Cancer genetics fundamentals

It is often said that cancer is genetic. What exactly does that mean? This article is our answer to that question at the turn of the millennium. We present models of carcinogenesis, review basic cancer genetics terminology, and explain some of the fundamental genetic changes common to all types of cancer. These are organized into 6 sections of (1) self-sufficiency in growth signals, (2) insensitivity to growth-inhibitory signals, (3) evasion of programmed cell death, (4) limitless replicative potential, (5) sustained angiogenesis, and (6) tissue invasion and metastases. Underlying all of these changes are the even more fundamental enabling factors of genetic instability on both the chromosomal and the gene level. Finally, we look toward the future in a field where the future is now!

Abstract P4-06-01: Provider practice and compliance with NCCN clinical guidelines for BRCA1/2 testing: Findings from Dr. Susan Love Research Foundation's The Health of Women (HOW) StudyTM

BRCA1/2-attributable cancers disproportionately contribute to breast cancer mortality, but are relatively infrequent in the general population, making healthcare practices surrounding BRCA1/2 mutation carrier status difficult to study. This analysis leverages a large dataset of over 40,000 individuals with and without breast cancer from Dr. Susan Love Research Foundation's The Health of Women (HOW) StudyTM to evaluate factors associated with healthcare provider compliance with National Comprehensive Cancer Network (NCCN) guidelines for BRCA1/2 testing. Data from women ages 18 and older who completed baseline and family history questionnaires were included in our sample (n=22,410). We examined whether: (1) genetic testing receipt was aligned with NCCN guidelines for BRCA1/2 genetic testing, (2) guideline-consistent use of BRCA1/2 testing varied by race and education, (3) those who had genetic testing received pre-test genetic counseling, and (4) guideline-consistent BRCA1/2 testing differed among those who received pre-test genetic counseling. In this population, 4326 women (19.5%) reported BRCA1/2 testing. Of these women, 70.3% of women were eligible for testing based on NCCN guidelines (vs. 29.8% who did not qualify). Women with higher levels of education were less likely to be over-tested or under-tested than those with lower levels of education (p<0.001); no differences were observed by Hispanic ethnicity (Hispanic vs. non-Hispanic, p=.71) or race (white vs. non-white, p=0.23). Among those tested for BRCA1/2, 65.6% (n=2976) received pre-test genetic counseling. Those who received pretest counseling were more likely to receive genetic testing consistent with NCCN guidelines than those who did not receive pretest counseling (73.8% vs 63.6%, p<0.001). 58% received post-test counseling by a genetics provider (n=2515) compared to 33.9% who received genetic results from their primary care provider or another provider (n=1465). Those who received genetic test results from a genetics provider were more likely to have received BRCA1/2 testing that was compliant with NCCN guidelines than those who received their genetic test results from another type of provider, though by a modest amount (74.2% vs 70.6%, p=0.01). In this population, we found that pretest-genetic counseling was associated with higher rates of NCCN guideline-consistent recommendations for BRCA1/2 genetic testing, and a woman's educational level appears to be associated with higher rates of guideline concordant use of BRCA1/2 testing. Overall, these findings showed higher rates of BRCA1/2 testing and receipt of counseling than previously reported, which may be partially reflective of this unique study population of motivated volunteers. As genetics is increasingly incorporated into cancer prevention, there is an urgent need to examine adherence to genetic testing guidelines to ensure appropriate use.

Citation Format: Roberts MC, Loud J, Klein WMP, Silver MI. Provider practice and compliance with NCCN clinical guidelines for BRCA1/2 testing: Findings from Dr. Susan Love Research Foundation's The Health of Women (HOW) StudyTM [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-06-01.

Importance of PLD2 in an IL-23 driven psoriasiform dermatitis model and potential link to human psoriasis

Phospholipase D2 (PLD2), a major isoform of the PLD family, has been reported to regulate inflammatory responses. Thus far, the relevance of PLD2 in psoriasis, an inflammatory skin disease, has not been explored. In the current study, we examined PLD2 expression in the skin of psoriasis patients and the role of PLD2 in an interleukin (IL)-23-induced mouse model of psoriasiform dermatitis. Both in situ hybridization and bulk RNA sequencing showed PLD2 gene expression is significantly higher in lesional relative to non-lesional skin of psoriasis patients or the skin of healthy subjects. PLD2 expression is also enriched in residual lesions from patients on biologic therapies. Murine in vivo studies showed that PLD2 deficiency significantly reduced psoriasiform inflammation in IL-23-injected ears, as reflected by decreases in ear thickness, expression of defensin beta 4A and the S100 calcium binding protein A7A, macrophage infiltrate, and expression of CXCL10 and IL-6. However, the expression of type 17 cytokines, IL-17A and IL-17F, were not reduced. Dual knockout of PLD1 and PLD2 offered little additional protection compared to PLD2 knockout alone in the IL-23 model. In addition, pharmacological inhibition with a pan-PLD1/PLD2 inhibitor also suppressed IL-23-induced psoriasiform dermatitis. Bone-marrow-derived macrophages from wild type (WT) and PLD2 knockout (KO) mice exhibited little difference in viability and sensitivity to lipopolysaccharide and/or interferon gamma, or resiquimod (R848). PLD2 deficiency did not alter the differentiation and function of Th17 cells in an ex vivo study with splenocytes isolated from WT and PLD2 KO mice. Overall, these data suggest that PLD2 may play a role in the pathophysiology of psoriasis. Reducing macrophage infiltrate and cytokine/chemokine production might contribute to an anti-inflammatory effect observed in PLD2 knockout mice. Further studies are required to better understand the mechanisms by which PLD2 contributes to skin lesions in psoriasis patients and psoriasiform dermatitis models.