PANCREATIC CANCER ON VERGE OF CURE?

Well yes, by blocking the key proteins that protect the tumor growth

though immunotherapy - enlisting the immune system to attack tumors - is showing promise against some cancers, this is not the case in pancreatic cancer. Now, new research reveals there is a protein called CXCR2 that helps pancreatic cancer avoid and then exploit the immune system. Using mice, the researchers show drugs that block CXCR2 may offer a way to stop tumor spread and boost immunotherapy. 

The researchers suggest CXCR2 inhibitors might make immunotherapy work for pancreatic cancer patients.

The study, led by researchers from the Beatson Institute in Glasgow, United Kingdom, is published in the journal Cancer Cell.

Over the last 40 years, the survival rate for many cancershas improved dramatically. However, for pancreatic cancer, a disease that is rarely detected in its early stages, survival remains pitifully low - the vast majority of patients do not live more than 5 years after diagnosis.

Hopes were raised when immunotherapy came on the scene. This approach - particularly in the form of "checkpoint inhibitors" that prime immune cells to attack tumors - is showing promise in several cancers, including melanoma and lung cancer. But results for pancreatic cancer have been disappointing.

An important factor in the failure of checkpoint drugs to attack pancreatic cancer has been the ability of tumors to surround themselves with a protective shield of proteins and cells that stop the primed immune cells from reaching and attacking the tumor.

Researchers at the Beatson Institute have been investigating a protein called CXCR2 for a while. They recently discovered CXCR2 plays a role in cancer - helping to drive tumorgrowth in mice with skin and bowel cancer. So they decided to investigate its role in pancreatic cancer.

Tumors did not spread in mice lacking CXCR2

First, the researchers analyzed tumor tissue from pancreatic cancer patients who had undergone surgery. They found high levels of CXCR2 on immune cells in the tumor surroundings. They also discovered that higher levels of CXCR2 correlated with worse outcomes for patients.

They then took a closer look at the role of CXCR2 by studying mice genetically engineered to develop pancreatic cancer. They also bred some of the mice to lack CXCR2.

Co-senior author Prof. Owen Sansom, of the Beatson Institute, explains what they found:

"The mice lacking CXCR2 still developed pancreatic cancer and survived just as long as the others. But, remarkably, their tumors didn't spread."

When they took a closer look, the team found in the mice lacking CXCR2 that immune system cells called T cells - known to be involved in attacking cancer cells - had broken through the protective shield and invaded the tumors.

In another set of experiments in mice with late stage pancreatic cancer, the researchers showed those treated with an experimental drug that blocks CXCR2 survived longer than untreated mice.

The team also found the CXCR2 inhibitor had a more powerful effect when combined with a chemotherapy drug called gemcitabine - the current gold standard of care for pancreatic cancer.

The combination stopped the tumors spreading, and on closer inspection, the team again saw that the T cells had broken through the protective shield and invaded the tumors.

Co-senior author Dr. Jennifer Morton, also of the Beatson Institute says that "one of the most striking effects of blocking CXCR2 was the rush of T cells into the tumor." 

This was a particularly crucial discovery - could it mean that a CXCR2 inhibitor might have the same boosting effect in immunotherapy and allow primed T cells access to the tumor?

Could blocking CXCR2 prime tumors for immunotherapy?

The team went back to the mice with late-stage pancreatic cancer that had already been treated with CXCR2 inhibitor and treated remaining survivors with a checkpoint inhibitor drug. In most of these, the immunotherapy had a longer lasting effect.

Finally, the researchers tried to work out why CXCR2 appears to have such a key role in helping tumors spread. They concluded it has to do with two types of immune cell: neutrophils and myeloid-derived suppressor cells. CXCR2 acts as a type of homing device for these cells, helping them navigate to sites of injury or tissue damage.

When the immune system spots the injury or damage, it sends out alarm molecules into the bloodstream to summon neutrophils to start containing and fixing the problem. The neutrophils use their CXCR2 receptors to pick up the navigation direction from the alarm molecules.

Also, while less clear-cut, it appears the myeloid-derived suppressor cells also use CXCR2 to guide them to the site of the damage, except their role is to switch the process off again when the problem is fixed.

However, it seems that pancreatic cancer subverts the roles of these two types of cell and somehow exploits them to help tumors grow and spread. The researchers say this could be the reason the pancreatic tumors had such high levels of CXCR2 - because they were full of neutrophils and suppressor cells, at the expense of T cells.

There is still a lot of work to do to unravel exactly what is going on. Prof. Samson says it looks as if the roles of neutrophils and suppressor cells change as disease progresses, and explains:

"In early pancreatic tumors the neutrophils and myeloid-derived suppressor cells seem to slow tumor growth. But later on, they fuel the spread of the disease, which is ultimately what kills people."

