I am going to, this is a 15-minute presentation where the goal is to give a broad overview of what BRCA1 and 2 are, and then how they are important in DNA damage response. So we all know about this, the genetic and hereditary cancer syndrome, and it's just to put the genes back into context of why we study them. So cancer syndromes are higher than normal, people and families who have cancer syndromes like breast, ovarian, and endometrial cancer are at high risk or are thought to be linked to hereditary cancer syndromes, and that those factors might be proven or suspected, and this is just a pedigree of a family showing the prevalence of different types of cancers in that family. So a few years now, or 30 years ago, Mary-Claire King did this wonderful study with her collaborators and colleagues across the United States and Canada, and then eventually Europe, where they discovered that there are two genes that are linked to, in particular, hereditary breast and ovarian cancer syndrome, and those genes are called BRCA1 and BRCA2, which is the breast cancer gene one and the breast cancer gene two. They are located on chromosome 13 and chromosome 17, and what that means is that here, these genes have been linked to development of breast and ovarian cancer and maybe endometrial cancer, and that's still a work in progress, and that when women and all men inherit a mutation, a deleterious mutation in one of these genes, they're at very high risk for developing breast and ovarian cancer over their lifetime. And what does that mean, really? So the last point down here, where it says if one copy of either gene is mutated in the germline, this is part of the H-box syndrome, and this is an autosomal dominant disorder, and that means that you only need one copy to be mutated, and it is autosomal because it's in one of the pairs of chromosomes, not the sex chromosomes, not an X or Y. And so if a man has a mutation in BRCA1 or BRCA2, his offsprings has a 50% chance of inheriting the gene, and also, of course, if a woman has a mutation, her offsprings have a 50% chance of inheriting the gene. So why are these genes important and why are they linked to cancer development? So genomic instability in cancers manifests themselves in these ways, by translocations, aneuploidy, chromosome loss, DNA amplification, and chromosomal deletions. The image at the bottom represents a karyotype of an ovarian cancer patient's DNA, and you can see, so red means up, amplifications, and blue means down, deletions, usually, and ovarian cancer is one of those diseases that are part of the hereditary breast and ovarian cancer syndrome that are linked to having a lot of genomic instability. And we know that now, that these genomic instabilities are prefaced by having a mutation in BRCA1 or BRCA2 and the family of proteins that it interacts with. So how are these DNA damage factors happening? What precedes that? So we know that they're endogenous factors. So endogenous factors means different reagents, molecules that are within the cell that can cause DNA damage, and then there are exogenous factors, like radiation, as we were just talking about, sunlight, drugs like cisplatin and etoposide. And what we know, in general, is that you have a normal genome that these BRCA1, BRCA2 genes, and I will show you more in terms of how they interact with each other, they are enlisted in repairing the DNA. And when they can repair the DNA in an efficient way, the cells stop growing, or they repair the DNA and they go back to their normal function. However, if there is a mutation and the cells acquire more mutations in other genes that are important in repairing the DNA, you see that it promotes these unemployed, these mutations, amplifications of the genome, and those mutations and amplifications and destruction of the integrity of the genome leads to cancer. So where do these genes play an important role? So cells grow, and some cells, so some cells are quiescent where they grow and then they stop growing and they do their normal function, like neurons. And then there's cells like the breast cells and the epithelium in the endometrium and epithelium in the fallopian tubes, where they grow and they grow cyclically. And so the cell cycle has to be controlled in order to prevent cancer. And this is where BRCA1 and BRCA2 and their family of proteins are vital. So the cell cycle is tightly regulated at each step. And what we have is distinct checkpoints. So sometimes you will hear about the different checkpoints in the cell cycle. The G1 to S phase is a checkpoint that's very important in DNA damage repair, along with, and so S phase is where DNA is synthesized. And then there's a G2 checkpoint where the DNA is, again, reviewed and monitored. And BRCA1 and BRCA2 are important here. And then M phase is mitosis, where the cells are dividing. And then you have the G0 phase, where the cells are resting, they're doing their function, what they're supposed to be doing. And so because there are all these phases in the cell cycle, we have multiple ways of repairing our DNA. And also because there are different factors that can damage the DNA, the cells have developed different pathways and proteins that are responsible for different parts. So for this presentation, I'm going to focus on homoavirus recombination, because that is the topic of the presentation. So this pathway