PPM1D modulates hematopoietic cell fitness and response to DNA damage and is a therapeutic target in myeloid malignancy

PPM1D encodes a phosphatase that is recurrently activated across cancer, most notably in therapy-related myeloid neoplasms. However, the function of PPM1D in hematopoiesis and its contribution to tumor cell growth remain incompletely understood. Using conditional mouse models, we uncover a central role for Ppm1d in hematopoiesis and validate its potential as a therapeutic target. We find that Ppm1d regulates the competitive fitness and self-renewal of hematopoietic stem cells (HSCs) with and without exogenous genotoxic stresses. We also show that although Ppm1d activation confers cellular resistance to cytotoxic therapy, it does so to a lesser degree than p53 loss, informing the clonal competition phenotypes often observed in human studies. Notably, loss of Ppm1d sensitizes leukemias to cytotoxic therapies in vitro and in vivo, even in the absence of a Ppm1d mutation. Vulnerability to PPM1D inhibition is observed across many cancer types and dependent on p53 activity. Importantly, organism-wide loss of Ppm1d in adult mice is well tolerated, supporting the tolerability of pharmacologically targeting PPM1D. Our data link PPM1D gain-of-function mutations to the clonal expansion of HSCs, inform human genetic observations, and support the therapeutic targeting of PPM1D in cancer.

Investigation of the Readability and Reliability of Online Health Information for Cancer Patients During the Coronavirus Pandemic

For cancer patients undergoing treatment who may be at higher risk of COVID-19, access to high-quality online health information (OHI) may be of particular importance amidst a plethora of harmful medical misinformation online. Therefore, we assessed the readability and quality of OHI available for various cancer types and treatment modalities. Search phrases included "cancer radiation COVID," "cancer surgery COVID," "cancer chemotherapy COVID," and "cancer type COVID," for the fourteen most common cancer types (e.g., "prostate cancer COVID" and "breast cancer COVID"), yielding a total of 17 search phrases. The first 20 sources were recorded and analyzed for each keyword, yielding a total of 340 unique sources. For each of these sources, the approximate grade level required to comprehend the text was calculated as a mean of five validated readability scores; subsequently, for the first ten results of each search, the DISCERN tool was manually used to assess quality. Search terms were translated into Spanish and French, and a quality assessment using the Health on the Net Code (HONcode) accreditation was conducted. The median grade level readability for all sources was 13 (IQR 11-14). Median DISCERN scores for the 170 sources assessed were 55 out of 75, suggesting good quality. OHI with quality scores below the median DISCERN score had a median readability of 12.5 (IQR 11-14) grade reading level vs 14 (IQR 12-17) for those above the median DISCERN score (T-test P < 0.0001). Percentages of HONcode-accredited websites were 34.9%, 39.9%, and 38.6% for English, Spanish, and French OHI, respectively. We conclude that efforts are needed to make high-quality OHI available at the appropriate reading level for patients with cancer; such efforts may contribute to the alleviation of disparities in access to healthcare information.