Eleven years disease-free: role of chemotherapy in metastatic BRCA2-related breast cancer

Multifunctional DNAzyme-Anchored Metal-Organic Framework for Efficient Suppression of Tumor Metastasis

High mortality and rapid development of metastasis requires the development of more effective antimetastasis strategies. However, conventional therapeutic methods, including surgery, radiation therapy, and chemotherapy, show less effectiveness in curbing the metastatic spread of cancer cells and the formation of metastases. A therapeutic platform, targeting the early stage of metastasis cascade, could effectively prevent metastasis dissemination. Herein, Fe/Mn-based metal-organic frameworks (FMM) were constructed for the delivery of a specific DNAzyme with high catalytic cleavage activity on the metastasis-involved Twist mRNA, thus efficiently inhibiting the invasion of cancer cells through DNAzyme-catalyzed gene silencing. Highly potent combined gene/chemodynamic therapy is achieved from the self-supplied DNAzyme cofactors and efficient glutathione depletion. Importantly, by virtue of the intrinsic photo-to-thermal conversion of the FMM nanocarriers, our combined therapeutic strategy could be further promoted under photothermal stimuli to speed up the Fenton reaction and to accelerate the release of the Twist DNAzyme with efficient gene therapy. Consequently, the effective elimination of tumors and the blockage of metastasis are simultaneously achieved under photothermal/magnetic resonance imaging guidance. This work aims at developing versatile theranostic agents to combat metastatic tumors.

Cytotoxic and targeted therapy for BRCA1/2-driven cancers

Tumors arising in BRCA1/2 germline mutation carriers usually demonstrate somatic loss of the remaining BRCA1/2 allele and increased sensitivity to platinum compounds, anthracyclines, mitomycin C and poly (ADP-ribose) polymerase inhibitors (PARPi). Exposure to conventional platinum-based therapy or PARPi results in the restoration of BRCA1/2 function and development of resistance to systemic therapy, therefore, there is a need for other treatment options. Some studies suggested that the use of specific drug combinations or administration of high-dose chemotherapy may result in pronounced tumor responses. BRCA1/2-driven tumors are characterized by increased immunogenicity; promising efficacy of immune therapy has been demonstrated in a number of preclinical and clinical investigations. There are outstanding issues, which require further consideration. Platinum compounds and PARPi have very similar mode of antitumor action and are likely to render cross-resistance to each other, so their optimal position in cancer treatment schemes may be a subject of additional studies. Sporadic tumors with somatically acquired inactivation of BRCA1/2 or related genes resemble hereditary neoplasms with regard to the spectrum of drug sensitivity; the development of user-friendly BRCAness tests presents a challenge. Many therapeutic decisions are now based on the BRCA1/2 status, so the significant reduction of the turn-around time for predictive laboratory assays is of particular importance.

Adding Nanotechnology to the Metastasis Treatment Arsenal

Metastasis is a major cause of cancer-related mortality, accounting for 90% of cancer deaths. The explosive growth of cancer biology research has revealed new mechanistic network information and pathways that promote metastasis. Consequently, a large number of antitumor agents have been developed and tested for their antimetastatic efficacy. Despite their exciting cytotoxic effects on tumor cells in vitro and antitumor activities in preclinical studies in vivo, only a few have shown potent antimetastatic activities in clinical trials. In this review, we provide a brief overview of current antimetastatic strategies that show clinical efficacy and review nanotechnology-based approaches that are currently being incorporated into these therapies to mitigate challenges associated with treating cancer metastasis.

