Etiology and Treatment Options of Triple Negative Breast (TNBC) Waseem Gul Lone 1, Mosin S Khan 1, Manzoor Raina 1, Mudassir Makhdoomi 1, Rashid Mir 1, Mubashir Nazir 1, Javeed Ahmad Tantray 2, Kaiser Jamil 2, Syed Mudassar 1# 1 Department of Clinical Biochemistry, Sher- I- Kashmir Institute of Medical Sciences (SKIMS) Soura, Srinagar, Kashmir- 190011, India 2 Department of Genetics, Bhagwan Mahaveer Medical Research Centre, AC Guards Hyderabad- 500 004, India # E- mail of Corresponding author: andrabim@yahoo.com Abstract Triple negative breast cancer (TNBC) is defined by the absence of ER, PR and normal HER- 2 expression. It is heterogeneous in its clinical course and certainly in its molecular characteristics. It largely, but not completely, overlaps with the basal- like breast cancer subtype, identified by gene expression profiling. TNBC are highly proliferative and have p53 mutations in 50% of cases and most BRCA1- mutated tumors fall in this category. The management and treatments available for TNBC are discussed in this review. The lack of a well- characterized target for treatment leaves only systemic chemotherapy as the mainstay of treatment in TNBC. Approximately 60-70% of patients are chemosensitive, while the remaining majority does not respond. Targeted therapies that take advantage of the unique molecular perturbations found in triple- negative breast cancer are needed. Keywords: Breast (BC), Estrogen receptor (ER), Progesterone receptor (PR), Human epidermal growth factor receptor 2 (HER- 2), Triple negative breast cancer (TNBC). Background Approximately 20% of all breast cancers are referred to as triple- negative breast cancers, an aggressive variant of breast cancer characterized by lack of expression of the estrogen receptor (ER), progesterone ADR Journals 2014. All Rights Reserved Page 5
receptor (PR) and the human epidermal growth factor receptor 2 (HER- 2) [1]. This convenient naming system is based on routing immunohistochemistry performed in the clinic. It is also referred to as the basal- like breast cancers due to the expression of basal epithelial cell type markers and is one of the five intrinsic breast cancer subtypes distinguished on the basis of their gene expression patterns. However, the overlap between the two different identification systems is approximately 80%, with discordance in the expression of basal markers, immune response markers, and types of p53 mutation [2-5]. 5-40% of TNBC tumors have BRCA- related epigenetic downregulation and increased expression of the inhibitors of BRCA1 function. This indicates that the label triple- negative breast cancer describes a more heterogeneous subtype than other breast cancer subtypes [6-8]. Role of BRCA1 in TNBC Breast cancers are either familial or sporadic; 5-10% of breast cancers are hereditary and associated with BRCA1 and [5, BRCA2 mutations 9]. BRCA1 is essential in regulating DNA repair. Mutations of this gene lead to genomic instability and high risk of breast cancer. Patients with BRCA1 mutations have a lifetime risk of developing breast cancer of more than 80% [8].Tumors that develop in BRCA1 mutations carriers are characterized by ER negativity and no HER2 expression. Cluster analysis of microarray RNA expression demonstrated that tumors with familial- BRCA1 mutants strongly segregate with triple- negative sporadic tumors. Moreover, another common characteristic of triple- negative breast tumors is X chromosome inactivation and X inactive specific protein (XIST) expression which require a functional BRCA1, a protein defective in both TNBC and BRCA1- associated breast tumors [3]. This suggests that patients with inherited mutations in BRCA1 often develop breast cancer that is basal- like or of the TN subtype. From a cohort of 482 patients, 99 were BRCA- tested and 10 showed mutations in BRCA1; of these 10 patients, 8 were classified as triplenegative. Another abnormality in TN tumors, in addition to aberrations in the BRCA1 pathway, is a high proliferation rate which is associated with a high index for Ki67, aberrations in p53, enhancement of MAP kinases activities and dysregulation of cell survival pathways such as Akt signaling [3]. ADR Journals 2014. All Rights Reserved Page 6
