Tumor relapse and metastasis remain major obstacles for improving overall cancer survival, which may be due at least in part to the existence of cancer stem cells (CSCs). CSCs are characterized by tumorigenic properties and the ability to self-renew, form differentiated progeny, and develop resistance to therapy. CSCs use many of the same signaling pathways that are found in normal stem cells, such as Wnt, Notch, and Hedgehog (Hh). The origin of CSCs is not fully understood, but data suggest that they originate from normal stem or progenitor cells, or possibly other cancer cells. Therapeutic targeting of both CSCs and bulk tumor populations may provide a strategy to suppress tumor regrowth. Development of agents that target critical steps in the Wnt, Notch, and Hh pathways will be complicated by signaling cross-talk. The role that embryonic signaling pathways play in the function of CSCs, the development of new anti-CSC therapeutic agents, and the complexity of potential CSC signaling cross-talk are described in this Review.

COVID-19-associated coagulopathy (CAC) is a life-threatening complication of SARS-CoV-2 infection. However, the underlying cellular and molecular mechanisms driving this condition are unclear. Evidence supports the concept that CAC involves complex interactions between the innate immune response, the coagulation and fibrinolytic pathways, and the vascular endothelium, resulting in a procoagulant condition. Understanding of the pathogenesis of this condition at the genomic, molecular and cellular levels is needed in order to mitigate thrombosis formation in at-risk patients. In this Perspective, we categorize our current understanding of CAC into three main pathological mechanisms: first, vascular endothelial cell dysfunction; second, a hyper-inflammatory immune response; and last, hypercoagulability. Furthermore, we pose key questions and identify research gaps that need to be addressed to better understand CAC, facilitate improved diagnostics and aid in therapeutic development. Finally, we consider the suitability of different animal models to study CAC.

Induction of epithelial-to-mesenchymal transition (EMT) in cancer stem cells (CSCs) can occur as the result of embryonic pathway signaling. Activation of Hedgehog (Hh), Wnt, Notch, or transforming growth factor-β leads to the upregulation of a group of transcriptional factors that drive EMT. This process leads to the transformation of adhesive, non-mobile, epithelial-like tumor cells into cells with a mobile, invasive phenotype. CSCs and the EMT process are currently being investigated for the role they play in driving metastatic tumor formation in breast cancer. Both are very closely associated with embryonic signaling pathways that stimulate self-renewal properties of CSCs and EMT-inducing transcription factors. Understanding these mechanisms and embryonic signaling pathways may lead to new opportunities for developing therapeutic agents to help prevent metastasis in breast cancer. In this review, we examine embryonic signaling pathways, CSCs, and factors affecting EMT.

We examined sera from 160 HIV-infected individuals for antibodies reactive to HIV-1 gp160 epitopes defined by seven synthetic peptides. Seropositive individuals were placed into three groups based upon levels of circulating CD4+ cells. These groups consisted of individuals with (1) more than 400 CD4+ cells, (2) 200-400 CD4+ cells, and (3) fewer than 200 CD4+ cells/mm3. The percentage of sera containing antibodies reactive with two immunodominant gp160 epitopes (a.a. 304-321 and 600-611) was unchanged between groups, regardless of CD4 cell numbers. The percentage of sera containing antibodies reactive with weakly immunogenic gp160 epitopes, such as those defined by peptides 425-448 and 846-860, declined in the groups as CD4 values decreased. Our results suggest that the patterns of antibody reactivity to gp160 epitopes change as CD4 levels decline. A narrowing of the humoral immune response to epitopes on the envelope of HIV-1 appears to occur with disease progression.

Sera from human immunodeficiency virus type 1 (HIV-1)-infected individuals from the United States and Tanzania were examined for antibody reactivity to four synthetic peptides which corresponded to the principal neutralizing determinant from the V3 region of HlV-1 gpl20. We observed that the majority of sera from both countries contained antibodies reactive with a V3 peptide whose sequence is based on that of the HIV-1 MN isolate. We were unable to establish a relationship between the presence ofV3-reactive antibodies, as measured by enzyme-linked immunosorbent assay and neutralization of homologous HIV-1 isolates, in sera from either the United States or Tanzania. We observed that some sera which contained high antibody titers to the V3 peptides failed to neutralize HIV-1, while others with no antibody reactivity to the panel of V3 peptides exhibited in vitro neutralizing activity. These results suggest that neutralizing epitopes exist outside the V3 loop and that the presence of V3-reactive antibodies in sera does not imply in vitro neutralization of the homologous HIV-1 isolate. In addition, it appears that the V3 loop may consist of both neutralizing and nonneutralizing epitopes. The identification of neutralizing as well as nonneutralizing epitopes will be important for the design of potential HIV-1 vaccines.