Intrinsic Resistance to Chemotherapy in Breast Cancer

Deciphering cellular and molecular mechanism of MUC13 mucin involved in cancer cell plasticity and drug resistance

There has been a surge of interest in recent years in understanding the intricate mechanisms underlying cancer progression and treatment resistance. One molecule that has recently emerged in these mechanisms is MUC13 mucin, a transmembrane glycoprotein. Researchers have begun to unravel the molecular complexity of MUC13 and its impact on cancer biology. Studies have shown that MUC13 overexpression can disrupt normal cellular polarity, leading to the acquisition of malignant traits. Furthermore, MUC13 has been associated with increased cancer plasticity, allowing cells to undergo epithelial-mesenchymal transition (EMT) and metastasize. Notably, MUC13 has also been implicated in the development of chemoresistance, rendering cancer cells less responsive to traditional treatment options. Understanding the precise role of MUC13 in cellular plasticity, and chemoresistance could pave the way for the development of targeted therapies to combat cancer progression and enhance treatment efficacy.

Effect of quercetin on doxorubicin cytotoxicity in sensitive and resistant human MCF7 breast cancer cell lines

Chemoresistance is the major cause of cancer recurrence, relapse and eventual death. Doxorubicin resistance is one such challenge in breast cancer. The use of quercetin, an antioxidant, in combination with doxorubicin has been investigated for offering protection to normal cells from the toxic side effects of doxorubicin in addition to modulation of its resistance. The present study aimed to investigate the effects of quercetin in prevention of a doxorubicin-chemoresistant phenotype in both doxorubicin-sensitive and -resistant human MCF-7 breast cancer cell lines. A doxorubicin-resistant MCF-7 cell line was established. The development of resistant cells was closely monitored for changes in morphological features. Sensitivity to doxorubicin and the doxorubicin/quercetin combination was assessed using the tetrazolium assay. To determine the mechanism by which quercetin sensitizes the doxorubicin MCF-7-resistant cell line to doxorubicin, gene expression alterations in breast cancer-related genes were examined using the reverse transcription-quantitative PCR (RT-qPCR) array technology. Resistant MCF cells were successfully developed and the inhibitory concentration (IC50) value of doxorubicin increased from 0.133 to 4 µM (wild-type to resistant). The effects of the quercetin/doxorubicin combination exhibited different effects on wild-type vs. resistant cells. The IC50 of doxorubicin was reduced in wild cells, whereas resistant cells showed an increase in cell viability at lower concentrations and a potentiation of the effects of doxorubicin only at higher concentrations. Annexin V/propidium iodide staining demonstrated that quercetin drives cells into late apoptosis and necrosis, but in resistant cells, necrosis predominates. RT-qPCR results revealed that quercetin led to a reversal in doxorubicin effects via up- and downregulation of important genes such as SNAI2, PLAU and CSF1 genes. Downregulation of cell migration genes, SNAI2 (-31.23-fold) and plasminogen activator, urokinase (PLAU; -30.62-fold), and the apoptotic pathway gene, colony stimulating factor 1 (CSF1; -17.25-fold) were the most important querticin-associated events. Other gene alterations were also observed involving cell cycle arrest and DNA repair pathways. The results of the present study indicated that quercetin could lead to a reversal of doxorubicin resistance in breast cancer cells via downregulation of the expression of important genes, such as SNAI2, PLAU and CSF1. Such findings may represent a potential strategy for reversing breast cancer cell-related chemoresistance.

