Molecular Subtypes of Breast Cancer

Molecular classification of breast cancer into five distinct subtypes based on the genes of breast tumour cells.

1. Cancer Research MOLECULAR SUBTYPES OF BREAST CANCER

2. MOLECULAR SUBTYPES OF BREAST CANCER Mr . Shaktiprasad Pradhan M.Pharm, Ph.D* Research Professional, UDPS [email protected] Utkal University, Bhubaneswar Odisha, India

3. . INTRODUCTION 3

4. The Breast The human female breast is an apocrine gland having remarkable and complex structure. Most part of a woman's breast consists of fat & connective tissue, along with less conspicuous parts including milk ducts, lobes, lobules, arteries and lymph nodes. Each breast has 15 to 20 lobes (sections) & each lobe is made up of many lobules (smaller structures) that end in tiny bulbs that can produce milk. Lobes, lobules & bulbs are linked by a network of thin tubes, known as ducts . Ducts carry milk from the bulbs, where it's produced, toward the areola (dark area of skin in the center of the breast). (Cont.) 4

5. . They join together into larger ducts ending at the nipple , where milk becomes available to a hungry infant. The actual milk producing structures are nearly the same in all women. Space around the lobules and ducts are filled with fatty tissue, ligaments and connective tissue. Breast has no muscle tissue, but muscles do lie underneath the breasts, separating them from ribs. Oxygen, nutrients & other life sustaining nourishments are delivered to breast tissues by the blood in arteries and capillaries. 5

6. Anatomy of a female breast 6 1. Chest wall 2. Pectoralis muscles 3. Lobules 4. Nipple surface 5. Areola 6. Lactiferous duct tube 7. Fatty tissue 8. Skin.

7. . BREAST CANCER 7

8. Breast Cancer Cancer is the most dreaded disease of the current time & caused by abnormalities in the genetic material of the cells due to the effects of carcinogens, such as tobacco smoking & chewing, radiation, chemicals or infectious agents etc. Cancer is usually classified according to the tissue from which the cancerous cells originate that is location as well as the normal cell type they most resemble which is histology. Breast cancer is the cancer that starts in the cells of the breast & the most common cause of cancer among women worldwide, both in incidence and death. (Cont.) 8

9. Breast cancer causes change in the size or shape of the breast, a lump or thickening in the breast or armpit, discharge from the nipple, change in the colour or texture of the skin of the breast or areola such as scaly , dimpled , puckered or wrinkled . Simple Breast Cancer 9 .

10. . Breast cancer is the second most common type of cancer and the fifth most common cause of cancer death globally apart from sexes. In India Breast cancer, is the most extensive cancer category contributing about 18% of all cancers & 27% of all women malignancies worldwide according to the World Health Organization (WHO). Breast cancer is increasing particularly in developing countries where the majority of cases are diagnosed in late stages. However, breast cancer is the most detectable & most treatable kind of cancer among all human malignancies. 10

11. . CLASSIFICATION OF BREAST CANCER 11

12. Types of Breast Cancer Basically breast cancers are of 2 different types as Non-invasive breast cancer & Invasive breast cancer. Non-invasive breast cancer: (2 types) Cancer that are contained within the milk ducts or lobules in the breast. They have not grown into or invaded, the normal breast tissue. Non-invasive cancers are called carcinoma in situ and are sometimes referred to as pre cancers. These are of 2 types as Ductal carcinoma in situ (DCIS) Lobular carcinoma in situ (LCIS) (Cont.) 12

13. . Invasive breast cancers: (7 types) Breast cancers that have spread outside the ducts or lobules of the breast into surrounding breast tissue. Early breast cancer  is the term that refers to cancer that is contained within the breast and may have spread to surrounding lymph nodes in the breast or armpit (axilla) but not anywhere else in the body. Type-1, Invasive ductal carcinoma (IDC) Type-2, Invasive lobular carcinoma (ILC) Type-3, Paget’s disease (PD) Type-4, Inflammatory breast cancer (IBC) Type-5, Phyllodes tumour (PT) Type-6, Locally advanced breast cancer (LABC) Type-7, Metastatic breast cancer (MBC) (Cont.) 13

