The Guardian of the Genome – the role of P53 in Cancer Prevention and in increasing/decreasing Autistic Behaviors

 

The p53 protein is called the guardian of the genome because it plays a critical role in maintaining genomic stability. It does this by surveying the genome for signs of DNA damage. If p53 detects DNA damage, it activates a number of different cellular responses to prevent the damaged cell from dividing and passing on that damage. These responses can include:

• p53 can halt the cell cycle giving the cell time to repair the damaged DNA.
• p53 can activate genes that are involved in DNA repair.
• If the DNA damage cannot be repaired, p53 can trigger cell death.

p53 protects your genome by preventing damaged cells from dividing and passing on DNA damage.

 

What about p53 and autism?

We have seen many times that cancer genes overlap with autism genes; that is the case today with p53. The protein p53 acts like a transcription factor turning on or off key genes in the brain that affect learning and behavior. 

Protein p53’s Role in Autism-like Behavior and Memory

Scientists have discovered a direct link between the protein p53 and autism-like behavior in mice. The researchers studied the effects of manipulating p53 levels in the mouse hippocampus.

Reduced levels resulted in repetitive behavior, diminished sociability, and impaired learning, especially in male mice. This pivotal work uncovers the intricate role of p53 in neurodevelopmental disorders like autism.

Key Facts:

1.     Lowered hippocampal p53 levels in mice led to repetitive behavior, decreased sociability, and hindered hippocampus-dependent learning.

2.     Elevated p53 levels were observed during periods of enhanced communication between hippocampal neurons, related to positive learning outcomes.

3.     Previous research from 2018 identified p53’s significant role in irregular brain cell activity seen in both ASD and epilepsy.

 

In this study, Tsai and his colleagues lowered hippocampal p53 levels in mice, looking for changes in gene expressions related to behavior. They observed that the decreased p53 levels: 

·        Promoted repetitive behavior in mice.

·        Reduced sociability in mice.

·        Impaired hippocampus-dependent learning and memory, especially in male mice.

The researchers also observed that p53 levels were elevated after a period of active communication between hippocampal neurons called long-term potentiation. Flexible neuron firing — known as plasticity — is related to positive learning and memory outcomes. 

In a 2018 study, Tsai and his colleagues identified p53 as a key protein involved in the irregular brain cell activity seen in ASD and epilepsy. In future studies, they aim to explore how p53 coordinates the expression of those autism-linked genes to guide behavior. 

 

The full paper: 

Tumor suppressor p53 modulates activity-dependent synapse strengthening, autism-like behavior and hippocampus-dependent learning

Synaptic potentiation underlies various forms of behavior and depends on modulation by multiple activity-dependent transcription factors to coordinate the expression of genes necessary for sustaining synaptic transmission. Our current study identified the tumor suppressor p53 as a novel transcription factor involved in this process. We first revealed that p53 could be elevated upon chemically induced long-term potentiation (cLTP) in cultured primary neurons. By knocking down p53 in neurons, we further showed that p53 is required for cLTP-induced elevation of surface GluA1 and GluA2 subunits of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). Because LTP is one of the principal plasticity mechanisms underlying behaviors, we employed forebrain-specific knockdown of p53 to evaluate the role of p53 in behavior. Our results showed that, while knocking down p53 in mice does not alter locomotion or anxiety-like behavior, it significantly promotes repetitive behavior and reduces sociability in mice of both sexes. In addition, knocking down p53 also impairs hippocampal LTP and hippocampus-dependent learning and memory. Most importantly, these learning-associated defects are more pronounced in male mice than in female mice, suggesting a sex-specific role of p53 in these behaviors. Using RNA sequencing (RNAseq) to identify p53-associated genes in the hippocampus, we showed that knocking down p53 up- or down-regulates multiple genes with known functions in synaptic plasticity and neurodevelopment. Altogether, our study suggests p53 as an activity-dependent transcription factor that mediates the surface expression of AMPAR, permits hippocampal synaptic plasticity, represses autism-like behavior, and promotes hippocampus-dependent learning and memory.

  

How to upregulate p53?

It is important to note that increasing p53 levels does not guarantee that p53 will be activated.

Researchers are still in the early stages of developing drugs that can specifically activate p53.

There are a number of food products that have been shown to increase p53 levels in cells, such as cruciferous vegetables like broccoli.

If you refer to the excellent Gene Cards resource, you will find that very many drugs can help activate p53. Almost 500 are listed – too many for me to review here.

https://www.genecards.org/cgi-bin/carddisp.pl?gene=TP53

 

One example is the old antihistamine Clemastine that has been recommended in this blog, for completely different reasons. A paper in 2023 suggests “Repurposing Clemastine to Target Glioblastoma (brain cancer)”.

Indole-3-carbinol (I3C) gets listed as does Epigallocatechin gallate (EGCG).

I have mentioned previously that I3C is one reason (unrelated to sulforaphane) that broccoli can be beneficial in some autism.

