Gemcitabine and Oxaliplatin in Patients With Metastatic Breast Cancer Resistant to or Pretreated With Both Anthracyclines and Taxanes

The role of CircRNA/miRNA/mRNA axis in breast cancer drug resistance

Multidrug resistance is one of the major obstacles in the treatment of cancers. This undesirable feature increases the mortality rate of cancers, including breast cancer. Circular RNA (CircRNA)/microRNA (miRNA)/messenger RNA (mRNA) is one of the important axes with major roles in the promotion and resistance of breast cancer. This heterogeneous pathway includes mRNA of oncogenes and tumor suppressors, which are controlled by miRNAs and CircRNAs. Unfortunately, this network could be easily deregulated, resulting in drug resistance and tumor development. Therefore, understanding these dysregulations may thus help to identify effective therapeutic targets. On this basis, we try to review the latest findings in the field, which could help us to better comprehend this significant axis in breast cancer.

Correlation of Platinum Cytotoxicity to Drug-DNA Adduct Levels in a Breast Cancer Cell Line Panel

Platinum drugs, including carboplatin and oxaliplatin, are commonly used chemotherapy drugs that kill cancer cells by forming toxic drug-DNA adducts. These drugs have a proven, but modest, efficacy against several aggressive subtypes of breast cancer but also cause several side effects that can lead to the cessation of treatment. There is a clinical need to identify patients who will respond to platinum drugs in order to better inform clinical decision making. Diagnostic microdosing involves dosing patients or patient samples with subtherapeutic doses of radiolabeled platinum followed by measurement of platinum-DNA adducts in blood or tumor tissue and may be used to predict patient response. We exposed a panel of six breast cancer cell lines to ¹⁴C-labeled carboplatin or oxaliplatin at therapeutic and microdose (1% therapeutic dose) concentrations for a range of exposure lengths and isolated DNA from the cells. The DNA was converted to graphite, and measurement of radiocarbon due to platinum-DNA adduction was quantified via accelerator mass spectrometry (AMS). We observed a linear correlation in adduct levels between the microdose and therapeutic dose, and the level of platinum-DNA adducts corresponded to cell line drug sensitivity for both carboplatin and oxaliplatin. These results showed a clear separation in adduct levels between the sensitive and resistant groups of cell lines that could not be fully explained or predicted by changes in DNA repair rates or mutations in DNA repair genes. Further, we were able to quantitate oxaliplatin-DNA adducts in the blood and tumor tissue of a metastatic breast cancer patient. Together, these data support the use of diagnostic microdosing for predicting patient sensitivity to platinum. Future studies will be aimed at replicating this data in a clinical feasibility trial.

Optimal outcomes for liver-dominant metastatic breast cancer with transarterial chemoembolization with drug-eluting beads loaded with doxorubicin

The purpose of this study was to evaluate the efficacy of image-guided delivery of locoregional chemotherapy to breast cancer hepatic metastases using doxorubicin-loaded drug-eluting beads (DEBDOX). An IRB-approved multi-center, prospective, open, non-controlled repeat treatment registry to investigate the safety and efficacy of doxorubicin microspheres in the treatment of patients with unresectable liver metastasis from breast cancer was reviewed. Statistical analysis was performed with differences of P < 0.05 considered significant. About 40 patients with metastatic breast cancer (MBC) to the liver underwent a total of 75 image-guided procedures with hepatic arterial drug-eluting beads loaded with doxorubicin (DEBDOX). Treatment was well tolerated with a total of eight patients sustaining 13 adverse events within the 30 days of each treatment session. All adverse events were either a grade I or grade II in toxicity. After a median follow-up of 12 months in all patients, the hepatic progression-free survival was a median of 26 months and overall survival was a median of 47 months. The treatment of hepatic metastasis from MBC using DEBDOX is an effective local therapy with very high response rates and a very safe toxicity profile. In comparison to chemotherapy alone, consideration of hepatic-directed therapy is warranted in patients with liver-dominant metastatic disease.

Synergistic antitumor activity of gemcitabine and ABT-737 in vitro and in vivo through disrupting the interaction of USP9X and Mcl-1

The Bcl-2 antagonist ABT-737 targets Bcl-2/Bcl-xL, but not Mcl-1, which may confer resistance to this agent in various cancers with high levels of Mcl-1. Here, we showed that the combination of gemcitabine and ABT-737 exhibited synergistic cytotoxicity and induced significant apoptosis in multiple cancer types, including lung, renal, bladder, and prostate cancers. The enhanced apoptosis induced by gemcitabine plus ABT-737 was accompanied by the greater extent of mitochondrial depolarization, caspases-3 activation, and PARP cleavage in 95-D and 5637 cell lines. Importantly, in ABT-737-resistant cancer cells, the interaction between USP9X and Mcl-1, which was increased by ABT-737 treatment, could be disrupted by gemcitabine, thus resulting in enhanced ubiquitination and the subsequent degradation of Mcl-1 and ultimately in the synergism of these two drugs. Moreover, the increased anticancer efficacy of gemcitabine combined with ABT-737 was further validated in a human lung cancer 95-D xenograft model in nude mice. Taken together, our data first showed the synergistic anticancer capabilities achieved by combining gemcitabine and ABT-737 and, second, opened new opportunities to use antiapoptotic Bcl-2 family members, which drive tumor cell resistance in current anticancer therapies, therapeutically.