14. Subtypes of Breast Cancer The subtypes of breast cancer are based on the genes, a cancer expresses. Hormone receptor positive breast cancer: (3 types) About two-thirds of breast cancers are hormone receptor positive, which means that they need female hormones estrogen and/or progesterone to grow and reproduce. Estrogen receptor (ER) positive , Progesterone receptor (PR) positive , Hormone receptor (HR) negative are the 3 classes. HER2 positive breast cancer: HER2 positive breast cancer cells have too much of the protein called human epidermal growth factor receptor-2 on the surface of the cancer cells & they may be either hormone receptor positive or negative type. Triple negative breast cancer (TNBC): Triple negative breast cancer does not have any of the three receptors ER, PR, HER2 commonly found on breast cancer cells (lack estrogen, progesterone and HER2 receptors) . (Cont.) 14

15. 15 BREAST CANCER TYPES SUB TYPES Non-invasive B C Invasive B C Lobular Carcinoma In Situ (LCIS) Ductal Carcinoma In Situ (DCIS) Invasive Ductal Carcinoma (IDC) Invasive Lobular Carcinoma (ILC) Paget’s Disease (PD) Inflammatory B C (IBC) Phyllodes Tumour (PT) Locally Advanced B C (LABC) Metastatic B C (MBC) Hormone Receptor Positive B C HER 2 Positive B C Triple Negative B C Estrogen Receptor Positive Progesterone Receptor Positive Hormone Receptor Negative

16. . NEED OF MOLECULAR CLASSIFICATION OF BREAST CANCER 16

17. Need of Molecular Classification of Breast Cancer Breast cancer remains a heterogeneous disease showing marked diversities spanning its morphology, clinical presentation, prognosis and response to various therapies. Heterogeneity exists between breast cancers affecting distinct ethnic backgrounds showing molecular differences amongst histologically similar breast cancer types. Traditional breast cancer classification, mainly based on clinicopathologic features and assessment of routine biomarkers , may not capture the varied clinical courses of individual breast cancers. The molecular classification of breast cancer aims to provide an accurate diagnosis of the disease and prediction of breast tumor behavior to facilitate oncologic decision making. (Cont.) 17

18. . Molecular classification can be more powerful than histopathology as a predictive factor for different treatments, causing less frequent use of chemotherapy with considerable advantages in reducing toxicities as well costs. Gene expression analysis has demonstrated distinct molecular classes of breast cancer that can be translated into more prognostically and therapeutically useful information than, provided by existing histological classification. The information provides insights into new treatment strategies and patient stratifications that impact on the management as well the treatment of breast cancer. Ongoing research may provide more precise prognostic and predictive information about breast cancer also a breakthrough step towards “personalization” of breast cancer treatment. 18

19. . MOLECULAR SUBTYPES OF BREAST CANCER 19

20. Molecular Subtypes of Breast Cancer During the early nineties , immunohistochemistry (IHC) was used to segregate breast cancers into two main classes estrogen receptor positive (ER+) and estrogen receptor negative (ER−) . In the early 2000s , by the emergence of nucleic acid in situ hybridization, two new categories were identified as human epidermal growth factor receptor‑2 (HER2) positive (HER2+) & negative (HER2-) . Low grade breast cancers have positive ER and PR, but the high grade breast cancers are found to be negative for ER and PR and also have an over expression or amplification of HER2 with complex karyotypes. The development of gene expression profiling, provides a classification system later on, based on gene expression analysis and this consisted of four major molecular classes of breast cancer luminal‑like , basal‑like , HER‑2 positive, normal‑like . (Cont.) 20

21. . Consequent studies suggested the existence of more molecular classes of breast cancer, with the molecular spectrum expansion. Currently, two methods can determine the breast cancer subtype gene‐based assays and IHC‐based markers . The 70 & 80 gene signatures combined, classify patients into various subtypes of breast cancer. There are five main intrinsic or molecular subtypes of breast cancer exists that are based on the genes, which the breast cancer expresses: Luminal A (LUMA) Luminal B (LUMB) HER2 over expressing (HER2) Basal like (BLBC) Normal breast cell like/ normal like (NLBC) (Cont.) 21

22. . Luminal A (LUMA)  breast cancer is hormone receptor positive chiefly estrogen receptor positive (ER+) , HER2 negative (HER2-) and has low levels of the protein Ki-67 , which helps control how fast cancer cells grow. Luminal tumors are the most common subtypes among breast cancer, with luminal A being the majority . Luminal A is the most prevalent subtype of breast cancer with fairly high survival rates & fairly low recurrence rates. These cancers are low grade (tumour grade 1 or 2) , tend to grow slowly and have the best prognosis having higher expression of ER related genes . Luminal A breast cancers  response well to hormone therapy but poorly to conventional chemotherapy . (Cont.) 22

