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  1. Madden SF, Cremona M, Farrelly AM, Low WH, McBryan J
    Cancer Gene Ther, 2023 Feb;30(2):324-334.
    PMID: 36266450 DOI: 10.1038/s41417-022-00548-0
    To prevent the development of endocrine-resistant breast cancer, additional targeted therapies are increasingly being trialled in combination with endocrine therapy. The molecular mechanisms facilitating cancer cell survival during endocrine treatment remain unknown but could help direct selection of additional targeted therapies. We present a novel proteomic timecourse dataset, profiling potential drug targets in a population of MCF7 cells during 1 year of tamoxifen treatment. Reverse phase protein arrays profiled >70 proteins across 30 timepoints. A biphasic response to tamoxifen was evident, which coincided with changes in growth rate. Tamoxifen strongly impeded cell growth for the first 160 days, followed by gradual growth recovery and eventual resistance development. The growth-impeded phase was distinguished by the phosphorylation of Stat3 (y705) and Src (y527). Tumour tissue from patients treated with neo-adjuvant endocrine therapy (<4 months) also displayed increased Stat3 and Src signalling. Inhibitors of Stat3 (napabucasin) and Src (dasatinib), were effective at killing tamoxifen-treated MCF7 and T47D cells. Sensitivity to both drugs was significantly enhanced once tamoxifen had induced the growth-impeded phase. This novel proteomic resource identifies key mechanisms enabling cell survival during tamoxifen treatment. It provides valuable insight into potential drug combinations and timing that may prevent the development of endocrine resistance.
    Matched MeSH terms: Tamoxifen/therapeutic use
  2. Yankuzo HM, Emilia ST, Shaari R, Yaacob NS
    Asian Pac J Cancer Prev, 2014;15(16):6721-6.
    PMID: 25169515
    BACKGROUND: The aim of this preliminary study was to address variations of responses observed with different starting tumor sizes of 10 and 15 mm, and the effects of different doses of tamoxifen (TAM) on experimental rat mammary tumors.

    MATERIALS AND METHODS: Thirty-five inbred female Sprague Dawley rats aged 43 days were administered with three weekly doses of N-methyl-N-nitrosourea (NMU) intraperitoneally (ip) at 50 mg/kg body weight. Animals were randomized (beginning from 10 mm tumor size) into four TAM-treated (50, 100, 200 and 500 μg/day) groups of six animals each, and another group (n=6) treated with TAM 100 μg/day at starting tumour size of 15 mm. The animals were treated by oral gavage daily for 8 weeks before sacrifice.

    RESULTS: Serum urea and creatinine, and overall physical tumor burden were significantly modulated in animals treated with variable doses of TAM compared to the untreated controls (n=5). Final body weight and tumor number were significantly different in the 10 mm-treated animals compared to those treated at 15 mm. There were no significant differences in histopathological features among all the groups.

    CONCLUSIONS: Our findings suggest the importance of standardizing tumour size and drug doses before initiation of treatment, particularly in the direct comparison of basic end-tumour physical parameters.

    Matched MeSH terms: Tamoxifen/therapeutic use*
  3. Yaacob NS, Ismail NF
    PMID: 24646375 DOI: 10.1186/1472-6882-14-106
    The Malaysian Tualang honey (TH) is not only cytotoxic to human breast cancer cell lines but it has recently been reported to promote the anticancer activity induced by tamoxifen in MCF-7 and MDA-MB-231 cells suggesting its potential as an adjuvant for the chemotherapeutic agent. However, tamoxifen produces adverse effects that could be due to its ability to induce cellular DNA damage. Therefore, the study is undertaken to determine the possible modulation of the activity of 4-hydroxytamoxifen (OHT), an active metabolite of tamoxifen, by TH in non-cancerous epithelial cell line, MCF-10A, in comparison with MCF-7 cells.
    Matched MeSH terms: Tamoxifen/therapeutic use
  4. Love RR, Hossain SM, Hussain MM, Mostafa MG, Laudico AV, Siguan SS, et al.
    Eur J Cancer, 2016 06;60:107-16.
    PMID: 27107325 DOI: 10.1016/j.ejca.2016.03.011
    PURPOSE: In premenopausal women with metastatic hormone receptor-positive breast cancer, hormonal therapy is the first-line therapy. Gonadotropin-releasing hormone analogue + tamoxifen therapies have been found to be more effective. The pattern of recurrence risk over time after primary surgery suggests that peri-operative factors impact recurrence. Secondary analyses of an adjuvant trial suggested that the luteal phase timing of surgical oophorectomy in the menstrual cycle simultaneous with primary breast surgery favourably influenced long-term outcomes.