Type 2 diabetes drug could be beneficial for head and neck cancer patients

Researchers at the University of Cincinnati (UC) College of Medicine have found that adding increasing doses of an approved Type 2 diabetes drug, metformin, to a chemotherapy and radiation treatment regimen in head and neck cancer patients is not well tolerated if escalated too quickly, but allowing slower escalation could be beneficial. These findings are being presented via poster June 4 at the 2016 American Society of Clinical Oncology (ASCO) Annual Meeting: Collective Wisdom, being held June 3-7 in Chicago.

Trisha Wise-Draper, MD, PhD, assistant professor in the Division of Hematology Oncology at the UC College of Medicine, a member of both the Cincinnati Cancer Center and UC Cancer Institute and principal investigator on this study, says retrospective studies have shown improved outcomes in tumors treated with chemotherapy and radiation if they were also on metformin for diabetes. 

"In head and neck squamous cell carcinoma, which develops in the mucous membranes of the mouth, nose and throat, diabetic patients taking a medication called metformin had better overall survival compared to those not on metformin when also treated with chemotherapy and radiation," she says. "Additionally, pancreatic cancer patients treated with chemotherapy and metformin required higher doses of metformin--1,000 milligrams twice a day--to experience positive results. 

"In basic science studies, metformin has been shown to stop mTOR, a molecular pathway present and active in this type of head and neck cancer, and pretreatment with metformin resulted in a decrease in the occurrence of oral cavity tumors in animal models. In this study, we wanted to see if the combination of escalating doses of metformin with the chemotherapy agent cisplatin and radiation for head and neck cancer tumors in non-diabetic patients would be effective."

Wise-Draper says that metformin, which is an approved Type 2 diabetes medication, was provided by their investigational pharmacy. Metformin was administered orally in escalating doses for 7 to 14 days prior to starting the cisplatin and radiation and continued throughout standard treatment. Blood samples were collected before and after metformin treatment as well as during chemotherapy. Flow cytometry, a technique used to count cells, was used to detect the percent of circulating immune activated cells, and clinical laboratory tests including glucose, B12 and C-peptide (an amino acid that is important for controlling insulin) were performed.

"This is part of an ongoing clinical trial," says Wise-Draper. "We found that eight patients with advanced head and neck cancer have been enrolled so far; we plan to have 30 total. Due to the relatively quick escalation of metformin, the patients' tolerance was poor with higher doses of metformin when initiated 7 days prior to their chemotherapy and radiation therapy regimen. 

"Therefore, the protocol was modified to allow slower escalation over 14 days. The most common toxicities observed included nausea (71 percent of patients) and vomiting (43 percent of patients), increase in creatinine (57 percent of patients), decreased white blood cell count (43 percent of patients) and pain when swallowing (43 percent of patients) with only nausea being directly attributed to metformin and the rest attributed to cisplatin and radiation."

She adds that there wasn't a substantial change in T cell or glucose levels with administration of metformin in the small sample of patients but that there were increased C-peptide levels in response to metformin administration.

"These results show that the combination of metformin and cisplatin and radiation was poorly tolerated when metformin was escalated quickly. However, there has been no significant increase in side effects thus far with the addition of metformin," Wise-Draper says. "The trial is continuing with escalation of metformin over a longer period of time to provide more data; we will also try to increase our sample size."

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Bacterial RNA-editing tool could disable viruses or halt disease

Move over DNA, its RNA’s time to shine. A revolutionary RNA-editing tool promises to transform our understanding of RNA’s role in our growth and development, and provide a new avenue for treating infectious diseases and cancer.

RNA was once thought to be a mere middleman, carrying genetic messages from the DNA in the nucleus out to cellular structures called ribosomes, where it directs the production of proteins. In recent decades we have learned that it does much more, from controlling what form a protein will take to influencing whether a particular gene is able to generate a protein.

In other words, although we might think that we are governed by our DNA, it is really RNA that pulls the strings. So people are understandably keen to develop tools to study, track and even manipulate RNA inside living cells.

Genetic warfare

In 2013, a team led by Feng Zhang at the Broad Institute of MIT and Harvard – and another team working independently – figured out how to manipulate a genetic bacterial immune system that can identify and attack an invading pathogen by snipping up sections of its DNA. This CRISPR-Cas system from the bacterium Streptococcus pyogenes is now being used to target and cut up DNA sequences – including those in human cells.

Now Zhang’s team has discovered another version of the CRISPR-Cas system in a bacterium called Leptotrichia shahii. Only this one, called C2c2, selectively cuts up RNA.

