LRP5 regulates the expression of STK40, a new potential target in triple-negative breast cancers

Triple-negative breast cancers (TNBCs) account for a large proportion of breast cancer deaths, due to the high rate of recurrence from residual, resistant tumor cells. New treatments are needed, to bypass chemoresistance and improve survival. The WNT pathway, which is activated in TNBCs, has been identified as an attractive pathway for treatment targeting. We analyzed expression of the WNT coreceptors LRP5 and LRP6 in human breast cancer samples. As previously described, LRP6 was overexpressed in TNBCs. However, we also showed, for the first time, that LRP5 was overexpressed in TNBCs too. The knockdown of LRP5 or LRP6 decreased tumorigenesis in vitro and in vivo, identifying both receptors as potential treatment targets in TNBC. The apoptotic effect of LRP5 knockdown was more robust than that of LRP6 depletion. We analyzed and compared the transcriptomes of cells depleted of LRP5 or LRP6, to identify genes specifically deregulated by LRP5 potentially implicated in cell death. We identified serine/threonine kinase 40 (STK40) as one of two genes specifically downregulated soon after LRP5 depletion. STK40 was found to be overexpressed in TNBCs, relative to other breast cancer subtypes, and in various other tumor types. STK40 depletion decreased cell viability and colony formation, and induced the apoptosis of TNBC cells. In addition, STK40 knockdown impaired growth in an anchorage-independent manner in vitro and slowed tumor growth in vivo. These findings identify the largely uncharacterized putative protein kinase STK40 as a novel candidate treatment target for TNBC.

Abstract A38: The Wnt noncanonical receptor ROR1 regulates neuroblastoma cell growth and motility through two distinct mechanisms

Neuroblastoma is a pediatric tumor derived from the sympathetic nervous system, responsible for about 15% of cancer deaths in children. The Wnt signaling pathway, which is required for both normal embryonic development and the maintenance of different types of adult stem cells, including sympathoadrenal progenitors, plays a major role in the onset and progression of several types of human cancer. In a screen of several human neuroblastoma cell lines, we found that none showed a constitutive activation of the canonical Wnt/β-catenin signaling, arguing against a major role of this pathway in this type of cancer. In a previous study, we demonstrated that the receptor tyrosine kinase-like orphan receptor 1 (ROR1) can be triggered by noncanonical Wnt ligands, resulting in its phosphorylation on serine/threonine residues. We found that several neuroblastoma cells express high levels of ROR1, which can be associated in some cases with constitutive phosphorylation of this receptor through an autocrine mechanism. We showed that ROR1 down-regulation through lentiviral shRNAs strongly reduced the growth of different neuroblastoma cells, including SJNB-10, SK-N-AS and Kelly. Conversely, ROR1 knockdown in other neuroblastoma cells significantly reduced cell motility, without affecting growth. To assess the potential role of autocrine noncanonical Wnt signaling in neuroblastoma cell motility and/or growth, we used two different approaches, based on the inhibition of Wnt secretion using the small molecule IWP2, or the sequestration of Wnt ligands by ext-Fzd8, a decoy receptor containing the extracellular domain of the Wnt co-receptor Frizzled 8. These studies revealed that IWP-2 and ext-Fzd8 could both inhibit ROR1 constitutive phosphorylation and reduce cell motility, but they had no effect on cell growth, indicating that different mechanisms are responsible for the activation of this receptor in neuroblastoma cells. It has been recently reported that the putative tyrosine kinase domain of ROR1 could play a role in the survival of lung cancer cells. We found that the inactivation of ROR1 ATP-binding domain using the CRISPR/Cas9 technology did not affect the growth of SJNB-10 and Kelly cells, implying that the catalytic activity of this receptor is not required for its effects in neuroblastoma cells.

In conclusion, we demonstrated that ROR1 can play a dual role in neuroblastoma cell motility and growth through two distinct mechanisms, respectively dependent and independent of noncanonical Wnt ligands, suggesting that this receptor could represent a novel therapeutic target for the treatment of this type of cancer.

Citation Format: Alexis Guernet, Sardar Faisal Mahmood, Hassan Ainani, Youssef Anouar, Luca Grumolato. The Wnt noncanonical receptor ROR1 regulates neuroblastoma cell growth and motility through two distinct mechanisms. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr A38.