    METHODS: Two hundred forty-nine premenopausal women with incurable or metastatic hormone receptor-positive breast cancer entered a trial in which they were randomised to historical mid-luteal or mid-follicular phase surgical oophorectomy followed by oral tamoxifen treatment. Kaplan-Meier methods, the log-rank test, and multivariable Cox regression models were used to assess overall and progression-free survival (PFS) in the two randomised groups and by hormone-confirmed menstrual cycle phase.

    RESULTS: Overall survival (OS) and PFS were not demonstrated to be different in the two randomised groups. In a secondary analysis, OS appeared worse in luteal phase surgery patients with progesterone levels <2 ng/ml (anovulatory patients; adjusted hazard ratio 1.46, 95% confidence interval [CI]: 0.89-2.41, p = 0.14) compared with those in luteal phase with progesterone level of 2 ng/ml or higher. Median OS was 2 years (95% CI: 1.7-2.3) and OS at 4 years was 26%.

    CONCLUSIONS: The history-based timing of surgical oophorectomy in the menstrual cycle did not influence outcomes in this trial of metastatic patients. ClinicalTrials.gov number NCT00293540.

    Study site: Bangladesh, The Philippines, China, Nigeria,
    Indonesia, Malaysia, Taiwan, Morocco, and Vietnam
    Matched MeSH terms: Tamoxifen/therapeutic use*
  5. Ngoo KS, Rohaizak M, Naqiyah I, Shahrun Niza AS
    Singapore Med J, 2009 May;50(5):519-21.
    PMID: 19495524
    Breast cancer is a rare condition among men with a reported incidence of about one percent. Nevertheless, it is thought to behave similarly in both genders. Due to its rarity, male breast cancer is not widely reported, especially in the Asian population.
    Matched MeSH terms: Tamoxifen/therapeutic use
  6. Teh LK, Mohamed NI, Salleh MZ, Rohaizak M, Shahrun NS, Saladina JJ, et al.
    AAPS J, 2012 Mar;14(1):52-9.
    PMID: 22183189 DOI: 10.1208/s12248-011-9313-6
    CYP2D6 plays a major role in the metabolism of tamoxifen, and polymorphism of P-glycoprotein has been associated with resistance of many drug therapies. This study investigates the clinical impact of genetic variants of CYP2D6 and ABCB1 in breast cancer patients treated with tamoxifen. Blood samples from 95 breast cancer patients treated with tamoxifen were collected and genotyped for CYP2D6 and ABCB1 variants using allele-specific PCR method. Recurrence risks were calculated using Kaplan-Meier analysis and compared using the log-rank test. Patients carrying CYP2D6*10/*10 and heterozygous null allele (IM) showed higher risks of developing recurrence and metastasis (OR 13.14; 95% CI 1.57-109.94; P = 0.004) than patients with CYP2D6*1/*1 and *1/*10 genotypes. Patients with homozygous CC genotypes of ABCB1 C3435T showed a shorter time to recurrence. Patients who were CYP2D6 IM and homozygous CC genotype of C3435T have statistically significant higher risks of recurrence (P = 0.002). Similarly, median time to recurrence in these patients was only 12 months (95% CI = 0.79-23.2) compared to those without this combination which was 48 months (95% CI = 14.7-81.2). Patients with CYP2D6 IM and homozygous CC genotype of ABCB1 C3435T have shorter times to recurrence. The results confirmed the findings of previous studies and support FDA recommendation to perform pre-genotyping in patients before the choice of therapy is determined in breast cancer patients.
    Matched MeSH terms: Tamoxifen/therapeutic use*
  7. Chin FW, Chan SC, Abdul Rahman S, Noor Akmal S, Rosli R
    Breast J, 2016 Jan-Feb;22(1):54-62.
    PMID: 26510986 DOI: 10.1111/tbj.12518