UBE2T promotes breast cancer tumor growth by suppressing DNA replication stress

Breast cancer is a leading cause of cancer-related deaths among women, and current therapies benefit only a subset of these patients. Here, we show that ubiquitin-conjugating enzyme E2T (UBE2T) is overexpressed in patient-derived breast cancer samples, and UBE2T overexpression predicts poor prognosis. We demonstrate that the transcription factor AP-2 alpha (TFAP2A) is necessary for the overexpression of UBE2T in breast cancer cells, and UBE2T inhibition suppresses breast cancer tumor growth in cell culture and in mice. RNA sequencing analysis identified interferon alpha-inducible protein 6 (IFI6) as a key downstream mediator of UBE2T function in breast cancer cells. Consistently, UBE2T inhibition downregulated IFI6 expression, promoting DNA replication stress, cell cycle arrest, and apoptosis and suppressing breast cancer cell growth. Breast cancer cells with IFI6 inhibition displayed similar phenotypes as those with UBE2T inhibition, and ectopic IFI6 expression in UBE2T-knockdown breast cancer cells prevented DNA replication stress and apoptosis and partly restored breast cancer cell growth. Furthermore, UBE2T inhibition enhanced the growth-suppressive effects of DNA replication stress inducers. Taken together, our study identifies UBE2T as a facilitator of breast cancer tumor growth and provide a rationale for targeting UBE2T for breast cancer therapies.

Hypoxia-regulated microRNAs: the molecular drivers of tumor progression

Hypoxia is a common feature of the tumor microenvironment (TME) of nearly all solid tumors, leading to therapeutic failure. The changes in stiffness of the extracellular matrix (ECM), pH gradients, and chemical balance that contribute to multiple cancer hallmarks are closely regulated by intratumoral oxygen tension via its primary mediators, hypoxia-inducible factors (HIFs). HIFs, especially HIF-1α, influence these changes in the TME by regulating vital cancer-associated signaling pathways and cellular processes including MAPK/ERK, NF-κB, STAT3, PI3K/Akt, Wnt, p53, and glycolysis. Interestingly, research has revealed the involvement of epigenetic regulation by hypoxia-regulated microRNAs (HRMs) of downstream target genes involved in these signaling. Through literature search and analysis, we identified 48 HRMs that have a functional role in the regulation of 5 key cellular processes: proliferation, metabolism, survival, invasion and migration, and immunoregulation in various cancers in hypoxic condition. Among these HRMs, 17 were identified to be directly associated with HIFs which include miR-135b, miR-145, miR-155, miR-181a, miR-182, miR-210, miR-224, miR-301a, and miR-675-5p as oncomiRNAs, and miR-100-5p, miR-138, miR-138-5p, miR-153, miR-22, miR-338-3p, miR-519d-3p, and miR-548an as tumor suppressor miRNAs. These HRMs serve as a potential lead in the development of miRNA-based targeted therapy for advanced solid tumors. Future development of combined HIF-targeted and miRNA-targeted therapy is possible, which requires comprehensive profiling of HIFs-HRMs regulatory network, and improved formula of the delivery vehicles to enhance the therapeutic kinetics of the targeted cancer therapy (TCT) moving forward.

Expression of BCRP/ABCG2 Protein in Invasive Breast Cancer and Response to Neoadjuvant Chemotherapy

BACKGROUND

Breast cancer resistance protein (BCRP), or ABCG2 (ATP-binding cassette sub-family G member 2), is an ATP-binding cassette (ABC) transporter that mediates energy-dependent transport of substrate drugs out of the cell. Its overexpression may contribute to intrinsic drug resistance in vitro. However, the current literature has not yet clarified the clinical significance of BCRP/ABCG2 in invasive breast carcinoma.

OBJECTIVES

The purpose of this study was to validate the expression of BCRP/ABCG2 in invasive breast carcinoma and its role in response to neoadjuvant chemotherapy.

METHODS

In this study, a pretherapeutic core biopsy was performed in 222 patients. BCRP/ABCG2 expression in carcinoma tissue was measured by immunohistochemistry. BCRP/ABCG2 expression correlations with clinicopathological features, molecular subtypes, and therapy response after neoadjuvant chemotherapy were investigated.