Pathobiology of TNBC A majority of TNBC is invasive ductal carcinoma of no special type and the remaining is medullary carcinoma, invasive lobular, metaplastic carcinoma etc. The triple negativity can occur in many histological subtypes of breast cancer, with possible implications on their pathogenesis, progression and prognosis [6]. On the other hand, most triple negative tumors have pathobiological features in common with basal- like breast cancers. Basal- like breast tumors are preferentially low in ER and HER2 expression, and are significantly associated with several basal cytokeratin (CK) markers, including CK5/6, CK14, CK17 and the epidermal growth factor receptor (EGFR). A common misconception is that all basallike breast cancers are TNBC; however, only 77% of basal- like breast cancers are triple- negative, with 71% 91% of TNBC being basal- like [6]. Treatment Options Breast cancer management approaches have undergone enormous changes over the last two decades with targeted therapy based on hormone receptor status becoming the mainstay [1]. Estrogen and progesterone are the critical hormones involved in normal breast development and tumorigenesis which act upon after binding to estrogen receptor (ER) and progesterone receptor (PR) [10-14]. Breast carcinomas that originate from intrinsically ER and PR positive luminal cells are designated as ER and PR positive carcinomas, respectively [15]. Additionally, human epidermal growth factor receptor- 2 (HER- 2/ neu) encoded by an oncogene, CerB2, is a transmembrane cell surface glycoprotein expressed at low levels in normal non- neoplastic epithelia, including breast duct epithelium. However, its over expression is commonly evident in primary BC [1]. Screening for ER, PR and HER- 2/ neu status in breast tumors has become a standard method in determining the appropriate therapy for Breast cancer patient management throughout the world [1]. However, triple- negative breast cancer (TNBC) is thought to have a worse prognosis [4]. TNBC has been associated with younger age groups and patients presenting with later stages of the disease [2]. BRCA1 mutations are present in a substantial proportion (25%) of patients with TNBC and the similarities of these tumors with the basal- like subtype suggest that the therapeutic approach can be shared between these tumors. Preclinical studies have shown that these tumors are sensitive ADR Journals 2014. All Rights Reserved Page 7
to alkylating agents, such as mitomycin C and platinum analogues (cisplatin and carboplatin). Currently, cytotoxic chemotherapy (CT) is the only option of treatment for metastatic TNBC [10]. Women with TNBC do not seem to benefit from endocrine therapy or trastuzumab [16-18]. Some molecular- targeted therapies have demonstrated efficacy in this subgroup of patients. Bevacizumab (Bev), a monoclonal antibody against vascular endothelial growth factor, used in association with conventional CT was evaluated in randomized studies that included TNBC patients [13]. Results for this subgroup showed a benefit for this medication. Other examples of drugs with potential benefit for TNBC are cetuximab (epidermal growth- factor receptor inhibition) and poly (adenosine diphosphate- ribose) polymerase (PARP) inhibition [16]. Due to the lack of specific information, there are no published evidence- based clinical guidelines with explicit recommendations about which systemic treatment scheme is more appropriate for these patients with advanced TNBC. The clinical impact of molecular- targeted therapy in the TN population is still not clear [19]. Most information about TN patients comes from subgroup analyses of larger trials and to our knowledge no systematic synthesis of the studies has been performed so far. As a group, patients with TN tumors have a relatively poor outcome and cannot be treated with endocrine therapy or therapies targeted to human epidermal growth factor receptor type 2.50 [20-23]. Indeed, this group remains a poorly studied one: there are only a few studies designed specifically to evaluate the effect of CT in TNBC. This review aimed to evaluate the efficacy of different targeted therapies in