    The cytochrome P450, family 2, subfamily D, polypeptide 6 (CYP2D6) is an enzyme that is predominantly involved in the metabolism of tamoxifen. Genetic polymorphisms of the CYP2D6 gene may contribute to inter-individual variability in tamoxifen metabolism, which leads to the differences in clinical response to tamoxifen among breast cancer patients. In Malaysia, the knowledge on CYP2D6 genetic polymorphisms as well as metabolizer status in Malaysian breast cancer patients remains unknown. Hence, this study aimed to comprehensively identify CYP2D6 genetic polymorphisms among 80 Malaysian breast cancer patients. The genetic polymorphisms of all the 9 exons of CYP2D6 gene were identified using high-resolution melting analysis and confirmed by DNA sequencing. Seven CYP2D6 alleles consisting of CYP2D6*1, CYP2D6*2, CYP2D6*4, CYP2D6*10, CYP2D6*39, CYP2D6*49, and CYP2D6*75 were identified in this study. Among these alleles, CYP2D6*10 is the most common allele in both Malaysian Malay (54.8%) and Chinese (71.4%) breast cancer patients, whereas CYP2D6*4 in Malaysian Indian (28.6%) breast cancer patients. In relation to CYP2D6 genotype, CYP2D6*10/*10 is more frequently observed in both Malaysian Malay (28.9%) and Chinese (57.1%) breast cancer patients, whereas CYP2D6*4/*10 is more frequently observed in Malaysian Indian (42.8%) breast cancer patients. In terms of CYP2D6 phenotype, 61.5% of Malaysian Malay breast cancer patients are predicted as extensive metabolizers in which they are most likely to respond well to tamoxifen therapy. However, 57.1% of Chinese as well as Indian breast cancer patients are predicted as intermediate metabolizers and they are less likely to gain optimal benefit from the tamoxifen therapy. This is the first report of CYP2D6 genetic polymorphisms and phenotypes in Malaysian breast cancer patients for different ethnicities. These data may aid clinicians in selecting an optimal drug therapy for Malaysian breast cancer patients, hence improve the clinical outcome of the patients.
    Matched MeSH terms: Tamoxifen/therapeutic use
  8. Gao Y, Zhang W, Liu C, Li G
    Sci Rep, 2019 12 11;9(1):18844.
    PMID: 31827114 DOI: 10.1038/s41598-019-54289-6
    Resistance to tamoxifen is a major clinical challenge. Research in recent years has identified epigenetic changes as mediated by dysregulated miRNAs that can possibly play a role in resistance to tamoxifen in breast cancer patients expressing estrogen receptor (ER). We report here elevated levels of EMT markers (vimentin and ZEB1/2) and reduced levels of EMT-regulating miR-200 (miR-200b and miR-200c) in ER-positive breast cancer cells, MCF-7, that were resistant to tamoxifen, in contrast with the naïve parental MCF-7 cells that were sensitive to tamoxifen. Further, we established regulation of c-MYB by miR-200 in our experimental model. C-MYB was up-regulated in tamoxifen resistant cells and its silencing significantly decreased resistance to tamoxifen and the EMT markers. Forced over-expression of miR-200b/c reduced c-MYB whereas reduced expression of miR-200b/c resulted in increased c-MYB We further confirmed the results in other ER-positive breast cancer cells T47D cells where forced over-expression of c-MYB resulted in induction of EMT and significantly increased resistance to tamoxifen. Thus, we identify a novel mechanism of tamoxifen resistance in breast tumor microenvironment that involves miR-200-MYB signaling.
    Matched MeSH terms: Tamoxifen/therapeutic use*
  9. Raihan J, Ahmad U, Yong YK, Eshak Z, Othman F, Ideris A
    BMC Cancer, 2019 Apr 04;19(1):315.
    PMID: 30947706 DOI: 10.1186/s12885-019-5516-5
    BACKGROUND: Different strains of Newcastle disease virus (NDV) worldwide proved to have tumouricidal activity in several types of cancer cells. However, the possible anti-cancer activity of Malaysian NDV AF2240 strain and its mechanism of action remains unknown. The ability of cytokine-related apoptosis-inducing NDV AF2240 to treat breast cancer was investigated in the current study.