The role of PARP inhibition in triple-negative breast cancer: Unraveling the wide spectrum of synthetic lethality

Triple-negative breast cancer (TNBC) accounts for approximately 15-20% of all breast cancers and is characterized by a lack of immunohistochemical expression of estrogen receptors (ER), progesterone receptors (PR) and HER2. TNBC is associated with poor long-term outcomes compared with other breast cancer subtypes. Many of these tumors are also basal-like cancers which are characterized by an aggressive biological behavior with a distant recurrence peak observed early at 3 years following diagnosis. Furthermore, metastatic TNBC bears a dismal prognosis with an average survival of 12 months. Although the prevalence of genetic alterations among women with TNBC differs significantly by ethnicity, race and age, BRCA mutations (including both germline mutations and somatic genetic aberrations) are found in up to 20-25% of unselected patients and especially in those of the basal-like immunophenotype. Therefore, defects in the DNA repair pathway could represent a promising therapeutic target for this subgroup of TNBC patients. Poly(ADP-ribose) polymerase (PARP) inhibitors exploit this deficiency through synthetic lethality and have emerged as promising anticancer therapies, especially in BRCA1 or BRCA2 mutation carriers. Several PARP inhibitors are currently being evaluated in the adjuvant, neo-adjuvant, and metastatic setting for the treatment of breast cancer patients with a deficient homologous recombination pathway. In this article, we review the major molecular characteristics of TNBC, the mechanisms of homologous recombination, and the role of PARP inhibition as an emerging therapeutic strategy.

Role of BRCA Mutations in the Modulation of Response to Platinum Therapy

Recent years have seen cancer emerge as one of the leading cause of mortality worldwide with breast cancer being the second most common cause of death among women. Individuals harboring BRCA mutations are at a higher risk of developing breast and/or ovarian cancers. This risk is much greater in the presence of germline mutations. BRCA1 and BRCA2 play crucial role in the DNA damage response and repair pathway, a function that is critical in preserving the integrity of the genome. Mutations that interfere with normal cellular function of BRCA not only lead to onset and progression of cancer but also modulate therapy outcome of treatment with platinum drugs. In this review, we discuss the structural and functional impact of some of the prevalent BRCA mutations in breast and ovarian cancers and their role in platinum therapy response. Understanding the response of platinum drugs in the context of BRCA mutations may contribute toward developing better therapeutics that can improve survival and quality of life of patients.

Role of BRCA Mutations in the Modulation of Response to Platinum Therapy

Recent years have seen cancer emerge as one of the leading cause of mortality worldwide with breast cancer being the second most common cause of death among women. Individuals harboring BRCA mutations are at a higher risk of developing breast and/or ovarian cancers. This risk is much greater in the presence of germline mutations. BRCA1 and BRCA2 play crucial role in the DNA damage response and repair pathway, a function that is critical in preserving the integrity of the genome. Mutations that interfere with normal cellular function of BRCA not only lead to onset and progression of cancer but also modulate therapy outcome of treatment with platinum drugs. In this review, we discuss the structural and functional impact of some of the prevalent BRCA mutations in breast and ovarian cancers and their role in platinum therapy response. Understanding the response of platinum drugs in the context of BRCA mutations may contribute toward developing better therapeutics that can improve survival and quality of life of patients.

Cytotoxic and targeted therapy for hereditary cancers

There is a number of drugs demonstrating specific activity towards hereditary cancers. For example, tumors in BRCA1/2 mutation carriers usually arise via somatic inactivation of the remaining BRCA allele, which makes them particularly sensitive to platinum-based drugs, PARP inhibitors (PARPi), mitomycin C, liposomal doxorubicin, etc. There are several molecular assays for BRCA-ness, which permit to reveal BRCA-like phenocopies among sporadic tumors and thus extend clinical indications for the use of BRCA-specific therapies. Retrospective data on high-dose chemotherapy deserve consideration given some unexpected instances of cure from metastatic disease among BRCA1/2-mutated patients. Hereditary non-polyposis colorectal cancer (HNPCC) is characterized by high-level microsatellite instability (MSI-H), increased antigenicity and elevated expression of immunosuppressive molecules. Recent clinical trial demonstrated tumor responses in HNPCC patients treated by the immune checkpoint inhibitor pembrolizumab. There are successful clinical trials on the use of novel targeted agents for the treatment or rare cancer syndromes, e.g. RET inhibitors for hereditary medullary thyroid cancer, mTOR inhibitors for tumors arising in patients with tuberous sclerosis (TSC), and SMO inhibitors for basal-cell nevus syndrome. Germ-line mutation tests will be increasingly used in the future for the choice of the optimal therapy, therefore turnaround time for these laboratory procedures needs to be significantly reduced to ensure proper treatment planning.