23. . Luminal B (LUMB)  breast cancer is hormone receptor positive (ER+ and/or PR+) and either HER2+ or HER2- with high levels of Ki-67 protein. Luminal B breast cancers are often diagnosed at a younger age than those with luminal A subtypes. The subtype luminal B generally grow slightly faster than luminal A breast cancer subtype and their prognosis is slightly worse . These are more proliferative, larger sized tumour with high recurrence rate than luminal A & may be benefited more from the combined therapeutic strategy of chemotherapy as well endocrine/ hormonal treatment. Women with luminal B tend to have fairly high survival rates although not as high as those with luminal A subtype . (Cont.) 23

24. . HER2 enriched/ over expressed   breast cancer is hormone receptor negative (ER- & PR-) and HER2 positive (HER2+) . The molecular subtype HER2 enriched is not the same as HER2+ as about 30% of HER2 enriched subtype are HER2- . In about 1 of every 5  breast cancers, the cancer cells have extra copies of the gene that makes the  HER2 protein . HER2 enriched breast cancers tend to grow faster , poorer tumour grade than luminal cancers & have a worse prognosis . Women with HER2 enriched subtype may be diagnosed at a younger age than those, with subtypes luminal A & luminal B . HER2 enriched breast cancer is highly curable  due to the availability of HER2 targeted medications like Herceptin (Trastuzumab: anti-HER2 monoclonal antibody) , Perjeta (Pertuzumab) , Tykerb (Lapatinib) , Nerlynx (Neratinib) , Kadcyla (T-DM1) , Enhertu (Fam- Trastu .-Deruxtecan-Nxki) etc. (Cont.) 24

25. . Triple negative/ Basal like   breast cancer (BLBC) is hormone receptor ER & PR negative (lack or low) and HER2 negative but high expression of basal markers like keratins, EGFR etc. and likely to be of grade 3 tumors . The BLBC tumour cells look similar to the basal cells surrounding the mammary ducts & interestingly the triple negative tumours are basal like & most basal like tumours are triple negative type. (Cont.) 25

26. . Basal like breast cancer subtype is characterized with larger tumours than other subtypes, poor differentiation , high mitotic index, rapid growth & tumour necrosis . This subtype is more common in women with  BRCA1  gene mutations as most BRCA1 related breast cancers are both triple negative & basal like . Basal like subtype is also common among the younger and black women (more frequent in African, American women ). Risk factors for Basal like breast cancer subtype include: Earlier menarche High waist-to-hip ratio A lack of breast feeding (Cont.) 26

27. . Normal breast cell like/ Normal like   breast cancer (NLBC) is some what similar to luminal A subtype. This subtype is hormone receptor positive (ER+ and/or PR+) , HER2 negative (HER2-) and has low levels of Ki-67 protein, which helps control how fast the breast cancer cells grow. Although normal like breast cancer has a good prognosis , its prognosis is slightly worse than luminal A breast cancer’s prognosis. Normal like subtype is well differentiated with low proliferation index & is characterized by median overall survival . This subtype does not respond to neoadjuvant therapy, only to adjuvant chemotherapy . 27

28. . REFERENCES 28

29. References World Health Organization, International Agency for Research on Cancer, 2020. American Cancer Society: Breast cancer overview. 2020. Pradhan, Tripathi, Pradhan, Nature an Immunobooster for Breast Cancer, Book. Partridge India Publication, 2015. www.nationalbreastcancer.org/about-breast-cancer/ www.cancer.net/cancer-types/breast-cancer/introduction. ww5.komen.org/ BreastCancer /SubtypesofBreastCancer.html. Pradhan D, et al., Inhibition of proteasome activity by the dietary flavonoid Quercetin associated with growth inhibition in cultured breast cancer cells and xenografts. JYP.2015, 7(3): 225-233. Pradhan S, et al., Antiproliferation activity of Ocimum gratissimum aqueous extract on human breast cancer MCF-7 cell line. WJPR, 2018, 7(9): 421-428. Sorlie T, et al. Repeated observation of breast tumor sub types in independent gene expression data sets . PNAS-USA, 2003, 100(84): 18‑23. Brenton JD, et al. Molecular classification and molecular forecasting of breast cancer: Ready for clinical application? JCO, 2005, 23(7): 350‑60. 29

30. . Thank You 30