A phase II trial of oxaliplatin and trastuzumab in the treatment of HER2-positive metastatic breast cancer

We investigated the feasibility/efficacy of oxaliplatin in combination with trastuzumab as first-/second-line treatment of HER2-positive metastatic breast cancer (MBC). Patients received oxaliplatin/trastuzumab every 21 days and were evaluated every 6 weeks using RECIST criteria. The study closed early due to slow accrual. Twenty-five patients were evaluable; of these, 5 (20%) had objective responses to oxaliplatin/trastuzumab. Therapy was well tolerated (no grade-4 and gastrointestinal grade-3 toxicity in 4% of patients), but had only modest activity (median time-to-progression 1.8 months). Substitution of oxaliplatin for cisplatin or carboplatin, in combination with trastuzumab, does not appear to improve first-/second-line therapy in HER2-positive MBC.

Administration of reduced glutathione in FOLFOX4 adjuvant treatment for colorectal cancer: effect on oxaliplatin pharmacokinetics, Pt-DNA adduct formation, and neurotoxicity

Oxaliplatin is a promising drug for cancer therapy and the oxaliplatin/5-fluorouracil/leucovorin (FOLFOX) regimen has become the standard adjuvant treatment for colorectal cancer. However, the oxaliplatin-induced neurotoxicity still represents a clinical problem leading to a discontinuation of the therapy. Many strategies have been proposed in order to manage the neurotoxicity, but their effect on antitumoral efficacy is still unclear. In this study, we investigated the effect of reduced glutathione administration on neurotoxicity, oxaliplatin pharmacokinetics, and platinum-DNA (Pt-DNA) adduct formation in patients affected by colorectal cancer treated with FOLFOX4 adjuvant regimen. Twenty-seven patients were randomized to receive GSH 1500 mg/m or saline solution before oxaliplatin infusion. Evaluation of neurotoxicity, pharmacokinetics of plasmatic total and ultrafiltered Pt, and determination of Pt-DNA adduct formation on white blood cells was performed during the 5th, 9th, and 12th cycles. At the end of all cycles of therapy, the patients in the GSH arm showed a statistically significant reduction of neurotoxicity (P=0.0037) compared with the placebo arm. There were no significant differences in the main pharmacokinetic parameters between the two arms except a lower area under the plasma concentration-time curve and a smaller apparent steady-state volume of distribution (Vss) when GSH was coadministered. This difference can be explained by the natural function of GSH in the detoxification of oxaliplatin and by its ability to remove the Pt bound to plasma proteins. The determination of Pt-DNA adduct formation shows no statistically significant differences between the two arms. In conclusion, this study indicates that coadministration of GSH is an effective strategy to reduce the oxaliplatin-induced neurotoxicity without impairing neither the pharmacokinetics of oxaliplatin, nor the Pt-DNA adduct formation.

Metastatic breast cancer: the treatment challenge

As therapeutic options have multiplied, chemotherapy for metastatic breast cancer (MBC) has become increasingly complex. Furthermore, advances in the treatment of early-stage breast cancer, in particular the development of taxane-based regimens, have led to increased use of adjuvant chemotherapy. As a result, the decisions regarding the treatment of patients presenting with MBC have become more difficult, because many patients are likely to have received a variety of adjuvant chemotherapy regimens. The primary goal of treatment for MBC is palliation of disease--usually with prolongation of survival--with minimal toxicity. However, there is currently no "gold standard" in this setting, and the literature supports many choices for first- and second-line treatment. Other issues as yet unsettled in these patients are (1) whether to combine >or= 2 drugs or to use each drug alone until disease progression; (2) how to use novel targeted biologic agents; and (3) how to treat patients with HER2-overexpressing tumors after adjuvant treatment with trastuzumab. The role of taxanes, antimetabolites, and targeted agents in patients with MBC will be discussed in this review, particularly in the context of previous adjuvant therapy. The controversy surrounding the use of doublet or sequential therapy will also be discussed. Although considerable advances have been made toward answering these questions, many additional uncertainties have arisen, and further well-designed randomized studies are needed.

Considerations in treatment choice for metastatic breast cancer

Chemotherapy treatment choices for metastatic breast cancer (MBC) have become increasingly complex as therapeutic options multiply. In addition, the more frequent use of adjuvant chemotherapy coupled with the introduction of new standard adjuvant therapies has made these choices more difficult. Another issue that remains unsettled is whether to employ combination therapy or to use each agent singly until its value is exhausted. The results of recent studies investigating this issue have revealed higher response rates, time to tumor progression and, in some cases, improved overall survival with doublet therapy. However, there was no planned crossover in these trials and, as such, the absolute benefits of doublet therapy remain undetermined. The future of therapy for MBC appears to be combining effective single-agent chemotherapy with novel biologic agents. For example, compared with paclitaxel alone, therapy comprising paclitaxel plus bevacizumab produced a doubling of response rate and progression-free survival. However, similar data are required for both the first- and the second-line setting, and for other chemotherapy agents, for example, docetaxel and navelbine. Trastuzumab is the treatment of choice for patients with HER2-positive tumors. Its use in combination with chemotherapy, particularly the taxanes, is well established. However, much remains to be learned about biologic agents; for example, trials need to establish whether these therapies should be continued at the time of progression or whether other treatments should be given in their place. A recent study in patients whose disease had progressed after trastuzumab and chemotherapy and who were subsequently given lapatinib, has reported promising outcomes for this agent. When presented with the many options that are now available for the treatment of MBC, we must keep in mind the primary goal of such treatment: palliation of disease with minimal toxicity. Furthermore, a concurrent requirement for prolongation of survival is now commonplace. However, it is clear that there is currently no "gold standard" treatment for MBC, although the future of therapy appears to be the combination of effective single agents with novel biologic therapies.