Causal Diagrams: Pitfalls and Tips

Graphical models are useful tools in causal inference, and causal directed acyclic graphs (DAGs) are used extensively to determine the variables for which it is sufficient to control for confounding to estimate causal effects. We discuss the following ten pitfalls and tips that are easily overlooked when using DAGs: 1) Each node on DAGs corresponds to a random variable and not its realized values; 2) The presence or absence of arrows in DAGs corresponds to the presence or absence of individual causal effect in the population; 3) "Non-manipulable" variables and their arrows should be drawn with care; 4) It is preferable to draw DAGs for the total population, rather than for the exposed or unexposed groups; 5) DAGs are primarily useful to examine the presence of confounding in distribution in the notion of confounding in expectation; 6) Although DAGs provide qualitative differences of causal structures, they cannot describe details of how to adjust for confounding; 7) DAGs can be used to illustrate the consequences of matching and the appropriate handling of matched variables in cohort and case-control studies; 8) When explicitly accounting for temporal order in DAGs, it is necessary to use separate nodes for each timing; 9) In certain cases, DAGs with signed edges can be used in drawing conclusions about the direction of bias; and 10) DAGs can be (and should be) used to describe not only confounding bias but also other forms of bias. We also discuss recent developments of graphical models and their future directions

Coverage of the Humeral Head by the Coracoacromial Arch: Relationship with Rotator Cuff Tears

The pathogenetic roles of the coracoacromial arch in the development of rotator cuff tears are still controversial. This study compared the anteroposterior coverage of the humeral head by the coracoacromial arch between shoulders with and without full-thickness rotator cuff tears. Forty-two shoulders from 21 embalmed cadaveric specimens were macroscopically examined. Specimens were divided into 2 groups:shoulders with full-thickness cuff tears (tear group) and those with intact cuff tendons (normal group). The coverage angle of each component of the coracoacromial arch was measured using true lateral photographs. We also measured the angle of the total arc of the coracoacromial arch, as well as the angle of the anterior acromial projection. These data were compared between the tear group and the normal group. Although no significant differences were observed in the total arc of the coracoacromial arch between the groups, the tear group had significantly less coverage by the coracoacromial ligament than did the normal group (p＜0.05). Moreover, greater anterior acromial projection was observed in the tear group (p＜0.05). These results suggest that greater coverage of the bony structures on the rotator cuff may correlate with the development of rotator cuff tears

Acquired drug resistance conferred by a KRAS gene mutation following the administration of cetuximab: a case report

BACKGROUND: Although a number of studies have reported acquired drug resistance due to administration of epidermal growth factor receptor antibody inhibitors, the underlying causes of this phenomenon remain unclear. CASE PRESENTATION: Here we report a case of a 75-year-old man with liver metastasis at 3 years after a successful transverse colectomy to treat KRAS wild-type colorectal cancer. While initial administration of epidermal growth factor receptor inhibitors proved effective, continued use of the same treatment resulted in new peritoneal seeding. An acquired KRAS mutation was found in a resected tissue specimen from one such area. This mutation, possibly caused by administration of epidermal growth factor receptor inhibitors, appears to have conferred drug resistance. CONCLUSION: The present findings suggest that administration of epidermal growth factor receptor inhibitors results in an acquired KRAS mutation that confers drug resistance

In vitro throughput screening of anticancer drugs using patient-derived cell lines cultured on vascularized three-dimensional stromal tissues

