Gallbladder Cancer and Aflatoxin: Do We Have Sufficient Evidence?

My recently published article in Gastroenterology:

https://www.sciencedirect.com/science/article/pii/S001650851736345X?via%3Dihub

"Dear Editors:

Gallbladder carcinoma (GBC) is the most common malignancy of the biliary tract and the third most common gastrointestinal tract malignancy. About 178,100 new cases were diagnosed around the world in 2012, but the number of deaths from the disease was relatively high by comparison at 142,800.1 The incidence of GBC is especially high in South America, affecting 27 per 100,000 people.2 The high rates of GBC in South America and Asia including India, Pakistan, Korea, and Japan have been attributed to high rates of gallstones (GS) and chronic Salmonella infection, both of which are known risk factors for GBC.3 However, other risk factors, including those emanating from environmental exposure and heritable genetic traits and gender predisposition etc, have been focus of researchers for a long time so as to develop preventive strategies.

We read with great interest the recent article on association of aflatoxins with GBC published in Gastroenterology.4 In this case-control study of patients with GBC and GS versus patients with GS without cancer, the authors report an association between exposure to aflatoxin (based on plasma level of AFB1-lysine) with GBC, and based on which they further suggest that reducing aflatoxin exposure may reduce the incidence of GBC. Aflatoxins are secondary metabolites of Aspergillus flavus and Aspergillus parasiticus, and contaminate a variety of staple foods, particularly maize and groundnuts, in low-income countries. However, as per an estimate, approximately 4.5 billion of the world's population is exposed to aflatoxins,5 affecting many tropical countries comprising parts of Africa, Asia, and Latin America, but GBC is not as rampant disease in these geographical areas as compared with hepatocellular carcinoma, which has s more established connection with aflatoxin exposure based on the evidence from epidemiologic studies in exposed populations and mechanistic studies. In fact, GBC is a cancer type for which differences in incidence ratios point to variations in etiology in different populations.1

This study by Koshiol et al4 is based on the premise that GS are the strongest risk factor for GBC and this study allowed them to evaluate whether exposure to aflatoxin is associated with risk of GBC in the context of GS. It is important to note that in Asia, India has highest incidence of GS (10%–22%) as compared with China (5%) and Japan (5%).3 These data4 showing higher levels of aflatoxins adducts in the plasma of Chinese population with GS as a risk factor for GBC raises another pertinent question as to what makes patients with GS in India (another Asian country with higher GBC incidence, at 11,172 and 9450 cases of incidence and mortality in females has been reported just for 2012) less vulnerable for GBC as compared with their Chinese counterparts (27,699 cases of incidence and 22,475 cases of mortality in females), with incidence and mortality almost twice to that of India,6 even though China has lower incidence of GS in its population3 as compared with that of India? Does no association between aflatoxin exposure and patients with GBC in the Indian population as reported earlier in a recent study7 hold the key to the answer of this question?

Interestingly, the incidence of GBC has a specific geographic and ethnic variation in most populations; for example, in India GBC is most prevalent in northern and northeastern states of Uttar Pradesh, Bihar, Orissa, West Bengal, and Assam, with a 10 times lower incidence per 100,000 in South India compared with the North, the age-adjusted incidence rate for females being 0.8 in Chennai in the south and 8.9 in Delhi in the north.3,6 This stark difference in the incidence of GBC within a country where exposure to aflatoxins is almost similar suggests a need for further studies to explore the role of aflatoxins in a disease with as complex an etiology as GBC with more variables to be taken into considerations. Although this study4 explored the role of R249S mutation in the TP53 gene, which has been known to be associated with aflatoxin-related hepatocellular carcinoma, no association between GBC and this mutation was observed indicating the need for discovery of more genetic markers to serve as surrogate for aflatoxins’ exposure in the populations. Further studies in other populations using polymorphic variants of genes and proteins such as glutathione S-transferase and cytochrome-P450, known to be involved in the metabolism of aflatoxins as well as known genetic risk factors associated with GBC,8 are needed to generate more robust datasets after multivariate analyses so as to adjust for confounding factors, if any, which may otherwise distort the apparent exposure–disease relationship.

References

1

Ferlay J, et al. Available from: globocan.iarc.fr.

2

E.C. Lazcano-Ponce, et al.

CA Cancer J Clin, 5 (2001), pp. 349-364

CrossRefView Record in Scopus

3

R.K. Sharma, et al.

PLoS One, 11 (2016), p. e0166351

CrossRef

4

J. Koshiol, et al.

Gastroenterology, 153 (2017), pp. 488-494

View Record in Scopus

5

J.H. Williams, et al.

Am J Clin Nutr, 80 (2004), pp. 1106-1122

View Record in Scopus

6

C. Are, et al.

J Surg Oncol, 115 (2017), pp. 580-590

CrossRefView Record in Scopus

7

T. Ikoma, et al.

Asian Pac J Cancer Prev, 17 (2016), pp. 3499-3503

View Record in Scopus

8

K. Srivastava, et al.

Mutat Res, 728 (2011), pp. 67-79

ArticleDownload PDFView Record in Scopus

Conflicts of interest The authors disclose no conflicts."