A siRNA screen identifies RAD21, EIF3H, CHRAC1 and TANC2 as driver genes within the 8q23, 8q24.3 and 17q23 amplicons in breast cancer with effects on cell growth, survival and transformation

RNA interference has boosted the field of functional genomics, by making it possible to carry out 'loss-of-function' screens in cultured cells. Here, we performed a small interfering RNA screening, in three breast cancer cell lines, for 101 candidate driver genes overexpressed in amplified breast tumors and belonging to eight amplicons on chromosomes 8q and 17q, investigating their role in cell survival/proliferation. This screening identified eight driver genes that were amplified, overexpressed and critical for breast tumor cell proliferation or survival. They included the well-described oncogenic driver genes for the 17q12 amplicon, ERBB2 and GRB7. Four of six other candidate driver genes-RAD21 and EIF3H, both on chromosome 8q23, CHRAC1 on chromosome 8q24.3 and TANC2 on chromosome 17q23-were confirmed to be driver genes regulating the proliferation/survival of clonogenic breast cancer cells presenting an amplification of the corresponding region. Indeed, knockdown of the expression of these genes decreased cell viability, through both cell cycle arrest and apoptosis induction, and inhibited the formation of colonies in anchorage-independent conditions, in soft agar. Strategies for inhibiting the expression of these genes or the function of the proteins they encode are therefore of potential value for the treatment of breast cancers presenting amplifications of the corresponding genomic region.

Pituitary adenylate cyclase-activating polypeptide (PACAP) promotes both survival and neuritogenesis in PC12 cells through activation of nuclear factor κB (NF-κB) pathway: involvement of extracellular signal-regulated kinase (ERK), calcium, and c-REL

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a trophic factor that promotes neuronal survival and neurite outgrowth. However, the signaling pathways and the transcriptional mechanisms involved are not completely elucidated. Our previous studies aimed at characterizing the transcriptome of PACAP-differentiated PC12 cells revealed an increase in the expression of nuclear factor κB2 (NF-κB2) gene coding for p100/p52 subunit of NF-κB transcription factor. Here, we examined the role of the NF-κB pathway in neuronal differentiation promoted by PACAP. We first showed that PACAP-driven survival and neuritic extension in PC12 cells are inhibited following NF-κB pathway blockade. PACAP stimulated both c-Rel and p52 NF-κB subunit gene expression and nuclear translocation, whereas c-Rel down-regulation inhibited cell survival and neuritogenesis elicited by the neuropeptide. PACAP-induced c-Rel nuclear translocation was inhibited by ERK1/2 and Ca(2+) blockers. Furthermore, the neuropeptide stimulated NF-κB p100 subunit processing into p52, indicative of activation of the NF-κB alternative pathway. Taken together, our data show that PACAP promotes both survival and neuritogenesis in PC12 cells by activating NF-κB pathway, most likely via classical and alternative signaling cascades involving ERK1/2 kinases, Ca(2+), and c-Rel/p52 dimers.

Vulnerability to homicide in Karachi: political activity as a risk factor

BACKGROUND

Previous studies analysing Karachi ambulance data from 1993 to 1995 identified neighbourhoods in Karachi disproportionately affected by homicide. As a step toward developing intervention programmes to curb violence, we conducted a study to identify risk factors for becoming a homicide victim in a high violence area of Karachi.

METHODS

We interviewed families of 35 cases, individuals intentionally killed through acts of violence between January 1994 and January 1997, and 85 community-based controls frequency matched by sex, from Orangi, a high violence area of Karachi.

RESULTS

Most of our cases and controls were male (97% and 92%, respectively) and had similar socioeconomic and ethnic backgrounds. All the victims were killed by firearms; 4 (11%) had been tortured prior to death. Most of the victims were killed in the streets (n = 25, 71%). Of these, 7 (36%) had been killed by law-enforcement officers, while 6 (24%) died from indiscriminate firing. People who were killed were 34 times more likely to have attended all political processions (29% versus 1%, odds ratio [OR] = 34; 95% CI: 4-749, P < 0.001), 19 times more likely to have attended political meetings (31% versus 2%, OR = 19; 95% CI: 4-136, P < 0.001), and 17 times more likely to have held an important position in a political party (29% versus 2%, OR = 17; 95% CI: 3-120, P < 0.001) than controls.

CONCLUSIONS

Homicide in Orangi was political. Efforts to improve trust between ethnic groups and to build legitimacy for non-violent forms of conflict resolution are important steps to limit future violence.

Thrombolytic therapy in acute myocardial infarction in Pakistan

To characterize features of acute myocardial infarction (AMI) in a Pakistani population, and assess the role of thrombolysis in our country, we studied 194 consecutive admitted patients with enzyme positive AMI. Males were affected three times more frequently; women, although affected less, had a higher incidence of complications than men. Premature coronary artery disease (CAD) was present in 50% patients presenting with AMI. An unusually high incidence of anterior wall myocardial infarction (39%) was seen. Complications were frequent with a predominance of LV failure symptoms. Cardiogenic shock was associated with a very high mortality, in excess of 93%. Streptokinase (SK) was administered in 60% patients with suspected transmural AMI. A statistically significant reduction in mortality was seen in the group that received SK (15.2%) compared to those who did not receive SK (24.7%), (p = < 0.05).