Clinical Application of Multigene Panels: Challenges of Next-Generation Counseling and Cancer Risk Management

Background

Multigene panels can be a cost- and time-effective alternative to sequentially testing multiple genes, especially with a mixed family cancer phenotype. However, moving beyond our single-gene testing paradigm has unveiled many new challenges to the clinician. The purpose of this article is to familiarize the reader with some of the challenges, as well as potential opportunities, of expanded hereditary cancer panel testing.

Methods

We include results from 348 commercial multigene panel tests ordered from January 1, 2014, through October 1, 2014, by clinicians associated with the City of Hope’s Clinical Cancer Genetics Community of Practice. We also discuss specific challenging cases that arose during this period involving abnormalities in the genes: CDH1, TP53, PMS2, PALB2, CHEK2, NBN, and RAD51C.

Results

If historically high risk genes only were included in the panels (BRCA1, BRCA2, MSH6, PMS2, TP53, APC, CDH1), the results would have been positive only 6.2% of the time, instead of 17%. Results returned with variants of uncertain significance (VUS) 42% of the time.

Conclusion

These figures and cases stress the importance of adequate pre-test counseling in anticipation of higher percentages of positive, VUS, unexpected, and ambiguous test results. Test result ambiguity can be limited by the use of phenotype-specific panels; if found, multiple resources (the literature, reference laboratory, colleagues, national experts, and research efforts) can be accessed to better clarify counseling and management for the patient and family. For pathogenic variants in low and moderate risk genes, empiric risk modeling based on the patient’s personal and family history of cancer may supersede gene-specific risk. Commercial laboratory and patient contributions to public databases and research efforts will be needed to better classify variants and reduce clinical ambiguity of multigene panels.

Genomic patterns resembling BRCA1- and BRCA2-mutated breast cancers predict benefit of intensified carboplatin-based chemotherapy

Introduction

BRCA-mutated breast cancer cells lack the DNA-repair mechanism homologous recombination that is required for error-free DNA double-strand break (DSB) repair. Homologous recombination deficiency (HRD) may cause hypersensitivity to DNA DSB-inducing agents, such as bifunctional alkylating agents and platinum salts. HRD can be caused by BRCA mutations, and by other mechanisms. To identify HRD, studies have focused on triple-negative (TN) breast cancers as these resemble BRCA1-mutated breast cancer closely and might also share this hypersensitivity. However, ways to identify HRD in non-BRCA-mutated, estrogen receptor (ER)-positive breast cancers have remained elusive. The current study provides evidence that genomic patterns resembling BRCA1- or BRCA2-mutated breast cancers can identify breast cancer patients with TN as well as ER-positive, HER2-negative tumors that are sensitive to intensified, DSB-inducing chemotherapy.

Methods

Array comparative genomic hybridization (aCGH) was used to classify breast cancers. Patients with tumors with similar aCGH patterns as BRCA1- and/or BRCA2-mutated breast cancers were defined as having a BRCA-like^CGH status, others as non-BCRA-like^CGH. Stage-III patients (n = 249) had participated in a randomized controlled trial of adjuvant high-dose (HD) cyclophosphamide-thiotepa-carboplatin (CTC) versus 5-fluorouracil-epirubicin-cyclophosphamide (FE₉₀C) chemotherapy.

Results

Among patients with BRCA-like^CGH tumors (81/249, 32%), a significant benefit of HD-CTC compared to FE₉₀C was observed regarding overall survival (adjusted hazard ratio 0.19, 95% CI: 0.08 to 0.48) that was not seen for patients with non-BRCA-like^CGH tumors (adjusted hazard ratio 0.90, 95% CI: 0.53 to 1.54) (P = 0.004). Half of all BRCA-like^CGH tumors were ER-positive.

