerase catalytic subunit (hTERT) transcripts in astrocytic gliomas.

Human telomerase catalytic subunit (hTERT) expression has been reported as a marker for malignancy in various tumor systems. The aim of the present study was to investigate the relative expression of hTERT (relhTERT) and its transcripts A+B+ (contained in the full-length product), Adel and Bdel in astrocytic gliomas (grades I-IV, n=38). relhTERT was assessed by duplex reverse transcription-PCR and the expression profile of Adel, Bdel and A+B+ transcripts by nested real time-PCR. relhTERT and A+B+ presence correlated well with each other ( P<0.001) and with histological grading [grades I-II (low) vs III-IV (high), P(relhTERT)=0.002 and P(A+B+)<0.001]. A+B+ was detected in one out of seven hTERT-positive low-grade tumors, while it was present in 96.3%, and predominantly expressed in 59.3% of high-grade tumors. Bdel predominance was observed only in three cases, irrespective of grading, while Bdel levels equal or close to those of A+B+ were found in 30.4% of grade IV tumors. In situ hybridization with specific Bplus and Bdel probes revealed positive signals for both mRNAs in association with relhTERT and respective variant profiles. In addition, this method was useful in assessing hTERT expression in cases where sampling errors for RT-PCR were unavoidable. Our findings show that except for differences in relhTERT, low- and high-grade astrocytic gliomas exhibit distinct hTERT variant profiles, most of which seem to be in line with the role attributed to hTERT regarding its contribution to the acquisition of malignant potential during astrocyte carcinogenesis. Low-grade tumors mainly express Adel and Bdel. High-grade tumors, especially grade IV, always express A+B+, mostly but not always in predominance over Adel and Bdel. In this same group, profiles with Bdel predominance or relatively equal A+B+/Bdel expression are also observed, and Adel is often missing. Whether these differences characterize tumors with different biological behavior remains to be elucidated.

Cyclin D1 overexpression in multiple myeloma. A morphologic, immunohistochemical, and in situ hybridization study of 71 paraffin-embedded bone marrow biopsy specimens.

Cyclin D1 expression was evaluated by immunohistochemical analysis and biotin-labeled in situ hybridization (ISH) in a series of 71 decalcified, paraffin-embedded bone marrow biopsy specimens from patients with multiple myeloma (MM). Cyclin D1 messenger RNA (mRNA) overexpression was detected by ISH in 23 (32%) of 71 cases, whereas cyclin D1 protein was identified by immunohistochemical analysis in 17 (24%) of 71 specimens. All cases that were positive by immunohistochemical analysis also were positive by ISH. Statistically significant associations were found between cyclin D1 overexpression and grade of plasma cell differentiation and between cyclin D1 overexpression and extent of bone marrow infiltration. Our findings demonstrate the following: (1) ISH for cyclin D1 mRNA is a sensitive method for the evaluation of cyclin D1 overexpression in paraffin-embedded bone marrow biopsy specimens with MM. (2) ISH is more sensitive than immunohistochemical analysis in the assessment of cyclin D1 expression. (3) Cyclin D1 overexpression in MM is correlated positively with higher histologic grade and stage.

In situ hybridization and reverse transcription-polymerase chain reaction for cyclin D1 mRNA in the diagnosis of mantle cell lymphoma in paraffin-embedded tissues.

