To understand the mechanisms leading to trastuzumab resistance in HER2-overexpressing breast tumors we created trastuzumab insensitive cell lines (SKBR3/100-8 and BT474/100-2). The cell lines maintain HER2 receptor overexpression, and show increase in EGFR. Upon trastuzumab treatment, SKBR3/100-8 and BT474/100-2 cell lines displayed increased growth rate and invasiveness. The trastuzumab resistance in SKBR3/100-8 and BT474/100-2 was accompanied with activation of the Wnt/β-catenin signaling pathway. Further investigation found that Wnt3 overexpression played a key role toward the development of trastuzumab resistance. The expression of Wnt3 in trastuzumab resistant cells increased nuclear expression of β-catenin and transactivated expression of EGFR. The increased Wnt3 in the trastuzumab resistant cells also promoted a parental EMT-like transition (epithelial to mesenchymal transition), increased N-cadherin, Twist, SLUG and decreased E-cadherin. Knockdown of Wnt3 by siRNA restored cytoplasmic expression of β-catenin, and decreased EGFR expression in trastuzumab resistant cells. Furthermore the EMT markers were decreased, E-cadherin was increased and the cell invasiveness was inhibited in response to the Wnt3 down-regulation. Conversely, SKBR3 cells which had been stably transfected with full-length Wnt3 exhibited EMT-like transition. The Wnt3 transfectants, SKBR3/Wnt3-7 and SKBR3/Wnt3-9, showed a significant decrease in E-cadherin and increase in N-cadherin, Twist and SLUG. The cells were less sensitive to trastuzumab compared to parental SKBR3 and vector transfected cells. In summary, our data suggests that Wnt3 overexpression activates Wnt/β-catenin signaling pathway that leads to transactivation of EGFR and promotes EMT-like transition. This could be an important mechanism leading to trastuzumab resistance in HER2 overexpressing breast cancer cells.

Qualitative and quantitative testing of circulating cell free DNA (CCFDNA) can be applied for the management of malignant and benign neoplasms. Detecting circulating DNA in cancer patients may help develop a DNA profile for early stage diagnosis in malignancies. The technical issues of obtaining, using, and analyzing CCFDNA from blood will be discussed.

Mechanisms of estrogen-induced tumorigenesis in the target organ are not well understood. It has been suggested that oxidative stress resulting from metabolic activation of carcinogenic estrogens plays a critical role in estrogen-induced carcinogenesis. We tested this hypothesis by using an estrogen-induced hamster renal tumor model, a well established animal model of hormonal carcinogenesis. Hamsters were implanted with 17␤-estradiol (␤E2), 17␣-estradiol (␣E2), 17␣-ethinylestradiol (␣EE), menadione, a combination of ␣E2 and ␣EE, or a combination of ␣EE and menadione for 7 months. The group treated with ␤E2 developed target organ specific kidney tumors. The kidneys of hamsters treated with ␣E2, ␣EE, or menadione alone did not show any gross evidence of tumor. Kidneys of hamsters treated with a combination of ␣E2 and ␣EE showed early signs of proliferation in the interstitial cells. Kidneys of hamsters treated with a combination of menadione and ␣EE showed foci of tumor with congested tubules and atrophic glomeruli. ␤E2-treated tumor-bearing kidneys showed >2-fold increase in 8-iso-prostaglandin F 2␣ (8-iso-PGF2␣) levels compared with untreated controls. Kidneys of hamsters treated with a combination of menadione and ␣EE showed increased 8-iso-PGF2␣ levels compared with untreated controls, whereas no increase in 8-iso-PGF2␣ was detected in kidneys of ␣EE-treated group. A chemical known to produce oxidative stress or a potent estrogen with poor ability to produce oxidative stress, were nontumorigenic in hamsters, when given as single agents, but induced renal tumors, when given together. Thus, these data provide evidence that oxidant stress plays a crucial role in estrogen-induced carcinogenesis.tumor ͉ hormonal carcinogenesis ͉ menadione ͉ prostaglandin ͉ metabolic activation S ex hormones are implicated in the development of a variety of human cancers (1-4). Estrogen administration to postmenopausal women is associated with an increased risk of endometrial and breast cancer (1-4). An increasing evidence of elevated breast cancer risk with increases in total lifetime exposure of women to estrogens has been presented (1-3). Recently, the clinical trial of estrogen plus progestin treatment therapy was stopped because of an increased risk of breast cancer (5). Knowledge of how estrogens induce proliferation and tumorigenesis in their target organ is not well defined (6-9). The mechanism of tumor induction by estrogens is being investigated in rodent models of hormonal carcinogenesis. The natural female sex hormone 17␤-estradiol (␤E2) and the synthetic estrogen diethylstilbestrol induce tumors in rats, mice, and hamsters (10-13). It must be noted that in rodent models, different estrogens tested have not shown similar carcinogenic potential despite their similar hormonal potencies (6, 14, 15). However, carcinogenic and noncarcinogenic estrogens differ in their metabolic activation profiles (14-17). Therefore, it is postulated that estrogen metabolism may play a key role in hormonal carcinogenesis.Estrogens can be met...

