The modification of the growth characteristics of the Landschütz ascites tumour by neuraminidase

The effect of Vibrio cholerae neuraminidase (VCN) on the in vivo growth characteristics of the Landschütz ascites tumour has been studied. A considerable reduction in tumour cell numbers following the transplantation of VCN-treated cells as compared to untreated cells has been shown which is readily reversible by in vitro incubation of the treated cells for a short period prior to transplantation. The possible significance of this is discussed.     

Transplantation of β-endorphin neurons into the hypothalamus promotes immune function and restricts the growth and metastasis of mammary carcinoma

Neurobehavioral stress has been shown to promote tumor growth and progression and dampen the immune system. In this study, we investigated whether inhibiting stress hormone production could inhibit the development of mammary carcinoma and metastasis in a rat model of breast carcinogenesis. To enhance β-endorphin (BEP), the endogenous opioid polypeptide that boosts immune activity and decreases stress, we generated BEP neurons by in vitro differentiation from fetal neuronal stem cells and transplanted them into the hypothalami of rats subjected to breast carcinogenesis. BEP-transplanted rats displayed a reduction in mammary tumor incidence, growth, malignancy rate, and metastasis compared with cortical cells-transplanted rats. BEP neuron transplants also reduced inflammation and epithelial to mesenchymal transition in the tumor tissues. In addition, BEP neuron transplants increased peripheral natural killer (NK) cell and macrophage activities, elevated plasma levels of antiinflammatory cytokines, and reduced plasma levels of inflammatory cytokines. Antimetastatic effects along with stimulation of NK cells and macrophages could be reversed by treatment with the opiate antagonist naloxone, the β-receptor agonist metaproterenol, or the nicotine acetylcholine receptor antagonist methyllycaconitine. Together, our findings establish a protective role for BEP against the growth and metastasis of mammary tumor cells by altering autonomic nervous system activities that enhance innate immune function.     

Immunohistochemical analysis of the mutant epidermal growth factor, ΔEGFR,in glioblastoma

The naturally occurring mutated form of the epidermal growth factor receptor, ΔEGFR (also named EGFRvIII and de2-7EGFR), greatly enhances glioblastoma (GBM) cell growth in vivo through several activities, such as down-regulating p27 and up-regulating BclX(L) while increasing signaling through the RAS-MAPK and PI3-K cascades. More than half of GBMs, especially of the de novo type, overexpress EGFR, and 50%–70% of these express ΔEGFR. However, little is known about the distribution of ΔEGFR-expressing tumor cells within surgical specimens. In order to address this clinically important issue, we performed immunohistochemical analyses of 53 GBMs obtained during surgery using the anti-ΔEGFR monoclonal antibody, DH8.3. We also simultaneously analyzed wild-type EGFR expression in these tissues using the anti-EGFR monoclonal antibody, EGFR. 113. ΔEGFR and wild-type EGFR expression were observed in 20/53 (38%) and 29/53 (55%), respectively. Nineteen (95%) of the ΔEGFR-positive tumors also expressed wild-type EGFR; one case was ΔEGFR-positive but wild-type EGFR-negative. In 13/20 (65%) of the ΔEGFR-positive tumors, tumor cells were scattered diffusely within the tumors, 6/20 showed geographical distribution of ΔEGFR-positive tumor cells, and one case showed homogeneous staining. In the wild-type EGFR-positive cases, almost all tumor cells expressed EGFR. The differential distribution of cells expressing the two receptors observed here may suggest either that ΔEGFR arises at a low frequency from wild-type EGFR-expressing cells, perhaps during the process of gene amplification, or that there is a paracrine-type of interaction between them.     

Synergistic effect of 3′-deoxyadenosine N 1-oxide and adenosine deaminase inhibitors on growth of Ehrlich ascites tumor cells in vivo