TNBC. The results of the meta- analysis showed that these patients might benefit from some of these new therapies: there were significant benefits in PFS associated with Bev, Sor and iniparib, regardless of the line of treatment; however, cetuximab results are inconclusive so far [18]. A possible effect of targeted therapies on OS could not be drawn from the published literature, as this end point was not consistently reported in most of the original trials for the TNBC population [22]. The only feasible OS metaanalysis was the one derived from the studies that tested iniparib, in which results were heterogeneous and did not reach statistical significance in a random- effects model analysis [21]. Historically, clinical studies in the advanced breast cancer setting have used PFS as the primary end point, 51 but there ADR Journals 2014. All Rights Reserved Page 8
is still controversy concerning whether it correlates with OS.52, 53 [19, 20]. In general, the toxicity reported in the studies was expected and not limiting. Bev plus CT was associated with higher rates of proteinuria, hypertension, neuropathy and bleeding events; hand/ foot skin reaction and mucositis were more common in patients who received Sor plus CT; neutropenia and rash were more frequent in patients who received cetuximab plus CT [17]. Despite these encouraging results, many unsolved questions remain regarding targeted therapies combined with CT in TNBC patients. There are still no answers for some important points: which is the most suitable chemotherapy scheme for the association, which are the best molecular- targeted therapies, how to determine the ideal treatment sequence, and the real impact of using targeted therapy combined with CT in overall survival. Various studies indicate that TNBC patients will benefit more from TOPO- 2A inhibitors as well as antiangiogenic and antimetastatic therapies [15]. Inhibition of these target genes is emerging as one of the most exciting and promising targeted therapeutic strategies to treat TNBC in which the intended targets are DNA repair, tumor angiogenesis and metastasis [12, 19]. Nonanatomic factors, such as histologic grade and biomarkers, can guide breast cancer management but are not included in the current TNM staging system. One of the database reviews identified 1842 consecutive eligible patients with breast cancer. When patients were stratified by TNM stage, overall survival curves for those with TNP breast cancer matched those for patients whose non- TNP breast cancer was 1 TNM stage higher. Multivariable analysis showed that TNP status was a powerful prognostic variable and the likelihood ratio test revealed that the prognostic accuracy of the TNM staging system that incorporated TNP was superior to the current TNM staging system (P <.001) [3]. A TNM staging system that incorporated TNP, reduced early- stage compression by 15%. The internationally recognized and easily reproducible examination of ER, PR and HER2 status exemplifies how nonanatomic factors can improve the prognostic accuracy of breast cancer staging 10]. More recently, TNBC has been further dissected into smaller, distinct subsets with unique molecular alterations and response to therapy [9, 10]. Large- scale genomic projects have yielded new knowledge ADR Journals 2014. All Rights Reserved Page 9
about the molecular characteristics of TNBC, including similarities with highgrade serous ovarian cancers, suggesting a possible coordinated treatment algorithm for these malignancies [7, 8]. Moreover, translation of preclinical findings has led to clinical trials, testing a plethora of targets and pathways in TNBC. These include epidermal growth factor receptor (EGFR), angiogenesis, DNA repair capacity, epigenetic regulation, androgen receptor (AR) and folate receptor (FR) signaling, cell- cycle control, and cell survival [5, 6]. Given the complexity of TNBC biology and the lack of "traditional" therapeutic targets, the advancement of care for women with TNBC will require a true partnership between clinicians, translational investigators and basic scientists. References 1. Ambroise M, Ghosh M, Mallikarjuna VS et al., Immunohistochemical profile of breast cancer patients at a tertiary care hospital in South India, Asian Pac J Prev 2011; 12(3): 625-29p. PMID: 21627355. 