BC Basics 2017

BC as a heterogeneous group of disorders Incidence- 1:9 Multi- stage process (initiation, promotion)

Heterogeneous approaches for diagnosis Triple test (imaging, FNA, examination) Sub- type: Immunostaining Genomics

ER receptor signaling enhancement in BC

ER signaling cascade According to the “canonical model”, following E2-binding, ER dimers bind to specific 13-bp DNA sequences in the estrogen receptor response element ERE characteristic of specific E2-regulated genes HSPs as quantity modulators

DNA bound ER-agonist complexes recruit several coactivators some with histone acetyl transferase (HAT) activities that allow repositioning of nucleosome and chromatin opening and interaction with the general transcription machinery organized around RNA polymerase.

What happens if and when the number of ERs is increased in a cell? b: ER activation by RTKs (EGFR, ERBB2, IGFR). Phosphorylation (P) by the Erk or Akt serine/threonine kinases leads to ligand-independent activation of the ER. formation of an ER–PI3K–Src–focal adhesion kinase (FAK) complex that activates Akt (d), and activation of Erk by ER–Src–PELP1 complexes (e) What happens if and when the number of ERs is increased in a cell?

Treatment Selective estrogen-receptor response modulators- TAMOXIPHEN Estrogen-receptor down -regulators (3rd line) Aromatase inhibitors- inhibition of aromatase inhibit the production of E2 in fat tissue and adrenal (PM women) Prophylactic Ovaries removal Similar approaches for PR

Growth factors response Convergence of 2 major cascades Promotes cell cycle, cell sustainability ERB2 participate in signaling w/o agonist Amplification of ERB2/ HER2 20% of breast cancers, poor prognosis

Directed/ tailored therapies Trastuzumab (Herceptin): a humanized monoclonal antibody targeted against the extracellular portion of HER2 Mechanism of action Inhibition of Cyclin D Reducing GF paracrine secretion Inducing immunologic response (?) Early diagnosis – improved prognosis Late diagnosis- resistance, Always small molecules TKI- Lapatinib (Glaxo) Oral, CYPD metabolism EGFR and HER competitive inhibitor Usually in combination for advanced cancers

Resistance Look at PTEN Activating mutations in each signaling cascade Increased HER2-HER3 heterodimers Changing the HER1 structure Other routes of signaling P53 New approach- combination therapies New improved formulations/ structures TKI-Herceptin MTORE inhibitors

Oestrogen-bound oestrogen receptor (ER), in association with a variety of co-activators (CoAs) (part a) and co-repressors (CoRs) (part b), exerts its classical genomic action as a transcription factor through the oestrogen response element (ERE) of target genes. ER can also mediate an ERE-independent genomic effect via interaction with other transcription factors, such as AP1, through AP1-binding sites of target genes (part c). In addition, ER can be activated via plasma membrane crosstalk with other growth factor receptor (GFR) pathways that phosphorylate (P) ER or its co-regulators. GFRs — for example, HER2, epidermal growth factor receptor (EGFR), insulin-like growth factor 1 receptor (IGF1R) and fibroblast growth factor receptor (FGFR) — undergo phosphorylation and dimerization upon ligand activation, which triggers their intracellular association with the regulatory subunit (p85) of PI3K, either directly or indirectly via an intermediate adaptor molecule such as insulin receptor substrate 1 (IRS1). This releases the inhibitory effect of p85 on the catalytic subunit p110 of PI3K. PI3K converts phosphatidylinositol bisphosphate (PIP2) to phosphatidylinositol trisphosphate (PIP3), which allows the activation of AKT and downstream signalling components of the PI3K pathway to promote cell growth, proliferation and survival. PTEN and inositol polyphosphate 4-phosphatase type II (INPP4B) are two phosphatases that negatively regulate the PI3K pathway by dephosphorylating PIP3 and PIP2, respectively. In addition, activation of receptor tyrosine kinases (RTKs) also activates the MAPK pathway. PI3K and MAPK pathway activation leads to phosphorylation of ER and ER coregulators. Cyclin D1 is a direct transcription target of ER or other GFR signalling pathways. Cyclin D1 activates cyclin-dependent kinase 4 (CDK4) and CDK6, which phosphorylates RB, which releases the E2F transcription factors and activates the expression of genes required for the G1 to S phase transition of the cell cycle. CDK4 and CDK6 are negatively regulated by specific and universal inhibitors including p16, p18, p21 and p27. p53 negatively regulates the cell cycle through the activation of p21. MDM2 inhibits p53 function. RB and p53 are important mediators of apoptosis and/or senescence with intrinsic or extrinsic signals such as genotoxic stress. The crosstalk between ER and GFR signalling, as well as constitutive activation of their downstream effectors, are potential mechanisms of oestrogen-independent cell growth of ER+ breast cancer, leading to aromatase inhibitor (AI) resistance. 4EBP1, eukaryotic translation initiation factor 4E-binding protein 1; AMPK, AMP-activated protein kinase; ASK1, apoptosis signal-regulating kinase 1; BAD, BCL-2-associated agonist of cell death; eIF4, eukaryotic translation initiation factor 4; FOXO, forkhead box protein O; GRB2, growth factor receptor-bound protein 2; GSK3, glycogen synthase kinase 3; JNK, JUN N-terminal kinase; LKB1, liver kinase B1; mTORC, mTOR complex; PDK1, 3-phosphoinositide-dependent protein kinase 1; RHEB, RAS homologue enriched in brain; SHIP, SH2 domain-containing inositol 5′ phosphatase.

Others – BRCA genes

Incidence Two genes predispose to BC if they are mutated* General population carriers: 0.2 to 0.3% Ashkenazi Jewish population: 2.5% Women with breast cancer: 3% Women with breast cancer onset before age 40 years: 6% up Women with ovarian cancer: 10% up High-risk families (higher incidence of BC and other C) : 20% A mutation in those genes confers a high risk to BC the early age of onset (+ other findings) – inherited risk= the greater risk ovarian, pancreatic, stomach, laryngeal, fallopian tube and prostate cancer

Genetics One mutated allele in the germline= hereditary risk Both are tumor suppressors- “haplo” is not a problem 2nd hit model of inherited cancers “pushing” to cellular tumor initiation (LOH) Both proteins participate in homologous recombination during repair of DSB (error safe) DNA Damage Response (DDR) elicits and depends on signaling cascades with multiple components Control check-points Genome integrity Replication fork faliure

BRCA2: Recruits recombinase RAD51 and binds to DNA (ss, ds) BRCA1: Connects to the damage sensing molecules and recruits effectors through multiple domains x8 repeats! BRCA2: Recruits recombinase RAD51 and binds to DNA (ss, ds)

Protein Ubi (by ring), chromatin change by H2X P, Enzymes-RAD, Recognition by ATM/ATR

So why BC? Reduced HR repair capacity leading to error prone mechanisms Malfunctioning off other tumor suppressors (P53, ATM) Why in Breast and Ovarian tissues? Sporadic cases: probably due to HR reduced efficiency but via mutations in other DDR participants.