RESULTS

The results showed that BCRP/ABCG2 was expressed in different molecular subtypes. The proportions of patients with high BCRP/ABCG2 expression were similar in luminal A and luminal B tumors (Luminal B, 80%; Luminal A, 78%), compared with other molecular subtypes (Triple-negative, 63%; HER-2+, 58%. P=0.05). BCRP/ABCG2 expression and the number of lymphatic metastases (𝑃=0.001) and tumor size (𝑃=0.011) demonstrated a statistically significant correlation. Low BCRP/ABCG2 expression was associated with an increased pathological complete response (pCR) rate of 38%, higher than the 19% in tumors with high BCRP/ABCG2 expression (P=0.002). In multivariable analysis, BCRP/ABCG2 and hormone receptor (HR) expression were identified as independent risk factors of pCR (P=0.003, P=0.013. respectively).

CONCLUSIONS

BCRP/ABCG2 is highly expressed in hormone receptor-positive breast cancer. High BCRP/ABCG2 expression is associated with lymphatic metastasis, tumor size, and poor pCR. BCRP/ABCG2 may be a novel potential biomarker that can predict clinical progression and therapy response after neoadjuvant chemotherapy.

Battling Chemoresistance in Cancer: Root Causes and Strategies to Uproot Them

With nearly 10 million deaths, cancer is the leading cause of mortality worldwide. Along with major key parameters that control cancer treatment management, such as diagnosis, resistance to the classical and new chemotherapeutic reagents continues to be a significant problem. Intrinsic or acquired chemoresistance leads to cancer recurrence in many cases that eventually causes failure in the successful treatment and death of cancer patients. Various determinants, including tumor heterogeneity and tumor microenvironment, could cause chemoresistance through a diverse range of mechanisms. In this review, we summarize the key determinants and the underlying mechanisms by which chemoresistance appears. We then describe which strategies have been implemented and studied to combat such a lethal phenomenon in the management of cancer treatment, with emphasis on the need to improve the early diagnosis of cancer complemented by combination therapy.

LncRNA MAFG-AS1 affects the tumorigenesis of breast cancer cells via the miR-574-5p/SOD2 axis

Amounting evidence suggested that long non coding RNAs (lncRNAs) played vital roles in the progression of various cancers. The aim of this study is to examine the biological roles and underlying mechanisms of lncRNA MAFG-AS1 in the tumorigenesis of breast cancer (BC) cells. Here we showed that downregulation of MAFG-AS1 inhibited the viability, migration, and invasion of BC cells. Mechanism investigation showed that inhibition of MAFG-AS1 induced apoptosis via the intrinsic apoptotic pathway and overexpression of Bcl-2 could inhibited it. Further, MAFG-AS1 acts as a sponge of miR-574-5p which directly binds to SOD2 mRNA. Re-expression of SOD2 using a 3'-UTR mutant SOD2 reversed the effects of silencing of MAFG-AS1 on BC cells. Finally, downregulation of MAFG-AS1 inhibited the growth of tumour in vivo. Together, MAFG-AS1 acts as an oncogene via regulation of miR-574-5p/SOD2 axis in BC cells.

Mechanisms of Resistance to Chemotherapy in Breast Cancer and Possible Targets in Drug Delivery Systems

Breast cancer (BC) is one of the most important cancers worldwide, and usually, chemotherapy can be used in an integrative approach. Usually, chemotherapy treatment is performed in association with surgery, radiation or hormone therapy, providing an increased outcome to patients. However, tumors can develop resistance to different drugs, progressing for a more aggressive phenotype. In this scenario, the use of nanocarriers could help to defeat tumor cell resistance, providing a new therapeutic perspective for patients. Thus, this systematic review aims to bring the molecular mechanisms involved in BC chemoresistance and extract from the previous literature information regarding the use of nanoparticles as potential treatment for chemoresistant breast cancer.