and the proteins that are important in this pathway is, we think, one of the most important ones. They repair double-strand breaks, and double-strand breaks are detrimental to the cell cycle control. It's a high-fidelity repair. And more than single-strand repair, it is important for the breaks that occur during mitosis, during DNA synthesis, all of that, where we have exchange of material, that the breaks are repaired so that the cells can either progress into having a normal function, or that they die by apoptosis. And so the genes that are very important, as I've been talking about, is BRCA1, BRCA2, and then the RAD complexes, and part of the fanclonia anemia, and also proteins involved in the fanclonia repair pathway. So this is an example. Of where the proteins that you think about in the context of women being diagnosed with the diseases that you treat, play a role. So this is, on the left, is a double-strand break that could have been generated at any point during the cell cycle, in particular the G1S phase or the G2M phase. And there are proteins that sense the damage, and then they mark the DNA, and BRCA gets recruited. It is thought to be a mediator, because it then recruits a whole bunch of other proteins. And those are the proteins, Check2, ATR, ATM, and those proteins, I hope, are ringing a bell to you, because those are also proteins that we know are important in hereditary breast and ovarian cancer syndrome, right? So then BRCA1 also recruits PALB2, which is a BRCA-like protein, and eventually Check1. And so once they have these proteins recruited to the sites of breakage, we have other proteins called effector proteins that actually end up repairing the break. And so in red, the red arrows is just to point out those other genes that are part of the hereditary breast and ovarian cancer syndrome, and also will be used as targets later on. So this is another synopsis of what the damages look like, the proteins that are involved in repairing the damages, and where we can use these different interventions. So we have single-strand breaks, and that's what the PARP protein repairs. But then, most importantly, the double-strand breaks, which is where it's a crisis. Either the cells stop, or it gets repaired, and they move forward. So cells with a normal complement of the BRCA proteins can repair their DNA, their damaged DNA, and they can go on to do their normal function, whereas cells that have one or no copy of the BRCA proteins are not able to repair their DNA. And what happens is that it's supposed to trigger a cell to undergo apoptosis. But unfortunately, we know that in the context of cancer, those people who have one copy that is, and one copy of a BRCA mutation, a functional protein, they do not necessarily die, but they survive and apply other mutations in other genes, and that can lead to cancer. So this is an example of work that was done now almost 10 years ago, where the genome of ovarian cancer patients was sequenced. And so we saw that this pathway, the homologous combination pathway, and DNA damage mediators, sensors, and effectors were mutated in ovarian cancer. And you can see here that the amount of genes, so BRCA1 and BRCA2 are the most commonly mutated genes within that pathway, but we also have the sensors and effectors, like ATM, ATR, the FANC complexes, which also mediate repair, but are either mutated or deleted in these cancers. And of course, we know why that's important. So we also know that because the tumors have these inability to repair their DNA effectively, they use these other pathways that I just briefly talked about that allows them to be susceptible to inhibition for other targeted drugs like bark inhibitors. So this is another example of another tumor type where DNA damage response genes, and in particular, BRCA genes are implicated. The red arrow down here, so this is endometrial cancer. The tumors, different types of endometrial cancer were sequenced a few years ago. And we also found that in a cohort of endometrial cancers, the high-grade serous-like tumors, they also have mutations in the BRCA1, BRCA2, like a homologous recombination deficiency-like phenotype. Okay, so this is my last slide. And this is just to summarize the different types of damages that the cells are exposed to on the top. And then the pathways that are important in repairing these damage, these DNA damages. We know that these proteins, BRCA1, BRCA2, PALB2, ATM, CHECK1, CHECK2, RAD51, CMD in the context of gynecologic cancers, are important for stopping the cells and preventing the cells from growing in their normal function. And those people who have a germline mutation are at higher risk for developing breast and ovarian cancer and potentially endometrial cancer. But that those, the somatic mutations, mutations within the tumor, those people who have mutations within the tumor in these genes are thought to be better responders to personal-based chemotherapy. And of course, we know that those tumors, those tumors that have this deficiency in this pathway are all susceptible to proper inhibition because the cells depend on other ways of repairing the DNA. So I'll stop here, but the presentation that I have has more information about the other pathways that you can use for your, as reference. So I'll take-

BRCA1

BRCA2

genes

DNA damage response

hereditary breast and ovarian cancer syndrome