"Hyperbole in research" by Dr. Shailesh Kumar

A great piece of write-up by dear friend of mine Dr. Shailesh Kumar, an accomplished cell biologist with long experience of working in the area of circadian rhythm:


"Hyperbole is the new phenomenon nowadays in public discourse and scientists too are not untouched. Recently John Oliver covered it very well on his TV show on how “promising” scientific results are being peddled as “conclusive” in visual and less so in print media. Path to future is treacherous one in science, yet we are tempted to extrapolate research findings as final panacea leading to false hope and ultimately disappointment. With advent of technological revolutions ranging from omics to microbiome, nanotech to personalized medicine, drug repurposing, most of the results from labs are being presented by researchers, universities and media as breakthroughs and paradigm shifters. Nonetheless these rhetorics are omnipresent, gone are those days where scientists used to work away from public glare driven by passion and curiosity. Sadly scientific communications are becoming more of Hollywoodish sci-fi trailers, which have led to immense attention from external media, funding bodies and policymakers. Given the sensibilities of media, I do not have much hopes of doing the due diligence while reporting scientific facts. It’s about time scientists, researchers stick together to correct misrepresentation of facts put out in the public domain through social media, blogs or televised media. Irony is, enthusiastic exaggeration of facts are so much in demand in external world that we are undermining policy debates and impacting clinical decisions and unverified therapies. Therefore scientific community should come together to fight this hype- n-hoopla sooner the better."

Another reason to continue Metformin for your type II diabetes !!

Fragile X syndrome is a genetic disease caused by defects in the Fragile X Mental Retardation 1 gene (FMR1), which triggers excess production of protein in the brain, as well as dysregulated connections between neurons and changes in behavior. The condition leads to impairments in speech and language, behavior and social interaction. It affects about 1 in 5,000 boys and 1 in 6,000 girls and is often co-diagnosed with autism, anxiety disorders and seizures. I have never personally worked on the Fragile X syndrome but I have indirectly been associated with ongoing research efforts about this disease through a close friend of mine and an accomplished neuroscientist Dr. Udai Bhan Pandey, currently an associate professor of Human Genetics at University of Pittsburgh. Earlier in his career, Dr. Pandey worked on Fragile X syndrome for his Ph.D. dissertation in the same lab in which I was working on a GI cancer model.  I vividly remember how passionately he used to talk about this disease and as to how there is no cure for fragile X syndrome back in 2003. Even today after 14 years, there is no cure yet.

A new study led by researchers at McGill University, the University of Edinburgh and Université de Montréal has found that Metformin improves social, behavioral and morphological defects in mice model of Fragile X syndrome. For those who are not aware about Metformin, it is a common drug used in individuals with high risk for diabetes type 2, obesity or impaired glucose tolerance. It has had a strong safety profile in children and adults with type 2 diabetes and obesity. 

Ilse Gantois, Arkady Khoutorsky, Jelena Popic, Argel Aguilar-Valles, Erika Freemantle, Ruifeng Cao, Vijendra Sharma, Tine Pooters, Anmol Nagpal, Agnieszka Skalecka, Vinh T Truong, Shane Wiebe, Isabelle A Groves, Seyed Mehdi Jafarnejad, Clément Chapat, Elizabeth A McCullagh, Karine Gamache, Karim Nader, Jean-Claude Lacaille, Christos G Gkogkas, Nahum Sonenberg. Metformin ameliorates core deficits in a mouse model of fragile X syndrome. Nature Medicine, 2017; DOI: 10.1038/nm.4335

In this study, Gantois et al. beautifully demonstrate that metformin, a type II diabetes drug that crosses the blood-brain barrier, corrects various neurological and behavioral phenotypes of fragile x syndrome in a mouse model known as Fmr1−/y.  These mice have increased abundance of an kinase (a type of cellular enzyme) known as RAF and enhanced activity of its related kinases and gene targets. These investigators found that a chronic (10-day) treatment with metformin reduced the abundance of RAF and suppressed the activation of enzymes such as MEK, ERK, mTOR, and translation initiation factor eIF4E in the prefrontal cortex and hippocampus of Fmr1−/y mice which are important molecules in the pathogenesis of fragile X disease. Decreased mTOR activity correlates with decreased expression of the gene encoding MMP9, a protease (another type of enzyme) that regulates synaptic function. Metformin suppressed repetitive behavior, the incidence of macroorchidism, and defects in dendritic spine development and synaptic activity in Fmr1−/y mice, phenotypes that are common in fragile x syndrome patients.

Please note that this study is conducted in mice model, and in spite of lot of similarities between mice and human, further tests will be needed to assess whether metformin can specifically improve cognitive function in mammals and assess the extent of its benefits versus its side effects which are many. Yet scientific community is very optimistic about these findings suggesting that metformin might be repurposed for use in fragile x patients.

