ASPM promotes prostate cancer stemness and progression by augmenting Wnt-Dvl-3-ß-catenin signaling.

Recurrent and hormone-refractory prostate cancer (PCA) exhibits aggressive behaviors while current therapeutic approaches show little effect of prolonging the survival of patients with PCA. Thus, a deeper understanding of the patho-molecular mechanisms underlying the disease progression in PCA is crucial to identify novel diagnostic and/or therapeutic targets to improve the outcome of patients. Recent evidence suggests that activation of Wnt signaling in cancer stem cells (CSCs) contributes to cancer progression in malignant tumors. Here, we report that a novel Wnt co-activator ASPM (abnormal spindle-like microcephaly associated) maintains the prostate CSC subpopulation by augmenting the Wnt-ß-catenin signaling in PCA. ASPM expression is incrementally upregulated in primary and metastatic PCA, implicating its potential role in PCA progression. Consistently, downregulation of ASPM expression pronouncedly attenuated the proliferation, colony formation, and the invasive behavior of PCA cells, and dramatically reduced the number of ALDH+ CSCs and inhibited cancer stemness and tumorigenicity. Mechanistically, ASPM interacts with disheveled-3 (Dvl-3), a cardinal upstream regulator of canonical Wnt signaling, and inhibits its proteasome-dependent degradation, thereby increasing its protein stability and enabling the Wnt-induced ß-catenin transcriptional activity in PCA cells. In keeping with the role of ASPM as a CSC-regulator, ASPM co-localizes with ALDH in PCA tissues and its expression exhibits high intra-tumoral heterogeneity. The proportion of high-ASPM-expressing cells in the tumor inversely correlates with the relapse-free survival of PCA patients. Collectively, our data points to ASPM as a novel oncoprotein and an essential regulator of Wnt signaling and cancer stemness in PCA, which has important clinical and therapeutic significance.

Correction: ASPM promotes prostate cancer stemness and progression by augmenting Wnt-Dvl-3-ß-catenin signaling.

In the published version of this paper the author Shu-Pin Huang's surname was incorrectly given as Hwang instead of Huang. This has now been corrected in the HTML and PDF versions of the paper.

Metronomic chemotherapy prevents therapy-induced stromal activation and induction of tumor-initiating cells.

Although traditional chemotherapy kills a fraction of tumor cells, it also activates the stroma and can promote the growth and survival of residual cancer cells to foster tumor recurrence and metastasis. Accordingly, overcoming the host response induced by chemotherapy could substantially improve therapeutic outcome and patient survival. In this study, resistance to treatment and metastasis has been attributed to expansion of stem-like tumor-initiating cells (TICs). Molecular analysis of the tumor stroma in neoadjuvant chemotherapy-treated human desmoplastic cancers and orthotopic tumor xenografts revealed that traditional maximum-tolerated dose chemotherapy, regardless of the agents used, induces persistent STAT-1 and NF-κB activity in carcinoma-associated fibroblasts. This induction results in the expression and secretion of ELR motif-positive (ELR+) chemokines, which signal through CXCR-2 on carcinoma cells to trigger their phenotypic conversion into TICs and promote their invasive behaviors, leading to paradoxical tumor aggression after therapy. In contrast, the same overall dose administered as a low-dose metronomic chemotherapy regimen largely prevented therapy-induced stromal ELR+ chemokine paracrine signaling, thus enhancing treatment response and extending survival of mice carrying desmoplastic cancers. These experiments illustrate the importance of stroma in cancer therapy and how its impact on treatment resistance could be tempered by altering the dosing schedule of systemic chemotherapy.