To show its promise, Zhang’s team inserted C2c2 into E. coli bacteria, where it silenced a gene by cutting up a form of RNA that carries the gene’s information to the ribosomes.

Silencing genes with C2c2 could make pathogens harmless, says John Rossi at City of Hope medical centre in Duarte, California, who is leading efforts to use RNA molecular tools to fight HIV.

Binding appeal

C2c2 should be able to do more than silence genes. It can also be modified so it binds to RNA but doesn’t cut it up, says Zhang. This means that it could conceivably form part of an editing system to tag RNA so that its movement in the cell can be tracked. This would allow us to alter RNA in a living system and track what effect those alterations are having on the cell or animal as a whole.

“RNA is the blueprint through which genes regulate cellular processes,” says Oliver Rackham at the University of Western Australia. “The exciting thing about this study is that it now opens up the RNA world to the ease of experimental design afforded by CRISPR.”

Rackham is interested in how using C2c2 to target a specific E. coli RNA led to “collateral damage” – RNAs that looked a little like the target molecule were attacked too. Although it might be useful to reduce that collateral damage for some applications, he says it could prove beneficial in others – in a cancer treatment, for example, wiping out “bystander” RNA as well as target RNA might offer a more effective way to fight a tumour.

The tool shop

There is such a hunger for RNA tools that earlier this year, Gene Yeo at the University of California, San Diego, and Jennifer Doudna at the University of California, Berkeley, used some hefty synthetic modifications on the existing CRISPR-Cas system to make it target RNA rather than DNA.

Doudna and Yeo’s tool can already track RNA in mammalian cells, whereas the C2c2 system has so far only been tested in bacteria. But Zhang is confident that with further development C2c2 will be able to bind to mammalian RNAs without cleaving them too.

Both RNA editing tools will be useful, but C2c2 might be more versatile because it is based on a natural RNA targeting system rather than an engineered one.

One thing is clear, says Yeo. “This is the decade where RNA rears its head as being very important for understanding cellular behaviour and disease.”

RNA GAME IS ON.....

The gene editing technique CRISPR promises to treat all kinds of genetically-linked conditions, 
but it's so far limited to tweaking DNA, not the RNA that does everything from carrying protein sequence info to regulating gene expression. 

That may change soon, however. Scientists have discovered that a commonplace mouth bacterium (Leptotrichia shahii) can be programmed to break down whatever RNA you want. 

You could rip apart viruses, which are frequently based solely around RNA, or kill a cancer cell by denying it the chance to make vital proteins.

This isn't a cure-all right now. Researchers have to refine their approach before it works in humans, and it's hard to say whether or not this RNA editing will be as effective in practice. As you might surmise, though, the potential is huge. If this works as well as it suggests, you could fight a wider array of illnesses with gene editing, even those that are notoriously 
difficult to treat using conventional methods.

CRISPR DNA EDITITING

The researchers originally identified C2c2 in Leptotrichia shahii in a systematic search for previously unidentified CRISPR systems within diverse bacterial genomes. For the present study, the team focused on C2c2, as its sequence contained two copies of a domain—called ­higher eukaryotes and prokaryotes nucleotide-binding (HEPN)—which, thus far, has only been found in RNases.

The group first tested whether C2c2 could be used to provide E. coli immunity against an RNA phage. When the team introduced L. shahii C2c2 locus and RNA phage-specific spacer sequences into E. coli via a plasmid, the bacteria continued to proliferate. E. coli containing the C2c2 locus and control spacer sequences not found in the phage genome did not grow as well.

Purified C2c2 enzymes from L. shahii are ssRNA-specific, the researchers found; they did not cleave double-stranded RNA or ssDNA in vitro. Tinkering with various ssRNA sequence targets, the researchers also found that the C2c2-CRISPR RNA complex preferentially made cuts at uracil residues and certain  secondary structures of ssRNA.

Mutating the putative catalytic site within either of C2c2’s HEPN domains and introducing the mutated enzyme sequence via a plasmid prevented the protection of E. coli from phage infection, the researchers showed. In vitro, none of the four mutated enzyme versions could cut RNA, suggesting that both HEPN domains are necessary for C2c2 to work.

It is likely that the C2c2 CRISPR system could be manipulated to introduce new functions beyond the cutting of RNA—for example, to knock down gene expression—because a HEPN-inactive C2c2 mutant bound but did not cleave its RNA target, the team noted in its report.

Like Cas9, the researchers also showed that C2c2 could be targeted to knock down expression of non-phage RNA. Unlike Cas9, which cuts DNA only within the sequence dictated by the CRISPR RNA, C2c2 could make cuts within the target sequence and adjacent, nonspecific sequences, depending on the conformation of the RNA molecule and amount of exposed ssRNA, the researchers showed.