The last time I mentioned EGCG, a catechin found in green tea, a doctor reader contacted me to tell me that he has taken it for 20 years for its antiangiogenic properties. Antiangiogenic means that something prevents or slows down the growth of new blood vessels. Cancer cells need a blood supply to grow and spread. They produce proteins called angiogenic factors, which stimulate the growth of new blood vessels. Antiangiogenic drugs work by blocking the effects of angiogenic factors or by targeting the cells that produce them. This can starve cancer cells of the blood they need to grow and spread.  It seems to have worked well for our reader!

We have seen that EGCG has been proposed to treat girls with Rett syndrome.

EGCG has been shown to have a number of beneficial effects in cells and animal models of Rett syndrome. For example, EGCG has been shown to: 

·        Increase levels of the p53 tumor suppressor protein

·        Reduce oxidative stress

·        Improve mitochondrial function

·        Promote synaptic plasticity

·        Protect neurons from damage

One of our readers finds that Broccoli powder (Broccomax) provides a boost to his daughter with Rett syndrome. Is it the sulforaphane or it the Indole-3-carbinol (I3C)? My bet would be on the I3C from the broccoli.  You can buy I3C itself.

 

Conclusion

More p53 please!

Eating well is much more than just about vitamins.  Eating all those healthy foods mentioned above that many people avoid will boost your p53 levels.

Ultimately there will be an expensive new drug to boost p53 in cancer patients.

Very many old drugs do have secondary effects that include boosting or activating p53.

Curcumin, not surprisingly, boosts p53 and helps protect people of Indian origin from cancer via their traditional diet.

Genistein, resveratrol, EGCG, broccoli powder are all supplements that boost p53.

It is nice to see that Clemastine, my favorite old antihistamine that may promote myelination in some, stabilize activated microglia in some, many also increase p53 sufficiently to be seen as a potential anti-cancer therapy.

Maybe keep an eye out for Dr Tsai, particularly if you are interested in Fragile X or p53. Here he is: 

https://mcb.illinois.edu/directory/profile/nptsai

A RORα Agonist for Autism?

Today’s post is again about RORα, which was suggested to be a nexus where different biological dysfunctions that lead to autism may converge. I think you can consider RORα like a dimmer switch on your lights, you need to adjust the brightness to give the effect you want.

Fine tuning RORα to tune autism gene expression

I recently came across some research where the scientist clearly has the same idea. He has been working on a synthetic RORα/γ agonist for some years and has investigated its use as both a cancer therapy and an autism therapy.

I have become rather interested in cancer therapies because there are so many overlaps between what can lead to cancer and what exists in autism. The big research money is of course in cancer research.

Tumor suppressor genes/proteins like PTEN and p53 have been shown to be disturbed in autism, as is Bcl-2. The Bcl-2 family of proteins regulate cell death (apoptosis); some members induce cell death and other inhibit it; the balance is important.

Generally it seems that most people with autism might benefit from more PTEN and Bcl-2. 

Therapeutic Effect of a Synthetic RORα/γ Agonist in an Animal Model of Autism  

Autism is a developmental disorder of the nervous system associated with impaired social communication and interactions as well excessive repetitive behaviors. There are no drug therapies that directly target the pathology of this disease. The retinoic acid receptor-related orphan receptor α (RORα) is a nuclear receptor that has been demonstrated to have reduced expression in many individuals with autism spectrum disorder (ASD). Several genes that have been shown to be downregulated in individuals with ASD have also been identified as putative RORα target genes. Utilizing a synthetic RORα/γ agonist, SR1078, that we identified previously, we demonstrate that treatment of BTBR mice (a model of autism) with SR1078 results in reduced repetitive behavior. Furthermore, these mice display increased expression of ASD-associated RORα target genes in both the brains of the BTBR mice and in a human neuroblastoma cell line treated with SR1078. These data suggest that pharmacological activation of RORα may be a method for treatment of autism. 

The RORs have been linked to autism in human in several studies. In 2010, Nguyen and co-workers reported that RORα protein expression was significantly reduced in the brains of autistic patients and this decrease in expression was attributed to epigenetic alterations in the RORA gene.¹⁵ Additional work from this group demonstrated that multiple genes associated with autism spectrum disorder are direct RORα target genes and suggested that reduction of RORα expression results in reduced expression of these genes associated with the disorder leading to the disease.¹⁶ Independently, Devanna and Vernes demonstrated that miR-137, a microRNA implicated in neuropsychiatric disorders, targets a number of genes associated with autism spectrum disorder including RORA.¹⁷ There are also additional links between RORα and autism. Deficiency of Purkinje cells is one of the most consistently identified neuroanatomical abnormalities in brains from autistic individuals^18,19 and RORα is critical in development of the Purkinje cells.²⁰⁻²³ Significant circadian disruptions have also been recognized in autistic patients,²⁴⁻²⁷ and RORs play a critical role in regulation of the circadian rhythm.^7,28 Additionally, the staggerer mouse displays behaviors that are associated with autism including abnormal spatial learning, reduced exploration, limited maze patrolling, and perseverative behavior relative to wt mice.²⁹⁻³³