Summary The simultaneous administration of 3-deoxyadenosine N ^l-oxide (3-dANO) and the adenosine deaminase inhibitors erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) or 2-deoxycoformycin (2-dCF) to mice bearing Ehrlich ascites tumor cells resistant to 3-dANO resulted in 80%–90% inhibition of tumor growth in vivo. 3-dANO and 2-dCF increased the survival time of tumor-bearing mice by a factor of 2. In vitro studies showed that the 3-dANO resistant Ehrlich cells initiate the metabolism of 3-dANO by a reduction to 3-deoxyadenosine, which is converted primarily to 3-deoxyinosine by adenosine deaminase and, to a small extent, phosphorylated to the cell toxic agent 3-dATP. By the addition of EHNA or 2-dCF it was possible to block the formation of 3-deoxyinosine, resulting in a profound stimulation in the accumulation of 3-dAtP. The development of resistance to 3-dANO was studied in cell cultures and found to be accompanied by changes in the enzyme activities of the reductase, the adenosine kinase, and the adenosine deaminase.Abbreviations 3-dANO 3-deoxyadenosine N ^l-oxide - 3-dA 3-deoxyadenosine - 3-dI 3-deoxyinosine - 3-dATP 3-deoxyadenosine triphosphate - EHNA erythro-9-(2-hydroxy-3-nonyl) adenine - 2-dCF 2-deoxycoformycin This work was supported by the Danish Medical Research Council, Gerda and Åge Haensch Foundation, Dirktør Åge Henriksens Foundation, P. Carl Petersens Foundation and the Danish Cancer Society     

Effect of perductal paclitaxel exposure on the development of MNU-induced mammary carcinoma in female S–D rats

The amount of the immunoreactive protein for the tissue inhibitor of the matrix metalloproteinase-1 (TIMP-1) was studied prospectively from the pretreatment sera of 71 breast carcinoma patients using an enzyme-linked immunoassay (ELISA). The study consisted of patients with a primary breast carcinoma diagnosed between 1988 and 1991. The median follow-up time was more than 10years, and routine adjuvant treatment was not used in the primary treatment. High TIMP-1 (> 196ng/ml) was found to correlate with a poor relapse-free survival (RFS) in primary node-negative breast carcinoma. After 10years of the follow-up only 42% of the patients with a high preoperative serum TIMP-1-level were free of the relapse, whereas 82% of the patients with a low serum TIMP-1 enjoyed a long RFS-time (log rank p =0.009). High serum TIMP-1 also indicated poor RFS (p=0.02) and overall survival (p=0.05) in stage I breast carcinoma. In Kaplan–Meier analysis the RFS was 89% in patients with a low serum level of TIMP-1 compared to 52% in patients with a high serum concentration of TIMP-1. In conclusion, preoperative high serum TIMP-1 levels predict poor outcome in primary breast carcinoma. In multivariate analysis preoperative high serum TIMP-1 increases the risk of relapse 3.4-fold during the first 10years of follow-up in primary node-negative breast carcinoma.     

Improving function of cytotoxic T-lymphocytes by transforming growth factor-β inhibitor in oral squamous cell carcinoma

Immunotherapy with immune-checkpoint therapy has recently been used to treat oral squamous cell carcinomas (OSCCs). However, improvements in current immunotherapy are expected because response rates are limited. Transforming growth factor-β (TGF-β) creates an immunosuppressive tumor microenvironment (TME) by inducing the production of regulatory T-cells (Tregs) and cancer-associated fibroblasts and inhibiting the function of cytotoxic T-lymphocytes (CTLs) and natural killer cells. TGF-β may be an important target in the development of novel cancer immunotherapies. In this study, we investigated the suppressive effect of TGF-β on CTL function in vitro using OSCC cell lines and their specific CTLs. Moreover, TGFB1 mRNA expression and T-cell infiltration in 25 OSCC tissues were examined by in situ hybridization and multifluorescence immunohistochemistry. We found that TGF-β suppressed the function of antigen-specific CTLs in the priming and effector phases in vitro. Additionally, TGF-β inhibitor effectively restored the CTL function, and TGFB1 mRNA was primarily expressed in the tumor invasive front. Interestingly, we found a significant negative correlation between TGFB1 mRNA expression and the CD8⁺ T-cell/Treg ratio and between TGFB1 mRNA expression and the Ki-67 expression in CD8⁺ T-cells, indicating that TGF-β also suppressed the function of CTLs in situ. Our findings suggest that the regulation of TGF-β function restores the immunosuppressive TME to active status and is important for developing new immunotherapeutic strategies, such as a combination of immune-checkpoint inhibitors and TGF-β inhibitors, for OSCCs.     