Takahashi Y., Morimura R., Tsukamoto K., et al. In vitro throughput screening of anticancer drugs using patient-derived cell lines cultured on vascularized three-dimensional stromal tissues. Acta Biomaterialia 183, 111 (2024); https://doi.org/10.1016/j.actbio.2024.05.037.The development of high-throughput anticancer drug screening methods using patient-derived cancer cell (PDC) lines that maintain their original characteristics in an in vitro three-dimensional (3D) culture system poses a significant challenge to achieving personalized cancer medicine. Because stromal tissue plays a critical role in the composition and maintenance of the cancer microenvironment, in vitro 3D-culture using reconstructed stromal tissues has attracted considerable attention. Here, a simple and unique in vitro 3D-culture method using heparin and collagen together with fibroblasts and endothelial cells to fabricate vascularized 3D-stromal tissues for in vitro culture of PDCs is reported. Whereas co-treatment with bevacizumab, a monoclonal antibody against vascular endothelial growth factor, and 5-fluorouracil significantly reduced the survival rate of 3D-cultured PDCs to 30%, separate addition of each drug did not induce comparable strong cytotoxicity, suggesting the possibility of evaluating the combined effect of anticancer drugs and angiogenesis inhibitors. Surprisingly, drug evaluation using eight PDC lines with the 3D-culture method resulted in a drug efficacy concordance rate of 75% with clinical outcomes. The model is expected to be applicable to in vitro throughput drug screening for the development of personalized cancer medicine. Statement of significance: To replicate the cancer microenvironment, we constructed a cancer-stromal tissue model in which cancer cells are placed above and inside stromal tissue with vascular network structures derived from vascular endothelial cells in fibroblast tissue using CAViTs method. Using this method, we were able to reproduce the invasion and metastasis processes of cancer cells observed in vivo. Using patient-derived cancer cells, we assessed the possibility of evaluating the combined effect with an angiogenesis inhibitor. Further, primary cancer cells also grew on the stromal tissues with the normal medium. These data suggest that the model may be useful for new in vitro drug screening and personalized cancer medicine

Cancer of Unknown Primary Site:A Review of 28 Cases and the Efficacy of Cisplatin/Docetaxel Therapy at a Single Institute in Japan

We evaluated the efficacy and toxicity of cisplatin/docetaxel (CDDP/TXT) chemotherapy and identified prognostic factors in Japanese patients with cancer of unknown primary site (CUP). Twenty-eight consecutive patients seen at a single institute were reviewed retrospectively. Sixteen patients were treated with TXT 80mg/m2, followed by CDDP 75mg/m2. The overall response rate to CDDP/TXT treatment was 62.5%, with a median survival time (MST) of 22.7 months. Common adverse reactions were myelosuppression and hyponatremia. The MST of all 28 patients with CUP was 8.3 months, and the 1-year overall survival rate was 45.6%. Univariate analysis identified 5 prognostic factors:performance status, liver involvement, bone involvement, pleural involvement, and lymph node involvement. In conclusion, CDDP/TXT chemotherapy is effective with tolerable toxicity in patients with CUP. Japanese patients with CUP might be chemosensitive and may survive longer

Astrocytic dysfunction induced by ABCA1 deficiency causes optic neuropathy

Astrocyte abnormalities have received great attention for their association with various diseases in the brain but not so much in the eye. Recent independent genome-wide association studies of glaucoma, optic neuropathy characterized by retinal ganglion cell (RGC) degeneration, and vision loss found that single-nucleotide polymorphisms near the ABCA1 locus were common risk factors. Here, we show that Abca1 loss in retinal astrocytes causes glaucoma-like optic neuropathy in aged mice. ABCA1 was highly expressed in retinal astrocytes in mice. Thus, we generated macroglia-specific Abca1-deficient mice (Glia-KO) and found that aged Glia-KO mice had RGC degeneration and ocular dysfunction without affected intraocular pressure, a conventional risk factor for glaucoma. Single-cell RNA sequencing revealed that Abca1 deficiency in aged Glia-KO mice caused astrocyte-triggered inflammation and increased the susceptibility of certain RGC clusters to excitotoxicity. Together, astrocytes play a pivotal role in eye diseases, and loss of ABCA1 in astrocytes causes glaucoma-like neuropathy

Circulating Tumor DNA as a Novel Biomarker Optimizing Chemotherapy for Colorectal Cancer

Liquid biopsy is a minimally invasive method for detecting soluble factors, including circulating tumor DNA (ctDNA), in body fluids. ctDNA carrying tumor-specific genetic or epigenetic alterations is released into circulation from tumor cells. ctDNA in the plasma contains somatic mutations that have occurred in the tumor, and reflects tumor progression and therapeutic effects promptly and accurately. Furthermore, ctDNA is useful for early detection of recurrence and estimation of prognosis and may be utilized for diagnosis and personalized medicine for treatment selection. Thus, in the near future, it will be possible to select the most appropriate treatment based on real-time genetic information using ctDNA