Mantle cell lymphoma (MCL) is characterized by the chromosomal translocation t(11;14), which involves rearrangement of the bcl-1 proto-oncogene to the immunoglobulin heavy chain gene and results in overexpression of cyclin D1 mRNA. In this study, we evaluated the diagnostic relevance of three methods that may be helpful in the diagnosis of MCL: in situ hybridization (ISH) and a stringent reverse transcriptase-polymerase chain reaction (RT-PCR) protocol for cyclin D1 mRNA, and immunohistochemistry for cyclin D1 protein. The study group included 37 paraffin-embedded specimens (25 from lymph nodes and 12 from extranodal tissues) from 30 patients. MCL diagnosis was performed according to the Revised European-American Classification of Lymphoid Neoplasms. Twenty-nine patients with non-MCL lymphoproliferative disorders comprised the control group. Biotin-labeled ISH was performed in 28 cases of MCL, 24 (86%) of which were found to be positive. As shown by ISH in extranodal tissues, cyclin D1 mRNA was present not only in neoplastic lymphoid cells, but in other cell types as well. For this reason, RT-PCR results were considered reliable for MCL diagnosis only on informative material (from tissues that do not normally express cyclin D1); this method was evaluated as positive in 16 of 18 (89%) MCL cases. Cyclin D1 immunopositivity was present in 20 of 29 (69%) MCL cases. No members of the control group were found to express cyclin D1 mRNA by either ISH or RT-PCR under the stringent conditions used. In conclusion, stringent RT-PCR for cyclin D1 expression can be helpful in MCL diagnosis in paraffin-embedded material from lymph nodes. ISH is a sensitive method for cyclin D1 mRNA detection; its sensitivity is superior to that of cyclin D1 immunohistochemistry and similar to that of the stringent RT-PCR used. ISH is very specific as well, clearly more specific than RT-PCR, because it allows the correlation of molecular findings with morphology. This method can be applied on all types of paraffin-embedded tissues and provides an accurate tool for MCL diagnosis.

Fas ligand expression in thyroid carcinomas: a potential mechanism of immune evasion.

Fas ligand (FasL) induces apoptosis by cross-linking the Fas receptor and is expressed by cells of the immune system. Recently, FasL was found in malignant tumors, suggesting that it helps them escape immune surveillance by eliminating infiltrating lymphocytes. We investigated the presence of FasL immunohistochemically in 48 thyroid carcinomas and by Western blotting and RT-PCR in 5 thyroid carcinoma cell lines. We found that in contrast to normal thyroid tissue, FasL was highly expressed in all papillary, follicular, and Huerthle carcinomas. Medullary carcinomas lacked or had minimal FasL expression. In papillary carcinomas, high levels of expression correlated independently with aggressive histology and unfavorable clinical presentation. FasL was also present in all thyroid cell lines. Thyroid carcinoma cells killed Fas-sensitive targets in a FasL-dependent manner in a coculture experiment. Cross-linking of Fas induced apoptosis in thyroid carcinoma cells only in the presence of cycloheximide. We conclude that FasL is specifically expressed in thyroid carcinomas of follicular epithelial origin, may help them evade the immune system, and may have prognostic implications in papillary carcinoma, as it is associated with a more aggressive phenotype. Thyroid carcinoma cells avoid Fas-mediated suicide possibly by expressing an inhibitor of the Fas apoptotic pathway.

Fas ligand is present in tumors of the Ewing's sarcoma family and is cleaved into a soluble form by a metalloproteinase.

Fas ligand (FasL) exists in transmembrane and soluble forms and induces apoptosis on cross-linking with the Fas receptor. We evaluated the biological significance of FasL and Fas in 61 tumor tissues and 9 cell lines of the Ewing's sarcoma family of tumors (ESFT). FasL was present in 62.5% and Fas in 79.4% of primary ESFT. Metastatic tumors had higher expression of FasL (95%), suggesting association with a metastatic phenotype. FasL was detected in the cytoplasm and membrane of ESFT cells by immunofluorescence. Western blotting revealed transmembrane and soluble FasL in cytosolic extracts and soluble FasL in conditioned media. Both transmembrane and soluble FasL induced apoptosis of Fas-sensitive Jurkat cells in co-culture experiments with ESFT cells or their media. Treatment with phenanthroline and the synthetic metalloproteinase inhibitor BB-3103 reduced the levels of soluble FasL in the media, suggesting that in ESFT, FasL is processed by a metalloproteinase and released in the extracellular milieu. The released soluble FasL may serve to attack cells of the immune system and/or interfere with the binding of transmembrane FasL with Fas, and results in down-regulation of transmembrane FasL. Synthetic metalloproteinase inhibitors may modify the ratio of transmembrane to soluble FasL.

Fas/Fas ligand up-regulation and Bcl-2 down-regulation may be significant in the pathogenesis of Hashimoto's thyroiditis.