Expression of α-taxilin in hepatocellular carcinoma correlates with growth activity and malignant potential of the tumor

The membrane traffic system has been recognized to be involved in carcinogenesis and tumor progression in several types of tumors. α-taxilin is a newly identified membrane traffic-related molecule, and its up-regulation has been reported in embryonic and malignant tissues of neural origin. In the present study, we analyzed the expression of α-taxilin in relation to clinicopathological features of hepatocellular carcinomas (HCC) and proliferative activity of the tumor determined by proliferating cell nuclear antigen labeling index (PCNA-LI). Twenty-nine surgically resected nodules of HCC (8 well-, 11 moderately-, and 10 poorly-differentiated) were studied. Fifteen cases showed 'strong staining', while 14 cases showed 'weak staining' for α-taxilin. A significantly higher expression of α-taxilin was observed in less-differentiated (p=0.005), and more invasive (p=0.016) HCCs. The 'strong staining' group showed significantly higher PCNA-LI than the 'weak staining' group (the medians of PCNA-LI were 59.4% vs. 14.4%, p<0.0001). We also evaluated the expression of α-taxilin in hepatoma cell lines (PLC/PRF/5, Hep G2 and HuH-6) in association with cell proliferation. The expression levels of α-taxilin protein were correlated with their growth rates. In conclusion, the expression of the α-taxilin protein was related with an increased proliferative activity and a less-differentiated histological grade of HCC. α-taxilin may be involved in cell proliferation of HCC, and its expression can be a marker of malignant potential of HCC.     

Dietary intakes of carotenoids and other nutrients in the risk of nasopharyngeal carcinoma: a case–control study in Italy

Background:

Dietary habits have been related to the risk of nasopharyngeal carcinoma (NPC), but information on a wide range of macro- and micronutrients is still lacking, particularly for low-incidence countries.

Methods:

We conducted a hospital-based case–control study in Italy on 198, histologically confirmed, NPC cases of Caucasian ethnicity of 18–76 years of age. Controls were 594 Caucasian cancer-free patients admitted to general hospitals for acute conditions. Nutrients intake was assessed through a validated food-frequency questionnaire. Adjusted odds ratios (ORs) and the corresponding confidence intervals (CIs) were estimated through logistic regression.

Results:

Dietary intake of carotenoids were inversely related to NPC risk, notably carotene (OR for highest vs lowest quartile=0.46; 95% CI: 0.26–0.79), α-carotene (OR=0.57; 95% CI: 0.33–0.97), and β-carotene (OR=0.42; 95% CI: 0.24–0.75). Increased NPC risk was observed for elevate cholesterol intake (OR=1.85; 95% CI: 1.12–3.05).

Conclusion:

Study findings suggest a protective effect of carotenoids against NPC in a low-risk population, adding further support to a possible beneficial role of a diet rich in fruits and vegetables in cancers of the head and neck.     

Therapeutic targeting of oncogenic transforming growth factor-β1 signaling by antisense oligonucleotides in oral squamous cell carcinoma

The transforming growth factor-β1 (TGF-β1) signaling pathway is important in human oral squamous cell carcinoma (OSCC). Accordingly, the aims of this study were to evaluate the effect of antisense TGF-β1 oligonucleotides (ODNs) on OSCC in cell culture and in a xenograft model, as well as to evaluate any effects ODNs have on proliferating cell nuclear antigen (PCNA) and matrix metalloproteinase-2 (MMP-2) expression in the xenograft model. We performed real-time cell electronic sensing (RT-CES) to determine the effect of antisense TGF-β1 ODNs on SCC-9?cell growth. To examine the in?vivo effect of antisense TGF-β1 ODN therapy, SCC-9?cells were grafted into nude mice. Antisense ODNs were injected into the mass daily. Tumor size, body weight and duration of survival were assessed daily. Specimens from the main mass were used for immunohistochemical staining to analyze PCNA and MMP-2 expression. In?vitro treatment with antisense TGF-β1 ODNs decreased TGF-β1 expression and growth of SCC-9?cells. In the xenograft model, the antisense TGF-β1 ODN group exhibited a significantly decreased tumor growth rate compared to the control, which received Dulbecco's modified Eagle's medium (DMEM) (P=0.022). However, mean survival time and body weights were not significantly different between the groups (P>0.05). Immunohistochemistry showed that tumors from animals that received antisense TGF-β1 ODNs had significantly lower expression levels of PCNA and MMP-2 compared to tumors from animals in the DMEM group (P<0.05). In conclusion, antisense TGF-β1 ODN therapy significantly inhibits tumor growth compared to controls, however, there are no significant differences between groups with respect to changes in body weight.     