CM082 Enhances the Efficacy of Chemotherapeutic Drugs by Inhibiting the Drug Efflux Function of ABCG2

The overexpression of ATP-binding cassette (ABC) transporters is one of the important mechanisms of multidrug resistance (MDR). Some tyrosine kinase inhibitors (TKIs) such as CM082 might be a potential ABC transporter inhibitor, thus potentially reversing MDR. We used a 3-(4,5-dimethylthiazol-2-yl)-2,5-dimethyltetrazolium bromide (MTT) assay to determine the cytotoxicity and reversal effect of CM082. A xenograft model was established to evaluate the reversal MDR efficacy in vivo. The intracellular accumulation and efflux of ABCG2 substrates were measured by flow cytometry. We investigated the binding sites of ABCG2 via photolabeling ABCG2 with [125I]-iodoarylazidoprazosin (IAAP). Quantitative real-time PCR and western blot were utilized to analyze mRNA and protein expression. We found that CM082 could enhance the efficacy of substrate in ABCG2-overexpressing cells both in vitro and in vivo. Furthermore, CM082 significantly increased intracellular accumulation of ABCG2 substrates by inhibiting the efflux activity. CM082 stimulated ABCG2 ATPase activity and competed with [125I]-IAAP photolabeling of ABCG2 in a concentration-dependent manner. However, CM082 did not alter ABCG2 expression at protein and mRNA levels or inhibit vascular endothelial growth factor (VEGF) downstream signaling of AKT and extracellular signal-regulated kinase (ERK). Further research is encouraged to confirm whether CM082 concomitant with anticancer drugs of ABCG2 substrates could improve the clinical outcomes of cancer treatment in cancer patients with ABCG2 overexpression.

xCT (SLC7A11) expression confers intrinsic resistance to physical plasma treatment in tumor cells

Cold physical plasma is a partially ionized gas investigated as a new anticancer tool in selectively targeting cancer cells in monotherapy or in combination with therapeutic agents. Here, we investigated the intrinsic resistance mechanisms of tumor cells towards physical plasma treatment. When analyzing the dose-response relationship to cold plasma-derived oxidants in 11 human cancer cell lines, we identified four 'resistant' and seven 'sensitive' cell lines. We observed stable intracellular glutathione levels following plasma treatment only in the 'resistant' cell lines indicative of altered antioxidant mechanisms. Assessment of proteins involved in GSH metabolism revealed cystine-glutamate antiporter xCT (SLC7A11) to be significantly more abundant in the 'resistant' cell lines as compared to 'sensitive' cell lines. This decisive role of xCT was confirmed by pharmacological and genetic inhibition, followed by cold physical plasma treatment. Finally, microscopy analysis of ex vivo plasma-treated human melanoma punch biopsies suggested a correlation between apoptosis and basal xCT protein abundance. Taken together, our results demonstrate that xCT holds the potential as a biomarker predicting the sensitivity of tumor cells towards plasma treatment.

Drug resistance and combating drug resistance in cancer

Cancer is the second leading cause of death in the US. Current major treatments for cancer management include surgery, cytotoxic chemotherapy, targeted therapy, radiation therapy, endocrine therapy and immunotherapy. Despite the endeavors and achievements made in treating cancers during the past decades, resistance to classical chemotherapeutic agents and/or novel targeted drugs continues to be a major problem in cancer therapies. Drug resistance, either existing before treatment (intrinsic) or generated after therapy (acquired), is responsible for most relapses of cancer, one of the major causes of death of the disease. Heterogeneity among patients and tumors, and the versatility of cancer to circumvent therapies make drug resistance more challenging to deal with. Better understanding the mechanisms of drug resistance is required to provide guidance to future cancer treatment and achieve better outcomes. In this review, intrinsic and acquired resistance will be discussed. In addition, new discoveries in mechanisms of drug resistance will be reviewed. Particularly, we will highlight roles of ATP in drug resistance by discussing recent findings of exceptionally high levels of intratumoral extracellular ATP as well as intracellular ATP internalized from extracellular environment. The complexity of drug resistance development suggests that combinational and personalized therapies, which should take ATP into consideration, might provide better strategies and improved efficacy for fighting drug resistance in cancer.

Influences of adjuvant treatments in hormone receptor positive breast cancer on receptor conversion in recurrent breast cancer

BACKGROUND

To examine influences on the receptor status of a local cohort of patients with recurrent breast cancer after primary diagnosis of hormone receptor positive breast cancer.

METHODS

We retrospectively analyzed 2078 female patients with primary hormone receptor positive breast cancer treated at the university hospital of Wuerzburg between 2000 and 2013. Main focus was on discordance in receptor status in recurrent disease.

