I'll have to beg to differ here... from this article itself it states

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5356589/

To asses our hypothesis in an in vivo model, subcutaneous tumors were generated in nude mice with HT29 cells. Tumor-bearing animals were treated daily with the vehicle, 1 mg/kg JWH-133 or 5 mg/kg JWH-133 for 14 days. Tumor volume was calculated every day, and at the end of the experiment tumors were dissected. As shown in Figure ​Figure6A,6A, tumors increased their growth rate significantly in response to 1 mg/kg of JWH-133 with respect to the vehicle-treated group; whereas a 5 mg/kg of JWH-133 produced the opposite effect, a reduction in tumor growth rate (although significant effect is only observed at day 14).

And, contrary to what they state, we can see a clear deviation in tumor volume in the in vivo study from day 8, not day 14. Sure, they might say the word significant only on the 14th day, but there is already a change from the vehicle well before that from the chart they provided.

The study cites no conflicts, but I am wondering what the criteria to declare a conflict are. So for example, we see Esther Martínez-Martínez cited in this paper:

https://www.ncbi.nlm.nih.gov/pubmed/24910342

whose key results state this

CBD reduced breast cancer metastasis in advanced stages of the disease as the direct result of down-regulating the transcriptional regulator Id1. However, this was associated with moderate increases in survival. We therefore screened for analogues that could co-target cannabinoid anti-tumour pathways (CBD- and THC-associated) and discovered the compound O-1663. This analogue inhibited Id1, produced a marked stimulation of ROS, up-regulated autophagy and induced apoptosis. Of all the compounds tested, it was the most potent at inhibiting breast cancer cell proliferation and invasion in culture and metastasis in vivo.

And to me, it makes the most sense to see the subtle ways in which researchers present their arguments from a somewhat guarded standpoint, as there is no money to be made in declaring CBD as an anti-cancer agent, but perhaps there is money to be made in patenting compound O-1663.

I would take any such studies with a grain of salt, especially when they are writing things that appear to contradict the data they themselves are presenting in order to present a more streamlined narrative.

Personally I am biased as well, so it was a relief to see the 5 mg/kg approach did reduce tumor volume.