Silencing of Src by siRNA inhibits laryngeal carcinoma growth through the Src/PI-3 K/Akt pathway in vitro and in vivo

This study aimed to investigate the expression, function, and possible mechanism of Src in the Hep-2 cell line. We used Src-specific small interfering RNA (siRNA) to inhibit the expression of Src in Hep-2 cells. RT-PCR and Western blot were applied to evaluate the expression level of Src after RNA interference, and the MTT assay and flow cytometry were used to observe the expression of PI-3 K and Akt. siRNA can downregulate the expression of Src in Hep-2 cells. Downregulation of Src decreased PI-3 K and Akt expression. We found that Src knockdown inhibits the proliferation of Hep-2 cells and the growth of laryngeal carcinoma in vivo. This study has demonstrated that Src participates in the regulation of apoptosis through the Src/PI-3 K/Akt signaling pathway in the Hep-2 cell line. Silencing of Src by siRNA is a viable approach in laryngeal carcinoma treatment.     

Projecting the number of patients with colorectal carcinoma by phases of care in the US: 2000–2020

Objective This study provides projections of colorectal cancer prevalence by phases of care (initial, monitoring, and last year of life) to the year 2020 and describes the estimation method. Methods Cancer prevalence by phase of care was estimated from colorectal cancer incidence and survival from the Surveillance, Epidemiology, and End Results (SEER) Program data, population estimates and projections from the US Census Bureau, and all cause mortality data from the Human Mortality Life Tables. Assumptions of constant incidence and survival were used for projections from 2000 to 2020. Modeled and directly observed patient months by phase of care were compared for 1996 −1998 to provide validation of estimates. Results Prevalence of colorectal cancer is estimated to increase from 1,002,786 (0.36%) patients to 1,522,348 (0.46%) patients between 2000 and 2020. The estimated number of person-months in the initial and last year of life phases of care will increase 43%, while the monitoring phase of care will increase 54%. Modeled person-months by phase of care were consistent with directly observed measures of person months by phase of care in 1996–1998. Conclusions Under assumptions of current cancer control strategies we project that colorectal cancer prevalence will increase more rapidly than the US population, largely due to the aging of the US population. This suggests that considerable resources will be needed in the future for initial, continuing and last year of life treatment of colorectal cancer patients unless notable breakthroughs in primary prevention occur in the future years.     

Associations of lifestyle and diet with the risk of nasopharyngeal carcinoma in Singapore:a case–control study

Background: Nasopharyngeal carcinoma (NPC) is a commonly diagnosed cancer in Southeast Asia. Many stud-ies have examined the risk factors for NPC, yet the roles of some risk factors remain inconclusive. The purpose of this study was to examine associations between modifiable lifestyle factors and the risk of NPC in the Singaporean population. Methods: We conducted a case–control study in Singapore with 300 patients and 310 controls who were recruited between 2008 and 2012. Each control was selected and individually matched to each patient based on sex, ethnicity, and age (±5 years). A total of 290 pairs of cases and controls were matched successfully. We examined lifestyle factorssuch as tobacco smoking, alcohol drinking, various salted and preserved food consumption, and weaning practices. Results: After adjusting for covariates, multivariate analysis showed that those participants who were current smok-ers and had ever smoked tobacco had a higher risk of NPC than participants who had never smoked, with odds ratios (ORs) of 4.50 (95% confidence interval [CI] 2.58–7.86; P < 0.001) and 2.52 (95% CI 1.54–4.12; P < 0.001), respectively. Those who consumed salted vegetables at least once a week also showed a significantly increased risk of NPC than those who never or rarely consumed salted vegetables, with an OR of 4.18 (95% CI 1.69–10.38; P = 0.002). Conclusion: Smoking (currently and ever-smoked) and consuming salted vegetables once a week or more were lifestyle risk factors for NPC, and changes of these factors for the better may reduce the risk of NPC.     

Is the efficacy of sorafenib treatment in patients with hepatocellular carcinoma affected by age?