RESULTS

196 patients with the primary diagnosis of hormone receptor positive breast cancer developed recurrent disease. 29.1% of patients revealed discordance in estrogen receptor (ER), progesterone receptor (PgR) or HER2 receptor (ER⁺ to ^-: 33.3%; PgR⁺ to ^-: 59.6%; HER2⁺ to ^-: 8.8%; HER2^- to ⁺: 17.5%). Aggressive tumor biology such as low grading or involvement of axillary lymph nodes showed increased risk of receptor conversion in relapse. Premenopausal patients with adjuvant application of tamoxifen and the application of chemotherapy had a significantly lower risk for the development of ER negative recurrent disease. Receptor changes to ER and PgR negativity in recurrent disease showed a trend to worse overall survival (OS).

CONCLUSIONS

Histological analysis of recurrent disease is indispensable, since one-third of patients with hormone receptor positive breast cancer develop change in the receptor status.

Cluster of differentiation 147 mediates chemoresistance in breast cancer by affecting vacuolar H+-ATPase expression and activity

Vacuolar H⁺-ATPase (V-ATPase) serves a key role in adjusting and maintaining the intracellular pH, as well as in regulating the drug resistance of tumor cells. In recent years, the expression level of V-ATPase has been considered to be able to predict the sensitivity of breast cancer cells to chemotherapy drugs. Cluster of differentiation 147 (CD147) is known to serve a key role in the development and progression of breast cancer. The present study aimed to identify the role CD147 and V-ATPase in chemoresistance in breast cancer, and to characterize the regulation of CD147 on V-ATPase. Firstly, the expression levels of CD147 and V-ATPase were detected in chemotherapy-resistance breast cancer samples. It was demonstrated that V-ATPase was highly expressed in chemotherapy-resistance breast cancer samples, and that its expression was correlated with CD147 expression. Subsequently, MCF-7 and MDA-MB-231 cells were used to study the regulatory effect of CD147 on the expression and function of V-ATPase. Gene transfection or small interfering RNA transfection were used to control the expression of CD147 in the two cell lines. The results revealed that the overexpression of CD147 increased the expression of V-ATPase in MCF-7 cells, whereas CD147 knockdown decreased V-ATPase expression in MDA-MB-231 cells. It was also observed that CD147 affected the V-ATPase activity, regulating the transmembrane pH gradient of cancer cells. These results demonstrated that CD147 was associated with the sensitivity of chemotherapeutic drugs of epirubicin and docetaxel, while pantoprazole was able to partially reverse the CD147-mediated chemoresistance in breast cancer. Therefore, the current study provided a possible mechanism for further examination of drug resistance in breast cancer.

The Evolution and Ecology of Resistance in Cancer Therapy

Despite continuous deployment of new treatment strategies and agents over many decades, most disseminated cancers remain fatal. Cancer cells, through their access to the vast information of human genome, have a remarkable capacity to deploy adaptive strategies for even the most effective treatments. We note there are two critical steps in the clinical manifestation of treatment resistance. The first, which is widely investigated, requires deployment of a mechanism of resistance that usually involves increased expression of molecular machinery necessary to eliminate the cytotoxic effect of treatment. However, the emergence of a resistant phenotype is not in itself clinically significant. That is, resistant cells affect patient outcomes only when they form a sufficiently large population to allow tumor progression and treatment failure. Importantly, proliferation of the resistant phenotype is by no means certain and, in fact, depends on complex Darwinian dynamics governed by the costs and benefits of the resistance mechanisms in the context of the local environment and competing populations. Attempts to target molecular machinery of resistance have had little clinical success largely because of the diversity within the human genome-therapeutic interruption of one mechanism simply results in its replacement by an alternative. We explore an alternative strategy for overcoming treatment resistance that seeks to understand and exploit the critical evolutionary dynamics that govern proliferation of the resistant phenotypes. In general, this approach has shown that, although emergence of resistance mechanisms in cancer cells to every current therapy is inevitable, proliferation of the resistant phenotypes is not and can be delayed and even prevented with sufficient understanding of the underlying ecoevolutionary dynamics.