Conclusions

Distinct aCGH patterns differentiated between HER2-negative patients with a markedly improved outcome after adjuvant treatment with an intensified DNA-DSB-inducing regimen (BRCA-like^CGH patients) and those without benefit (non-BRCA-like^CGH patients).

Systemic treatment for hereditary cancers: a 2012 update

The history of specific therapy for hereditary tumors dates back to mid 1980s and involves a number of reports demonstrating regression of familial colon polyps upon administration of sulindac. Virtually no clinical studies on other hereditary cancer types were available until the year 2009, when Byrski et al. presented the data on unprecedented sensitivity of BRCA1-associated breast malignancies to cisplatin. This breakthrough has revived interest to the treatment of cancer in germ-line mutation carriers. Recent trials and clinical observations have confirmed the efficacy of platinating agents and PARP inhibitors in BRCA1/2-driven breast, ovarian and pancreatic carcinomas. Pegylated liposomal doxorubicin may be considered as a promising treatment option for BRCA1/2-related ovarian cancer after the failure of platinum-containing therapy. Several novel drugs have been recently introduced in the management of rare familial tumor syndromes. Vandetanib, a low-molecular weight RET kinase inhibitor, demonstrated substantial efficacy in the treatment of hereditary and sporadic medullary thyroid cancer. Vismodegib, an inhibitor of SMO oncoprotein, caused regression of basal-cell carcinomas in patients with Gorlin syndrome. Down-regulation of mTOR kinase by everolimus has been successfully used for the therapy of subependymal giant-cell astrocytomas in patients with tuberous sclerosis. The achievements in the prevention, diagnostics and treatment of hereditary cancers may serve as an excellent example of triumph of translational medicine.

Genomic instability in breast and ovarian cancers: translation into clinical predictive biomarkers

Breast and ovarian cancer are among the most common malignancies diagnosed in women worldwide. Together, they account for the majority of cancer-related deaths in women. These cancer types share a number of features, including their association with hereditary cancer syndromes caused by heterozygous germline mutations in BRCA1 or BRCA2. BRCA-associated breast and ovarian cancers are hallmarked by genomic instability and high sensitivity to DNA double-strand break (DSB) inducing agents due to loss of error-free DSB repair via homologous recombination (HR). Recently, poly(ADP-ribose) polymerase inhibitors, a new class of drugs that selectively target HR-deficient tumor cells, have been shown to be highly active in BRCA-associated breast and ovarian cancers. This finding has renewed interest in hallmarks of HR deficiency and the use of other DSB-inducing agents, such as platinum salts or bifunctional alkylators, in breast and ovarian cancer patients. In this review we discuss the similarities between breast and ovarian cancer, the hallmarks of genomic instability in BRCA-mutated and BRCA-like breast and ovarian cancers, and the efforts to search for predictive markers of HR deficiency in order to individualize therapy in breast and ovarian cancer.

Genetics, genomics, and cancer risk assessment: State of the Art and Future Directions in the Era of Personalized Medicine

Scientific and technologic advances are revolutionizing our approach to genetic cancer risk assessment, cancer screening and prevention, and targeted therapy, fulfilling the promise of personalized medicine. In this monograph, we review the evolution of scientific discovery in cancer genetics and genomics, and describe current approaches, benefits, and barriers to the translation of this information to the practice of preventive medicine. Summaries of known hereditary cancer syndromes and highly penetrant genes are provided and contrasted with recently discovered genomic variants associated with modest increases in cancer risk. We describe the scope of knowledge, tools, and expertise required for the translation of complex genetic and genomic test information into clinical practice. The challenges of genomic counseling include the need for genetics and genomics professional education and multidisciplinary team training, the need for evidence-based information regarding the clinical utility of testing for genomic variants, the potential dangers posed by premature marketing of first-generation genomic profiles, and the need for new clinical models to improve access to and responsible communication of complex disease risk information. We conclude that given the experiences and lessons learned in the genetics era, the multidisciplinary model of genetic cancer risk assessment and management will serve as a solid foundation to support the integration of personalized genomic information into the practice of cancer medicine.