Hashimoto's thyroiditis (HT) is an autoimmune disorder characterized by diffuse thyroid lymphocytic infiltration and follicle destruction. Cross-linking of the Fas receptor with its own ligand (FasL) triggers apoptosis in various systems, whereas the Bcl-2 protooncogene inhibits apoptotic cell death. The involvement of Fas, FasL, and Bcl-2 in the apoptotic process in HT was evaluated in 15 thyroid tissue samples from patients with HT stained for apoptosis and for Fas, FasL, and Bcl-2 protein expression. Eight samples from healthy thyroid tissue were used for comparison. Thyroid follicles in HT samples exhibited strong staining for Fas and FasL and a high percentage of apoptosis (30.3 +/- 14.5%, mean +/- SD), in contrast to normal control follicles that exhibited moderate Fas, minimal or no FasL, and hardly any apoptosis. Immunostaining for Bcl-2 was high in normal, and weak in involved, thyroid follicles. Infiltrating lymphocytes stained weakly for FasL and strongly for Bcl-2. We conclude that follicular cells in HT undergo apoptosis by concomitant up-regulation of FasL and Fas and down-regulation of Bcl-2 protein. The lymphocytes do not seem to be directly engaged in the process with their own FasL, but they may provide the appropriate cytokine milieu that, in turn, up-regulates Fas and/or FasL leading to apoptosis.

Telomerase activity in precancerous hepatic nodules.

BACKGROUND: Recent studies have demonstrated that telomerase, a reverse transcriptase linked to cellular "immortalization," is activated in a variety of malignant human tumors. This study was conducted to determine whether telomerase activity represents a marker of malignant transformation in precancerous (dysplastic) nodules arising in patients with cirrhosis. METHODS: Telomerase activity was evaluated in frozen tissue samples of 14 cirrhotic liver specimens and 30 large nodular lesions contained therein, including 13 large regenerative nodules/low grade dysplastic nodules, 10 high grade dysplastic nodules, and 7 hepatocellular carcinomas (HCCs). A modified telomeric repeat amplification protocol was used. RESULTS: There was a clear-cut difference in telomerase activity levels between HCC (positive or strongly positive) and cirrhotic liver samples (weakly positive or negative). The majority of large noncancerous nodules (86%) exhibited telomerase activity levels similar to HCCs. However, such activity was not limited to dysplastic lesions but also was detected in some large regenerative nodules. CONCLUSIONS: These findings suggest that telomerase activation is an early event in large nodule formation in cirrhosis, which may facilitate the action of other factors in the process of carcinogenesis. Telomerase activity in large hepatic nodules is not always indicative of malignant transformation.

In vitro evaluation of the cytotoxicity of calcium hydroxide-based root canal sealers.

The cytotoxicity of three calcium hydroxide-containing root canal sealers (Sealapex, CRCS and Apexit) was tested by using L929 and BHK 21/C13 cells. After setting for 24 h, the sealers were covered with cell suspension. Cytotoxicity was determined by a quantitative technique at 24 h, 48 h and 72 h. All the sealers were found to be cytotoxic. Sealapex showed the highest cytotoxicity, causing a significant decrease in cell density. CRCS was less toxic than Sealapex and more toxic than Apexit. Apexit proved to be the least toxic material.

Effects of tamoxifen and CV 205502 on the morphology and the evolution of the noncancerous mouse mammary gland.

Tamoxifen (TAM, 0.01 mg/animal, three times a week) and the experimental prolactin-lowering CV 205502 (CV, 1 microgram/animal, daily) were administered prophylactically, alone or combined, to virgin C3H/Sy mice during the early period of promotion in this spontaneous mammary carcinogenesis system (end of 2nd-5th month of age), in order to study their influence on the morphology and evolution of the noncancerous mammary gland during therapy and after treatment cessation. During TAM administration the epithelial cells of the growing part of the gland exhibited myoepithelial- and, late in the treatment period, apoptotic-like features instead of the secretory ones expected, accompanied by intense basement membrane alterations, thickening of the surrounding connective tissue and arrested adipocyte maturation. These effects reversed progressively after drug withdrawal. The epithelial alterations were more intense and longer lasting in the TAM+CV-group, while growth arrest of the glands was observed in both groups parallel to the degree and the duration of these morphological changes. In these groups, tumor incidence was diminished, as expected, but the tumors that developed late after treatment cessation were of low histological differentiation. The above morphological observations show that TAM inhibits noncancerous mammary gland growth during the reproductive period by altering stromal and epithelial differentiation, effects that reverse progressively after treatment discontinuation and are potentiated by a prolactin-lowering agent in this animal study.