Cancer is a prevalent disease in the elderly population and hepatocellular carcinoma (HCC) is a major health problem among all tumors. Curative treatments for early-stage include liver transplantation, resection and percutaneous ablation. Transarterial chemoembolization (TACE) and sorafenib, classified as non-curative treatments, can improve survival for patients with intermediate and advanced tumors, respectively. Even if the incidence of HCC progressively increases with advanced age in all populations, reaching a peak at 70 years, few reports concerning correct management of HCC in elderly patients exist. Moreover, data from large randomized controlled trials (RCT) poorly reflect the elderly population that is often quantitatively and qualitatively underrepresented, as a result of the presence of tight enrolment criteria. The aim of this brief review is to highlight the main concerns, pitfalls and warnings regarding the management of HCC in elderly patients, with particular focus on systemic therapy with sorafenib.     

Escape from negative regulation of growth by transforming growth factor β and from the induction of apoptosis by the dietary agent sodium butyrate may be important in colorectal carcinogenesis

There are a number of lines of evidence suggesting that transforming growth factor (TGF) has an important role in the control of intestinal growth and differentiation.In vivo localization studies show that TGF expression occurs predominantly in the differentiated non proliferating cells of the intestinal epithelium. The use of an antisense expression vector for TGF resulted in an increased tumorigenicity in an antisense-transfected cancer cell line.In vitro proliferation studies showed colorectal premalignant adenoma cells to be more sensitive to the growth inhibitory effects of TGF than colorectal cancer cells. Furthermore the conversion of an adenoma to a carcinoma was accompanied by a reduced response to the inhibitory effects of TGF. The acquisition of partial or complete resistance to the inhibitory effects of TGF may be an important late event in colorectal carcinogenesis.Of further interest is the possibility that clonal selection could occur even more rapidly in colorectal tumour cells which not only had lost response to TGF inhibition but produced TGF and were growth stimulated by it. This could have the advantage of not only inhibiting the growth of surrounding less malignantly advanced cells but of also escaping from their potential growth suppressive influence. Carcinogenesis is not, however, simply losing response to negative regulators of growth; the fully malignant cell has to acquire new characteristics of invasiveness and metastatic potential. Growth factors including TGF may have a role in the complex cascade of events leading to the activation of proteolytic enzymes which are involved in progression to an invasive phenotype.Cell proliferation in the large bowel, as well as being under the control of endogenous growth factors, is also under the influence of dietary components in the lumen such as the naturally occurring fatty acid sodium butyrate. Sodium butyrate at physiological concentrations induces apoptosis (programmed cell death) in colonic tumour cell lines. Since sodium butyrate occurs naturally in the colorectum, being produced by bacterial fermentation of dietary fibre, it may be involved in the control of cell death in human colorectal epithelium. This could, in part, explain the apparent protective effects of dietary fibre. Clonal evolution and tumour progression in colorectal carcinogenesis could therefore involve loss of response to endogenous growth factors such as TGF and an escape from the induction of programmed cell death by dietary factors.     

Drinking of maté and the risk of cancers of the upper aerodigestive tract in Latin America: a case–control study

Cancers of the upper aerodigestive tract (UADT: oral cavity, oropharynx, hypopharynx, larynx, esophagus) have high incidence rates all over the world and they are especially frequent in some parts of Latin America. In this study, we have evaluated the role of the consumption of maté, a hot herb-based beverage, based on 1168 UADT squamous-cell carcinoma cases and 1,026 frequency-matched controls enrolled from four centers in Brazil and Argentina. The effect of maté drinking on the risk of head-and-neck cancers was borderline significant. A significant effect was observed only for cancer of the esophagus (OR 3.81 (95% CI 1.75–8.30)). While duration of maté drinking was associated with the risk of all UADT cancers, the association with cumulative maté consumption was restricted to esophageal cancer (p-value of linear trend 0.006). The analyses of temperature at which maté was drunk were not conclusive. The increased risk associated with maté drinking was more evident in never-smokers and never-alcohol drinkers than in other individuals. Our study strengthens the evidence of an association between maté drinking and esophageal cancer; the hypothesis of an association with other UADT cancers remains to be clarified.     