Dr. Nahum Sonenberg, a pioneering scientist of our times, best known for his seminal contributions to our understanding of translation of proteins from RNAs, and notable for the discovery of the mRNA 5' cap-binding protein, eIF4E, the rate-limiting component of the eukaryotic translation apparatus and also a senior author of this research work says about Metformin:  "Basically, it's something like a wonder drug,"

https://en.wikipedia.org/wiki/Nahum_Sonenberg

'Wonder drug' in the past few years, metformin has generated extensive interest for its potential in treating numerous health problems such as cancer, cardiovascular diseases, neurological diseases and aging. Numerous preclinical, epidemiological and clinical studies in the past have suggested that metformin use is associated with inhibition of cancer cell growth and reduction in all-cancer incidents in comparison with users of other hypoglycemic drugs. So if you are type 2 diabetes patient and your doctor has advised you to take metformin, you have another good reason to keep taking this drug regularly without fail.

http://www.healthline.com/health/metformin-oral-tablet#about3

Dual Targeting of NEDD9/AURKA and ROCK pathways could be a viable therapeutic strategy to treat triple negative breast cancer.

Despite major discoveries in cancer biology in recent years, metastases (spread of primary tumor cells) are the cause of 90% of human cancer deaths. Very little is known about the genetic and biochemical determinants of metastasis. Metastasis is a multistage process involving abnormal tumor cell migration and invasion, transit in the blood or lymph, extravasation and colonization in the normal tissues at secondary sites. Acquisition of invasive behavior involves activation of signaling pathways controlling cytoskeletal dynamics, as well as turnover of cell–matrix and cell–cell adhesions. Cancer invasion is a heterogeneous and adaptive process involving changes in cell morphology and generation of cell polarity. Cancer cells display exceptional ability to adapt to different environmental conditions engaging in different migration strategies. Cancer cells can migrate either individually in the absence of cell–cell junctions, or collectively upon retention of cell–cell adhesions. In turn, cancer cells can use a number of strategies when migrating individually such as they could change their shape between elongated-mesenchymal, rounded- amoeboid, spike-mediated or while migrating collectively they would behave as if in a multicellular streaming or tumor budding to accomplish collective invasion into normal tissues at a different site.

Scaffolding protein known as NEDD9 is a critical regulator of cancer cell migration especially for individual mesenchymal type of migration for many types of tumor cells and its elevated expression has been reported in many tumor types including breast, lung, and melanoma. Mesenchymal migration is characterized by an elongated cell morphology, multiple focal/3D adhesions, and the ability to degrade ECM by matrix metalloproteinases (MMPs) creating a path through the basement membrane/tissue. A major regulator of mesenchymal migration, Rac1 GTPase, is activated by a number of guanine nucleotide exchange factors (GEFs), including melanoma-specific DOCK3, which in turn is recruited/activated by NEDD9.

In a recent study conducted by a former colleague and friend Dr. Elena Pugacheva, an Associate Professor at University of West Virginia, amoeboid movement of triple negative breast cancer (TNBC) cells was found to be defective in some respects such as decreased cell contractility. It is important to note that a triple negative breast cancer diagnosis means that the tumor is estrogen receptor-negative, progesterone receptor-negative and HER2-negative, thus giving rise to the name “triple negative breast cancer.” While this type of breast cancer is typically responsive to chemotherapy, the bad news is when TNBC tumor recurs then it becomes hard to treat as they do not respond to hormonal therapy (such as tamoxifen or aromatase inhibitors) or therapies that target HER2 receptors, such as Herceptin (chemical name: trastuzumab) which is commonly used to treat other types of breast cancer in case of tumor recurrence. For doctors and researchers, there is intense interest in finding new medications that can treat this kind of breast cancer.

Dr. Pugacheva and her team at West Virginia University School of Medicine provides a mechanistic explanation as to how NEDD9 drives invasion processes in TNBC cells which paves roads to develop new therapeutic strategies so as to use a combination of anti-NEDD9/AURKA and anti-ROCK–targeting compounds to inhibit these movement signaling cascades relevant in TNBCs. In this study, investigators report that deficiency in NEDD9 signaling itself leads to inhibition of key aspects of both mesenchymal and amoeboid migration in TNBC cells, resulting in substantial hindrance on cell invasion and metastasis. NEDD9 deficiency in TNBC cells results in rounded/amoeboid morphology along with a decrease in the total number of mature (pFAK/pPaxillin positive) adhesions and an increase in the number of recently formed adhesion structures. Together, these findings suggest that NEDD9 is also required for the disassembly of fibrillar adhesions similar to vinculin, which regulates the recruitment and release of focal adhesion proteins in a force-dependent manner. Overall this work strongly suggests that a dual targeting strategy (using both anti-NEDD9/AURKA and anti-ROCK–targeting compounds) could be an efficient therapeutic approach to hinder the metastasis of triple negative breast cancers, indicating towards an important need for further clinical evaluation of this therapeutic regimen to impede the spread of disease and improve patient survival in patients setting.

For details, please refer to the original work:

http://mcr.aacrjournals.org/content/15/6/670

http://directory.hsc.wvu.edu/Individual/Index/31447

For further reading about NEDD9 signaling pathway please refer to:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2758619/

http://cancerres.aacrjournals.org/content/early/2010/10/07/0008-5472.CAN-10-0353