    METHODS: A total of 90 mice were used and divided into 15 groups, each group comprising of 6 mice. Tumour, body weight and mortality of the mice were determined throughout the experiment, to observe the effect of NDV and NDV + tamoxifen treatments on the mice. In addition, the toxic effect of the treatments was determined through liver function test. In order to elucidate the involvement of cytokine production induced by NDV, a total of six cytokines, i.e. IL-6, IFN-γ, MCP-1, IL-10, IL12p70 and TNF-α were measured using cytometric bead array assay (plasma) and enzyme-linked immunosorbent spot (isolated splenocytes).

    RESULTS: The results demonstrated that 4 T1 breast cancer cells in allotransplanted mice treated with AF2240 showed a noticeable inhibition of tumour growth and induce apoptotic-related cytokines.

    CONCLUSIONS: NDV AF2240 suppression of breast tumour growth is associated with induction of apoptotic-related cytokines. It would be important to further investigate the molecular mechanism underlaying cytokines production by Newcastle disease virus.

    Matched MeSH terms: Tamoxifen/therapeutic use
  10. Teh CH, Abdulghani M, Morita H, Shiro M, Hussin AH, Chan KL
    Planta Med, 2011 Jan;77(2):128-32.
    PMID: 20665368 DOI: 10.1055/s-0030-1250159
    13 α,21-Dihydroeurycomanone (1), a known quassinoid of Eurycoma longifolia Jack was recrystallized from chloroform into a novel crystal structure in space group P2 (1). Its X-ray data were compared with those of eurycomanone ( 2). Following intraperioneal injections at similar doses of 2.44 µmol/kg/day for 3 consecutive days, 2 displayed comparable potency with tamoxifen but was more potent than 1 in the anti-estrogenic effect against 17 α-ethynylestradiol (EE)-induced uterotrophy of immature rats.
    Matched MeSH terms: Tamoxifen/therapeutic use
  11. Chong HY, Taib NA, Rampal S, Saad M, Bustam AZ, Yip CH
    Asian Pac J Cancer Prev, 2010;11(4):913-7.
    PMID: 21133600
    BACKGROUND: Locally advanced breast cancer (LABC) is characterized by the presence of a large primary tumour (>5 cm) associated with or without skin or chest-wall involvement (T4) or with fixed (matted) axillary lymph nodes in the absence of any evidence of distant metastases. These cancers are classified as stage IIIA and IIIB according to the AJCC Staging System. Treatment of choice involves combinations of surgery, chemotherapy, radiotherapy and/or hormonal therapy. Current guidelines recommend primary surgery or neoadjuvant therapy followed by surgery. The primary objective of this study was to compare the outcome of LABC patients subjected to neoadjuvant chemotherapy before surgery and those who underwent surgery as the primary treatment and to determine prognostic predictors. Secondary objectives were to evaluate the response after neoadjuvant therapy and to determine the treatment compliance rate.

    METHODS: This retrospective study of Stage III breast cancer patients was conducted over a 5 year period from 1998 to 2002. The survival data were obtained from the National Registry of Births and Deaths with the end-point of the study in April 2006. The Kaplan Meier method was applied for survival analysis. Cox regression analysis by stepwise selection was performed to identify important prognostic factors.

    RESULTS: Out of a 155 evaluable patients, 74 (47.7%) had primary surgery, 62 (40%) had neoadjuvant chemotherapy, 10 patients (6.5%) were given Tamoxifen as the primary treatment, while 9 patients (5.8%) defaulted any form of treatment. After neoadjuvant chemotherapy, 9 patients defaulted further treatment, leaving 53 evaluable patients. Out of these 53 evaluable patients, 5 patients (9.4%) had complete pathological response, 5 (9.4%) a complete clinical response, and 26 (49.1%) had partial response after neoadjuvant chemotherapy. The 5-year survival in the primary surgery group was 56.7 % compared to 44.7% in the neoadjuvant chemotherapy group (p<0.01). The important prognostic factors were race, size of tumour, nodal status, estrogen receptor status and response to neoadjuvant chemotherapy.

    CONCLUSION: Patients who had primary surgery had better survival than those who underwent neoadjuvant chemotherapy, which may be due to bias in the selection of patients for neoadjuvant chemotherapy. Out of a total of 155 patients, 25.1% defaulted part of the treatment, or did not receive optimal treatment, emphasizing the importance of psychosocial support and counselling for this group of patients.

    Matched MeSH terms: Tamoxifen/therapeutic use
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