Bypassing Mechanisms of Mitochondria-Mediated Cancer Stem Cells Resistance to Chemo- and Radiotherapy

Cancer stem cells (CSCs) are highly resistant to conventional chemo- and radiotherapeutic regimes. Therefore, the multiple drug resistance (MDR) of cancer is most likely due to the resistance of CSCs. Such resistance can be attributed to some bypassing pathways including detoxification mechanisms of reactive oxygen and nitrogen species (RO/NS) formation or enhanced autophagy. Unlike in normal cells, where RO/NS concentration is maintained at certain threshold required for signal transduction or immune response mechanisms, CSCs may develop alternative pathways to diminish RO/NS levels leading to cancer survival. In this minireview, we will focus on elaborated mechanisms developed by CSCs to attenuate high RO/NS levels. Gaining a better insight into the mechanisms of stem cell resistance to chemo- or radiotherapy may lead to new therapeutic targets thus serving for better anticancer strategies.

Application of Evolutionary Principles to Cancer Therapy

The dynamic cancer ecosystem, with its rich temporal and spatial diversity in environmental conditions and heritable cell phenotypes, is remarkably robust to therapeutic perturbations. Even when response to therapy is clinically complete, adaptive tumor strategies almost inevitably emerge and the tumor returns. Although evolution of resistance remains the proximate cause of death in most cancer patients, a recent analysis found that evolutionary terms were included in less than 1% of articles on the cancer treatment outcomes, and this has not changed in 30 years. Here, we review treatment methods that attempt to understand and exploit intratumoral evolution to prolong response to therapy. In general, we find that treating metastatic (i.e., noncurable) cancers using the traditional strategy aimed at killing the maximum number of tumor cells is evolutionarily unsound because, by eliminating all treatment-sensitive cells, it enables rapid proliferation of resistant populations-a well-known evolutionary phenomenon termed "competitive release." Alternative strategies, such as adaptive therapy, "ersatzdroges," and double-bind treatments, shift focus from eliminating tumor cells to evolution-based methods that suppress growth of resistant populations to maintain long-term control.

Release of Ca2+ from the endoplasmic reticulum and its subsequent influx into mitochondria trigger celastrol-induced paraptosis in cancer cells

Celastrol, a triterpene extracted from the Chinese “Thunder of God Vine”, is known to have anticancer activity, but its underlying mechanism is not completely understood. In this study, we show that celastrol kills several breast and colon cancer cell lines by induction of paraptosis, a cell death mode characterized by extensive vacuolization that arises via dilation of the endoplasmic reticulum (ER) and mitochondria. Celastrol treatment markedly increased mitochondrial Ca²⁺ levels and induced ER stress via proteasome inhibition in these cells. Both MCU (mitochondrial Ca²⁺ uniporter) knockdown and pretreatment with ruthenium red, an inhibitor of MCU, inhibited celastrol-induced mitochondrial Ca²⁺ uptake, dilation of mitochondria/ER, accumulation of poly-ubiquitinated proteins, and cell death in MDA-MB 435S cells. Inhibition of the IP₃ receptor (IP₃R) with 2-aminoethoxydiphenyl borate (2-APB) also effectively blocked celastrol-induced mitochondrial Ca²⁺ accumulation and subsequent paraptotic events. Collectively, our results show that the IP₃R-mediated release of Ca²⁺ from the ER and its subsequent MCU-mediated influx into mitochondria critically contribute to celastrol-induced paraptosis in cancer cells.