Drug therapy for hereditary cancers

Tumors arising in patients with hereditary cancer syndromes may have distinct drug sensitivity as compared to their sporadic counterparts. Breast and ovarian neoplasms from BRCA1 or BRCA2 mutation carriers are characterized by deficient homologous recombination (HR) of DNA, that makes them particularly sensitive to platinum compounds or inhibitors of poly (ADP-ribose) polymerase (PARP). Outstandingly durable complete responses to high dose chemotherapy have been observed in several cases of BRCA-related metastatic breast cancer (BC). Multiple lines of evidence indicate that women with BRCA1-related BC may derive less benefit from taxane-based treatment than other categories of BC patients. There is virtually no reports directly assessing drug response in hereditary colorectal cancer (CRC) patients; studies involving non-selected (i.e., both sporadic and hereditary) CRC with high-level microsatellite instability (MSI-H) suggest therapeutic advantage of irinotecan. Celecoxib has been approved for the treatment of familial adenomatous polyposis (FAP). Hereditary medullary thyroid cancers (MTC) have been shown to be highly responsive to a multitargeted tyrosine kinase inhibitor vandetanib, which exerts specific activity towards mutated RET receptor. Given the rapidly improving accessibility of DNA analysis, it is foreseen that the potential predictive value of cancer-associated germ-line mutations will be increasingly considered in the future studies.

Studying therapy response and resistance in mouse models for BRCA1-deficient breast cancer

Worldwide, more than one million women are diagnosed with breast cancer every year, making it the most common malignancy of females in the developed world. Germline mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 account for 4-6% of all breast cancer cases, and mutation carriers have a lifetime risk of 80% for developing breast cancer and 40% for developing ovarian cancer. Current treatment options are limited and often do not lead to cure. In the 17 years since the discovery of BRCA1, the generation of mouse models for BRCA1 deficiency has greatly aided our understanding of it's role in tumorigenesis. In contrast to human BRCA1 mutation carriers, mice carrying heterozygous mutations in Brca1 did not develop spontaneous tumors. This led to the generation of conditional mouse models in which tissue-specific Brca1 deletion induces formation of mammary tumors that closely resemble human BRCA1-mutated breast tumors. These models have proven useful for studying BRCA1-related tumor development, drug response and resistance. BRCA1-deficient cancer cells are defective in DNA repair mediated by homologous recombination (HR) and therefore highly sensitive to DNA-damaging agents such as platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors. However, BRCA1-mutated tumors can develop resistance to these drugs; hence improved treatment strategies are critical. Existing mouse models have already proven useful for preclinical testing of (combinations of) therapeutic agents that may be beneficial for the treatment of patients with BRCA1-mutated tumors. In this review, we discuss the progress made towards modeling BRCA1-deficient breast cancer in mice and what we have learned from preclinical studies using these models.

Melphalan as a treatment for BRCA-related ovarian carcinoma: can you teach an old drug new tricks?

Late-stage ovarian carcinoma is almost universally fatal. BRCA mutations are associated with an improved outcome and enhanced sensitivity to platinum chemotherapy, yet recurrence and platinum resistance remain a major problem and highly effective regimens following platinum failure do not yet exist. Here we report a remarkable case of cure following platinum-resistant stage III ovarian carcinoma in a woman with a BRCA2 mutation. The patient was subsequently treated with oral melphalan therapy and has not recurred in over 25 years. Melphalan is a bifunctional alkylator that creates inter- and intra-strand DNA cross-links. In a pharmaceutical screen, melphalan was shown to be selectively toxic to BRCA2-deficient breast cancer cell lines and produced a longer relapse-free survival in mice than did cisplatin or olaparib. There is increasing evidence to consider BRCA mutation status when selecting chemotherapy regimens, and melphalan treatment for BRCA-related ovarian cancer merits further investigation. Focusing attention on long-term survivors may provide new mechanistic insights into the biology of chemo-responsiveness.