2. Anders C, Carey LA, Understanding and treating triple-negative breast cancer, Oncology (Williston Park) 2008; 22(11): 1233-39p. PMID: 18980022. 3. Bagaria SP, Ray PS, Sim MS et al., Personalizing Breast Staging by the Inclusion of ER, PR, and HER2, JAMA Surg 2014; 149(2): 125-29p. PMID: 24306257. 4. Bidard FC, Conforti R, Boulet T et al., Does triplenegative phenotype accurately identify basal- like tumor? An immunohistochemical analysis based on 143 'triple- negative' breast cancers, Ann Oncol 2007; 18(7): 1285-86p. PMID:17675400. 5. Claus EB, Stowe M, Carter D et al., The risk of a contralateral breast cancer among women diagnosed with ductal and lobular breast carcinoma in situ: data from the Connecticut Tumor Registry, Breast 2003; 12(6): 451-56p. PMID: 14659121. 6. Fu M, Maresh EL, Helguera G et al., Rationale and pre- clinical efficacy of a novel anti- EMP2 antibody for the treatment of invasive breast cancer, Mol Ther 2014; 13(4): 902-15 p. 7. Gluz O, Liedtke C, Gottschalk N et al., Triple-negative breast cancer--current ADR Journals 2014. All Rights Reserved Page 10
status and future directions, Ann Oncol 2009; 20(12): 1913-27p. PMID: 19901010. 8. Herold CI, Anders CK, New targets for triple-negative breast cancer, Oncology (Williston Park) 2013; 27(9): 846-54p. PMID: 24282978. 9. Higginson IJ, Astin P, Dolan S, Where do cancer patients die? Tenyear trends in the place of death of cancer patients in England, Palliat Med. 1998; 12(5): 353-63p. PMID: 9924598. 10. Kang SP, Martel M, Harris LN, Triple negative breast cancer: current understanding of biology and treatment options, Curr. Opin.Obstet. Gynecol 2008; 20: 40-46p. PMID: 18197004. 11. Kumar R, A clinicopathologic study of breast lumps in Bhairahwa, Nepal, Asian Pac J Prev 2010; 11(4): 855-58p. PMID: 21133590. 12. Liedtke C, Cardone L, Tordai A et al., PIK3CA-activating mutations and chemotherapy sensitivity in stage II-III breast cancer, Breast Res 2008; 10(2): R27. PMID: 18371219. 13. Miller K, Wang M, Gralow J et al., Paclitaxel plus bevacizumab versus paclitaxel alone for metastatic breast cancer, N.Engl. J. Med 2007; 357: 2666-76p. PMID: 18160686. 14. Misrahi M, Atger M, d'auriol L et al., Complete amino acid sequence of the human progesterone receptor deduced from cloned cdna, Biochem Biophys Res Commun 1987; 143(2): 740-48p. PMID: 3551956. 15. Patil AV, Singhai R, Bhamre RS et al., Ki-67 biomarker in breast cancer of Indian women, N Am J Med Sci 2011; 3(3): 119-28p. PMID: 22540077. 16. Peppercorn J, Perou CM, Carey LA, Molecular subtypes in breast cancer evaluation and management: divide and conquer, Invest 2008; 26:1-10p. PMID: 18181038. 17. Rouzier R, Perou CM, Symmans WF et al., Breast cancer molecular subtypes respond differently to preoperative chemotherapy, Clin Res 2005; 11(16): 5678-85p. PMID: 16115903. 18. Reis-Filho JS, Tutt AN, Triple negative tumors: a critical review, Histopathology 2008: 52: 108-18p. PMID: 18171422. ADR Journals 2014. All Rights Reserved Page 11
19. Sayed- Ahmed MM, Hafez MM, Al- Shabanah OA et al., Increased expression of biological markers as potential therapeutic targets in Saudi women with triple-negative breast cancer, Tumori 2013; 99(4): 545-54p. PMID: 24326846. Pharmacogenomics 2012; 13(9): 1023 35p. PMID: 22838950. 20. Trivers KF, Lund MJ, Porter PL et al., The epidemiology of triple-negative breast cancer, including race, Causes Control 2009; 20(7): 1071 82p. PMID: 19343511. 21. Umar A, Kang H, Timmermans AM et al., Identification of a putative protein profile associated with tamoxifen therapy resistance in breast cancer, Mol Cell Proteomics 2009; 8(6): 1278 94p. PMID: 19329653. 22. van Agthoven T, Sieuwerts AM, Meijer-van Gelder ME et al., Relevance of breast cancer antiestrogen resistance genes in human breast cancer progression and tamoxifen resistance, J Clin Oncol 2009; 27(4): 542 49p. PMID: 19075277. 23. Woo HI, Kim KK, Choi H et al., Effect of genetic polymorphisms on therapeutic response and clinical outcomes in pancreatic cancer patients treated with gemcitabine, ADR Journals 2014. All Rights Reserved Page 12