Abundant circulating microRNAs in breast cancer patients fluctuate considerably during neoadjuvant chemotherapy

Previous studies have revealed the aberrant expression of a number of microRNAs (miRNA/miRs) in the blood circulation of patients with breast cancer (BC). The aim of the present study was to assess the effect of neoadjuvant chemotherapy on the levels of a panel of BC-associated miRNAs, which are at relatively low (let-7, miR-10b, miR-34, miR-155, miR-200c and miR-205) or abundant (miR-21, miR-195 and miR-221) levels in the circulation. Patients with primary operable or locally advanced BC were enrolled in the study. The plasma levels of the miRNAs at baseline and at the fourth cycle of treatment were compared. Patients with stage II disease exhibited higher basal miRNAs levels than those with higher stages. The difference was most evident for miR-155 and miR-21 (P=0.05). From the initial to the fourth cycle of chemotherapy, the miRNA levels changed substantially. In samples in which the miRNA levels generally declined, a marked decrease (≤15,500-fold) was evident for the abundant miRNAs. Notably, the occurrence of a decrease in miRNA levels was more frequent in patients with smaller tumor sizes (P<0.05 for miR-21 and miR-195). This proof-of-concept study provides evidence that highly expressed miRNAs are affected most frequently by chemotherapy, particularly in patients with early stage tumors. This information may be valuable in assessing the response of the patients to therapy.

Nanotechnology approaches for personalized treatment of multidrug resistant cancers

The efficacy of chemotherapy is substantially limited by the resistance of cancer cells to anticancer drugs that fluctuates significantly in different patients. Under identical chemotherapeutic protocols, some patients may receive relatively ineffective doses of anticancer agents while other individuals obtain excessive amounts of drugs that induce severe adverse side effects on healthy tissues. The current review is focused on an individualized selection of drugs and targets to suppress multidrug resistance. Such selection is based on the molecular characteristics of a tumor from an individual patient that can potentially improve the treatment outcome and bring us closer to an era of personalized medicine.

Recombinant human PDCD5 protein enhances chemosensitivity of breast cancer in vitro and in vivo

Resistance to paclitaxel is common for treatment of breast cancer. Programmed cell death 5 (PDCD5) accelerates apoptosis in different cell types in response to various stimuli; moreover PDCD5 has been shown to be down-regulated in many tumors. In this study, protein levels of PDCD5 were found to be up-regulated in paclitaxel-treated MDA-MB-231 breast cancer cells. MTT, CCK-8, and clonogenic assays have shown that recombinant human PDCD5 (rhPDCD5) alone could not produce an obvious growth inhibition. However, upon paclitaxel triggering apoptosis, rhPDCD5 protein potentiated chemotherapeutic drugs-induced growth arrest in MDA-MB-231, SK-BR-3, and ZR-75-1 breast cancer cells. In vivo, we use a human breast cancer xenograft model to study. We found that rhPDCD5 dramatically improves the antitumor effects of paclitaxel treatment by intraperitoneal administration. These data suggest that rhPDCD5 has the potential to use as a therapeutic agent to enhance the paclitaxel sensitivity of breast cancer cells.

ABCG2 is associated with HER-2 expression, lymph node metastasis and clinical stage in breast invasive ductal carcinoma

Background

ABCG2 is an ABC transporter. It has been demonstrated that endogenous ABCG2 expression in certain cancers is a possible reflection of the differentiated phenotype of the cell of origin and likely contributes to intrinsic drug resistance. But little is known about the contribution of ABCG2 to the drug resistance and the clinicopathological characteristics in breast cancer. In the present study, we investigated the expression of ABCG2 and the correlations between ABCG2 expression and patients' clinicopathological and biological characteristics.

Methods

Immunohistochemistry was employed on the tissue microarray paraffin sections of surgically removed samples from 196 breast cancer patients with clinicopathological data.

Results

The results showed that ABCG2 was expressed in different intensities and distributions in the tumor cells of the breast invasive ductal carcinoma. A positive stain for ABCG2 was defined as a brown stain observed in the cytoplasm and cytomembrane. A statistically significant correlation was demonstrated between ABCG2 expression and HER-2 expression (p = 0.001), lymph node metastasis (p = 0.049), and clinical stage (p = 0.015) respectively.

Conclusion

ABCG2 correlated with Her-2 expression, lymph node metastasis and clinical stage in breast invasive ductal carcinoma. It could be a novel potential bio-marker which can predict biological behavior, clinical progression, prognosis and chemotherapy effectiveness.