Chemokines are a family of small cytokines, which guide a variety of immune/inflammatory cells to the site of tumor in tumorigenesis. A dysregulated expression of chemokines is implicated in different types of cancer including prostate cancer. The progression and metastasis of prostate cancer involve a complex network of chemokines that regulate the recruitment and trafficking of immune cells. The chemokine CCL2 and its main receptor CCR2 have been receiving particular interest on their roles in cancer pathogenesis. The up-regulation of CCL2/CCR2 and varied immune conditions in prostate cancer, are associated with cancer advancement, metastasis, and relapse. Here we reviewed recent findings, which link CCL2/CCR2 to the inflammation and cancer pathogenesis, and discussed the therapeutic potential of CCL2/CCR2 axis in cancer treatment based on results from our group and other investigators, with a major focus on prostate cancer.

Clinically, HER2 proto-oncogene amplification is found in about 25–30% of human breast cancers, where it is correlated to a poor prognosis. Constitutive STAT3 activation is found in about 50–60% of the breast tumors and associated with tumorigenesis and drug resistance. In this study, we showed that STAT3 was phosphorylated in HER2-overexpressing, ER-positive human breast tumors and, furthermore, phosphorylated STAT3 promoted the stem-like cell phenotype. We examined the dysregulation of the stem cell markers (Oct-4, Sox-2 and CD44) and the tumorsphere formation in HER2-overexpressing human breast cancer cell lines. We demonstrated that the STAT3 inhibitor, Stattic, treatment abolished the cancer stem cell phenotype in HER2-positive breast cancers. Combined treatment of Herceptin and Stattic showed the synergistic effect on the cancer cell growth in vitro. In addition, when the STAT3 gene was knocked down, the expression of the stem cell markers Oct-4, Sox-2 and CD44 were downregulated and tumorsphere formation was abolished. HER2-elicited STAT3 signaling may provide a potential model for drug resistance induced by stem-like cell characteristics. This mechanism may be responsible for acquiring resistance to Herceptin in the treatment of HER2-overexpressing breast tumors. Based on our findings, targeting pSTAT3 could overcome Herceptin-induced resistance in HER2-overexpressing breast tumors.

Breast cancer is the most common cancer in women and distant site metastasis is the main cause of death in breast cancer patients. There is increasing evidence supporting the role of epithelial-mesenchymal transition (EMT) in tumor cell progression, invasion, and metastasis. During the process of EMT, epithelial cancer cells acquire molecular alternations that facilitate the loss of epithelial features and gain of mesenchymal phenotype. Such transformation promotes cancer cell migration and invasion. Moreover, emerging evidence suggests that EMT is associated with the increased enrichment of cancer stem-like cells (CSCs) and these CSCs display mesenchymal characteristics that are resistant to chemotherapy and target therapy. However, the clinical relevance of EMT in human cancer is still under debate. This review will provide an overview of current evidence of EMT from studies using clinical human breast cancer tissues and its associated challenges.

Poly (ADP-ribose) polymerases (PARPs) play an important role in various cellular processes, such as replication, recombination, chromatin remodeling, and DNA repair. Emphasizing PARP’s role in facilitating DNA repair, the PARP pathway has been a target for cancer researchers in developing compounds which selectively target cancer cells and increase sensitivity of cancer cells to other anticancer agents, but which also leave normal cells unaffected. Since certain tumors (BRCA1/2 mutants) have deficient homologous recombination repair pathways, they depend on PARP-mediated base excision repair for survival. Thus, inhibition of PARP is a promising strategy to selectively kill cancer cells by inactivating complementary DNA repair pathways. Although PARP inhibitor therapy has predominantly targeted BRCA-mutated cancers, this review also highlights the growing conversation around PARP inhibitor treatment for non-BRCA-mutant tumors, those which exhibit BRCAness and homologous recombination deficiency. We provide an update on the field’s progress by considering PARP inhibitor mechanisms, predictive biomarkers, and clinical trials of PARP inhibitors in development. Bringing light to these findings would provide a basis for expanding the use of PARP inhibitors beyond BRCA-mutant breast tumors.

In vitro studies have shown that insulin-like growth factor (IGF) is a mitogen for breast cancer cells. However, the associations of plasma IGF-I with tumor histopathology in high-risk groups need further investigation. We hypothesize that plasma IGF-I and serum IGFBP3 concentrations in breast cancer patients may provide useful information on the progression of their disease, and determine the probability of recurrence and survival. We have carried out a retrospective study on 130 minority breast cancer patients. Plasma IGF-I and serum IGFBP3 were correlated with tumor histopathology, menopausal status, treatment modality, recurrence rates, and probability of survival. Plasma IGF-I and serum IGFBP3 were measured by radioimmunoassay. Our studies show that breast cancer patients have elevated plasma IGF-I and serum IGFBP3 levels. In addition we observed the following: IGF-I did not correlate with age and nodal stage. IGF-I and IGFBP3 increased with tumor size (T4). IGF-I did not correlate with estrogen receptor status, but did increase in progesterone-receptor-positive patients. IGF-I levels were higher in premenopausal patients and in women with cancer recurrence. Tamoxifen reduced IGF-I levels significantly and reduced the risk of recurrence. The survival probability was greater in patients with plasma IGF-I levels <120 ng/ml. In conclusion, lowering of plasma IGF-I may offer the following benefits: (a) reduce the risk of developing breast cancer in high-risk groups; (b) slow the progression of breast cancer in patients at early stages of cancer; (c) lower the risk of recurrence, and (d) increase the probability of survival.