CDK4/6 inhibition confers protection of normal gut epithelia against gemcitabine and the active metabolite of irinotecan.

Cancer chemotherapy relies on a high ratio of toxicity toward cancer cells vs. nonmalignant cells, making it desirable to protect normal cells. Among the nonmalignant cells, epithelia of the gut belong to the most vulnerable ones toward chemotherapeutics. Here, we use a murine intestinal organoid model to assess a strategy for protecting such epithelia against chemotherapy. Cell cycle progression was first stalled by palbociclib, a clinically established cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. Washout of the drug allowed subsequent outgrowth of gut organoids. This transient cell cycle arrest conferred near-complete protection of the cells toward the nucleoside analogue gemcitabine. Moreover, pre-treatment with palbociclib protected the organoids against SN-38, the topoisomerase I-inhibiting metabolite of irinotecan, which is otherwise known for its severe gastrointestinal toxicities. In contrast, RB1-mutated cancer cells were not protected against gemcitabine or SN-38 when pre-treated with palbociclib. Taken together, these results outline a strategy for protecting nonmalignant cells against the toxicities of chemotherapeutics commonly used to treat advanced colorectal and pancreatic cancer. We propose that this strategy is particularly promising to protect the gut when treating RB1-deficient tumors that fail to arrest the cell cycle in response to CDK4/6 inhibitors. [Figure: see text].

Preparation and Cultivation of Colonic and Small Intestinal Murine Organoids Including Analysis of Gene Expression and Organoid Viability.

Organoids are complex three-dimensional structures, which contain different cell types and help to overcome many limitations of conventional 2D cell culture techniques. Here, we present a protocol for the cultivation of murine matched-pairs of small intestinal and colonic epithelial organoids, and colonic tumor organoids derived from the chemical colorectal cancer (CRC) AOM/DSS mouse model. Therefore, intestinal crypts or tumor tissue containing stem cells are isolated from the same donor mouse and cultivated in Matrigel®. The culture medium is supplemented with different growth factors to model the intestinal stem cell niche, allowing their self-renewal and differentiation. Matched-pair organoids enable the analysis of pharmacological effects and the tumor selectivity of drugs. Graphic abstract: Schematic overview of colonic matched pair organoid preparation, generated from the chemical AOM/DSS colorectal cancer mouse model. Please note that normal colon-derived organoids (green) differ in their morphology from tumor-derived organoids (red). Normal colonic-derived organoids display a thicker and crypt-like epithelial layer, whereas tumor-derived organoids are round with a thin epithelial layer.

The glucocorticoid antagonist RU-486 suppresses HIV infectivity and replication.

The effects of RU-486, a glucocorticoid antagonist, on HIV infection and replication in depressed and nondepressed women were studied using ex vivo models of HIV infection. RU-486 treatment of cells decreased HIV reverse transcriptase activity of monocyte-derived macrophages in a model of acute infectivity. RU-486 also decreased HIV viral replication in the chronically-infected T-cell line ACH-2, but not in the promonocyte cell line U1. No differences were associated with depression status. Thus, glucocorticoid antagonism may suppress HIV infectivity and replication ex vivo. Studies to determine the role of glucocorticoid antagonists in the host defense against HIV should be performed.

Immune suppression and immune activation in depression.

Depression has been characterized as a disorder of both immune suppression and immune activation. Markers of impaired cellular immunity (decreased natural killer cell cytotoxicity) and inflammation (elevated IL-6, TNFα, and CRP) have been associated with depression. These immunological markers have been associated with other medical illnesses, suggesting that immune dysregulation may be a central feature common to both depression and to its frequent medical comorbidities. Yet the significant associations of findings of both immune suppression and immune activation with depression raise questions concerning the relationship between these two classes of immunological observations. Depressed populations are heterogeneous groups, and there may be differences in the immune profiles of populations that are more narrowly defined in terms of symptom profile and/or demographic features. There have been few reports concurrently investigating markers of immune suppression and immune activation in the same depressed individuals. An emerging pre-clinical literature suggests that chronic inflammation may directly contribute to the pathophysiology of immune suppression in the context of illnesses such as cancer and rheumatoid arthritis. This literature provides us with specific immunoregulatory mechanisms mediating these relationships that could also explain differences in immune disturbances between subsets of depressed individuals We propose a research agenda emphasizing the assessment of these immunoregulatory mechanisms in large samples of depressed subjects as a means to define the relationships among immune findings (suppression and/or activation) within the same depressed individuals and to characterize subsets of depressed subjects based on shared immune profiles. Such a program of research, building on and integrating our knowledge of the psychoneuroimmunology of depression, could lead to innovation in the assessment and treatment of depression and its medical comorbidities.

Selective serotonin reuptake inhibitor suppression of HIV infectivity and replication.

OBJECTIVE: To test the hypothesis that the selective serotonin reuptake inhibitor (SSRI) citalopram would down-regulate human immunodeficiency virus (HIV) infectivity and that the greatest effects would be seen in people with depression. Depression is a risk factor for morbidity and mortality in HIV/acquired immune deficiency syndrome. Serotonin (5-HT) neurotransmission has been implicated in the pathobiology of depression, and pharmacologic therapies for depression target this system. The 5-HT transporter and 5-HT receptors are widely distributed throughout the central nervous and immune systems. Depression has been associated with suppression of natural killer cells and CD8(+) lymphocytes, key regulators of HIV infection. METHODS: Ex vivo models for acute and chronic HIV infection were used to study the effects of citalopram on HIV viral infection and replication in 48 depressed and nondepressed women. For both the acute and chronic infection models, HIV reverse transcriptase activity was measured in the citalopram treatment condition and the control condition. RESULTS: The SSRI significantly down-regulated the reverse transcriptase response in both the acute and chronic infection models. Specifically, citalopram significantly decreased the acute HIV infectivity of macrophages. Citalopram also significantly decreased HIV viral replication in the latently infected T-cell line and in the latently infected macrophage cell line. There was no difference in down-regulation by depression status. CONCLUSIONS: These studies suggest that an SSRI enhances natural killer/CD8 noncytolytic HIV suppression in HIV/acquired immune deficiency syndrome and decreases HIV viral infectivity of macrophages, ex vivo, suggesting the need for in vivo studies to determine a potential role for agents targeting serotonin in the host defense against HIV.