SR1078 is a relatively low potency compound with limited RORα efficacy (3–5 μM EC₅₀E_max ∼ 40%),⁸ but the efficacy compares favorably to other classes of compounds that have been optimized such as a 38% decrease in the same model induced by the mGluR5 allosteric modulator GRN-529⁴⁹ and a 47% reduction by the mGluR5 antagonist MPEP.⁴⁵ Both of these compounds have been optimized and display high potency (single digit nanomolar range at mGluR5) and strong efficacy.^53,54 Thus, we believe that focused optimization of RORα ligands will provide compounds that will have improved efficacy in this model. It should also be noted that SR1078 has both RORα and RORγ agonist activity⁸ and a RORα selective agonist has not yet been developed. Thus, it is possible that the RORγ activity of this compound may also play a role in its efficacy in this model of autism. In summary, we have demonstrated that a synthetic RORα/γ agonist is able to increase the expression of key genes whose decrease in expression is associated with ASD both in cell culture and in vivo. Furthermore, the agonist decreases repetitive behavior in an animal model of autism suggesting that it is possible that ROR agonists may hold utility in treatment ASD. 

Regulation of p53 Stability and Apoptosis by a ROR Agonist

Activation of p53 function leading to cell-cycle arrest and/or apoptosis is a promising strategy for development of anti-cancer therapeutic agents. Here, we describe a novel mechanism for stabilization of p53 protein expression via activation of the orphan nuclear receptor, RORα. We demonstrate that treatment of cancer cells with a newly described synthetic ROR agonist, SR1078, leads to p53 stabilization and induction of apoptosis. These data suggest that synthetic ROR agonists may hold utility in the treatment of cancer.  

Levels of Bcl-2 and P53 Are Altered in Superior Frontal and Cerebellar Cortices of Autistic Subjects 

Results showed that levels of Bcl-2 decreased by 38% and 36% in autistic superior frontal and cerebellar cortices, respectively when compared to control tissues. By the same token, levels of P53 increased by 67.5% and 38% in the same brain areas in autistic subjects vs. controls respectively. Calculations of ratios of Bcl-2/P53 values also decreased by 75% and 43% in autistic frontal and cerebellar cortices vs. controls respectively. The autistic cerebellar values were significantly reduced (p < 0.08) vs. control only. There were no significant differences in levels of β-actin between the two groups. Additionally, there were no correlations between Bcl-2, P53, and β-actin concentrations vs. age or PMI in either group.

These results confirm and extend previous data that levels of Bcl-2 and P53 are altered in three important brain tissues, i.e. frontal, parietal, and cerebellar cortices of autistic subjects, alluding to deranged apoptotic mechanisms in autism.  

Conclusion

Increasing PTEN and Bcl-2 is already part of my Polypill, via the use of Atorvastatin.

There are of course many other genes miss-expressed in autism and we cannot give a drug for each one. We need to identify a handful of nexus, where multiple anomalies can be resolved with a single intervention.

It is good that Thomas Burris, the lead researcher, has been working on SR1078 for at least 6 years, let’s hope he continues to persevere.

I think it highly likely that some types of autism will need the opposite therapy, a RORα antagonist.

My method of attempting to modulate RORα will be different. I come back to my earlier gross simplification of autism :- 

As we have seen in earlier posts, the hormonal dysfunction, this time the balance between testosterone and estradiol, has a direct effect on RORα (and vice versa).

The schematic illustrates a mechanism through which the observed reduction in RORA in autistic brain may lead to increased testosterone levels through downregulation of aromatase. Through AR, testosterone negatively modulates RORA, whereas estrogen upregulates RORA through ER.

androgen receptor = AR 

estrogen receptor = ER

As you might know, many hormones are interrelated, so what are thought of as male/female sex hormones have much wider effects. They impact growth hormones and play a big role in calcium metabolism. They also affect serotonin.

We know that in most autism aromatase is reduced, estradiol is reduced and that there is reduced expression of estrogen receptor beta.

In the ideal world it might indeed be best to use an agonist or antagonist to fine tune RORα.

We have a chicken and the egg situation. Is RORα out of tune in autism because the hormones are disturbed, or vice versa?

We do know that hormones generally have feedback loops, but we also know that increasing a hormone like estradiol via obesity is not fully matched by a corresponding reduction in aromatase. So it looks highly plausible that you can tune RORα via estradiol, and that this could be a long term strategy, not just a short term strategy.

In the case of people with low T3 thyroid hormone centrally (in the brain), giving exogenous T3 may help initially, but in the long term it does not because feedback loops to the thyroid will reduce production of the pro-hormone T4. In the extreme you will make the thyroid gland shut down, this does happen to people using thyroid hormones for depression and even weight loss. 

T3 is quite commonly prescribed by alternative practitioners in the US for autism and also for depression in older people. In Europe this hormone is rarely even available. 

Many phytoestrogens are used as OTC autism therapies. These are dietary estrogens that are structurally similar to the human hormone estradiol and so produce estrogen-like effects. They include soy products, fenugreek, kudzu, EGCG etc.