Transforming growth factor-β activities in‘in vivo’ lines of hormone-dependent and independent mammary adenocarcinomas induced by medroxyprogesterone acetate in BALB/c mice

Summary We have determined the presence of transforming growth factor- (TGF-)-like polypeptides in mammary adenocarcinomas induced by medroxyprogesterone acetate (MPA) in BALB/c mice. In hormone-dependent tumors (HD) from nontreated and MPA-treated mice a high molecular weight (43 kDa) transforming activity was purified by Bio-Gel P-60 chromatography. This TGF was able to confer the neoplastic phenotype on NRK-49F cells without the addition of epidermal growth factor (EGF), though its activity was potentiated by EGF. It did not compete for binding to the EGF receptor, had no mitogenic activity on monolayer cultures of NRK fibroblasts, and was a potent inhibitor of DNA synthesis induced in these cells by EGF and insulin. In HD and hormone-independent tumors (HI) another TGF with a Mr of 13 kDa was isolated. This transforming activity showed the same biological properties as 43 kDa TGF, with the exception that in the absence of EGF it did not stimulate soft agar growth of NRK-49F cells. The synthesis of both factors in in vivo HD tumors seems to be under MPA control, since it is much lower in HD tumors from MPA-treated mice. Further purification of the 13 and 43 kDa TGFs by hydrophobic interaction HPLC demonstrated that each one eluted in a different position, and that their elution profile differed from the TGF- from human platelets. The biological activity of the 13 and 43 kDa TGFs was not neutralized by a specific anti-TGF- antibody.     

Combinational effect of PPARγ agonist and RXR agonist on the growth of SGC7901 gastric carcinoma cells in vitro

In order to investigate the inhibitory effects and mechanisms of troglitazone (TGZ), a peroxisome proliferator-activated receptor γ (PPARγ) agonist, and retinoid X receptor (RXR) agonist (9-cis-retinoic acid (RA)) on gastric carcinoma cells SGC7901, SGC7901 cells were treated with TGZ and 9-cis-RA, respectively, or in combination. Then, the cell growth, apoptosis, morphological changes, and the expression of PPARγ, RXRγ, Bcl-2, and Bax were detected by MTT assay, flow cytometry, HE staining, immunocytochemistry staining, and Western blot assay, respectively. Our results showed that the growth of SGC7901 cells was inhibited and the cells got sparser at the concentrations of 50 μmol/L TGZ, 20 μmol/L 9-cis-RA, or combination of TGZ (25 μmol/L) and 9-cis-RA (10 μmol/L). Immunocytochemistry and Western blot showed that after 72 h, the expression of PPARγ, RXRγ, and Bax were upregulated; Bcl-2 was downregulated compared with the negative control group. These data indicated that PPARγ agonist and RXR agonist could inhibit the proliferation of SGC7901 cells via inducing the apoptosis, which involved the increase in the level of Bax/Bcl-2. The combination of RXR agonist and PPARγ agonist could induce the maximal inhibitory effects on tumor growth and apoptosis via promoting the formation of RXR/PPARγ heterodimer.     

Role of transforming growth factor-α-related peptides in the autocrine/paracrine control of experimental breast cancer growthin vitro by estradiol,prolactin, and progesterone

Summary We have recently suggested that estradiol (E₂), prolactin (oPrl), and progesterone (Pg) support the growth of the hormone-responsive N-nitrosomethylurea (NMU) rat mammary tumor in soft agar through autocrine/paracrine mechanisms. To gain insight into the nature of these hormonally regulated growth factors, we tested the ability of two monoclonal antibodies (MAb-425 and 528) directed against the epidermal growth factor receptor (EGF-R) to inhibit the colony-stimulating effects of conditioned media (CM) obtained from E₂, oPrl, and Pg-treated NMU rat mammary tumors. Since both MAbs are specific for human EGF-R, MCF-7 breast cancer cells grown in soft agar in the absence of serum were used as our indicator system. Both MAb-425 and 528 totally abolished the colony-stimulating effect of genuine EGF, while having no agonistic/antagonistic action when added alone. Both MAb-425 and 528 markedly inhibited the colony-stimulating effect of rat mammary tumor E₂-CM in a dose-dependent fashion. MAb-425 was also found to inhibit the growth-promoting action of Pg-CM, although this effect appeared to be somewhat less consistent and pronounced than that observed with E₂-CM. In contrast, the colony-stimulating effect of Prl-CM was only rarely and, usually, modestly affected by the addition of either MAb-425 or 528. Our data suggest that in the NMU mammary tumor grown in soft agar, EGF/TGF-related peptides are produced upon exposure to E₂ and possibly Pg but only rarely following Prl administration. The possible role of these growth factors as mediators of hormonal effects in our experimental system remains to be established.